Analyte: sulfate

The sulfate ion (also sulphate ion), SO42-, is the end base of sulfuric acid, H2SO4, which is a diprotic strong acid with pKa values of -3 and 1.99, and thus fully dissociated in most aqueous solutions. Sulfate is doubly charged and carries a hydration layer comprised of 3.1 associated water molecules. The full dissociation, the number of charges, and high molar conductivity results in high sensitivity when the chloride ion is monitored by conductivity detection. Some properties of the sulfate ion are summarized in the table below.

Sulfate analysis

Sulfate is typically analysed by ion chromatography (IC) with suppressed conductivity detection and quite many different IC columns can accomplish the separation using either carbonate-bicarbonate eluents or hydroxide eluents. However, the retention may vary significantly between different columns depending on the nature of the ion exchange groups and their proximity. Some HILIC columns may also retain sulfate, and this may thus be an alternative analysis technique, whereas reversed-phase (RP) and ion-exclusion chromatography (IEC, ICE) tend to not give sufficient retention.

Table of some sulfate ion properties at 25 °C

IonMolecular weight, MMolar conductivity, λ0Diffusion coefficient, DIonic radius, rHydration shell, Δr
(g/mol)(S·cm2/mol)(mm2/ms)(pm)(pm)
Sulfate, SO42-96.0641601.0723043
M, was retrieved from Chemical Aid Molecular Mass Calculator. Values for λ0 & D, are from CRC Handbook of Chemistry and Physics, 75th Ed., D.R. Lide (Ed.), CRC Press Inc. (1994), Boca Raton, pp 5-90 to 5-92. Data for r & Δr, plus the number of water molecules, n, mentioned in the text, are from Y. Marcus, J. Chem. Soc. Faraday Trans., 87 (1991) 2995-2999. The pKa values mentioned in the text are from Organic Chemistry Data pKa compilation.

Learn more

To learn more, browse the application examples below or contact Diduco to discuss your specific analysis.

Applications

Electrolytes in rechargeable batteries for cars, mobile phones, and other portable electric devices typically contain negatively charged counterions that together with lithium and a non-aqueous solvent form an ionic liquid. The bis(fluorosulfonyl)imide anion is a rather new ionic liquid constituent which thus need new quality control procedures.
Official quality control method for the second-generation antiepileptic drug topiramate which also have shown effect against migranes. This analysis was performed according to the United States Pharmacopeia monograph and determines the degradation products sulfamate and sulfate which can be formed during storage in humid environments or at elevated temperatures.
Official procedure for quality control of drinking water according to the United States Environmental Protection Agency. This procedure allows quantification of the seven common inorganic anions fluoride, chloride, nitrite, bromide, nitrate, phosphate and sulfate in the ranges recommended by WHO and national authorities.
Many medicines and dietary supplements are bases that carry a positive charge, and consequently these small molecules are accompanied by negatively charged counterions. Such anionic excipients may influence the properties of the pharmaceutical formulation and can also influence the effect of the active ingredient since different ion pairs can have different dissolution rates or abilities to penetrate cell walls.
Oral glucosamine is a dietary supplement that is marketed to support the structure and function of joints and claimed to provide pain relief for people with arthritis and osteoarthritis, although there is no clear evidence that its benefit is significantly above placebo.
Gradient elution is a powerful tool when aiming to separate many compounds having a wide range of different chemical characteristics. Hydroxide gradients are the most common in ion chromatography since they can be converted into pure water with nearly zero conductivity.
Many medicines and dietary supplements are bases that carry a positive charge, and consequently these small molecules are accompanied by negatively charged counterions. Such anionic excipients may influence the properties of the pharmaceutical formulation and can also influence the effect of the active ingredient since different ion pairs can have different dissolution rates or abilities to penetrate cell walls.
Older version of the official procedure for quality control of drinking water according to the United States Environmental Protection Agency.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.
Separation of inorganic anion standards at eluent conditions recommended by the column manufacturer.

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