在线固相萃取-超高效液相色谱-线性离子阱串联质谱法直接测定水中10种藻类毒素

建立了全自动在线固相萃取-超高效液相色谱-线性离子阱串联质谱法直接测定水中10种藻类毒素的方法.利用程序实现多次进样,通过在线固相萃取对藻类毒素进行富集,然后切换六通阀,将富集的目标物冲洗至分析柱进行分离后,进入线性离子阱质谱检测.10种藻类毒素在相应的浓度范围内线性关系良好,相关系数均大于0.99,检出限在0.0015~0.0050μg/L之间,3个浓度水平(0.02、0.10和1.00μg/L)的加标回收率为83.7%~98.5%.结果表明,在线固相萃取极大简化了前处理过程,线性离子阱串联质谱法提高了痕量藻类毒素测定的灵敏度,增强子离子扫描(EPI)谱库的建立为藻类毒素的确证提供保障.本方法适用于水体中多种藻类毒素的快速确证和定量测定.     

QuEChERS-超高效液相色谱-串联质谱法快速测定3种叶菜中矮壮素和丙环唑残留

建立了菜心、芥蓝和小白菜中矮壮素和丙环唑残留的分析方法.以QuEChERS法进行样品前处理,采用含1％ HAc的乙腈溶液提取,无水MgSO4、C18及PSA吸附剂净化,超高效液相色谱-串联质谱(UPLC-MS/MS)法测定.对提取溶剂、吸附剂和色谱柱的选择进行了研究探讨.结果表明矮壮素在1～1 000 μg/L、丙环唑在1～500 μg/L浓度范围内均有良好的线性关系.矮壮素和丙环唑的检出限分别为0.1 μg/kg和0.01 μg/kg;在0.010、0.10和0.50 mg/kg 3个添加浓度水平下,菜心、芥蓝和小白菜中矮壮素和丙环唑回收率为75.0％～96.2％;相对标准偏差为0.9％～8.3％;方法定量限为最低添加浓度0.010 mg/kg.该方法快速、简便、准确,满足叶菜中矮壮素和丙环唑残留分析的要求.     

Zinc sulfide nanosheets as a novel solid‐phase extraction material for flavonoids

As a novel solid‐phase extraction material, zinc sulfide nanosheets were prepared by a simple method and were used to extract flavonoids. We used scanning electron microscopy to show its nanosheet morphology and energy dispersive X‐ray spectroscopy and powder X‐ray diffraction to confirm its chemical and phase compositions. Coupled to a high‐performance liquid chromatography, the zinc sulfide nanosheets were packed into a microcolumn and were used to extract four model flavonoids to examine their extraction ability. The parameters of sample loading and elution were investigated. Under optimized conditions, the analytical method for flavonoids was established. For the method, wide linearities from 1 to 250 μg/L and low limits of detection from 0.25 to 0.5 μg/L were obtained. The relative standard deviations for single column repeatability and column to column reproducibility were less than 7.7 and 10.4%, respectively. The established method was also used to analyze two real samples and the recoveries from 88.7 to 98.2% further proved the reliability of the method. Moreover, the zinc sulfide nanosheets have good stability and that in one column can be reused for more than 50 times. This work proves that the prepared zinc sulfide nanosheets are a good candidate as the flavonoids sorbent.     

Chiral separation of novel diazenes on a polysaccharide‐based stationary phase in the reversed‐phase mode

Chiral high‐performance liquid chromatography separation of two recently synthesized liquid crystalline materials C1 and C2 was studied in the reversed‐phase mode. Both materials have an azo‐moiety and one chiral center in their molecular structures. They were available in racemic and pure S forms. For the enantiomeric separations, a Chiralpak AY‐RH stationary phase based on amylose tris(5‐chloro‐2‐methylphenylcarbamate) coated on 5 μm silica was used. The compounds were analyzed in both of their possible forms, the more thermodynamically stable E form and the labile Z form. The conditions and time scale of the UV‐induced E to Z transition were briefly evaluated. Under the optimized conditions, we were able to baseline separate S and R enantiomers of both of the studied materials not only in their E forms, but also in their Z forms. In comparison to the separation in the normal‐phase mode, which we have reported recently, the resolution in the reversed‐phase mode is significantly better. Interestingly, peak reversal was noticed for the S and R enantiomers when the separation was carried out with E versus Z forms of both compounds.     

Analysis of microcystins using high‐performance liquid chromatography and magnetic solid‐phase extraction with silica‐coated magnetite with cetylpyridinium chloride

Microcystins (MCs), produced by freshwater cyanobacteria, can be serious water pollutants, so it is important to monitor their concentration in drinking water. We have developed a method for rapid and accurate determination of microcystin levels in environmental water, using magnetic solid‐phase extraction and high‐performance liquid chromatography with UV detection. The magnetic composite material, which was combined with cetylpyridinium chloride, was prepared by hydrothermal synthesis. The optimal extraction of microcystins in water sample was achieved by optimizing the amount of adsorbent, time of adsorption, ratio of eluting solvent, and volume of eluent. Under the optimal conditions, the limit of detection of MC‐LR was 0.001 μg/L, and the limit of quantification was 0.0028 μg/L. The limit of detection of MC‐RR was 0.001 μg/L, and the limit of quantification was 0.003 μg/L. These values are far lower than those established by the International Health Organization for the maximum concentration of microcystins in drinking water. The magnetic solid‐phase extraction adsorbent used in this method has the advantages of simple preparation, low price, and easy solid–liquid separation, and it can be used for the rapid and sensitive monitoring of trace microcystins in environmental water samples.     

Quality assessment of crude and processed Arecae semen based on colorimeter and HPLC combined with chemometrics methods

Raw Arecae Semen, the seed of Areca catechu L., as well as Arecae Semen Tostum and Arecae semen carbonisata are traditionally processed by stir‐baking for subsequent use in a variety of clinical applications. These three Arecae semen types, important Chinese herbal drugs, have been used in China and other Asian countries for thousands of years. In this study, the sensory technologies of a colorimeter and sensitive validated high‐performance liquid chromatography with diode array detection were employed to discriminate raw Arecae semen and its processed drugs. The color parameters of the samples were determined by a colorimeter instrument CR‐410. Moreover, the fingerprints of the four alkaloids of arecaidine, guvacine, arecoline and guvacoline were surveyed by high‐performance liquid chromatography. Subsequently, Student's t test, the analysis of variance, fingerprint similarity analysis, hierarchical cluster analysis, principal component analysis, factor analysis and Pearson's correlation test were performed for final data analysis. The results obtained demonstrated a significant color change characteristic for components in raw Arecae semen and its processed drugs. Crude and processed Arecae semen could be determined based on colorimetry and high‐performance liquid chromatography with a diode array detector coupled with chemometrics methods for a comprehensive quality evaluation.     

Enantioseparation characteristics of the chiral stationary phases based on natural and regenerated chitins

Natural and regenerated chitins were derivatized with 3,5‐dimethyphenyl isocyanate. The corresponding chiral stationary phases were prepared by coating the resulting chitin derivatives on 3‐aminopropyl silica gel. The swelling capacity of the chitin derivatives, enantioseparation capability, as well as eluents tolerance of the chiral stationary phases were evaluated. The results demonstrated no remarkable difference in enantioseparation capability between natural and regenerated chitins based chiral stationary phases. The similar enantioseparation characteristics of two chiral stationary phases could be understood by comparing the IR spectra of related chitin derivatives. The one of the two chiral stationary phases prepared by coating the chitin derivative with a lower molecular weight generally provided better enantioseparations. All chiral stationary phases can work in 100% chloroform, 100% ethyl acetate, 100% acetone, and the mobile phases containing a certain amount of tetrahydrofuran. The chiral stationary phase prepared from the chitin derivative with the highest swelling capacity exhibited better enantioseparations than others. This chiral stationary phase was damaged by flushing with 100% tetrahydrofuran, however, the enantioseparation capability was recovered again after the column was allowed to stand for 1 month. Furthermore, the recovered chiral stationary phase provided better enantioseparations for some chiral analytes than before.     

Simultaneous determination of pyrametostrobin and its two metabolites in cucumber and soil using a quick,easy, cheap,effective, rugged,and safe method with HPLC–MS/MS

An easy, effective and sensitive analytical method for the simultaneous determination of a novel fungicide pyrametostrobin and its two metabolites pyrametostrobin‐M1 and pyrametostrobin‐M2 in cucumber and soil was developed using a quick, easy, cheap, effective, rugged, and safe method with high‐performance liquid chromatography and tandem mass spectrometry. The extraction solvent was acetonitrile, and cleanup sorbents were primary secondary amine and graphitized carbon black for cucumber samples and primary secondary amine for soil samples. The three target compounds were successfully separated between 3.2 and 3.9 min using a Waters CORTECS™ C₁₈ column connected to an electrospray ionization source. All the matrix‐matched samples at three fortified levels (10, 100 and 1000  μg/kg) provided satisfactory recoveries in the range of 78.8–93.8% with relative standard deviations below 6.9%. The limits of quantitation for the three compounds were below 0.183 μg/kg. The proposed method was validated by analyzing real samples.     

Chiral separation of quinolones by liquid chromatography and capillary electrophoresis

The quinolones are derivatives of oxoquinolines and mostly known for their antibacterial and antiviral activities. Many quinolones are chiral compounds having asymmetric centers and important due to their enantioselective biological activities. In order to study the biological activities of quinolone enantiomers, to control the manufacturing of homochiral drugs and to prepare necessary quantities of pure enantiomers for preclinical or clinical trials, respective chiral separation methods are urgently needed. In this context, the present review discusses chromatographic and electrophoretic methods for the enantioseparation of chiral quinolones and provides some useful information on their physical and pharmaceutical properties. The drawbacks of currently used techniques are revealed and ways to overcome them are outlined. Moreover, recommendations for an optimal choice of a separation protocol are given.     

Comparison of ultra high performance supercritical fluid chromatography,ultra high performance liquid chromatography,and gas chromatography for the separation of synthetic cathinones

A comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones has been conducted. Nine different mixtures of bath salts were analyzed in this study. The three different chromatographic techniques were examined using a general set of controlled synthetic cathinones as well as a variety of other synthetic cathinones that exist as positional isomers. Overall 35 different synthetic cathinones were analyzed. A variety of column types and chromatographic modes were examined for developing each separation. For the ultra high performance supercritical fluid chromatography separations, analyses were performed using a series of Torus and Trefoil columns with either ammonium formate or ammonium hydroxide as additives, and methanol, ethanol or isopropanol organic solvents as modifiers. Ultra high performance liquid chromatographic separations were performed in both reversed phase and hydrophilic interaction chromatographic modes using SPP C18 and SPP HILIC columns. Gas chromatography separations were performed using an Elite‐5MS capillary column. The orthogonality of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography was examined using principal component analysis. For the best overall separation of synthetic cathinones, the use of ultra high performance supercritical fluid chromatography in combination with gas chromatography is recommended.