Development of Microchip Isotachophoresis Coupled with Ion Mobility Spectrometry and Evaluation of Its Potential for the Analysis of Food, Biological and Pharmaceutical Samples

Abstract

An online coupling of microchip isotachophoresis (µITP) with ion mobility spectrometry (IMS) using thermal evaporation interface is reported for the first time. This combination integrates preconcentration power of the µITP followed by unambiguous identification of trace compounds in complex samples by IMS. Short-chain carboxylic acids, chosen as model analytes, were first separated by the µITP in a discontinuous electrolyte system at pH 5–6, and subsequently evaporated at 130 °C during their transfer to the IMS analyzer. Various parameters, affecting the transfer of the separated sample components through the evaporation system, were optimized to minimize dispersion and loss of the analytes as well as to improve sensitivity. The following analytical attributes were obtained for carboxylic acids in the standard solutions: 0.1–0.3 mg L−1 detection limits, 0.4–0.9 mg L−1 quantitation limits, linear calibration range from the quantitation limit to 75 mg L−1, 0.2–0.3% RSD of the IMS response and 98–102% accuracy. The analytical potential of the developed µITP-IMS combination was demonstrated on the analysis of various food, pharmaceutical and biological samples, in which the studied acids are naturally present. These include: apple vinegar, wine, fish sauce, saliva and ear drops. In the real samples, 0.3–0.6% RSD of the IMS response and 93–109% accuracy were obtained.

Analytics, Properties and Applications of Biologically Active Stilbene Derivatives

“…The ionic substances included in the leading electrolytes should have the highest possible mobility, while the terminating electrolytes should have the lowest mobility (µLd > µanalyte > µTm). The masses and sizes of ions, ionic charges and radii, the ability to form complexes or dissociate, changes in pH during the process or pK values, as well as the viscosities of solvents and their dielectric constant affect the differences in electrophoretic mobilities of individual ionic substances [123,124].…”