Quantitative determination of nitrilotriacetic acid and related aminopolycarboxylic acids in inland waters : Analysis by gas chromatography

Abstract

Quantitative methods were developed for detecting nitrilotriacetic acid (NTA) iminodiacetic acid (IDA), N-methyl-iminodiacetic acid (NMIDA), glycine (GLY), sarcosine (SARC), and N-oxalyl-iminodiacetic acid (N-oxalyl-IDA) in a variety of water samples and N-nitroso-iminodiacetic acid (N-nitroso-IDA) in river water. NTA, NMIDA, and N-oxalyl-IDA were converted to their corresponding n-butyl esters; IDA, GLY, and SARC were converted to N-trifluoroacetyl n-butyl ester derivatives; N-nitroso-IDA was converted to the N-trifluoroacetyl n-butyl ester derivative of IDA. These volatile derivatives were separated and analyzed on an ethylene glycol adipate gas chromatographic column. For quantitative analysis, the amount of each amino acid injected was 3 to 200 ng, and the amount of each amino acid separated from the water sample was 0.25 to 1000 μg. Response values for NTA, IDA, NMIDA, GLY, and SARC were reproducible and showed no statistical bias for river water sample concentrations of 20 to 0.025 mg/l. Relative standard deviations ranged from 8 to 13%. The response value for N-nitroso-IDA varied with concentration but was reproducible at any given concentration. Each or all of the above amino acids could be detected in samples of river water, well water, water containing nitrate ions, water containing formaldehyde, primary sewage effluent, and secondary sewage effluent.