Topic: inorganic anions

The seven common inorganic anions often quantified simultaneously using ion chromatography (IC) include fluoride (F^–), chloride (Cl^–), bromide (Br^–), nitrite (NO₂^–), nitrate (NO₃^–), sulfate, i.e., sulphate (SO₄^2-), and phosphate (PO₄^3-), the latter which is separated as hydrogen phosphate (HPO₄^2-) at the typical IC eluent pH around 11.

The US EPA (United States Environmental Protection Agency) has published method 300.0A, later updated to 300.1A, which thoroughly describes the analysis setup and requirements for reliable IC quantification of these seven anions in the mg/L (ppm) range in water samples using isocratic carbonate-bicarbonate eluents. This method is based entirely on suppressed conductivity detection, but nitrite and nitrate, and to some extent also bromide, could instead be determined using low UV absorption spectrometry at 210 nm.

The requirements of the EPA 300.1A method are met by several brand instruments, columns and eluents that successfully can accomplish baseline separation and sufficient sensitivity with low noise. However, the analysis will be more challenging and might require different columns and conditions when additional inorganic anions or organic acids are present in the sample, or when some anions are in abundant excess.

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

Applications

ion chromatography

Preserving eluent quality with dedicated storage protected from ambient carbon dioxide

To ensure that liquid chromatography analysis methods meet regulatory demands of retention repeatability as dictated by pharmacopoeia and the ICH guidelines, it is important to protect weakly buffered eluents from ambient carbon dioxide. The formation of carbonate species will otherwise change the pH and strength of the eluent, thus shifting retention.

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

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

Comparing suppressed and non-suppressed ion chromatography

Suppressed ion chromatography with conductivity detection is a powerful and sensitive technique to analyse charged ionic species, especially anions of strong acids. The chemically regenerated membrane suppressor Xenoic® XAMS can enable analysis of such anions down to levels of a few microgram per litre (part per billion, ppb).

ion chromatography

Determination of fluoride ion to monitor biodegradation of perfluorinated acids

Although perfluoroalkyl substances (PFAS) are known for their persistence in natural ecosystems, there are certain bacterial strains that can help to decompose them. This published scientific paper studied bacterial degradation of certain perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) by including ion chromatography analysis of fluoride ions, set up on a HPLC instrument with added suppressed conductivity detection.

ion chromatography

Published case study of analytical quality by design method development and validation

Diduco has published a scientific peer-reviewed case study on how modern analytical method development can be performed in the pharmaceutical industry. The work was performed according to analytical quality by design (AQbD) principles to establish the design space and robust setpoint of the ion chromatography assay, and then validated according to the guidelines established by the International Council for Harmonization (ICH).

ion chromatography

Quantification of anions in water using an improved ion chromatography system

Anion analysis can be performed at several conditions, using various columns on different systems and still be able to meet official requirements. A common approach is isocratic separation with carbonate-bicarbonate eluents, and this example showcase how such analyses can be improved and streamlined with autosampler injections, continuous suppression and protected eluents.

ion chromatography

Published routine method for quantification of anions in tap water and natural waters

Quantification of the seven common anions is an important part of water quality control. This published ion chromatography method is from a scientific paper that presents full validation data according to the ICH guidelines to meet the requirements of laboratories acting under the ISO 17025 accreditation.

ion chromatography

Quantification of common anions in beer using a passivated HPLC system

For brewers, ensuring consistent beer quality from batch to batch is essential. Consumers expect the same flavour every time they choose their favourite beer, making analytical testing a key part of brewery quality control.

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

Modernized assay for foscarnet following ICH guidelines

New preliminary assay for the antiviral medication foscarnet which is a DNA polymerase inhibitor that is used to combat herpes viruses, including drug-resistant cytomegalovirus, and to treat patients with HIV as part of salvage therapy. This method was developed by Diduco to meet the requirements in the ICH guidelines, as a contribution to the United States Pharmacopoeia initiative for modernized monograph methods.

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

Alternative method for determination of voriconazole impurity E

Voriconazole is an antifungal medication that is included on the WHO Model list of Essential Medicines. During synthesis of the active ingredient a resolving agent for chiral amines is often used, and it is thus necessary that the quality control prove that this substance is not present at harmful levels in the final product.

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 approach 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