Analyte: sulfate

The sulfate ion (also sulphate ion), SO₄^2-, 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. Some properties of the sulfate ion are summarized in the table below.

Sulfate analysis

Sulfate is frequently analysed by ion chromatography (IC) with suppressed conductivity detection along with the other common inorganic anions, and quite many different IC columns can accomplish the separation using either carbonate-bicarbonate eluents or hydroxide eluents. Note, however, that the retention may vary significantly between different columns depending on the nature of the ion exchange groups and their proximity. The full dissociation, the number of charges, and the rather high molar conductivity results in high sensitivity when the sulfate ion is monitored by suppressed conductivity detection.

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

Ion	Molecular weight, M	Molar conductivity, λ₀	Diffusion coefficient, D	Ionic radius, r	Hydration shell, Δr
	(g/mol)	(S·cm²/mol)	(mm²/ms)	(pm)	(pm)
Sulfate, SO₄^2-	96.064	160	1.07	230	43
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

ion chromatography

Screening of contaminants and forced degradation products in lithium ion battery electrolyte

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.

ion chromatography

Determination of sulfamate and sulfate in topiramate tablets according to USP monograph

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.

ion chromatography

Quantification of common anions in bottled drinking water according to EPA method 300.1A

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.

ion chromatography

Generic method for isocratic separation of fifteen common pharmaceutical counterions

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.

ion chromatography

Analysis of dietary supplement capsules with glucosamine using a generic method for counterions

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.

ion chromatography

Hydroxide gradient elution of organic acids and inorganic anions

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.

ion chromatography

Generic method for isocratic separation of ten common pharmaceutical counterions

ion chromatography

Quantification of common anions in drinking water according to EPA method 300.0A

Older version of the official procedure for quality control of drinking water according to the United States Environmental Protection Agency.

ion chromatography