Headspace membrane introduction mass spectrometry for trace level analysisof VOCs in soil and other solid matrixes

A new MIMS-derived technique, headspace membrane introduction mass spectrom etry (HS-MIMS), is described for direct trace level analysis of volatile or ganic compounds (VOCs) in soil and other dry or wet solid matrixes. A silic one membrane interface is placed about 15 cm from the ion source, and a clo sed airspace (headspace) is created by connecting a toggle valve to the 1/4 in. tubing that connects the membrane interface to the ion source. For the VOC analysis, the headspace is evacuated and the solid sample vessel is he ated to 90 degrees C. The VOCs are rapidly desorbed from the sample, pervap orated through the membrane, and preconcentrated for 4 min in the evacuated headspace. Then, the toggle valve is opened and the trapped VOCs are relea sed into the ion source region of a quadrupole mass spectrometer. By electr on ionization and selected-ion monitoring, a relatively sharp and intense p eak is obtained and used for quantification. The HS-MIMS analysis shows exc ellent linearity and reproducibility and detection limits for many VOCs typ ically of 50-100 ng/kg (ppt).