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A corona discharge ionization-ion mobility spectrometry (CD-IMS) with a novel sample inlet system was designed and constructed as a detector for capillary gas chromatography. In this design, a hollow needle was used instead of a solid needle which is commonly used for corona discharge creation, helping us to have direct axial interfacing for GC-IMS. The capillary column was passed through the needle, resulting in a reaction of effluents with reactant ions on the upstream side of the corona discharge ionization source. Using this sample introduction design, higher ionization efficiency was achieved relative to the entrance direction through the side of the drift tube. In addition, the volume of the ionization region was reduced to minimize the resistance time of compounds in the ionization source, increasing chromatographic resolution of the instrument. The effects of various parameters such as drift gas flow, makeup gas flow, and column tip position inside the needle were investigated. The designed instrument was exhaustively validated in terms of sensitivity, resolution, and reproducibility by analyzing the standard solutions of methyl isobutyl ketone, heptanone, nonanone, and acetophenone as the test compounds. The results obtained by CD-IMS detector were compared with those of the flame ionization detector, which revealed the capability of the proposed GC-IMS for two-dimensional separation (based on the retention time and drift time information) and identification of an analyte in complex matrixes.

In this research work, the capability of low-temperature plasma (LTP) as an ionization source for ion mobility spectrometry (IMS) has been investigated for the first time. This new ionization source enhances the potential of IMS as a portable analytical tool and allows direct analysis of various chemical compounds without having to evaporate the analyte or seek a solvent or reagent whatsoever. The effects of parameters such as the flow rate of the discharge gas, plasma voltage, and positioning of the LTP on the IMS signal were investigated. The positive reactant ions generated by the LTP ionization source were similar to those created in a corona discharge ionization source, where the proton clusters ((H(2)O)(n)H(+)) are the most abundant reactant ion, and in the negative mode, in addition to a saturated electron peak, several negative reactant ions (e.g., NO(x)(-)) were observed too. These reactant ions subsequently ionized the gaseous samples directly and liquids or solids after evaporation by plasma desorption. The ion mobility spectra of a few selected compounds, including explosives, drugs, and amines, were obtained to evaluate the new ionization source in positive and negative modes, and the reduced mobility values (K(0)) of the originated ions were calculated. Furthermore, the method has also been applied to obtain the figures of merit for acetaminophen as a test compound. The results obtained are promising enough to ensure the use of LTP as a desorption/ionization source in IMS for analytical applications.

This study describes a novel technique for direct analysis of thiocyanate in human saliva using negative electrospray-ion mobility spectrometry (ESI-IMS) and without any considerable sample pretreatment. The ESI-IMS system with nearly complete desolvation cannot be useful for salivary thiocyanate analysis because complete overlapping occurs between the format peak of the solvent and the thiocyanate peak. In addition, the chloride ions existing in saliva produce a very broad peak, which has a drastically interfering effect on SCN(-) determination. In this study, with a little change in the operation conditions of the apparatus (lowering the flow rate of the drift gas), it was possible to overcome these problems. The desolvation process was decreased in the lower flow of drift gas, and this caused the SCN(-) peak to be separated completely from other interference peaks such as chloride ions. The results obtained in this proposed methodology provide the detection limit of 0.003 microg/mL and the linear dynamic range from 0.01 to 1.00 microg/mL for the thiocyanate. Several human saliva samples were analyzed with the proposed negative ESI-IMS, and the satisfactory results confirm the capability of the method for direct analysis of salivary thiocyanate.

Application of ion mobility spectrometry (IMS) as the detection technique for a separation method based on molecular imprinted polymer (MIP) was investigated and evaluated for the first time. On the basis of the results obtained in this work, the MIP-IMS system can be used as a powerful technique for separation, preconcentration, and detection of the metronidazole drug in pharmaceutical and human serum samples. The method is exhaustively validated in terms of sensitivity, selectivity, recovery, reproducibility, and column capacity. The linear dynamic range of 0.05-70.00 microg/mL was obtained for the determination of metronidazole with IMS. The recovery of analyzed drug was calculated to be above 89%, and the relative standard deviation (RSD) was lower than 6% for all experiments. Various real samples were analyzed with the coupled techniques, and the results obtained revealed the efficient cleanup of the samples using MIP separation before the analysis by IMS as a detection technique.

In this study, a new design for electrospray ionization ion mobility spectrometry (ESI-IMS) was developed. This design has two important differences in comparison to the present ESI-IMS systems. First, a few centimeters of the cell comprising the electrospray needle was located outside of the oven used for heating the IMS cell. This modification prevents prespray solvent evaporation problems such as needle clogging and disturbance of the electrospray process. Second, in addition to the drift gas, a counterflow of a heated gas (desolvation gas) was used between the counter electrode and the ion gate to speed up the desolvation process (Hill, H. H., Jr. Anal. Chem. 1998, 70, 4929-4938). This modification increased the solvent evaporation and resulted in decreasing the drift time, increasing the peak intensity and increasing the resolving power (RP) or enhancing the resolution for separation of two adjacent ion peaks. In this work, the ion mobility spectra of different compounds including ethion, malathion, metalaxyl, fenamifos, methylamine, triethylamine, tributhylamine, codeine, and morphine were obtained to confirm enhancing of the resolving power of the ion peaks by using the desolvation gas. Furthermore, the method has also been applied to obtain the figures of merit for ethion as a test compound. The linear dynamic range for ethion was in the range 50-1000 microg/L with a limit of quantification of the 50 microg/L.