Application of the poly (POSS-octavinyl-co-N-methylacetamide-co-divinylbenzene) solid extraction column in analyzing preservatives.

In this study, a special poly solid-phase extraction (in-tube SPE) column consisting of poly (POSS-octavinyl-co-N-methylacetamide-co-divinylbenzene) [poly (POSS-OS-co-DVB-co-NMA)] was prepared based on the chemical structure of the preservatives, and was used as medium for extraction analysis in combination with UPLC. The composition of polymer SPE was optimized and characterized; good scanning electron microscopy (SEM) properties and satisfactory porosity were obtained with 30% monomer (POSS-OS:DVB:NMA = 2 wt%:13 wt%:15 wt%) and 70 wt% porogenic solvent (PEG20000:DMSO:ACN = 10 wt%:50 wt%:10 wt%). The experimental parameters of the in-tube SPE-UPLC analysis were optimized systematically. Then, the in-tube SPE-UPLC method was applied for analyzing the beverage sample, and correlation coefficients (R2) > 0.99 were obtained for the linear relationship within limits of 0.1~5.0 µg mL-1. Excellent extraction efficiency, good precision, and satisfactory limit of detection sensitivity between 0.03 and 0.10 µg mL-1 were obtained. The recovery ranged from 71.5 to 88.0%, with RSD ≤ 6.1%. Furthermore, the proposed method has the features of simple sample pretreatment, high throughput, rapid analysis, cost-effectiveness, and satisfactory sensitivity. Hence, the developed in-tube SPE-UPLC method based on the poly (POSS-OS-co-DVB-co-NMA) SPE column can be potentially used for simple and sensitive detection of preservatives.

A TIMS-TOF mass spectrometry study of disaccharides from in situ ESI derivatization with 3-pyridinylboronate.

3-Pyridinylboronate, a zwitterionic boronic acid, displayed effective in situ ESI for reversible covalent tagging of saccharides in both cation and anion modes. The ion mobilities of thus-generated ions were examined with the Bruker timsTOF fleX instrument. Nine disaccharides were examined using this method. They have identical mass-to-charge ratios, differing only in monomer compositions, regio-linkages, and anomeric configurations (α or ß). The IMS separations of the disaccharides from this method were compared with those from sodium adducts reported in the literature. The differentiation effects of this method on the disaccharide isomers were increased on average by an order of magnitude. Using this method, all the pairs of disaccharides selected from nine isomers were completely identified by comparing the mobility spectra of single-tagged and double-tagged ions.

On a separation voltage polarity switching transient capillary isotachophoresis method for higher sample loading capacity and better separation performance.

Limited sample loading capacity is one of the major reasons that prevents the utility of capillary electrophoresis (CE) as a routine separation method as compared to liquid chromatography (LC). In our previous study, separation voltage polarity switching transient capillary isotachophoresis (PS-tCITP) was proposed. Both sample loading capacity and separation resolution could be improved using a single PS-tCITP instead of routine transient capillary isotachophoresis (tCITP). In this study, a detailed investigation on the optimization strategy of the PS-tCITP method was performed systematically. A possible mechanism of sample preconcentration in multiple PS-tCITP was first proposed to better understand the multiple PS-tCITP process. Several optimization experiments were then performed, including single PS-tCITP, paused PS-tCITP and multiple PS-tCITP, sequentially using a mixture of five peptides. By selecting an optimum polarity switching time, sample loading capacity of 100% capillary volume could be achieved in a single PS-tCITP. Introducing an additional pause between each polarity switching in a single PS-tCITP further improved the separation resolution. Experimental results showed a baseline separation of five selected peptide standards at 100% sample loading volume using a 100 min pause in a single PS-tCITP. To further improve separation efficiency while still maintaining 100% sample loading volume, a multiple PS-tCITP technique was developed through this study. Compared to the separation performance of the optimal single PS-tCITP at 100% sample loading volume with a 10 min pause, the separation window was improved by 54% and the peak capacity was improved by 48% in the optimal four PS-tCITP with the same sample loading volume and pause.

Structural resolution of disaccharides through halogen anion complexation using negative trapped ion mobility spectrometry.

Carbohydrates are an indispensable part of early life evolution. The determination of their structures is a key step to analyze their critical roles in biological systems. A variation of composition, glycosidic linkage, and (or) configuration between carbohydrate isomers induces structure diversity and brings challenges for their structural determination. Ion mobility spectrometry (IMS), an emerging gas-phase ion separation technology, has been considered as a promising tool for performing carbohydrate structure elucidation. In this work, eight disaccharides were analyzed by trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) in the negative ion mode as the complexed form of [M + X]-, where M = disaccharide, and X = Cl, Br, and I. As compared to the positive ion analysis of the selected disaccharide in a sodiated form, a reversal charge state provided the ability to eliminate or even reverse the collision cross section (CCS) difference between disaccharide isomers. By the combination of TIMS analysis and the calculation of density functional theory, the only observed two conformers of ions [lactulose + I]- may result from different adduction sites for an iodide anion. Based on the comparison of different halogen adducts, the [M + I]- ion form exhibited more powerful ability for isomeric disaccharide differentiation with an average resolution (RP-P) of 1.17, which results in a 34.5% improvement as compared to the corresponding chloride adducts. This result indicates that the use of negative charge states, especially the complexation of an iodide anion, could be a supplemental strategy to commonly used positive ion analysis for carbohydrate separation.