Performance of the high sensitivity ion source for PCDD/PCDF analyses in human serum and adipose tissue

We installed the high sensitivity, EI-only, ion source in each of our high resolution mass spectrometers; VG ZAB-2F, 70/70E, and 70S. The increased sensitivity observed has made it possible for us to analyze chlorinated dioxins and furans in human serum. Detection levels of 20 fg on column, S/N > 3:1, are routine using these sources, and the range of linearity is significantly extended into the lower femtogram levels. Characteristic source operation includes the use of 500 uA trap current and much lower emission current that enables the use of soft ionization energy (28-36 eV) to reduce space charge effects caused by the ionized helium carrier gas and subsequently improve signal-to-noise ratios. The salient characteristics of this source are presented to demonstrate its capabilities by using data generated from ongoing studies quantifying background levels of PCDDs/PCDFs by stable isotope dilution high resolution gas chromatography mass spectrometry (HRGCMS) using selected ion recording (SIR) in less than 50g of human serum.