查看更多>>摘要：? 2022Solving and/or evaluating given problems or decision making in place and in real time is a goal of the analytical chemistry science. In this context, the performance of a commercial portable miniaturized liquid chromatograph (minLC) with LED UV (255 nm) detector was compared with those provided by two lab minLCs (capillary and nano) coupled on-line to in-valve in-tube solid phase microextraction (IT-SPME) with diode array detector (DAD). In addition, responses of the portable LC for in-field analysis in several conditions were tested. Besides, two evaluation tools, BETTER criteria for portability and HEXAGON pictogram for sustainability and greenness were applied for comparison purposes. The benchtop LCs provided lower limits of detection (LODs) as expected, in the order of low μg L?1, than those achieved by the portable LC, with LODs around mg L?1 for compounds covering several polarities (logKow between -1.72 and 3.82). The used portable LC gave excellent resolution, reducing the analysis time and being the consumption of solvents negligible. As a practical application, fruit washing residual waters, which contained a suitable level of concentrations of several biocides for employing the portable minLC, were analyzed and quantified from the three minLCs as a proof of concept with comparable results.
查看更多>>摘要：? 2022The function of mutual information (FUMI) theory proposes that it is possible to obtain a relative standard deviation (RSD) of the peak area of an analyte from baseline noises and a signal on a single chromatogram when the analyte concentrations are proportional to their peak areas. In this study, we demonstrate that the FUMI theory using noise parametrization by the difference method is applicable for the evaluations of repeatability and detection limit (DL) in high-performance liquid chromatography with electrochemical detection (HPLC-ECD). HPLC-ECD for determining vincristine (VCR) was taken as an example, and VCR was detected on a glassy carbon surface at +0.8 V vs. Ag/AgCl. In the comparisons of precision profiles (plots of RSD of peak area against concentrations of an analyte), the stochastically estimated RSD (N = 1) by the FUMI theory fell within the 95% confidence intervals of statistically estimated RSD (N = 6) by repetitive measurements. Furthermore, the DL obtained by the FUMI theory (3.3×SD) was almost the same value as that by the signal-to-noise ratio (S/N) = 3. Moreover, we introduced a manual method for signal-noise resolution to obtain noise parameters from a chromatogram with low-pass Bessel filter processing. In conclusion, our results show that the FUMI theory using noise parametrization by the difference method can be applied to the evaluations of repeatability and DL in HPLC-ECD without and with a low-pass Bessel filter.
查看更多>>摘要：? 2022 Elsevier B.V.We have recently demonstrated the remarkable performances of liquid chromatography (LC) using 2-μm-i.d. open tubular (OT) columns; peak capacities of 2000+ within less than three hours have been routinely obtained at an elution pressure of around 100 bar or less. However, only a small number of researchers have been involved in the research in this area; part of the reason is due to the issues associated with setting up open tubular liquid chromatography (OTLC) systems. While cautions should be taken here and there in carrying out separations, but none of the issues can inhibit us from performing OTLC separations. Therefore, we feel it desirable to write a tutorial on how to build an OTLC system. In this tutorial, we introduce the key components for the apparatus, how to construct/prepare them or where to purchase them, and how to assemble them together into a complete system. We further discuss the advantages and disadvantages of the system; we mention particularly the practical issues from using the narrow (2-μm-i.d.) columns and how to mitigate these issues.
查看更多>>摘要：? 2022 Elsevier B.V.A magnetic covalent organic framework material (M-COF) with conjugated structure, high surface area and good chemical stability, was prepared for the adsorption of nine organophosphorus pesticides (OPPs). The extraction recovery of the M-COF for nine target OPPs were 64–91%, and the extraction dynamics was relatively fast. Based on it, a method by combining magnetic solid phase extraction (MSPE) with sweeping micellar electrokinetic chromatography (MEKC) was developed for the determination of nine OPPs in environmental water and atmospheric particle samples. The enrichment factor (EF) of MSPE-sweeping-MEKC for nine target OPPs are 1740 and 3626 times, with the limits of detection of 0.78–2.33 μg L?1. This method was used to analyze nine OPPs in environmental samples, and the recovery of nine OPPs in spiked East Lake water, Triangle Lake water, the extracts of PM2.5, PM10 and TSP were 81.0–111%, 83.6–111%, 83.1–117%, 81.7–114% and 80.2–114%, respectively. The method is sensitive, rapid and simple, and can be used for the quantification of interest OPPs in environmental samples with complex matrix.
查看更多>>摘要：? 2022 Elsevier B.V.Compound structure change of the template molecule from rutin samples might affect the selectivity and adsorption of molecularly imprinted polymers based on magnetic halloysite nanotubes (MHNTs@MIPs). In the present study, not only MHNTs@MIPs were successfully characterized by TEM, SEM, EDS, FT-IR, TGA and VSM, but related compounds and potential degradation factors of template molecule rutin were also investigated in the polymerization and elution process of MHNTs@MIPs by high-performance liquid chromatography together with photodiode array and tandem mass spectrometry (HPLC-PDA-MS/MS) in negative ion mode. Nine flavonol components were detected in rutin active pharmaceutical ingredient samples, such as rutin, isoquercetrin, kaempferol-3-O-rutoside, isorhamnetin-3-O-rutoside, quercetin, kaempferol, isorhamnetin and two unknown triglycosides. Under acidic, basic, oxidative and solvent conditions, two common degradants with negative ESI-MS ions at m/z 317 and 349 were found. Meanwhile, protocatechuic acid and methyl ester were also observed as two characteristic oxidative degradants. Compared to above degradation results, rutin-dimethylsulfoxide adduct and oxidative degradant were observed in the synthesis supernatant, which demonstrated that appropriate solvents and strict control of the oxygen level were critical in the synthesis process. Therefore, degradation studies provide a solid foundation for the optimization of MHNT@MIP synthesis with rutin as a template, which can be potentially applied to other templates for further material performance investigation.
查看更多>>摘要：? 2022 Elsevier B.V.Adsorption and chromatographic properties of oxidized and hydrogenated ‘high pressure and high temperature’ synthesised diamond (HPHT) are studied using high-performance liquid chromatography. The retention factors of organic cation (benzyltributylammonium chloride), weak base (aniline), weak acid (benzoic acid), strong acid (benzenesulfonic acid), hydrophobic toluene, and hydrophilic uracil are obtained at varied pH, organic solvent content, and ionic strength of mobile phase. Both adsorbents exhibited moderate polarity with a mixed-mode retention mechanism with a combination of electrostatic, hydrophobic and hydrophilic interactions. Unexpectedly, hydrogenated HPHT revealed significant anion-exchange properties under acidic conditions and cation-exchange properties under alkaline conditions, while only cation-exchange selectivity was noted for oxidized HPHT across the enntire pH range. The retention factors obtained for a set of model compounds including n-alkyl-, polymethyl-, nitro- and halogenated benzenes correlated well with their hydrophobicity (logP) values. The thermal stability of the adsorbent and immutability of retention mechanisms involved was confirmed by linear van't Hoff plots for the investigated compounds.
查看更多>>摘要：? 2022 Elsevier B.V.Polybrominated diphenyl ethers (PBDEs) are commonly used as flame retardants in daily household products and have been found to be detrimental to human and animal health. Being highly stable, accumulation can take place easily in the environment. In our previous studies, an innovative sample preparation method named miniscale liquid-liquid extraction (msLLE) coupled to full evaporation dynamic headspace (FEDHS) concentration was developed, and then successfully coupled to an online water sampling system, allowing full automation from water sampling to sample preparation, sample detection and analysis. In the present work, the fully automated online sampling-quickMix-assisted-msLLE-FEDHS platform was optimized and applied to PBDEs in environmental aqueous samples. The online sampling system was set up with a modified sample vial (to have an inlet and outlet), two tubings and a peristaltic pump which was programmed to control the water flow into and out of the vial. After adding 2 mL of the extractant (n-hexane), and 7 mL of sampled water to a 10-mL vial, msLLE was enabled, assisted with a quickMix module to ensure a quick and efficient mode of mixing between the organic and aqueous phases. The organic extract was then transferred to the FEDHS setup for selective trapping and concentration of the PBDEs, while the solvent was removed. The trap consisted of Tenax TA adsorbent, which has favorable π-interaction with the PBDEs but not with n-hexane. Subsequently, the adsorbent tube was automatically transported to the injector of the gas-chromatography mass-spectrometric (GC–MS) system to thermally desorb the trapped PBDEs for detection and analysis. The optimized methodology was found to achieve low limits of detection (0.0031 to 0.018 μg/L) with good linearity (r2 ≥ 0.9932) and satisfactory absolute extraction recoveries (between 61.4% and 80.9%). The analysis of PBDEs in spiked genuine water sample attained satisfactory and repeatable relative recoveries (between 106.1% and 132.6% with%RSDs ≤ 8.6%).
查看更多>>摘要：? 2022This work demonstrates the potential of two-dimensional liquid chromatography (2D-LC) to increase the resolution capacity of multiple pesticides in a single analysis of samples that contain both chiral and achiral compounds. The setup is based on the combination of a chiral column in the first dimension and an achiral column in the second dimension using the on-line full comprehensive mode (LC × LC). This method was optimized for the separation of 24 pesticides (17 chiral and 7 achiral). The 2D-LC system was built with an active flow splitter pump in order to easily adjust the volume of sample transferred to the second dimension and to select and optimize independently the flow rate in the first dimension. The first-dimension optimization involved the comparison of enantioresolution abilities of three different polysaccharides chiral stationary phases as well as different elution conditions, while in the second-dimension parameters like stationary phase and organic modifier were explored. Other experimental variables that influence the two-dimensional peak capacity (orthogonality, sampling frequency, shift gradients, etc.) are discussed.
查看更多>>摘要：? 2022 Elsevier B.V.An effective and sensitive two-step stacking of arsenic species by electrokinetic injection and micelle-to-solvent stacking (MSS) using zwitterionic surfactant 3-(N,N-dimethylpalmitylammonio) propane sulfonate was successfully developed in a co-electro-osmotic flow (co-EOF) capillary zone electrophoresis (CZE). The fused silica capillaries were coated with 1% hexadimethrine bromide solution to satisfy the condition of the same EOF direction between the test anions and capillary. The background solution was 100 mM borax buffer (pH 9.2). The proposed method was performed by a CZE system equipped with a diode array detector, and the detection wavelength was monitored at 192 nm. The separation voltage was ?20 kV. The group of micelles and target analytes was stacked by field-enhanced sample injection at ?10 kV for 180 s. The second stacking step used 60% MeOH to serve as an organic solvent where the analytes were brought by the micelles to the MSS boundary. The enrichment factors of As(Ⅴ), As(Ⅲ), disodium methyl arsonate hexahydrate (MMA), and dimethylarsinic acid (DMA) were 1230, 840, 3820, and 1450, respectively, compared to typical injections in CZE. The limits of detection (S/N = 3) ranged from 0.382 to 0.911 ng mL?1. The intracapillary repeatabilities (%RSD, n = 3) were 0.5–1.0% for migration time and 0.3–0.7% for peak areas. The technology of two-step stacking by MSS in co-EOF CZE together with a simple extraction procedure for As(Ⅴ), As(Ⅲ), MMA and DMA were demonstrated in kelp and rice samples.
查看更多>>摘要：? 2022 Elsevier B.V.Natural products are rather complex samples containing a large number of compounds ranging from polar to nonpolar, small molecules to macromolecules, as well as numerous homologs/analogs with quite similar structures, which create great opportunities and treasures for discovery of bioactive drugs. For the purpose of better understanding the complex natural products and controlling their qualities, powerful analytical techniques for adequately separating chemical constituents and tracking potentially bioactive components are quite essential. Here, a design concept of bidirectional β-cyclodextrin (β-CD)–modified chromatographic stationary phase toward separation of bufadienolides extracted from toad is proposed. Bufadienolides could be divided into two classes: toad venom ligand (AAUBs) and toad toxin (AACBs) with remarkable differences in structures and polarity. The hydrophobic cavity of β-CD can encapsulate the steroid part of AACBs while the hydroxyls exposed on the β-CD surface have strong hydrophilic interactions with the arginine part of AACBs. Isothermal titration calorimetry and hydrogen nuclear magnetic resonance titration experiment further validate the rationality of this design. Furthermore, the β-CD-based stationary phase can be used as a hydrophilic material to construct a HILIC × RPLC 2D separation mode for the separation of AACBs, also works as a reverse phase material to construct a RPLC × RPLC 2D separation mode for the separation of AAUBs with good orthogonality. This study will open an avenue and provide a novel insight for high-efficiency two-dimensional separation of natural products.
NSTL
Elsevier