Sensitivity study of perfluorocarbons and heteroatom-containing fluorocarbons by negative ion chemical ionization mass spectrometry

Abstract

The relative response of various perfluorocarbons (PFCs) such as perfluorinated alkanes, alkenes, aromatics and heteroatom-containing fluorocarbons such as perfluorinated 2-butyltetrahydrofuran, tert-butanol, bis(isopropyl) ketone and 1H-heptane, with respect to the internal standard, perfluoro-cis-decalin, was studied using different negative ion chemical ionization (NICI) reagent gases. Under the NICI conditions used in our laboratory, methane was found to be the best NICI reagent gas for the optimization of the electron attachment (in terms of total ion current) for perfluorinated alkanes, alkenes, aromatics and 1-methyladamantane. Carbon dioxide and ammonia were found to be good NICI reagent gases for optimizing the response of hydrogen- and oxygen-containing fluorocarbons and highly symmetric PFCs such as perfluoroadamantane and perfluoro-trans-decalin. On the other hand, CF4 was found to yield the largest linear range in the calibration curve for perfluoro-C11-cycloalkanes (PCA) when perfluoro-cis-decalin was used as the internal standard. The employment of NH3 as the NICI reagent gas gave the most sensitive response to the increase of trace PCA concentration.