A new approach to determine salicylic acid in human urine and blood plasma based on negative electrospray ion mobility spectrometry after selective separation using a molecular imprinted polymer.

This paper deals with a method based on negative electrospray ionization ion mobility spectrometry (ESI-IMS) as a detection technique. The method was used to determine the salicylic acid in human urine and plasma after selective separation of salicylic acid (SA) via molecular imprinted polymer (MIP). The ion mobility spectrum of salicylic acid in negative mode and the reduced mobility value for its ion peak is reported in this paper for the first time. In order to combine the technique with negative ESI-IMS, suitable experimental conditions related to MIP (e.g., Soxhlet extraction) were selected. The method was exhaustively validated in terms of sensitivity, imprinting factor, enrichment factor, and sorption capacity. The linear dynamic range of 0.02-2.00 µg mL(-1) and the relative standard deviation (RSD) below 6% were obtained for the analysis of SA through this method. The average recovery was calculated about 92% for the analyzed drug. Finally, human urine and plasma were analyzed and the feasibility of the proposed method was successfully verified by the efficient clean-up of the samples using MIP separation before the analysis by ESI-IMS.

Simultaneous determination of nitrite and nitrate in potato and water samples using negative electrospray ionization ion mobility spectrometry.

Nowadays, nitrite and nitrate ions are analyzed in biological samples using laborious and expensive methods; such as HPLC, CE, MS-MS. In this work, the simultaneous analysis of nitrite and nitrate ions was conducted by electrospray ionization-ion mobility spectrometry (ESI-IMS), without using any complicated or laborious derivitization step. Ion mobility spectrometry with low cost, inexpensive maintenance and very fast analysis makes an attractive technique for the simultaneous determination of these ions in foodstuff and drinking water samples. The analyte interference was systematically investigated for binary mixture analysis. The obtained results provided detection limits of 3.8 and 4.7 µg/L for nitrite and nitrate, respectively. A linear dynamic range of about 2 orders of magnitude, and relative standard deviations below 5% were obtained by the proposed method for the analysis of both ions. Also, the proposed method was used to analyze various real samples of potato and drinking water samples, and the obtained results confirmed the capability of negative ESI-IMS for the simultaneous detection of nitrite and nitrate.

Electrospray ionization-ion mobility spectrometry as a detection system for three-phase hollow fiber microextraction technique and simultaneous determination of trimipramine and desipramine in urine and plasma samples.

A novel method based on three-phase hollow fiber microextraction technique (HF-LPME) coupled with electrospray ionization-ion mobility spectrometry (ESI-IMS) was developed for the simultaneous determination of two antidepressant drugs (trimipramine and desipramine) in urine and plasma samples. The effects of various parameters such as type of organic solvent, composition of donor and acceptor phase, stirring rate, salt addition, extraction time, and temperature were investigated. Under the optimized conditions, the relative standard deviation was in the range of 5-6%, and the method quantitation limit (MQL) of utilizing HF-LPME/ESI-IMS was 5 µg/L for both drugs. The relative recoveries obtained by the proposed method from urine and plasma samples were in the range 94% to 97% for trimipramine and 92% to 96% for desipramine. Finally, the feasibility of the proposed method was successfully confirmed by extraction and determination of trace amounts of trimipramine and desipramine in biological samples without any significant matrix effect.

Selective pretreatment and determination of phenazopyridine using an imprinted polymer-electrospray ionization ion mobility spectrometry system.

In this research, selective separation and determination of phenazopyridine (PAP) is demonstrated using molecular imprinted polymer (MIP) coupled with electrospray ionization ion mobility spectrometry (ESI-IMS). In the non-covalent approach, selective MIP produced using PAP and methacrylic acid (MAA) as a template molecule and monomer, respectively. The created polymer is utilized as a media for solid-phase extraction (SPE), revealing selective binding properties for the analyte from pharmaceutical and serum samples. A coupled MIP-IMS makes it possible to quantitize PAP in the range of 1-100 ng mL(-1) and with a 0.2 ng mL(-1) detection limit. Furthermore, the MIP selectivity is evaluated by application of some substances with analogous and different molecular structures to that of PAP. This method is successfully applied for the determination of PAP in pharmaceutical and serum samples.

A new method based on electrospray ionisation ion mobility spectrometry (ESI-IMS) for simultaneous determination of caffeine and theophylline.

In this work for the first time, simultaneous analysis of caffeine and theophylline was done by ion mobility spectrometry (IMS) only, without a powerful separation technique (e.g., HPLC). Ion mobility spectrometry with low cost, inexpensive maintenance and very fast analysis makes an attractive technique for the simultaneous determination of the caffeine and theophylline in foodstuff samples and biological matrices. In this study, the extraction protocol using molecular imprinted polymer-solid phase extraction (MIP-SPE) was successfully used to directly extract caffeine and theophylline from real samples. The results obtained provided the detection limits of 0.2 and 0.3µgmL(-1) for caffeine and theophylline, respectively. The linear dynamic range of about two orders of magnitude was obtained for these compounds. Also, the proposed method was used to analyse various real samples of green tea and spiked human plasma, and the obtained results confirmed the capability of ESI-IMS for simultaneous detection of caffeine and theophylline.

Selective method based on negative electrospray ionization ion mobility spectrometry for direct analysis of salivary thiocyanate.

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.

Selective separation and determination of primidone in pharmaceutical and human serum samples using molecular imprinted polymer-electrospray ionization ion mobility spectrometry (MIP-ESI-IMS).

Application of electrospray ionization ion mobility spectrometry (ESI-IMS) as the detection technique for separation method based on molecular imprinted polymer (MIP) was investigated and evaluated. The method is exhaustively validated, including sensitivity, selectivity, recovery, reproducibility, and column capacity. The linear dynamic range of 0.02-2.00 microg mL(-1) was obtained for primidone analysis with ESI-IMS. The recovery of drug analyzed was calculated to be above 90% and the relative standard deviation (RSD), was below 3% for all experiments. Various real samples were analyzed with the coupled techniques, and the results obtained revealed the efficient clean-up of the samples using MIP separation before the analysis by ESI-IMS as a detection technique.

Simultaneous determination of 2-furfural and 5-methyl-2-furfural using corona discharge ion mobility spectrometry.

A novel technique, corona discharge ion mobility spectrometry (CD-IMS), was developed for the qualitative and quantitative determination of 2-furfural (F) and 5-methyl-2-furfural (MF) in aqueous solutions. The limits of detection (LODs) were 5.3 x 10(-3) microg/mL for F and 6.7 x 10(-3) microg/mL for MF. The linear dynamic ranges of 1.16 x 10(-2) to 1.04 microg/mL and 2.20 x 10(-2) to 1.10 microg/mL were obtained for F and MF, respectively. The relative standard deviation was below 12% for both compounds. In addition to analysis of the individual compound, simultaneous determination of F and MF was also investigated. It was realized that F imposes a matrix effect on the MF signal and vice versa. The standard addition method was used to deal with the matrix effect. The recovery of the compounds in the synthetic samples validates the capability of the method.

Ion mobility spectrometry as a detector for molecular imprinted polymer separation and metronidazole determination in pharmaceutical and human serum samples.

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.

Improved design for high resolution electrospray ionization ion mobility spectrometry.

An improved design for high resolution electrospray ionization ion mobility spectrometry (ESI-IMS) was developed by making some salient modifications to the IMS cell and its performance was investigated. To enhance desolvation of electrospray droplets at high sample flow rates in this new design, volume of the desolvation region was decreased by reducing its diameter and the entrance position of the desolvation gas was shifted to the end of the desolvation region (near the ion gate). In addition, the ESI source (both needle and counter electrode) was positioned outside of the heating oven of the IMS. This modification made it possible to use the instrument at higher temperatures, and preventing needle clogging in the electrospray process. The ion mobility spectra of different chemical compounds were obtained. The resolving power and resolution of the instrument were increased by about 15-30% relative to previous design. In this work, the baseline separation of the two adjacent ion peaks of morphine and those of codeine was achieved for the first time with resolutions of 1.5 and 1.3, respectively. These four ion peaks were well separated from each other using carbon dioxide (CO(2)) rather than nitrogen as the drift gas. Finally, the analytical parameters obtained for ethion, metalaxyl, and tributylamine indicated the high performance of the instrument for quantitative analysis.

Direct determination of ammoniacal nitrogen in water samples using corona discharge ion mobility spectrometry.

In this study, direct determination of ammoniacal nitrogen residues in water samples using corona discharge ion mobility spectrometry (CD-IMS) was investigated. Pyridine was used as an alternate reagent gas to enhance selectivity and sensitivity of the method. The results indicate that the limit of detection (LOD) was about 9.2x10(-3)mugmL(-1) and the linear dynamic range was obtained from 0.03 to 2.00mugmL(-1). The relative standard deviation was about 11%. Furthermore, this method was successfully applied to the direct determination of ammoniacal nitrogen in river and tap water samples and the results were compared with the Nessler method. The comparison of the results validates the potential of the proposed method as an alternative technique for the analysis of the ammoniacal nitrogen in water samples.

Determination of veterinary drug residues in chicken meat using corona discharge ion mobility spectrometry.

A positive corona discharge ion mobility spectrometry (CD-IMS) has been evaluated for the determination of three residual veterinary drugs including furazolidone (FUR), chloramphenicol (CAP), and enrofloxacin (ENR) in poultry for the first time. Pretreatment included extraction of the drugs from samples and further treatment of the extracts by solid phase extraction (SPE) using C(18) sorbents. The limits of quantification (LOQs) were less than 20 microg kg(-1) for all compounds. The calibration plots for these compounds were linear to about three orders of magnitude. The validity of the method was demonstrated by the analysis of spiked and real samples.

Design for electrospray ionization-ion mobility spectrometry.

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.

Quantitative analysis of morphine and noscapine using corona discharge ion mobility spectrometry with ammonia reagent gas.

Morphine and noscapine were determined using corona discharge ion mobility spectrometry. The detection limits were 5.6x10(-11) and 6.7x10(-11)g for morphine and noscapine, respectively. The linear dynamic ranges of the calibration plots for the compounds were about three orders of magnitude. The method has also been successfully applied for simultaneous determination of the compounds using the standard addition method.

Analysis of 2,4,6-trinitrotoluene, pentaerythritol tetranitrate and cyclo-1,3,5-trimethylene-2,4,6-trinitramine using negative corona discharge ion mobility spectrometry.

In this study, the capability of negative corona discharge ion mobility spectrometry (IMS) for quantitative magnitude of several explosives including 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN) and cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) has been evaluated for the first time. The total current obtained with the negative corona discharge was about 100 times larger than that of IMS based on (63)Ni, which results in a lower detection limit and a wider linear dynamic range. The detection limits for PETN, TNT and RDX were 8x10(-11), 7x10(-11) and 3x10(-10) g, respectively. The calibration plots for these explosives showed linear dynamic ranges of about four orders of magnitude.