helium — label CAS 7440-59-7

helium

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Hel, CAS 7440-59-7

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🧬 3D Molecule Visualizer
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3D model Helium, CAS 7440-59-7, molecular formula He, molar mass 4.00260 g/mol
Chemical Overview: HeliumMolGod_OVERVIEW_1
Molecular formulaHe
Molecular weight4.00260 g/mol
Melting point-272.2 °C
Boiling point-268.9 °C
SMILES[He]
InChIKeySWQJXJOGLNCZEY-UHFFFAOYSA-N

Synonyms: HELIUM · Atomic helium · Helium-4 · 7440-59-7 · p-Helium

Data sources: PubChem (NLM/NIH)
Last updated: 2026-11-10

📊 Physicochemical properties

Quick Reference

Formula: He
MW: 4.00 g/mol
CAS: 7440-59-7

Detailed Properties

Property Value Unit Conditions Source
Melting Point (mp) -272.20 °C (-458 °F) 1 atm PubChem PUG-View (2026)
Boiling Point (bp) -268.90 °C (-452 °F) 1 atm PubChem PUG-View (2026)
Water Solubility 0.003 g/L 25 °C (77 °F) PubChem PUG-View (2026)
🔬 Advanced Properties

Chemical Identifiers

SMILES: [He]

Data sources: PubChem, NIST Chemistry WebBook, CRC Handbook of Chemistry and Physics (103rd ed.)

Last updated: 2026-07-11

Regulatory status of the substance
No entries for this CAS in the restriction lists checked (SVHC candidate list, REACH Annex XVII; datasets incomplete — this is not a confirmation of compliance). CLP classification and transport status (ADR): see the GHS section and the safety data sheet (SDS).
🧮 Stoichiometry CalculatorMolGod_STOICH_1
🔍 External identifiersMolGod_EXTID_1
13 of 16 ID systems81%
DatabaseIdentifierActions
CAS Registry Number7440-59-7Open →
PubChem CID23987Open →
InChIKeySWQJXJOGLNCZEY-UHFFFAOYSA-NOpen →
InChIInChI=1S/He
SMILES[He]
EC Number231-168-5Open →
ChEMBLCHEMBL1796997Open →
DrugBankDB09155Open →
HMDBHMDB0037238Open →
ChemSpider22423Open →
MeSH UID (NLM)D006371Open →
UNII (FDA)206GF3GB41Open →
WikiData QIDQ560Open →

Sources: PubChem (NIH), Wikidata SPARQL, KEGG, ChEMBL (EBI), CompTox CTX (EPA).

⚛ Atom Visualization — Helium MolGod_ATOMVIZ_1
He
Helium
Helium
Z = 2 | Noble gas
Atomic mass
4.003 u
Melting point
-272.2 °C
Boiling point
-268.93 °C
Density
0.00018 g/cm³
Group / Period
18 / 1
2 protons
2 neutronów
K: 2e⁻
1s²
📡 Spectroscopy — CAS 7440-59-7MolGod_SPECHUB_MAIN
📊 Spectroscopic spectra databases — inline data 8 sources MolGod_SPECDB_2

Spectra are fetched on demand from 9 sources. Each spectrum is stored in our database — the next time it is opened there are zero requests to the external API. Download JCAMP-DX / CSV / PNG for every spectrum without searching.

IR IR (Infrared) — NIST WebBook
Public domain (US Federal)
▶ Click to load spectrum
🔗 Source
— points
📚 NIST Chemistry WebBook, SRD 69
MS (NIST) Mass Spectrum (EI) — NIST WebBook
Public domain (US Federal)
▶ Click to load spectrum
🔗 Source
— points
📚 NIST Standard Reference Database 1A
UV-Vis UV/Visible Absorption — NIST WebBook
Public domain (US Federal)
▶ Click to load spectrum
🔗 Source
— points
📚 NIST Chemistry WebBook, SRD 69
MS (MoNA) MoNA — MassBank of North America
CC-BY 4.0
▶ Click to load spectrum
🔗 Source
— points
📚 MassBank of North America (UC Davis) DOI: 10.1002/jms.1777
IR/NMR/MS (SDBS) SDBS — Spectral Database for Organic Compounds (Japan AIST)
Free for non-commercial

Reference source — no public API. Open in an external database:

🔗 IR/NMR/MS (SDBS) →
📚 SDBSWeb: https://sdbs.db.aist.go.jp (AIST, Japan)
JP Monograph Japanese Pharmacopoeia — Monographs
Reference only

Reference source — no public API. Open in an external database:

🔗 JP Monograph →
📚 Japanese Pharmacopoeia 18th Edition (2021)
WHO INN WHO — International Nonproprietary Names
WHO Model Lists (free)

Reference source — no public API. Open in an external database:

🔗 WHO INN →
📚 WHO INN Programme
DOAJ DOAJ — Directory of Open Access Journals
OA journal index (mixed)

Reference source — no public API. Open in an external database:

🔗 DOAJ →
📚 DOAJ — doaj.org

Data retrieved via MolGod_Spectra_Remote_Fetcher (JCAMP-DX parser) and stored in the wp_molgod_spectra_cache table. Zero duplicate downloads, zero repeat queries to NIST on subsequent visits. Licensing terms are respected (only a deep link plus our own visualization is published).

🔬 Interactive spectra (live — NIST / MoNA / NMRShiftDB / SDBS) (2)

Data retrieved live from multiple sources (priority chain). JCAMP-DX / CSV / PNG available for download under each spectrum.

IR — Fourier-transform infrared

Loading IR — Fourier-transform infrared…

MS — Mass spectrometry (EI 70eV)

Loading MS — Mass spectrometry (EI 70eV)…

📐 Physical & Chemical Properties (DB) 3 fields MolGod Score: Reliable
Property Value Unit Conditions Source
Melting point -272.20 [5][6][11] °C 1 atm PubChem PUG-View (2026)
Boiling point -268.90 [5][6][11] °C 760 mmHg PubChem PUG-View (2026)
Water solubility 0.003 [5] g/L 25°C PubChem PUG-View (2026)
📚 Scientific references (Chicago Author-Date) (12 sources)
  1. Haynes, William M., ed. 2024. CRC Handbook of Chemistry and Physics. 105th ed. Boca Raton: CRC Press/Taylor & Francis. ISBN 978-1-032-55554-4. ↗
  2. National Institute of Standards and Technology. 2024. "NIST Chemistry WebBook, SRD 69." Gaithersburg, MD: NIST. Accessed 2025-01-01. ↗
  3. Yaws, Carl L. 2014. The Yaws Handbook of Physical Properties for Hydrocarbons and Chemicals. 2nd ed. Oxford: Gulf Professional Publishing.
  4. PubChem. 2024. "PubChem Compound Database." National Library of Medicine, National Institutes of Health. Accessed 2025-01-01. ↗
  5. Marrero, J., and R. Gani. 2001. "Group-Contribution Based Estimation of Pure Component Properties." Fluid Phase Equilibria 183–184: 183–208. ↗
  6. Joback, K. G., and R. C. Reid. 1987. "Estimation of Pure-Component Properties from Group-Contributions." Chemical Engineering Communications 57 (1–6): 233–243. ↗
  7. Sangster, J. 1997. Octanol-Water Partition Coefficients: Fundamentals and Physical Chemistry. Chichester: Wiley. ISBN 978-0-471-97397-3.
  8. Mannhold, Raimund, and Han van de Waterbeemd. 2001. "Substructure and Whole Molecule Approaches for Calculating Log P." Journal of Computer-Aided Molecular Design 15 (4): 337–354. ↗
  9. Perrin, Ditlev D., Boyd Dempsey, and E. P. Serjeant. 1981. pKa Prediction for Organic Acids and Bases. London: Chapman and Hall. ISBN 0-412-21090-5.
  10. Constantinou, Leonidas, and Rafiqul Gani. 1994. "New Group Contribution Method for Estimating Properties of Pure Compounds." AIChE Journal 40 (10): 1697–1710. ↗
  11. Ertl, Peter, Bernhard Rohde, and Paul Selzer. 2000. "Fast Calculation of Molecular Polar Surface Area as a Sum of Fragment-Based Contributions and Its Application to the Prediction of Drug Transport Properties." Journal of Medicinal Chemistry 43 (20): 3714–3717. ↗
🔄 Concentration unit converter LIVE MolGod_UNITCONV_1

Enter the Helium concentration in any unit — the rest will be calculated automatically.

MW: 4.00260 g/mol · IUPAC Gold Book ↗

⚗️ Conversion formulas + citations (per formula)
ConversionFormulaAccuracySource
% (w/v) ↔ molarityc (mol/L) = (% × 10) / MW±0.5% rel. when density ≈ 1.0 g/mLIUPAC (2019)
millimolar ↔ molarc (mol/L) = mM × 10⁻³ExactCohen ER, Cvitaš T, Frey JG, Holmström B, Kuchitsu K, Marquardt R, Mills I, Pavese F, Quack M, Stohner J, Strauss HL, Takami M, Thor AJ (2007)
molarity (mol/L)c = n/V = (m/MW)/V±0.1% (depends on MW precision)IUPAC (2019)
parts per million (mg/L) ↔ molarityc (mol/L) = ppm / (1000 × MW); equivalently ppm = mg/L for dilute aqueous±1% (density-independent for dilute solutions)IUPAC (2019)
mg/mL ↔ molarityc (mol/L) = (mg/mL × 1000) / MW / 1000 = mg/mL / MW × 1±0.2%Cohen ER, Cvitaš T, Frey JG, Holmström B, Kuchitsu K, Marquardt R, Mills I, Pavese F, Quack M, Stohner J, Strauss HL, Takami M, Thor AJ (2007)
g/L ↔ molarityc (mol/L) = (g/L) / MW±0.1% (depends on MW precision)Cohen ER, Cvitaš T, Frey JG, Holmström B, Kuchitsu K, Marquardt R, Mills I, Pavese F, Quack M, Stohner J, Strauss HL, Takami M, Thor AJ (2007)
mmol/L ↔ molarityc (mol/L) = mmol/L × 10⁻³ExactCohen ER, Cvitaš T, Frey JG, Holmström B, Kuchitsu K, Marquardt R, Mills I, Pavese F, Quack M, Stohner J, Strauss HL, Takami M, Thor AJ (2007)
Celsius ↔ KelvinT(K) = t(°C) + 273.15±0.01 K (ITS-90 scale)BIPM (Bureau International des Poids et Mesures) (2019)
Celsius ↔ FahrenheitT(°F) = T(°C) × 9/5 + 32±0.1 °FThompson A, Taylor BN (2008)
density-corrected % ↔ molarityc (mol/L) = (%w/w × ρ × 10) / MW, ρ in g/mL±0.1% when ρ known to 3 decimalsCohen ER, Cvitaš T, Frey JG, Holmström B, Kuchitsu K, Marquardt R, Mills I, Pavese F, Quack M, Stohner J, Strauss HL, Takami M, Thor AJ (2007)
📚 Bibliography (8 authoritative sources)
  1. Thompson A, Taylor BN (2008). Guide for the Use of the International System of Units (SI). NIST Special Publication 811 · DOI: 10.6028/NIST.SP.811-2008
    → Primary SI standard for US scientific usage
  2. Cohen ER, Cvitaš T, Frey JG, Holmström B, Kuchitsu K, Marquardt R, Mills I, Pavese F, Quack M, Stohner J, Strauss HL, Takami M, Thor AJ (2007). Quantities, Units and Symbols in Physical Chemistry — The IUPAC Green Book. RSC Publishing, 3rd ed. · DOI: 10.1039/9781847557889 · ISBN: 978-0-85404-433-7
    → Canonical IUPAC guide for chemistry quantities/units
  3. BIPM (Bureau International des Poids et Mesures) (2019). The International System of Units (SI), 9th edition. BIPM · ↗
    → International SI definitions (incl. redefined kilogram 2019)
  4. ISO/IEC (2022). Quantities and units — Part 1: General. International Organization for Standardization — ISO 80000-1:2022 · ↗
    → General rules for physical quantities and units
  5. ISO/IEC (2019). Quantities and units — Part 9: Physical chemistry and molecular physics. International Organization for Standardization — ISO 80000-9:2019 · ↗
    → Concentration / molality / amount-of-substance conventions
  6. Tiesinga E, Mohr PJ, Newell DB, Taylor BN (2021). CODATA recommended values of the fundamental physical constants: 2018. Rev. Mod. Phys. 93(2):025010 · DOI: 10.1103/RevModPhys.93.025010
    → Avogadro, gas constant, molar volume (2019 SI revision)
  7. IUPAC (2019). Compendium of Chemical Terminology — the IUPAC Gold Book (online). IUPAC · DOI: 10.1351/goldbook
    → Definitions of mass fraction, molality, normality, ppm, activity
  8. Mills IM, Cvitaš T, Homann K, Kallay N, Kuchitsu K (1988). Quantities, Units and Symbols in Physical Chemistry. Blackwell Scientific Publications, 1st ed. · ISBN: 0-632-01773-5
    → Historical predecessor of IUPAC Green Book
🛡️ Safety — CAS 7440-59-7MolGod_SAFEHUB_MAIN
Data limitations notice. The safety information on this page is for reference only and does not replace a full safety data sheet (SDS). Before using the product, consult the manufacturer's current safety data sheet and the GHS/CLP guidance. The CLP classification applies to the pure bulk substance, not to commercial formulations.

GHS/CLP classification — Regulation (EC) No 1272/2008 + UN GHS Rev. 9 (2021).

⚠ Warning
GHS04 — Gases under pressure
GHS04 Gases under pressure

🚨 Hazard statements (H)

  • H280 — Contains gas under pressure; may explode if heated

🛡 Precautionary statements (P)

  • P282 — Wear cold insulating gloves and either face shield or eye protection
  • P410 — Protect from sunlight

⚠ Classification based on a consensus of sources (PubChem / supplier notifications) — not verified against the harmonised classification in Annex VI (CLP). The scope of hazards may be broader than the official classification; verify against the supplier's current safety data sheet before use.

Translations: CLP Regulation (EC) 1272/2008, Annexes III and IV. Data: PubChem/NLM.

📚 Consolidated scientific references — Chicago Author-Date 10 sources

References collected from all Safety Hub tabs. CAS: 7440-59-7 · PubChem ↗

  1. Parlament Europejski i Rada UE. 2008. "Rozporządzenie (WE) nr 1272/2008 w sprawie klasyfikacji, oznakowania i pakowania substancji (CLP)." Dz.Urz. UE L 353. [↗] GHS, Regulations
  2. United Nations Economic Commission for Europe (UNECE). 2021. "Globally Harmonized System of Classification and Labelling of Chemicals (GHS), Ninth Revised Edition." United Nations, Geneva. [↗] GHS
  3. Goldfrank, Lewis R., Robert S. Hoffman, Mary Ann Howland, et al.. 2019. "Goldfrank's Toxicologic Emergencies, 11th ed.." McGraw-Hill Education, New York. ISBN 978-1-25-985961-8. Pierwsza pomoc, Toksykologia
  4. National Institute for Occupational Safety and Health (NIOSH). 2023. "NIOSH Pocket Guide to Chemical Hazards (DHHS Publ. 2005-149)." U.S. Department of Health and Human Services / CDC, Cincinnati, OH. [↗] Pierwsza pomoc, PPE, Toksykologia
  5. European Committee for Standardization (CEN). 2016. "EN 374-1:2016 — Protective gloves against dangerous chemicals and micro-organisms." CEN, Brussels. [↗] PPE
  6. UNECE. 2023. "European Agreement Concerning the International Carriage of Dangerous Goods by Road (ADR 2025)." United Nations, Geneva. [↗] Utylizacja, Regulacje
  7. National Fire Protection Association (NFPA). 2022. "NFPA 400 — Hazardous Materials Code." NFPA, Quincy, MA. [↗] Magazynowanie
  8. Urben, P.G. (ed.). 2017. "Bretherick's Handbook of Reactive Chemical Hazards, 8th ed.." Butterworth-Heinemann / Elsevier, Oxford. [↗] Magazynowanie
  9. Ministerstwo Klimatu i Środowiska RP. 2023. "Baza danych o produktach i opakowaniach oraz o gospodarce odpadami (BDO)." Ministerstwo Klimatu i Środowiska, Warszawa. [↗] Utylizacja
  10. International Agency for Research on Cancer (IARC / WHO). 2024. "IARC Monographs on the Identification of Carcinogenic Hazards to Humans — List of Classifications." WHO, Lyon. [↗] Toksykologia

Tabs with their own references (Emergency, PPE, Storage, Waste) contain additional bibliographic entries within their respective sections.

📈 Analytical statistics (t-test · RSD · Grubbs · Q-Dixon) ICH Q2

Paste a series of replicate measurements (CSV, or one number per line). The calculator computes the mean, standard deviation and 95% CI, and detects outliers (Grubbs + Dixon Q).

Separator: comma, space, tab, new line. Minimum 3 measurements.
📐 Statistical formulas
  • x̄ = Σxᵢ / n — arithmetic mean
  • s² = Σ(xᵢ - x̄)² / (n-1) — sample variance
  • s = √s² — standard deviation
  • RSD% = (s / x̄) × 100% — relative standard deviation
  • CI₉₅ = x̄ ± t(0.05, n-1) × s / √n — Student's t
  • G = |xᵢ - x̄| / s — Grubbs' test
  • Q = |xsuspect - xnearest| / |xmax - xmin| — Dixon Q-test

Source: ICH Q2(R2) Validation of Analytical Procedures · ICH PDF ↗

🔬 HPLC/GC methods (2 methods)
📄
Anticancer activity of an extract from needles and twigs of Taxus cuspidata and its synergistic effect as a cocktail with 5-fluorouracil
HPLCBMC Complementary and Alternative Medicine201188% ✓CC-BYResearch method (specificity, robustness)
Column: C18, 0.45 μm
Phase: mobile phase consisted of CH3CN-water (50:50, v/v) (A) and CH3CN-water (15:85, v/v)…
Detection: UV 370 nm
Flow: 0.80 mL/min
Temp.: 37.0 °C
Gradient: profile was as follows: 0-15 min, 0% A; 15-20 min,…
Shang W, Qiao J, Gu C, Yin W, Du J, Wang W, et al. Anticancer activity of an extract from needles and twigs of Taxus cuspidata and its synergistic effect as a cocktail with 5-fluorouracil. BMC Complementary and Alternative Medicine. 2011;11:123-123. doi:10.1186/1472-6882-11-123
🔗 DOI🏠 PMC📚 PubMed📄 PDF
BackgroundBotanical medicines are increasingly combined with chemotherapeutics as anticancer drug cocktails. This study aimed to assess the chemotherapeutic potential of an extract of Taxus cuspidata (TC) needles and twigs produced by artificial cuttage and its co-effects as a cocktail with 5-fluorouracil (5-FU).MethodsComponents of TC extract were identified by HPLC fingerprinting. Cytotoxicity analysis was performed by MTT assay or ATP assay. Apoptosis studies were analyzed by H & E, PI, TUNEL staining, as well as Annexin V/PI assay. Cell cycle analysis was performed by flow cytometry. 5-FU concentrations in rat plasma were determined by HPLC and the pharmacokinetic parameters were estimated using 3p87 software. Synergistic efficacy was subjected to median effect analysis with the mutually nonexclusive model using Calcusyn1 software. The significance of differences between values was estimated by using a one-way ANOVA.ResultsTC extract reached inhibition rates of 70-90% in different human cancer cell lines (HL-60, BGC-823, KB, Bel-7402, and HeLa) but only 5-7% in normal mouse T/B lymphocytes, demonstrating the broad-spectrum anticancer activity and low toxicity to normal cells of TC extract in vitro. TC extract inhibited cancer cell growth by inducing apoptosis and G2/M cell cycle arrest. Most interestingly, TC extract and 5-FU, combined as a cocktail, synergistically inhibited the growth of cancer cells in vitro, with Combination Index values (CI) ranging from 0.90 to 0.26 at different effect levels from IC50 to IC90 in MCF-7 cells, CI ranging from 0.93 to 0.13 for IC40 to IC90 in PC-3M-1E8 cells, and CI < 1 in A549 cells. In addition, the cocktail had lower cytotoxicity in normal human cell (HEL) than 5-FU used alone. Furthermore, TC extract did not affect the pharmacokinetics of 5-FU in rats.ConclusionsThe combinational use of the TC extract with 5-FU displays strong cytotoxic synergy in cancer cells and low cytotoxicity in normal cells. These findings s...
📄
Protection against cisplatin-induced acute kidney injury by hellgrammite extract: insights from comprehensive metabolomics
UHPLCFrontiers in Pharmacology202690% ✓CC-BYResearch method (specificity, robustness)
Column: HILIC, 2.7 μm
Phase: Mobile phase A was 20 mmol/L ammonium formate aqueous solution (pH = 3),…
Detection: MS
Flow: 0.40 mL/min
Temp.: 60.0 °C
Inj.: 5 μL
Gradient: program was: 0–11
Lin K, Lu G, Liu R, He Y, Yuan X, Li X, et al. Protection against cisplatin-induced acute kidney injury by hellgrammite extract: insights from comprehensive metabolomics. Frontiers in Pharmacology. 2026;17:1839763. doi:10.3389/fphar.2026.1839763
🔗 DOI🏠 PMC📚 PubMed📄 PDF
BackgroundCisplatin (CP), a highly potent antineoplastic agent, is severely limited in clinical use by dose-limiting toxicities, particularly acute kidney injury (AKI). The hellgrammite (Hel), a kind of rare edible and medicinal insect, is known in Traditional Chinese Medicine (TCM) for its ability to tonify the qi and kidneys. However, its potential to ameliorate CP-induced AKI remains unexplored.MethodsWe first evaluated the nutritional profile of Hel using high-performance liquid chromatography (HPLC) for amino acid composition analysis. Subsequently, a mouse model of CP-induced AKI was treated with different doses of Hel by gavage, then traditional pharmacology, and metabolomics were used to elucidate the effects and mechanism of Hel on CP-induced AKI mice.ResultsHel effectively ameliorated CP-induced alterations in biochemical indicators and alleviated kidney pathological changes. Hel administration rectified the kidney metabolic disturbances induced by CP, involving alterations in 38 differential metabolites associated with glycerophospholipid metabolism, purine metabolism, nicotinate and nicotinamide metabolism, and thiamine metabolism.DiscussionHel confers renoprotection by reversing metabolic disorders in CP-induced AKI, revealing actionable targets for AKI intervention.
acute kidney injurycisplatinhellgrammitemetabolomicstraditional pharmacology
📈 Method Validation (ICH Q2)

No validation data. Contact the method author.

Parameters per: ICH Q2(R2) ↗

📋 Method comparison
Technique Column Analysis time Detection Mobile phase Source
HPLC C18 — UV 370 nm mobile phase consisted of CH3CN-water (50:50, v/v) (A)… DOI ↗
UHPLC HILIC — MS Mobile phase A was 20 mmol/L ammonium formate aqueous… DOI ↗
🔧 Troubleshooting HPLC/GC
Broad peaks / tailing
Causes: Worn column, wrong mobile-phase pH, column overload, dead volume
Solution: Replace the column, check buffer pH (±0.2), reduce injection volume, check fittings
Baseline drift
Causes: Contaminated mobile phase, gradient issues, unstable temperature
Solution: Degas the phase, filter 0.22 µm, stabilise column temperature, flush the system
No peak
Causes: Wrong wavelength, analyte does not elute, thermal decomposition, wrong phase
Solution: Check λmax, extend the gradient, lower the temperature, change the mobile phase
Ghost peaks
Causes: System contamination, carry-over, contaminated vials
Solution: Clean the system (MeOH/H₂O), use new vials, inject a blank
Low recovery
Causes: Adsorption to walls, insufficient extraction, decomposition
Solution: Add IS, silanise glassware, optimise extraction, check stability

Sources: Snyder, Kirkland & Dolan ↗, Waters ↗

📊 HPLC method validation (ICH Q2(R1)) PARTIAL

3 metrics need experimental data

Parameter Value Unit ICH Q2 criterion Status
Linearity (R²) no data unitless R² ≥ 0.999 (≥0.99 for bioanalytical) —
LOD (S/N = 3:1) no data ng/mL S/N ≥ 3:1 (lowest detectable concentration) —
LOQ (S/N = 10:1) no data ng/mL S/N ≥ 10:1 (LOQ ≥ 3×LOD typically) —
Precision (RSD intraday, n=6) no data % RSD RSD ≤ 2% (intraday) / ≤ 3% (interday) for the API —
Accuracy (recovery, 3 levels) no data % (target 100±2%) Recovery 98-102% (target 100%) —
Linearity range no data e.g. 0.1-100 ng/mL Min. 80-120% of the nominal concentration —
Selectivity/Specificity no data qualitative No interference — analyte peak fully resolved (Rs ≥ 2.0) —
Robustness no data RSD < 2% at ±5% variation RSD < 2% under small parameter variations —
Legend: ✓ PASS ⚠ CAUTION ✗ FAIL — NO_DATA
📚 Scientific references (Chicago Author-Date) — click to expand

Analytical method validation standards — 4 independent sources (ICH + USP + AOAC + Snyder).

  1. International Conference on Harmonisation (ICH). 2005. Validation of Analytical Procedures: Text and Methodology Q2(R1). ICH Expert Working Group. [link ↗] — Gold-standard ICH guideline — accepted by EMA, FDA, MHLW, NMPA
  2. United States Pharmacopeia (USP) Convention. 2024. USP General Chapter <621> Chromatography. USP-NF 2024 ed. USP. [link ↗]
  3. AOAC International. 2016. Appendix F: Guidelines for Standard Method Performance Requirements. AOAC INTERNATIONAL. [link ↗] — AOAC SMPR — alternative to ICH Q2 for food/dietary supplements
  4. Snyder, Lloyd R., Joseph J. Kirkland, and John W. Dolan. 2010. Introduction to Modern Liquid Chromatography. 3rd ed. John Wiley & Sons. ISBN 978-0-470-16754-0. https://doi.org/10.1002/9780470508183 [link ↗] — Industry standard textbook — Chapter 11 covers method validation
  5. Snyder, L. R., J. J. Kirkland, and J. L. Glajch. 1997. Practical HPLC Method Development. 2nd ed. Wiley. ISBN 978-0-471-00703-6. — Classic method-development reference (DryLab heritage).
  6. Rozet, Eric, et al.. 2013. Analysis of recent pharmaceutical regulatory documents on analytical method validation. https://doi.org/10.1016/j.chroma.2007.03.111 [link ↗] — Comparison of FDA / EMA / ICH validation expectations — used for ICH Q2(R1) interpretation.
  7. Heyden, Yvan Vander, et al.. 2009. Robustness of pharmaceutical liquid chromatographic methods. https://doi.org/10.1016/j.jchromb.2008.10.052 [link ↗] — Plackett-Burman design for robustness — basis of ICH Q2 §3.7.
  8. Dong, Michael W.. 2019. HPLC and UHPLC for Practicing Scientists. 2nd ed. Wiley. ISBN 978-1-119-31378-3. https://doi.org/10.1002/9781119313793 [link ↗] — Modern (UHPLC) update of validation chapter — practical RSD/LOD examples.
  9. Meyer, Veronika R.. 2010. Practical High-Performance Liquid Chromatography. 5th ed. Wiley. ISBN 978-0-470-68218-0. — European pharmacopeial perspective — complements USP/AOAC.
  10. Kazakevich, Yuri V., and Rosario LoBrutto, eds.. 2007. HPLC for Pharmaceutical Scientists. Wiley-Interscience. ISBN 978-0-471-68162-4. https://doi.org/10.1002/9780470087954 [link ↗] — Pharma-focused validation case studies (specificity, robustness).
  11. European Medicines Agency (EMA). 2011. Guideline on bioanalytical method validation EMEA/CHMP/EWP/192217/2009. EMA Committee for Medicinal Products for Human Use. [link ↗] — EMA bioanalytical companion to ICH Q2(R1) for clinical samples.

· ⚠ SVHC/REACH regulatory warnings ↑

🔧 HPLC troubleshooting — decision tree 6 common problems

Diagnostics for the 12 most common HPLC problems with a decision tree (5 steps per problem). Source: Snyder/Kirkland/Dolan 3rd ed. Chapter 17 + LCGC LC Troubleshooting columns 1989-2024.

Broad peaks medium

Symptom: All peaks on the chromatogram are wider than expected (FWHM > 2× normal)

🔍 Diagnostic tree:
  1. 1. Check whether all peaks are broadened or only some
    → YES: All → instrumental problem (column or system)
    → NO: Only some → chemistry problem (interaction with the column for specific analytes)
  2. 2. Swap in a test column — does the problem disappear?
    → YES: COLUMN worn out — packing damaged, void in the first few mm. Replace it.
    → NO: Problem in the LC system
  3. 3. Check the dead volume — injection loop, connections, detector
    → YES: Loop > 100 µL for a 4.6 mm column or loose connections → replace ferrules, shorten tubing
    → NO: Continue diagnostics
  4. 4. Temperature test: raise the column from 25°C to 40°C
    → YES: Narrower peaks → mass-transfer kinetics too slow (increase T)
    → NO: Continue
  5. 5. Check flow rate vs the optimal van Deemter value for this column
    → YES: Optimum for 4.6mm/5µm = 1.0 mL/min, for 2.1mm/3µm = 0.4 mL/min
    → NO: Continue
⚠️ Common causes:
  • Column worn out (>2000 injections without a guard)
  • System dead volume > 100 µL (wrong loop, long tubing, loose ferrules)
  • Temperature too low (mass-transfer kinetics)
  • Flow rate outside the van Deemter optimum
  • Sample solvent stronger than mobile phase A
✓ Fixes:
  • ✓ Replace the column (when >2000 injections)
  • ✓ Check all connections — keep tubing as short as possible
  • ✓ Increase column T to 40°C (if the substance is stable)
  • ✓ Reduce flow to the van Deemter optimum
  • ✓ Dissolve the sample in mobile phase A (not in pure organic)
Peak tailing (T > 1.5) high

Symptom: Peaks have an extended "tail" on the late-elution side (asymmetry T = b/a > 1.5 per USP)

🔍 Diagnostic tree:
  1. 1. Does the substance contain basic groups (amino, pyridine)?
    → YES: Yes → silanol interactions! Add 0.1% TFA or 5-10 mM TEA to mobile phase A.
    → NO: Continue
  2. 2. Check the mobile-phase pH vs the substance pKa
    → YES: pH = pKa ± 1 → partial ionization, peak split. Move pH ≥ 2 units away from pKa.
    → NO: Continue
  3. 3. Check the column age (>1500 injections?)
    → YES: Yes → exposed silanols (column bleed). Replace with a column with higher endcapping (XTerra, Symmetry).
    → NO: Continue
  4. 4. Does the sample contain metals (Fe, Cu from glass vials)?
    → YES: Yes → use type II clear vials or PFA. Add 0.1mM EDTA to the sample.
    → NO: Continue
⚠️ Common causes:
  • Silanol interactions (basic analyte + silica gel free silanols)
  • pH at the boundary of the analyte pKa (peak split)
  • Old column (column bleed, high silanol activity)
  • Metals in the sample (chelation → tailing)
  • Column overload (>50 µg on a 4.6mm column)
✓ Fixes:
  • ✓ Add 0.1% TFA (UV) or 0.1% formic acid (LC-MS) to mobile phase A
  • ✓ Choose a column with high-purity endcapping: Waters XBridge BEH, Phenomenex Kinetex
  • ✓ Work at pH ≥ 2 units away from pKa
  • ✓ Add 0.1mM EDTA to the sample (Fe/Cu chelation)
  • ✓ Reduce the injection volume to ≤ 20 µL for a 4.6mm column
Baseline drift medium

Symptom: The baseline rises or falls systematically for >5 minutes

🔍 Diagnostic tree:
  1. 1. Are you running a gradient (B% increasing)?
    → YES: Yes → different absorption of phases A vs B at dλ. Solvent change in UV cutoff. Check the % organic UV absorbance.
    → NO: Continue (isocratic)
  2. 2. Check the column temperature — is it stable to ±0.5°C?
    → YES: Yes (stable) → continue
    → NO: Unstable → turn on the column thermostat (>25°C controlled)
  3. 3. Test: turn off the autosampler, run pump+column+detector alone
    → YES: Drift disappears → autosampler contamination (clean the needle, septum)
    → NO: Continue
  4. 4. Check the lamp age (D2 for UV)
    → YES: Yes (>1500 hours) → replace the lamp
    → NO: Continue
⚠️ Common causes:
  • Gradient elution with different UV cutoff of the phases
  • Unstable column T
  • Autosampler contamination of the needle/septum
  • Old UV lamp (>1500h)
  • Detector flow cell fouled
  • Column not equilibrated (<10 column volumes)
✓ Fixes:
  • ✓ Pre-equilibrate the column for 10-15 column volumes at 100% A
  • ✓ Column thermostat on, T 30-40°C stable
  • ✓ Clean the detector flow cell with 50:50 ACN:H2O
  • ✓ Replace the D2 lamp if >1500h
  • ✓ Use baseline subtraction (Chromeleon, Empower native function)
No peak / lost peak critical

Symptom: The expected analyte peak does not appear on the chromatogram

🔍 Diagnostic tree:
  1. 1. Did the injection actually take place?
    → YES: Check the autosampler log, pump pressure (should drop during injection)
    → NO: Autosampler problem → check the loop, needle, sample in the vial
  2. 2. Is the sample in the vial (correct volume, not evaporated)?
    → YES: Continue
    → NO: No sample — re-pipette
  3. 3. Sample stability — prepared >24h ago?
    → YES: Yes → degradation. Re-prepare a fresh sample.
    → NO: Continue
  4. 4. Check the detection wavelength vs the substance λmax
    → YES: Detection at λ does NOT match λmax → no signal. Scan DAD 200-400nm.
    → NO: Continue
  5. 5. Test: inject a pure standard (of known concentration, fresh)
    → YES: The standard gives a peak → problem with the sample (matrix, derivatization)
    → NO: No peak even with the standard → system problem (column, phase, gradient)
⚠️ Common causes:
  • Sample not drawn from the vial (autosampler bug)
  • Sample degraded (>24h pH/temp/light)
  • Detection at the wrong wavelength
  • Wrong mobile phase (e.g. forgotten TFA)
  • Column reversed / wrong stationary phase
  • Substance elutes at the front (V0) → unretained, not visible
✓ Fixes:
  • ✓ Re-prepare a fresh sample per the exact protocol
  • ✓ UV-Vis DAD scan 200-400nm + search for λmax
  • ✓ Check the mobile-phase composition — was TFA added?
  • ✓ Test the reverse column direction (carefully!)
  • ✓ For retention <1 min — lower the % B, MeOH instead of ACN
  • ✓ Check the "expected_rt" table in wp_molgod_hplc_methods
Pressure too high critical

Symptom: Pump pressure > 80% of the column max or system shutdown with a high-pressure error

🔍 Diagnostic tree:
  1. 1. Check that the column is connected correctly (arrow direction)
    → YES: OK
    → NO: Column reversed → flip it (never run it "backwards")
  2. 2. Test: remove the column from the system, run pump+detector alone
    → YES: Pressure drops to <50 bar → problem in the column (clogged)
    → NO: Pressure stays high → in-line filter clogged, frit fouled
  3. 3. Check the pre-column filter (in-line frit)
    → YES: Fouled and brown → replace it
    → NO: Continue
  4. 4. Back-flush the column with 50:50 ACN:H2O without the column — does it disappear?
    → YES: Particles stuck in the first mm — a 30 min flush may recover it
    → NO: Replace the column
⚠️ Common causes:
  • In-line filter (frit) clogged with particles
  • Buffer salting out (precipitation at high %B)
  • Sample contains suspended matter (filter 0.22 µm before injection)
  • Column clogged (column bed compaction)
  • Gradient with a buffer phase + high organic → salt precipitation
✓ Fixes:
  • ✓ ALWAYS filter the sample through 0.22 µm PVDF before injection
  • ✓ Replace the in-line filter every 100 injections (or when pressure rises >20%)
  • ✓ Do NOT use >20mM phosphate buffer + >70% ACN (the salt precipitates)
  • ✓ Flush the column for 30 min with 50:50 ACN:H2O in the reverse direction (when the manufacturer allows it)
  • ✓ Pre-column 4×3mm to protect the main column
Ghost peaks high

Symptom: Unexplained peaks on the chromatogram absent from the calibration

🔍 Diagnostic tree:
  1. 1. Test: blank injection (pure sample solvent)
    → YES: A ghost appears → contamination of the system or eluents
    → NO: Appears only with the sample → matrix
  2. 2. Does the ghost grow with the gradient (elutes at high %B)?
    → YES: Yes → overloaded column or strong-retained from a previous run
    → NO: Independent of the gradient → autosampler carryover
  3. 3. Increase carryover wash (between injections)
    → YES: Helps → carryover was to blame. Use a stronger wash protocol.
    → NO: Continue
  4. 4. Pure water injection — is there a peak?
    → YES: Yes → contamination of the water source (organics from the DI system)
    → NO: Continue
⚠️ Common causes:
  • Carryover in the autosampler needle/loop
  • Eluent contamination (even HPLC-grade)
  • Strong-retained components from previous runs
  • Plastic in the vials (phthalates, PEG from the caps)
  • Insufficiently purified DI water
✓ Fixes:
  • ✓ Strengthen the wash protocol: 100% B → 100% A → 50:50 (3 cycles)
  • ✓ Strong wash: 100% DMSO or 100% MeOH before calibration
  • ✓ Filter the eluents through 0.22 µm PTFE if in doubt
  • ✓ Use amber glass + Teflon-lined caps for samples
  • ✓ Periodic gradient ramp to 100% B for 10 min (clean-out)
📚 Scientific references (Chicago Author-Date) — click to expand
  1. Snyder, Lloyd R., Joseph J. Kirkland, and John W. Dolan. 2010. Introduction to Modern Liquid Chromatography. 3rd ed. John Wiley & Sons. Chapter 17 (Troubleshooting) pp. 559-616. ISBN 978-0-470-16754-0. https://doi.org/10.1002/9780470508183 [link ↗]
  2. Dolan, John W.. 2014. LC Troubleshooting (monthly column 1989-2024). LCGC North America. [link ↗] — John Dolan 35-letnia seria miesięcznych artykułów problemowych
  3. Kromidas, Stavros. 2017. HPLC Made to Measure: A Practical Handbook for Optimization. 2nd ed. Wiley-VCH. ISBN 978-3-527-31377-1. — Praktyczny przewodnik problem-solving dla labs analitycznych
  4. Dolan, John W.. 2013. When to Modify Method Conditions. 192-199. [link ↗] — Decision flow for changing flow rate / temperature / %B vs swapping columns.
  5. Dong, Michael W.. 2019. HPLC and UHPLC for Practicing Scientists. 2nd ed. Wiley. ISBN 978-1-119-31378-3. https://doi.org/10.1002/9781119313793 [link ↗] — Chapter 9 covers troubleshooting modern UHPLC systems (sub-2 µm particles).
  6. Meyer, Veronika R.. 2010. Practical High-Performance Liquid Chromatography. 5th ed. Wiley. ISBN 978-0-470-68218-0. — Solid step-by-step problem isolation chapter (eluents, columns, instruments).
  7. Snyder, L. R., J. J. Kirkland, and J. L. Glajch. 1997. Practical HPLC Method Development. 2nd ed. Wiley. ISBN 978-0-471-00703-6. — Method-development companion volume with troubleshooting cross-refs.
  8. Carr, Peter W.. 2009. The new physical chemistry of HPLC. 1764-1772. https://doi.org/10.1016/j.chroma.2008.11.094 [link ↗] — Theoretical basis for diagnosing efficiency losses (mass-transfer, eddy diffusion).
  9. Heyden, Yvan Vander, et al.. 2009. Robustness of pharmaceutical liquid chromatographic methods. 2120-2129. https://doi.org/10.1016/j.jchromb.2008.10.052 [link ↗] — How to diagnose method failures vs. system failures (Plackett-Burman).
  10. Engelhardt, Heinz. 2014. 100 Years of Chromatography. 2nd ed. Wiley-VCH. ISBN 978-3-527-33473-5. — Historical context for ghost-peak phenomenology (silica chemistry).
  11. Stoll, Dwight R., and Peter W. Carr. 2017. Two-Dimensional Liquid Chromatography: A State of the Art Tutorial. 519-531. https://doi.org/10.1021/acs.analchem.6b03506 [link ↗]
  12. Carr, Peter W.. 2009. The new physical chemistry of HPLC. 1764-1772. https://doi.org/10.1016/j.chroma.2008.11.094 [link ↗]
  13. Wu, Naijun, and Anton M. Clausen. 2007. Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations. 1167-1182. https://doi.org/10.1002/jssc.200700026 [link ↗]
  14. Engelhardt, Heinz. 2014. 100 Years of Chromatography. 2nd ed. Wiley-VCH. ISBN 978-3-527-33473-5.
  15. Vivó-Truyols, Gabriel, and Hans-Gerd Janssen. 2010. Probabilistic approach to peak deconvolution in chromatography. 8525-8531. https://doi.org/10.1021/ac101742z [link ↗]
📚 Technical FAQ — Helium (4) MolGod_TECHFAQ_1
❓ Jak przygotować roztwór standardowy helu o stężeniu 10 ppm (części na milion) w rozpuszczalniku organicznym?
Aby przygotować roztwór standardowy helu o stężeniu 10 ppm w rozpuszczalniku organicznym, należy obliczyć masę potrzebnego gazu. Masa molowa helu wynosi 4.00260 g/mol. Dla roztworu o objętości 1 litra (1 dm³), stężenie 10 ppm odpowiada 10 mg helu na 1 kg rozpuszczalnika, co dla wody dałoby około 10 µg/dm³. Dla uproszczenia przyjmując gęstość rozpuszczalnika organicznego ~1 g/cm³, potrzeba około 10 µg helu na 1 dm³ roztworu. Hel należy wprowadzić do rozpuszczalnika w kontrolowanych warunkach (np. za pomocą specjalnej butli z gazem i systemu dozującego), a następnie dokładnie wymieszać.
Helpful?
❓ W jakich warunkach należy przechowywać hel, aby uniknąć degradacji?
Hel powinien być przechowywany w temperaturze poniżej -180°C (np. w ciekłym azocie) lub w butlach pod wysokim ciśnieniem, aby uniknąć jego odparowania. Należy go chronić przed światłem słonecznym i źródłami promieniowania UV oraz przechowywać z dala od substancji reaktywnych chemicznie, które mogłyby spowodować jego zanieczyszczenie. Wilgotność względna otoczenia powinna być niska (<10%), aby zapobiec kondensacji pary wodnej na ściankach pojemnika.
Helpful?
❓ Czy hel reaguje z jakimikolwiek substancjami chemicznymi w warunkach laboratoryjnych?
Hel jest gazem szlachetnym i praktycznie nie reaguje z innymi pierwiastkami ani związkami chemicznymi pod normalnymi warunkami laboratoryjnymi. Jego energia jonizacji wynosi 2372 kJ/mol, co czyni go bardzo stabilnym i mało reaktywnym. Jednak w ekstremalnych warunkach (np. pod wpływem promieniowania jonizującego) może tworzyć nietrwałe związki, takie jak helowce (np. HeH⁺). W praktyce laboratoryjnej nie wykazuje znaczącej reaktywności i jest chemicznie obojętny wobec większości substancji.
Helpful?
❓ W jakich zastosowaniach laboratoryjnych hel znajduje praktyczne wykorzystanie?
Hel jest szeroko stosowany w laboratoriach jako gaz nośny w chromatografii gazowej (GC) ze względu na swoją obojętność chemiczną i niską polarność. Jest również używany do kriogenicznego chłodzenia aparatury badawczej, np. w spektrometrach mas (MS) czy magnetycznym rezonansie jądrowym (NMR). Ponadto służy jako gaz ochronny przy przechowywaniu próbek wrażliwych na tlen lub wilgoć oraz do kalibracji detektorów gazowych i systemów bezpieczeństwa.
Helpful?
🧮 Laboratory calculators (8) MolGod_LABCALC_1
Dilution (C₁V₁=C₂V₂)
Molarity (M=n/V)
pH Buffer (Henderson-Hasselbalch)
Beer-Lambert (A=εcl)
Mass → Moles
Concentration % → M
ppm → mg/L
Temperature C↔F↔K

Verified formulas: IUPAC Gold Book ↗, DOI ↗

📊 Spectroscopic Databases MolGod_SPECDB_3
🏷️ Label generator (QR) MolGod_LABEL_1
Helium• HELIUM / Atomic helium• CAS: 7440-59-7• Formula: He• Mass: 4.00 g/molWARNINGGHS HAZARD STATEMENTS:H280: Contains gas under pressure; may explode if heatedP282: Wear cold insulating gloves and either face shield or eye protectionP410: Protect from sunlightFOR LABORATORY USE ONLY!DH ScientificScience first. Commerce as consequence.Batch No.: Netto Mass: MFG:
📚 Scientific literature overview — CAS 7440-59-7MolGod_LITHUB_MAIN
⭐ Key findings (scientific literature) 17 publications
🏆 CAS 7440-59-7 — multi-criteria ranking (W12): 30% citations · 20% recency · 20% topic · 15% historical · 15% open access.
  1. #1
    et al. (2025) · Nature Communications
    Why it matters: Recent (2025) · open access
    SCORE 9.38 Mechanism Citations: 5 Open Access DOI ↗ PubMed ↗
  2. #2
    et al. (2026) · Organic & Biomolecular Chemistry
    Why it matters: Recent (2026) · open access
    SCORE 8.65 Mechanism Open Access DOI ↗ PubMed ↗
  3. #3
    A. Heinen, R. Huhn, Kirsten M. Smeele et al. (2008) · Anesthesiology
    Why it matters: Open access
    SCORE 8.08 Mechanism Citations: 87 Influential: 5 Open Access DOI ↗ PubMed ↗
  4. #4
    et al. (2026) · Biophysical Journal
    Why it matters: Recent (2026) · open access
    SCORE 7.85 Analytics Open Access DOI ↗ PubMed ↗
  5. #5
    et al. (2026) · Nature Communications
    Why it matters: Recent (2026) · open access
    SCORE 7.15 Mechanism Citations: 1 Open Access DOI ↗ PubMed ↗
  6. #6
    et al. (2025) · Cureus
    Why it matters: Recent (2025) · open access
    SCORE 7.15 Mechanism Citations: 1 Open Access DOI ↗ PubMed ↗
  7. #7
    et al. (2026) · Scientific Reports
    Why it matters: Recent (2026) · open access
    SCORE 7.05 Industrial Open Access DOI ↗ PubMed ↗
  8. #8
    et al. (2026) · Antioxidants
    Why it matters: Recent (2026) · open access
    SCORE 7.05 Mechanism Open Access DOI ↗ PubMed ↗
  9. #9
    Shikun ZUO, Xidong DU, Minqi ZHOU et al. (2026) · Meitian dizhi yu kantan
    Why it matters: Recent (2026) · open access
    SCORE 7.05 Mechanism Open Access DOI ↗
  10. #10
    Chuansheng Yin, Yunfei Xu, Jinchun Shi et al. (2026) · Matter and Radiation at Extremes
    Why it matters: Recent (2026) · open access
    SCORE 7.05 Mechanism Open Access DOI ↗
  11. #11
    et al. (2026) · Biology
    Why it matters: Recent (2026) · open access
    SCORE 6.25 Pharmacology Open Access DOI ↗ PubMed ↗
  12. #12
    et al. (2026) · Physics and Imaging in Radiation Oncology
    Why it matters: Recent (2026) · open access
    SCORE 6.25 Mechanism Open Access DOI ↗ PubMed ↗
  13. #13
    et al. (2026) · Materials
    Why it matters: Recent (2026) · open access
    SCORE 6.25 Mechanism Open Access DOI ↗ PubMed ↗
  14. #14
    Jiamei Wang, Shengfei Qin, Fenghua Zhao et al. (2026) · Scientific Reports
    Why it matters: Recent (2026) · open access
    SCORE 6.25 Mechanism Open Access DOI ↗
  15. #15
    Forouzan Mirmasoudi, Badie Ghavami (2026) · arXiv (2611.06448v2)
    Why it matters: Recent (2026) · open access
    SCORE 6.25 Mechanism Open Access
  16. #16
    Dibyendu Sardar, François Lique (2026) · arXiv (2609.34713v1)
    Why it matters: Recent (2026) · open access
    SCORE 6.25 Mechanism Open Access
  17. #17
    Ellis, J., Hedgeland, H., Alexandrowicz, G. et al. (2009) · IOP Publishing Ltd
    Why it matters: Open access
    SCORE 4.96 Mechanism Citations: 7 Open Access DOI ↗

Description

Hel, CAS 7440-59-7

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📈 HPLC gradient — optimizer (LSS) TEMPLATE

logP unknown — PubChem did not return an XLogP value. The gradient below is a generic 5–95% MeCN/H2O template over 15 min; verify parameters before use.

⚠ logP unavailable. PubChem did not return an XLogP3 value for this CAS number. The gradient values below are a generic template — not an LSS fit for this compound.
  • Column: C18
  • Buffer: phosphate
  • Flow: 1 mL/min
  • logP: logP unavailable
  • Ramp: 21% → 95% B, 15 min
  • Total analysis time: 28 min
t (min) %A %B flow (mL/min) Comment
0 79 21 1 start (equilibrium)
2 79 21 1 end of initial hold
17 5 95 1 end of LSS ramp
22 5 95 1 column wash
23 79 21 1 return to init
28 79 21 1 re-equilibration
📚 Scientific references (Chicago Author-Date)
  1. Snyder, Lloyd R., John W. Dolan, and Joseph J. Kirkland. 2010. Introduction to Modern Liquid Chromatography. Wiley. — Chapter 9 — gradient elution, LSS theory (cited as Snyder et al. 2010 in tool description).
  2. Schoenmakers, Peter J. 1986. Optimization of Chromatographic Selectivity: A Guide to Method Development. Elsevier. — Numerical optimization of gradient programs.
  3. Snyder, L. R., and J. W. Dolan. 2007. High-Performance Gradient Elution: The Practical Application of the Linear-Solvent-Strength Model. Wiley. — Foundational LSS reference for the %B_init = 5 + 8·logP heuristic implemented here.
  4. Nikitas, Pavlos, and Adrian Pappa-Louisi. 2009. "Retention models for isocratic and gradient elution in reversed-phase liquid chromatography." Journal of Chromatography A 1216: 1737-1755. [DOI ↗] — Modern review of gradient retention models — basis for non-LSS extensions.
  5. Carr, Peter W.. 2009. "The new physical chemistry of HPLC." Journal of Chromatography A 1216: 1764-1772. [DOI ↗]
  6. Dong, Michael W. 2019. HPLC and UHPLC for Practicing Scientists. Wiley. https://doi.org/10.1002/9781119313793. — Modern UHPLC gradient programming, sub-2 µm scaling rules.
  7. Wu, Naijun, and Anton M. Clausen. 2007. "Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations." Journal of Separation Science 30: 1167-1182. [DOI ↗]
  8. Stoll, Dwight R., and Peter W. Carr. 2017. "Two-Dimensional Liquid Chromatography: A State of the Art Tutorial." Analytical Chemistry 89: 519-531. [DOI ↗] — Reference for orthogonal gradient design (2D-LC second dimension).
  9. Dolan, John W.. 2013. "When to Modify Method Conditions." LCGC North America 31: 192-199.
  10. Meyer, Veronika R. 2010. Practical High-Performance Liquid Chromatography. Wiley. — Chapter 7 — practical gradient design with isokratyczny scouting.
  11. Stoll, Dwight R., and Peter W. Carr. 2017. "Two-Dimensional Liquid Chromatography: A State of the Art Tutorial." Analytical Chemistry 89: 519-531. [DOI ↗]
  12. Carr, Peter W.. 2009. "The new physical chemistry of HPLC." Journal of Chromatography A 1216: 1764-1772. [DOI ↗]
  13. Wu, Naijun, and Anton M. Clausen. 2007. "Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations." Journal of Separation Science 30: 1167-1182. [DOI ↗]
  14. Engelhardt, Heinz. 2014. 100 Years of Chromatography. Wiley-VCH.
  15. Vivó-Truyols, Gabriel, and Hans-Gerd Janssen. 2010. "Probabilistic approach to peak deconvolution in chromatography." Analytical Chemistry 82: 8525-8531. [DOI ↗]

REST: /wp-json/molgod/v1/hplc/gradient/7440-59-7

📐 HPLC peak symmetry calculator (USP Tf / As)

Calculate the USP tailing factor (Tf) and asymmetry (As) from the peak half-widths. Enter a (left half-width) and b (right half-width) measured at 5% or 10% of peak height.

📚 References (Chicago Author-Date)
  1. USP General Chapter <621>. 2024. "Chromatography." United States Pharmacopeial Convention. [link ↗] — Defines USP Tailing Factor T = (a+b)/(2a) measured at 5% peak height.
  2. International Council for Harmonisation (ICH). 2023. "Validation of Analytical Procedures Q2(R2)." ICH Expert Working Group. [link ↗] — Tailing factor is a system suitability parameter (Section 6).
  3. Foley, Joe P., and John G. Dorsey. 1983. "Equations for calculation of chromatographic figures of merit for ideal and skewed peaks." Analytical Chemistry 55: 730-737 https://doi.org/10.1021/ac00255a033 [link ↗] — Original asymmetry factor As = b/a at 10% height (Foley & Dorsey 1983).
  4. Snyder, Lloyd R., Joseph J. Kirkland, and John W. Dolan. 2010. "Introduction to Modern Liquid Chromatography." Wiley. https://doi.org/10.1002/9780470508183 [link ↗] — Chapter 2.4 — peak shape diagnostics and remedies.
  5. Dolan, John W.. 2003. "Peak tailing and resolution." LCGC North America 21: 610-614 [link ↗] — How tailing factor degrades effective resolution.
  6. Vivó-Truyols, Gabriel, and Hans-Gerd Janssen. 2010. "Probabilistic approach to peak deconvolution in chromatography." Analytical Chemistry 82: 8525-8531 https://doi.org/10.1021/ac101742z [link ↗] — Modern numerical deconvolution for asymmetric peaks.
  7. Kromidas, Stavros. 2017. "HPLC Made to Measure: A Practical Handbook for Optimization." Wiley-VCH. — Practical Tf and As thresholds for routine QC.
  8. Dong, Michael W.. 2019. "HPLC and UHPLC for Practicing Scientists." Wiley. https://doi.org/10.1002/9781119313793 [link ↗]
  9. Meyer, Veronika R.. 2010. "Practical High-Performance Liquid Chromatography." Wiley.
  10. Heyden, Yvan Vander, et al.. 2009. "Robustness of pharmaceutical liquid chromatographic methods." Journal of Chromatography B 877: 2120-2129 https://doi.org/10.1016/j.jchromb.2008.10.052 [link ↗]
  11. Stoll, Dwight R., and Peter W. Carr. 2017. "Two-Dimensional Liquid Chromatography: A State of the Art Tutorial." Analytical Chemistry 89: 519-531 https://doi.org/10.1021/acs.analchem.6b03506 [link ↗]
  12. Carr, Peter W.. 2009. "The new physical chemistry of HPLC." Journal of Chromatography A 1216: 1764-1772 https://doi.org/10.1016/j.chroma.2008.11.094 [link ↗]
  13. Wu, Naijun, and Anton M. Clausen. 2007. "Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations." Journal of Separation Science 30: 1167-1182 https://doi.org/10.1002/jssc.200700026 [link ↗]
  14. Engelhardt, Heinz. 2014. "100 Years of Chromatography." Wiley-VCH.
  15. Vivó-Truyols, Gabriel, and Hans-Gerd Janssen. 2010. "Probabilistic approach to peak deconvolution in chromatography." Analytical Chemistry 82: 8525-8531 https://doi.org/10.1021/ac101742z [link ↗]
📊 Resolution and plate count calculator (Rs, N, H)

Calculate the resolution Rs, the number of theoretical plates N and HETP (H) for a pair of HPLC peaks. Enter the retention times, peak widths (at 50% or at the base) and the column length.

📚 References (Chicago Author-Date)
  1. Snyder, Lloyd R., Joseph J. Kirkland, and John W. Dolan. 2010. "Introduction to Modern Liquid Chromatography." 3rd ed. John Wiley & Sons. ISBN 978-0-470-16754-0. https://doi.org/10.1002/9780470508183 [link ↗] — Chapter 2 covers resolution, plate count and HETP fundamentals (Snyder et al. 2010).
  2. USP General Chapter <621>. 2024. "Chromatography." USP-NF 2024 ed. United States Pharmacopeial Convention. [link ↗] — Defines Rs >= 1.5 acceptance criterion and N calculation methods.
  3. Dolan, John W.. 2003. "How much resolution is enough?." LCGC North America 21: 350-353 [link ↗] — Practical guidance on Rs targets for routine method development.
  4. Van Deemter, J. J., F. J. Zuiderweg, and A. Klinkenberg. 1956. "Longitudinal diffusion and resistance to mass transfer as causes of nonideality in chromatography." Chemical Engineering Science 5: 271-289 https://doi.org/10.1016/0009-2509(56)80003-1 [link ↗] — Origin of N = 5.54·(tr/w0.5)² half-height plate count formulation.
  5. Giddings, J. Calvin. 1965. "Dynamics of Chromatography, Part I: Principles and Theory." Marcel Dekker. ISBN 978-0-8247-1357-7. — Resolution equation Rs = (1/4)·√N·(α-1)/α·k/(1+k) (master equation).
  6. Foley, Joe P., and John G. Dorsey. 1983. "Equations for calculation of chromatographic figures of merit for ideal and skewed peaks." Analytical Chemistry 55: 730-737 https://doi.org/10.1021/ac00255a033 [link ↗] — Skewed-peak corrections to apparent N.
  7. Knox, John H.. 1977. "Practical aspects of LC theory." Journal of Chromatographic Science 15: 352-364 https://doi.org/10.1093/chromsci/15.9.352 [link ↗]
  8. Carr, Peter W.. 2009. "The new physical chemistry of HPLC." Journal of Chromatography A 1216: 1764-1772 https://doi.org/10.1016/j.chroma.2008.11.094 [link ↗]
  9. Dong, Michael W.. 2019. "HPLC and UHPLC for Practicing Scientists." 2nd ed. Wiley. ISBN 978-1-119-31378-3. https://doi.org/10.1002/9781119313793 [link ↗]
  10. Meyer, Veronika R.. 2010. "Practical High-Performance Liquid Chromatography." 5th ed. Wiley. ISBN 978-0-470-68218-0.
  11. Stoll, Dwight R., and Peter W. Carr. 2017. "Two-Dimensional Liquid Chromatography: A State of the Art Tutorial." Analytical Chemistry 89: 519-531 https://doi.org/10.1021/acs.analchem.6b03506 [link ↗]
  12. Carr, Peter W.. 2009. "The new physical chemistry of HPLC." Journal of Chromatography A 1216: 1764-1772 https://doi.org/10.1016/j.chroma.2008.11.094 [link ↗]
  13. Wu, Naijun, and Anton M. Clausen. 2007. "Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations." Journal of Separation Science 30: 1167-1182 https://doi.org/10.1002/jssc.200700026 [link ↗]
  14. Engelhardt, Heinz. 2014. "100 Years of Chromatography." 2nd ed. Wiley-VCH. ISBN 978-3-527-33473-5.
  15. Vivó-Truyols, Gabriel, and Hans-Gerd Janssen. 2010. "Probabilistic approach to peak deconvolution in chromatography." Analytical Chemistry 82: 8525-8531 https://doi.org/10.1021/ac101742z [link ↗]

Related products

🧪 System Suitability — live calculator (USP <621>)

Enter data from 5–6 injections (areas, tR, tailing, plates) — the calculator computes %RSD and means and checks compliance with USP <621>. You can paste CSV (comma-separated) or edit individual values.

📚 References (Chicago Author-Date)
  1. USP General Chapter <621>. 2024. "Chromatography (System Suitability section)." USP-NF 2024 ed. United States Pharmacopeial Convention. [link ↗] — Defines RSD area < 2%, tailing < 2.0, N > 2000 acceptance criteria.
  2. International Council for Harmonisation (ICH). 2023. "Validation of Analytical Procedures Q2(R2)." ICH Expert Working Group. [link ↗] — Section 5.4 — system suitability is part of method validation.
  3. US Food and Drug Administration (FDA). 2018. "Reviewer Guidance: Validation of Chromatographic Methods." US Food and Drug Administration. [link ↗] — CDER reviewer perspective on chromatographic validation expectations.
  4. Snyder, Lloyd R., Joseph J. Kirkland, and John W. Dolan. 2010. "Introduction to Modern Liquid Chromatography." 3rd ed. Wiley. — Chapter 2 — system suitability fundamentals (RSD, Tf, N).
  5. Heyden, Yvan Vander, et al.. 2009. "Robustness of pharmaceutical liquid chromatographic methods." — Robustness vs. system suitability — design-of-experiments framework.
  6. Rozet, Eric, et al.. 2013. "Analysis of recent pharmaceutical regulatory documents on analytical method validation."
  7. European Medicines Agency (EMA). 2011. "Guideline on bioanalytical method validation EMEA/CHMP/EWP/192217/2009." EMA. [link ↗] — EMA companion guideline with bioanalytical SS criteria.
  8. Dong, Michael W.. 2019. "HPLC and UHPLC for Practicing Scientists." 2nd ed. Wiley. — UHPLC-specific suitability adjustments (n=5 vs. n=6).
  9. Kazakevich, Yuri V., and Rosario LoBrutto, eds.. 2007. "HPLC for Pharmaceutical Scientists." Wiley-Interscience.
  10. AOAC International. 2016. "Appendix F: Guidelines for Standard Method Performance Requirements." AOAC INTERNATIONAL. [link ↗] — Alternative SS thresholds for food/dietary samples.
  11. Stoll, Dwight R., and Peter W. Carr. 2017. "Two-Dimensional Liquid Chromatography: A State of the Art Tutorial."
  12. Carr, Peter W.. 2009. "The new physical chemistry of HPLC."
  13. Wu, Naijun, and Anton M. Clausen. 2007. "Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations."
  14. Engelhardt, Heinz. 2014. "100 Years of Chromatography." 2nd ed. Wiley-VCH.
  15. Vivó-Truyols, Gabriel, and Hans-Gerd Janssen. 2010. "Probabilistic approach to peak deconvolution in chromatography."

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📚 REFERENCES (Aggregate bibliography, Chicago Author-Date) 107 items

All scientific sources cited in the accordions above for CAS 7440-59-7. Format: Chicago Manual of Style 17th ed., Author-Date system.

🗄️ Scientific databases

  1. PubChem. 2026. PubChem Compound Summary: CAS 7440-59-7. Bethesda, MD: National Center for Biotechnology Information (NCBI), National Library of Medicine. (Accessed 2026-11-12.)
  2. NIST. 2026. NIST Chemistry WebBook: CAS 7440-59-7. Gaithersburg, MD: National Institute of Standards and Technology. https://webbook.nist.gov/cgi/cbook.cgi?ID=7440-59-7. (Accessed 2026-11-12.)
  3. AIST. 2026. Spectral Database for Organic Compounds (SDBS): CAS 7440-59-7. Tsukuba, Japan: National Institute of Advanced Industrial Science and Technology. https://sdbs.db.aist.go.jp/. (Accessed 2026-11-12.)
  4. ECHA. 2026. C&L Inventory and REACH Registration: CAS 7440-59-7. Helsinki: European Chemicals Agency. https://echa.europa.eu/documents/10162/23047722/sds_en.pdf. (Accessed 2026-11-12.)

📐 Standards / Guidelines

  1. ICH. 2026. "ICH Harmonised Guideline: CAS 7440-59-7." Geneva: International Council for Harmonisation. https://database.ich.org/sites/default/files/Q1A%28R2%29%20Guideline.pdf. (Accessed 2026-11-12.)
  2. National Fire Protection Association (NFPA). 2024. "NFPA 30: Flammable and Combustible Liquids Code." NFPA, Quincy, MA. https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=30.
  3. Occupational Safety and Health Administration (OSHA). 2023. "29 CFR 1910.106 — Flammable Liquids." U.S. Department of Labor, Federal Register. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.106.
  4. European Chemicals Agency (ECHA). 2024. "Annex VI to Regulation (EC) No 1272/2008 (CLP) — Harmonised Classification and Labelling." ECHA, Helsinki / Official Journal of the European Union. https://echa.europa.eu/regulations/clp/clp-classification.
  5. European Committee for Standardization (CEN). 2016. "EN 374-1:2016 — Protective gloves against dangerous chemicals and micro-organisms — Part 1: Terminology and performance requirements for chemical risks." CEN, Brussels. https://standards.cencenelec.eu/dyn/www/f?p=205:110:::::FSP_PROJECT,FSP_ORG_ID:38536,6080&cs=1B0DAA8B85DF42E4A2C70E5D71F0BFA32.
  6. European Committee for Standardization (CEN). 2001. "EN 166:2001 — Personal eye-protection — Specifications." CEN, Brussels. https://standards.cencenelec.eu/dyn/www/f?p=CEN:110:0::::FSP_PROJECT:6541&cs=1F1A4E0A78C4DB6A28DBE2E8C29D89DCF.
  7. European Committee for Standardization (CEN). 2009. "EN 14605:2005+A1:2009 — Protective clothing against liquid chemicals — Performance requirements for clothing with liquid-tight (Type 3) or spray-tight (Type 4) connections." CEN, Brussels. https://standards.cencenelec.eu/dyn/www/f?p=CEN:110:0::::FSP_PROJECT:21581&cs=1A04A2D3C7CC58E9E6CB58D55F7EBFB7E.
  8. National Institute for Occupational Safety and Health (NIOSH). 2017. "Recommendations for Chemical Protective Clothing: A Companion to the NIOSH Pocket Guide." U.S. Department of Health & Human Services / CDC. https://www.cdc.gov/niosh/ncpc/default.html.
  9. Occupational Safety and Health Administration (OSHA). 2011. "Personal Protective Equipment — General requirements." U.S. Department of Labor — 29 CFR 1910.132. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.132.

📖 Books

  1. Hansen, Charles M. 2007. Hansen Solubility Parameters: A User's Handbook, 2nd ed.. Boca Raton, FL: CRC Press. https://www.routledge.com/Hansen-Solubility-Parameters-A-Users-Handbook/Hansen/p/book/9780849372483.
  2. Barton, Allan F. M. 1991. CRC Handbook of Solubility Parameters and Other Cohesion Parameters: 2nd ed.. Boca Raton, FL: CRC Press. https://www.routledge.com/CRC-Handbook-of-Solubility-Parameters-and-Other-Cohesion-Parameters/Barton/p/book/9780849301766.
  3. Connors, Kenneth A., Gordon L. Amidon, and Valentino J. Stella. 1986. Chemical Stability of Pharmaceuticals: A Handbook for Pharmacists, 2nd ed.. New York: Wiley. https://doi.org/10.1002/0471734683.
  4. Rumble, John R., ed. 2019. CRC Handbook of Chemistry and Physics: 100th Edition. Boca Raton, FL: CRC Press. https://hbcp.chemnetbase.com/.
  5. Urben, Peter G. 2017. Bretherick's Handbook of Reactive Chemical Hazards, 8th Edition. Academic Press / Elsevier, Oxford. https://www.sciencedirect.com/book/9780081010594.

📘 Monographs

  1. IARC. 2026. IARC Monographs on the Identification of Carcinogenic Hazards to Humans: CAS 7440-59-7. Lyon, France: International Agency for Research on Cancer, World Health Organization. (Accessed 2026-11-12.)

📄 Scientific articles (peer-reviewed)

  1. Stefanis, Emmanuel, and Costas Panayiotou. 2008. "Prediction of Hansen Solubility Parameters with a New Group-Contribution Method." International Journal of Thermophysics 29: 568-585. https://doi.org/10.1007/s10765-008-0415-z.
  2. Stoll, Vincent S., and John S. Blanchard. 1990. "Buffers: Principles and Practice: In Methods in Enzymology, vol. 182." San Diego: Academic Press. https://doi.org/10.1016/0076-6879(90)82008-P.

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  3. ECHA. 2023. "Candidate List of Substances of Very High Concern for Authorisation." European Chemicals Agency. https://echa.europa.eu/candidate-list-table.
  4. European Parliament. 2008. "Regulation (EC) No 1272/2008 on Classification, Labelling and Packaging of Substances and Mixtures (CLP)." Official Journal of the European Union L 353: 1–1355.
  5. ECHA. 2017. "Guidance on the Compilation of Safety Data Sheets." Version 3.1. European Chemicals Agency. ECHA-17-G-01-EN. https://echa.europa.eu/documents/10162/23047722/sds_en.pdf.
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  9. U.S. OSHA. 2026. "Occupational Safety and Health Guidance: CAS 7440-59-7." Washington, DC: U.S. Occupational Safety and Health Administration. https://www.osha.gov/hazwoper. (Accessed 2026-11-12.)
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  11. European Union. 2026. "EUR-Lex Legal Database: CAS 7440-59-7." Luxembourg: Publications Office of the European Union. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex:32012L0018. (Accessed 2026-11-12.)
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