To hyphenate ion pairing chromatog. and MS detection the authors used several types of formates as volatile ion pairing reagents (IPRs) instead of common tetraalkylammonium salts, as these salts tend to ppt. in the ion source. The formates were prepd. by mixing formic acid with the corresponding amine. Both tributyl- and trihexylammonium formate proved to be valuable IPRs for the sepn. of acidic compds. like nitrobenzoic acids, nitrobenzenesulfonic acids and nitrated phenols. Due to the weaker retention of the ion-pairs with trialkylammonium formates compared with tetraalkylammonium compds., either less org. modifier or a higher concn. of the IPR had to be used. With neg. atm. pressure chem. ionization mass spectrometry and electrospray ionization mass spectrometry it was possible to unambiguously identify several acidic oxidn. products of 2,4,6-trinitrotoluene (TNT) in ammunition wastewater and soil exts. 2-amino-4,6-dinitrobenzoic acid was often found to be the main metabolite of TNT in such water samples.