Development of Thermal Dissociation Atmospheric Chemical Ionization Source for Rapid Mass Spectrometry Analysis of Ambient Samples

A thermal dissociation atmospheric chemical ionization (TDCI) source was developed for the rapid chemical ionization of ambient analytes in complex matrices. The performance of TDCI has been experimentally explored by coupling the TDCI source to a commercial LTQ XL mass spectrometer, and the dissociation of chemical reagents, for example ionic liquids, has been systematically investigated using multiple stage mass spectrometer. The primary ions, generated through the thermal dissociation process of the ionic liquids, were accelerated by the bias voltage applied to the repelling electrode of the TDCI source, then reacted with the analytes present in the matrices of the raw samples to produce analyte ions. The analyte ions were finally guided into 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 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 conditions, TDCI was able to directly ionize a wide variety of compounds, including the poplar (e.g., amino acids, doping compounds) and nonpolar 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, the relative standard deviation of the method was in the range of 5.89%–11.1%, and the limit of detection (LOD) for naphthalene was estimated to be 2.9 × 10−7 g L−1.