Trace determination of free formaldehyde in DTP and DT vaccines and diphtheria–tetanus antigen by single drop microextraction and gas chromatography–mass spectrometry

An immersed single drop microextraction (SDME) method was successfully developed for the trace enrichment of formaldehyde from DTP and DT vaccines and diphtheria–tetanus antigen. The formaldehyde was derivatized by means of the Hantzsch reaction. The dehydropyridine derivative was extracted into a microdrop of chloroform that suspended in a 4 ml sample solution for a preset time. The microdrop was then retracted into the microsyringe and injected directly into a gas chromatography–mass spectrometry (GC–MS) injection port. Effects of different parameters such as the type of solvent, extraction time, stirring rate, and temperature were studied and optimized. The limit of detection was 0.22 ng/l and relative standard deviation (RSD) value was 6.2% (n = 5). The regression coefficient was satisfactory (r2 = 0.992) and linear range was obtained from 1 to 500 ng/l.