Development of Thermal Dissociation Atmospheric Chemical Ionization Source for Rapid Mass Spectrometric Analysis of Ambient Samples
A novel thermal dissociation atmospheric chemical ionization source(TDCI) was developed for rapid chemical ionization of ambient analytes in complex matrices.By coupling the TDCI source to a commercial LTQ XL mass spectrometer,the dissociation of chemical reagents such as ionic liquids was systematically investigated using multiple-stage mass spectrometric experiments.The primary ions generated through the thermal dissociation process of the ionic liquids were accelerated by the high voltage applied on the repelling electrode of the TDCI source,and then reacted with the analytes present in the matrices of the raw samples to produce ions of analytes,which were then guided to the LTQ instrument for mass analysis.The construction of the TDCI source was detailed in the text.The effects of the experimental parameters such as the pyrolysis temperature,the distance,and the angles formed between the electrodes were experimentally studied using the signals of characteristic fragments of the ionic liquid.Under the optimal experimental parameters,TDCI was able to directly ionize a wide variety of compounds,including the poplar(e.g.,amino acids,doping compounds) and non-polar chemicals(e.g,naphthalene) for sensitive detection using LTQ-MS,without any sample pretreatment.The average time for a single sample analysis was less than 30 s,and the relative standard deviation of the method was in the range of 5.9%-11.1%;the LOD for naphthalene was estimated to be 2.93×10-7 g/L.