Solid-phase extraction of aminobenzoic acids and aminotoluenesulfonic acids with graphitized carbon black

The extraction of amphoteric aromatic amines from water samples is difficult because of their high polarity. For the enrichment of aminobenzoic acids and aminotoluenesulfonic acids with solid-phase extraction, graphitized carbon black (GCB) was investigated. With few exceptions, the 12 analytes studied were extracted with recoveries > 60% at neutral or basic pH, whereas at pH 3 low recoveries were obtained. Addition of salt caused a decrease of about 50% in recoveries, addition of standard humic acid a decrease of about 20%. The capacity of GCB cartridges was determined with the breakthrough volume for 4-aminobenzoic acid at different concentrations to be 0.5-1% (w/w).