PULSED FLAME PHOTOMETER DETECTOR FOR GAS-CHROMATOGRAPHY

A new pulsed name photometer detector (PFPD) design is described with improved performance, Detection limits of 180 fg/s (sulfur), 7 fg/s (p hosphorus), and 2 pg/s (nitrogen) are demonstrated when 2 rms noise is considered as the detection limit. The minimum detected amount of sul fur was further reduced with a sulfur doping method to about 30 fg/s, The factors affecting the selectivity are analyzed in terms of operati ng the PFPD as a specific detector without any hydrocarbon interferenc es, The effect of the pulsed nature of the PFPD on the chromatographic peak area and height reproducibility is modeled and analyzed, It is s hown that above 3 Hz, the standard deviation of peak area is 2%, which is dominated by nondetector effects, The detector temperature effect was studied and is presented. The difference between light guide and l ens optics is discussed. The column operation with hydrogen as a carri er gas is compared to that with helium, and the injection of chlorinat ed and fluorinated solvents is shown and discussed. New ways of obtain ing additional information by using the added dimension of time are an alyzed. It is shown how the simultaneous use of dual gates can provide unambiguous heteroatom identification, It is also described how a dua l gate subtraction method results in a considerable enhancement of the interheteroatom selectivity, especially for phosphorus versus sulfur. The dual gate approach also provides up to an order of magnitude incr ease in the measurement dynamic range, Practical utilization of the PF PD is illustrated with the analysis of real-world samples, including t hiophene in benzene, pesticides in a broccoli extract, and a sulfur-co ntaining drug in human serum.