Two-dimensional liquid chromatography (2D-LC) has gained increased attention because of its high peak capacity for separating complex samples. However, preparative 2D-LC aimed at isolating compounds is significantly different compared with one-dimensional liquid chromatography (1D-LC) in terms of method development and system configuration; thus, it is less developed than its analytical counterpart. The use of 2D-LC in large-scale product preparation has rarely been reported. Hence, a preparative 2D-LC system was developed in this study. The system was composed of one set of preparative LC modules as a separation system, with a dilution pump, switch valves, and trap column array as the interface, to enable the simultaneous isolation of several compounds. Tobacco was used as a sample, and the developed system was applied to isolate nicotine, chlorogenic acid, rutin, and solanesol. The chromatographic conditions were developed by investigating the trapping efficiency of different types of trap column packings, and chromatographic behaviors under different overload conditions. The four compounds were isolated in one 2D-LC run with high purity. The developed system features low cost because it employs medium-pressure isolation, excellent automation owing to its use of an online column switch, high stability, and capability for large-scale production. The isolation of chemicals from tobacco leaves as pharmaceutical raw materials could aid in the development of the tobacco industry and promote the local agricultural economy.
Pesticides are widely used in most agricultural areas to protect food crops but adversely affect ecosystems and human beings. Pesticides have attracted great public concern due to their toxic properties and ubiquitous occurrence in the environment. China is one of the largest users and producers of pesticides globally. However, limited data are available on pesticide exposure in humans, which warrants a method for quantification of pesticides in human samples. In the present study, we validated and developed a comprehensive and sensitive method for the quantification of two phenoxyacetic herbicides, two metabolites of organophosphorus pesticides and four metabolites of pyrethroid pesticides in human urine using 96-well plate solid phase extraction (SPE) coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). For this purpose, a systematic optimization of the chromatographic separation conditions and MS/MS parameters was conducted. Six solvents were optimized for the extraction and clean-up of human urine samples. The targeted compounds in the human urine samples were well separated within 16 min in one analytical run. A 1 mL aliquot of human urine sample was mixed with 0.5 mL sodium acetate buffer (0.2 mol/L) and hydrolyzed by β-glucuronidase enzyme at 37 ℃ overnight. The eight targeted analytes were extracted and cleaned using an Oasis HLB 96-well solid phase plate and eluted with methanol. The separation of the eight target analytes was performed on a UPLC Acquity BEH C18 column (150 mm×2.1 mm, 1.7 μm) with gradient elution using 0.1% (v/v) acetic acid in acetonitrile and 0.1% (v/v) acetic acid in water. The analytes were identified using the multiple reaction monitoring (MRM) mode under negative electrospray ionization (ESI-) and quantified by isotope-labelled analogs. Para-nitrophenol (PNP), 3,5,6-tricholor-2-pyridinol (TCPY) and cis-dichlorovinyl-dimethylcyclopropane carboxylic acid (cis-DCCA) exhibited good linearities ranging from 0.2 to 100 μg/L, and 3-phenoxy benzoic acid (3-PBA), 4-fluoro-3-phenoxy benzoic acid (4F-3PBA), 2,4-dicholorphenoxyacetic acid (2,4-D), trans-dichlorovinyl-dimethylcyclopropane carboxylic acid (trans-DCCA) and 2,4,5-tricholorphenoxyacetic acid (2,4,5-T) showed linearity ranging from 0.1 to 100 μg/L with correlation coefficients all above 0.9993. Method detection limits (MDLs) and method quantification limits (MQLs) of targeted compounds were in the range of 0.02 to 0.07 μg/L and 0.08 to 0.2 μg/L, respectively. The spiked recoveries of target compounds at three levels of 0.5, 5 and 40 μg/L were 91.1% to 110.5%. The inter- and intra-day precisions of targeted analytes were 2.9% to 7.8% and 6.2% to 10%, respectively. This method was applied to the analysis of 214 human urine samples across China. The results showed that all the targeted analytes, except 2,4,5-T, were detected in human urine. The detection rates of TCPY
An improved solid phase extraction (SPE)-high performance liquid chromatography method was established to determine 15 carbonyl compounds, namely, formaldehyde (FOR), acetaldehyde (ACETA), acrolein (ACR), acetone (ACETO), propionaldehyde (PRO), crotonaldehyde (CRO), butyraldehyde (BUT), benzaldehyde (BEN), isovaleraldehyde (ISO), n-valeraldehyde (VAL), o-methylbenzaldehyde (o-TOL), m-methylbenzaldehyde (m-TOL), p-methylbenzaldehyde (p-TOL), n-hexanal (HEX), and 2,5-dimethylbenzaldehyde (DIM), in soil. The soil was ultrasonically extracted with acetonitrile, and the extracted samples were derivatized with 2,4-dinitrophenylhydrazine (2,4-DNPH) to generate stable hydrazone compounds. The derivatized solutions were cleaned using an SPE cartridge (Welchrom® BRP) packed with N-vinylpyrrolidone/divinylbenzene copolymer. Separation was performed on an Ultimate® XB-C18 column (250 mm×4.6 mm, 5 μm), isocratic elution was performed with acetonitrile-water (65∶35, v/v) as the mobile phase, and detection was performed at a wavelength of 360 nm. The 15 carbonyl compounds in the soil were then quantified using an external standard method. The proposed method improves the sample processing method described in the environmental standard HJ 997-2018: Soil and sediment-Determination of carbonyl compounds-High performance liquid chromatography. A series of experiments revealed the following optimal conditions for soil extraction: acetonitrile as the extraction solvent, extraction temperature of 30 ℃, and extraction time of 10 min. The results showed that the purification effect of the BRP cartridge was significantly better than that of the conventional silica-based C18 cartridge. The 15 carbonyl compounds showed good linearities, and all correlation coefficients were above 0.996. The recoveries ranged from 84.6% to 115.9%, the relative standard deviations (RSDs) ranged from 0.2% to 5.1%, and the detection limits were 0.02-0.06 mg/L. The method is simple, sensitive, and suitable for the accurate quantitative analysis of the 15 carbonyl compounds in soil specified in HJ 997-2018. Thus, the improved method provides reliable technical support for studying the residual status and environmental behavior of carbonyl compounds in soil.
The kidney-shaped, red-colord fruit from the plant, Schisandra chinensis (Turcz.) Baill, which belongs to the Schisandraceae family, is among the most popular remedies used in traditional Chinese medicine. The English name of the plant is "Chinese magnolia vine". It has been used in Asia since ancient times to treat a variety of ailments, including chronic cough and dyspnea, frequent urination, diarrhea, and diabetes. This is because of the wide range of bioactive constituents, such as lignans, essential oils, triterpenoids, organic acids, polysaccharides, and sterols. In some cases, these constituents affects the pharmacological efficacy of the plant. Lignans with a dibenzocyclooctadiene-type skeleton are considered to be the major constituents and main bioactive ingredients of Schisandra chinensis. However, because of the complex composition of Schisandra chinensis, the extraction yields of lignans are low. Thus, it is particularly important to study pretreatment methods used during sample preparation for the quality control of traditional Chinese medicine. Matrix solid-phase dispersion extraction (MSPD) is a comprehensive process involving destruction, extraction, fractionation, and purification. The MSPD method is simple, it requires only a small number of samples and solvents, it does not require any special experimental equipments or instruments, and it can be used to prepare liquid, viscous, semi-solid, solid samples. In this study, a method combining matrix solid-phase dispersion extraction with high performance liquid chromatography (MSPD-HPLC) was established for the simultaneous determination of five lignans (schisandrol A, schisandrol B, deoxyschizandrin, schizandrin B, and schizandrin C) in Schisandra chinensis. The target compounds were separated on a C18 column with a gradient elution of 0.1% (v/v) formic acid aqueous solution and acetonitrile as the mobile phases, and detection was performed at a wavelength of 250 nm. First, the effects of 12 adsorbents, including silica gel, acidic alumina, neutral alumina, alkaline alumina, Florisil, Diol, XAmide, Xion, and the inverse adsorbents, C18, C18-ME, C18-G1, and C18-HC, on the extraction yields of lignans were investigated. Second, effects of the mass of the adsorbent, the type of eluent, and volume of eluent on the extraction yields of lignans were investigated. Xion was chosen as an adsorbent for MSPD-HPLC analysis of lignans from Schisandra chinensis. Optimization of the extraction parameters showed that the MSPD method had a high lignan extraction yield with Schisandra chinensis powder (0.25 g) as a fixed value, Xion as the adsorbent (0.75 g), and methanol as the elution solvent (15 mL). Analytical methods were developed for five lignans from Schisandra chinensis and these methods showed good linearity (correlation coefficients (R2)≥ 0.9999) for
The detection of paralytic shellfish toxins in human biological matrices is important for the diagnosis and treatment of food poisoning caused by them. An ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was established for the determination of 14 paralytic shellfish toxins in plasma and urine. The effect of solid phase extraction (SPE) cartridges was also investigated and the pretreatment and chromatographic conditions were optimized. Under these optimal conditions, 0.2 mL water, 0.4 mL methanol, and 0.6 mL acetonitrile were successively added to plasma and urine samples for extraction. The supernatants from plasma extraction were subjected to an UHPLC-MS/MS analysis, whereas the supernatants from urine extraction were further purified using polyamide (PA) SPE cartridges and then analyzed by UHPLC-MS/MS. Chromatographic separation was conducted on a Poroshell 120 HILIC-Z column (100 mm×2.1 mm, 2.7 μm) with a flow rate of 0.5 mL/min. The mobile phase was 0.1% (v/v) formic acid aqueous solution containing 5 mmoL/L ammonium formate and acetonitrile containing 0.1% (v/v) formic acid. The analytes were detected in the multiple reaction monitoring (MRM) mode after being ionized by an electrospray ion (ESI) in positive and negative modes. Quantitation of the target compounds was performed using the external standard method. Under the optimal conditions, the method showed good linearity in the range of 0.24-84.06 μg/L, with correlation coefficients greater than 0.995. The limits of quantification (LOQs) for the plasma and urine samples were 1.68-12.04 ng/mL and 4.80-34.4 ng/mL, respectively. The average recoveries for all the compounds were 70.4%-123.4% at spiked levels of 1, 2, and 10 times the LOQs, the intra-day precisions were 2.3%-19.1% and the inter-day precisions were 5.0%-16.0%. The established method was used to determine the target compounds in the plasma and urine from mice intraperitoneally injected with 14 shellfish toxins. All 14 toxins were detected in the 20 urine and 20 plasma samples, with contents of 19.40-55.60 μg/L and 8.75-13.86 μg/L, respectively. The method is simple, sensitive, and only requires a small amount of sample. Therefore, it is highly suitable for the rapid detection of paralytic shellfish toxins in plasma and urine.
Quaternary ammonium compounds (QACs) are a class of cationic surfactants that can be used as the main active ingredient of disinfectants. The increased use of QACs is concerning as exposure from inhalation or ingestion to these compounds that has been associated with adverse effects on the reproductive and respiratory systems. Humans are exposed to QACs primarily by food consumption and inhalation of air. QAC residues pose significant threats to public health. Given the importance of assessing potential residue levels for QACs in food, therefore, a method was developed for the simultaneous detection of six common QACs and one emerging QAC (Ephemora) in frozen food by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) coupled with the modified QuEChERS method. The main factors governing the response, recovery, and sensitivity of the method, including extraction solvents, types and dosages of adsorbents, apparatus conditions, and mobile phases, were optimized in the course of sample pretreatment and instrument analysis. QAC residues in frozen food were extracted using 20 mL methanol-water (90∶10, containing 0.5% formic acid) for 20 min by the vortex shock method. The mixture was ultrasonicated for 10 min and centrifuged at 10000 r/min for 10 min. A 1-mL aliquot of the supernatant was transferred to a new tube and purified using 100 mg of PSA adsorbents. After mixing and centrifugation at 10000 r/min for 5 min, the purified solution was analyzed. Target analytes were separated on an ACQUITY UPLC BEH C8 chromatographic column (50 mm×2.1 mm, 1.7 μm) at a column temperature of 40 ℃ and a flow rate of 0.3 mL/min. The injection volume was 1 μL. Gradient elution was performed using methanol and 5 mmol/L ammonium acetate solution as the mobile phases. Multiple reaction monitoring (MRM) was conducted in the positive electrospray ionization (ESI+) mode. The matrix-matched external standard method was used to quantify seven QACs. The optimized chromatography-based method completely separated the seven analytes. Good linear relationships were obtained for the seven QACs in the range of 0.1-100.0 ng/mL. The correlation coefficient (r2) ranged from 0.9971 to 0.9983. The limits of detection and limits of quantification ranged from 0.5 to 1.0 μg/kg and 1.5 to 3.0 μg/kg, respectively. Accuracy and precision were determined by spiking salmon and chicken samples with 3.0, 10.0, and 100.0 μg/kg of analytes, in compliance with the current legislation, with six replicates per determination. The average recoveries of the seven QACs ranged from 65.4% to 101%. The relative standard deviations (RSDs) were between 0.64% and 16.8%. Matrix effects of the analytes were between -27.5% and 33.4% in salmon and chicken samples after purifying using PSA. The developed method was applied to the determination of seven QACs in rural samples. QACs were detected in only one sample; the level did not exceed European
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：