Hot phosphate-buffered water extraction coupled on line with liquid chromatography/mass spectrometry for analyzing contaminants in soil

We evaluated the feasibility of analyzing rapidly traces of polar and mediu m polar contaminants in soil by coupling on-line a hot phosphate-buffered w ater extraction apparatus to a liquid chromatography/mass spectrometer syst em. Coupling was accomplished by using a small C-18 sorbent trap for collec ting analytes and two six-port valves. The efficiency of this device was ev aluated by extracting 13 selected pesticides from 200 mg of laboratory-aged soils by varying the extraction temperature, the extractant volume, and th e now rate at which the extractant passed through the extraction cell and t he sorbent trap. In terms of extraction efficiency, robustness of the metho d, and extraction time, the best compromise was that of using 8 mL of extra ctant at 90 degrees C and 0.5 mL/min flow rate. Under these conditions, rec overies of 11 out of 13 analytes ranged between 82 and 103%, while those of the least hydrophilic pesticides, i.e., neburon and prochloraz, were 73 an d 63%, respectively. By increasing the extractant volume to 60 mL, addition al amounts of the two latter compounds could be recovered. Under this condi tion, however, the most hydrophilic analytes were in part no more retained by the C-18 sorbent trap. From a naturally 1.5-year aged soil, hot phosphat e-buffered water removed larger amounts of three herbicides and hydroxyterb uthylazine (a terbuthylazine degradation product) than pure water and Soxhl et extraction. This result seems to confirm that hot phosphate buffer is al so able to remove from soil those fractions of contaminants that, on aging, are sequestered into the humic acid framework.