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 (r(2)=0.992) and linear range was obtained from 1 to 500 ng/l.