Which compound can interfere with coulometric chloride assay?

Which compound can interfere with coulometric chloride assay?

• A. Acetoacetate
• B. Ascorbate
• C. Bromide
• D. Nitrate

Answer: (C)

Coulometric chloride assay determines chloride by generating silver ions electrochemically and letting them precipitate chloride as silver chloride. Any species that reacts with silver ions or forms its own insoluble silver salt can steal silver ions away from chloride, skewing the result. Bromide is the mainly interfering species because it forms silver bromide, an insoluble salt, with the generated silver ions. This consumes silver before chloride does, altering the charge required to reach the endpoint and producing inaccurate chloride measurements. Acetoacetate and ascorbate are not known to form the same stable insoluble silver salts under these conditions, so they don’t interfere in the same way. Nitrate doesn’t form an insoluble silver salt and generally doesn’t affect the assay.

Coulometric chloride assay determines chloride by generating silver ions electrochemically and letting them precipitate chloride as silver chloride. Any species that reacts with silver ions or forms its own insoluble silver salt can steal silver ions away from chloride, skewing the result.

Bromide is the mainly interfering species because it forms silver bromide, an insoluble salt, with the generated silver ions. This consumes silver before chloride does, altering the charge required to reach the endpoint and producing inaccurate chloride measurements.

Acetoacetate and ascorbate are not known to form the same stable insoluble silver salts under these conditions, so they don’t interfere in the same way. Nitrate doesn’t form an insoluble silver salt and generally doesn’t affect the assay.