List of Issues

Chinese Journal of Chromatography
2018, Vol. 36, No. 10
Online: 08 October 2018

Previous Issue    Next Issue



For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Select

Volume 36, Number 10 Content 2018, 36 (10):  0-0.  Abstract ( 182 )   PDF (5592KB) ( 34 )

Select

Advancements in complex target systematic evolution of ligands by exponential enrichment WU Zhenning, XUE Shujiang, YANG Yongjie 2018, 36 (10):  947-951.  DOI: 10.3724/SP.J.1123.2018.05019 Abstract ( 330 )   [Full Text(HTML)] () PDF (832KB) ( 110 )   Nucleic acid aptamers are single-stranded oligonucleotides that possess high affinity and specificity. They are also known as "chemical antibodies" and have a wide range of applications. Aptamers are usually generated by an in vitro process termed as systematic evolution of ligands by exponential enrichment (SELEX). Aptamers are often selected by employing purified soluble protein targets. However, the process of protein purification can be complex and laborious. Furthermore, several protein targets, such as low abundance proteins found in serums and membrane proteins found in cells, are difficult to purify. Complex target SELEX can avoid the purification step and maintain the native state of the target proteins. Even in the absence of detailed composition and characterization of a complex target, complex target SELEX can be performed with a high throughput for obtaining specific aptamers. In this study, complex target SELEX taken unpurified biological samples as targets will be described in order to provide a new idea for researchers screening aptamers.

Select

Advances on genotoxic impurities of sulfonate esters in pharmaceuticals LIU Xuewei, LI Cheng, HAN Haiyun, ZHANG Wenpeng, CHEN Dongying 2018, 36 (10):  952-961.  DOI: 10.3724/SP.J.1123.2018.05004 Abstract ( 734 )   [Full Text(HTML)] () PDF (995KB) ( 402 )   This article reviews the refinement of regulatory guidelines and progress of research on the control of genotoxic impurities in pharmaceuticals in the last decade. It outlines advances in the regulatory requirements for genotoxic impurities from strict avoidance to the currently accepted concept of threshold of toxicological concern (TTC), which is based on risk control considerations. Specific control limits, which are required by predominant administrative regulatory agencies, such as U. S. Food and Drug Administration (FDA), European Medicines Agency (EMA) and the international conference on harmonisation of technical requirements for registration of pharmaceuticals for human use (ICH), etc. Sulfonate esters, an important class of potential genotoxic impurities, are usually generated by side-reactions between sulfonic acids or their derivatives and relative low molecular mass alcohols, such as methanol, ethanol, and isopropanol. The resulting sulfonate esters are characterized with diverse chemical structures. Reaction mechanisms of the formation of sulfonate esters and various strategies to control them have been schematically described. A detailed summary has been given for the analytical methodology developed using high performance liquid chromatography (HPLC) and gas chromatography (GC) to determine trace amounts of sulfonate esters in pharmaceuticals. Furthermore, we have comprehensively discussed the options for the chromatographic methods, sample pretreatments, and derivatization methods, as well as each method's sensitivity and recovery at trace level. This review intended to provide constructive suggestions for the rational control of sulfonate esters in pharmaceuticals to ensure their clinical safety.

Select

Recent advances in the application of headspace gas chromatography-mass spectrometry ZHANG Xi, LIU Weilun, LU Ya'nan, LÜ Yunkai 2018, 36 (10):  962-971.  DOI: 10.3724/SP.J.1123.2018.05013 Abstract ( 1055 )   [Full Text(HTML)] () PDF (948KB) ( 724 )   As a sample preparation technique without extraction by organic solvent, headspace analysis is usually combined with gas chromatography-mass spectrometry (GC-MS) to analyze volatile organic compounds in complex matrices. Headspace gas chromatography-mass spectrometry (HS-GC-MS) is a fast, efficient, green, and sensitive technique, and thus it plays an important role in routine analysis. A brief overview of static headspace, dynamic headspace, headspace solid-phase microextraction and GC-MS is provided, followed by the impact of the analysis system and the optimization process. According to the matrix type classification, the application of HS-GC-MS in the analysis of food samples, environment samples, biology samples, etc. is reviewed. This report clearly indicates that the ongoing research on HS-GC-MS is active and new applications are emerging. It has significant prospects for the analysis of volatile organic compounds.

Select

Preparation of macroporous silica and its application on polysaccharide derivative based chiral stationary phase WU Haibo, XUE Xingya, LI Kuiyong, ZHOU Yongzheng 2018, 36 (10):  972-978.  DOI: 10.3724/SP.J.1123.2018.05007 Abstract ( 348 )   [Full Text(HTML)] () PDF (5106KB) ( 118 )   In order to prepare 100-nm macroporous silica, spherical silica (5 μm in particle size, 10 nm in pore diameter) was treated by hydrothermal or baking methods. During hydrothermal treatment, 22 g/L NaF was added, which efficiently promoted the enlargement of pore diameters. By this method, the average pore diameter of silica reached 100 nm after heating for 48 h at 160℃ in an autoclave, but showed a poor size distribution. In the baking method, pore diameter enlargement was controlled by modifying the baking temperature, time, and the amount of double salt LiCl-NaCl added. The addition of 1.125 g LiCl·H2O and 0.75 g NaCl per 10 g silica and baking at 500℃ for 3-5 h yielded silica with 100-nm pore diameters. This method was more efficient, easier, and better in the product pore diameter distribution than hydrothermal treatment. The obtained silica was very similar to commercial Fuji-1000 gel. The macroporous silicas obtained from the hydrothermal and baking treatments were both modified with aminopropyl silane and coated by cellulose tri(3,5-dimethylphenyl carbamate) to prepare chiral stationary phases (CSPs). The CSP based on the baking-treated silica exhibited much better selectivity and resolution for enantiomers.

Select

Determination of monofluoroacetic acid in plasma and urine by stable isotope dilution ion chromatography-triple quadrupole mass spectrometry ZHANG Xiaoyi, ZHANG Xiuyao, CAI Xinxin, LI Ruifen 2018, 36 (10):  979-984.  DOI: 10.3724/SP.J.1123.2018.06011 Abstract ( 296 )   [Full Text(HTML)] () PDF (865KB) ( 82 )   A method was developed for the determination of monofluoroacetic acid (MFA) in plasma and urine by ion chromatography-triple quadrupole mass spectrometry (IC-MS/MS). A plasma sample was extracted with 3% (v/v) perchloric acid aqueous solution, and the extract was centrifuged to remove the protein and lipids. A urine sample was acidulated with 3% (v/v) perchloric acid aqueous solution. The target analyte was extracted with methyl tert-butyl ether (MTBE) at a pH between 0.5 and 1.0. After the MTBE was removed by blowing with nitrogen, the MFA in the residues was dissolved into 0.1% (v/v) ammonia solution. The separation of MFA was carried out on a Dionex Ionpac AS 19 analytical column (250 mm×2 mm, 7.5 μm) with gradient elution using KOH solution electrolytically generated from an on-line eluent generation cartridge. Before the eluent flow entered the mass spectrometer, an in-line suppressor was used to remove potassium ions. The MFA was detected with a negative electrospray ionization source in the multiple reaction monitoring (MRM) mode, and quantified with the stable isotope internal standard method. The correlation coefficient of the linear calibration curve of MFA was greater than 0.999 at the corresponding ranges of 0.1-1000 μg/L. The average recoveries were 96.2%-120% of MFA in plasma and urine samples with relative standard deviations of 1.1%-13.1% (n=6). The limits of detection of MFA in plasma and urine samples were 0.03 μg/L and 0.1 μg/L, respectively. The method is simple, sensitive and accurate, and can be applied for the determination of MFA in plasma and urine samples.

Select

Determination of cholesterol and its six metabolism markers in serum by high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry HUANG Wenwen, GOU Xinlei, HU Tiejing, HU Guanghui, ZHAO Xinying 2018, 36 (10):  985-990.  DOI: 10.3724/SP.J.1123.2018.05029 Abstract ( 376 )   [Full Text(HTML)] () PDF (1730KB) ( 118 )   A method for the determination of cholesterol and its six metabolism markers (desmosterol, lathosterol, campesterol, stigmasterol, β-sitosterol, squalene) in serum by high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry (HPLC-Q/Orbitrap HRMS) was developed. The sample was ultrasonically extracted with acetonitrile. The separation was performed by using 95%(v/v) methanol-acetonitrile (2:8, v/v)-5%(v/v) water as the mobile phase. Isocratic elution was performed at a flow rate of 0.4 mL/min on an Acquity UPLC BEH C18 column (100 mm×2.1 mm, 1.7 μm) in 15 min. The atmospheric pressure chemical ionization (APCI)/positive mode was used in the MS detection. Cholesterol and its six metabolism markers were qualitatively and quantitatively determined by using the full MS scan/date dependent MS2 (Full MS/dd MS2) mode. The resolution of the precursor mass was 70000 FWHM, while the resolution of the product mass was 17500 FWHM. The correlation coefficients (r2) of all the seven target compounds were no less than 0.992 in the linear range. The limits of detection were between 0.8 μg/L and 62.1 μg/L, the recoveries were in the range of 82.1%-97.5% with the relative standard deviations in range of 1.6%-7.4%. The method is accurate, simple, and rapid, and can be used for the determination of cholesterol and its six metabolism markers in serum.

Select

Determination of 15 amide herbicides in rice using monolith column for on-line solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry ZHANG Haichao, AI Lianfeng, MA Yusong, WANG Jing, LI Xiaofei 2018, 36 (10):  991-998.  DOI: 10.3724/SP.J.1123.2018.05018 Abstract ( 315 )   [Full Text(HTML)] () PDF (1067KB) ( 112 )   A method based on on-line solid-phase extraction (SPE) coupled with high performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of 15 amide herbicides in rice. A poly(butyl methacrylate-co-ethylene dimethacrylate) monolithic column was utilized as the solid-phase column. The sample was extracted with acetonitrile, cleaned up with the monolithic column in online mode. Subsequently, the analyte was eluted from the extraction column onto the analytical column (Hypersil GOLD column) by 0.5%(v/v) formic acid aqueous solution-acetonitrile in gradient elution mode. Electrospray ionization mass spectrometry was performed in the positive mode and multiple reaction monitoring (MRM) mode. Under the optimized conditions, good linearities were obtained with correlation coefficients of more than 0.998. The limits of detection (LODs) and limits of quantification (LOQs) were in the range 0.20-2.0 μg/kg and 0.50-5.0 μg/kg, respectively. The average recoveries were in the range 75.5% to 121.3% at spiked levels of 2.0, 5.0, 10.0, and 50.0 μg/kg for 14 amide herbicides and 5.0, 10.0, 50.0, and 100.0 μg/kg for propanil. The relative standard deviations ranged from 2.89% to 12.38%. The proposed method is simple, rapid, and highly sensitive, and it can be applied to the simultaneous identification and quantification of the 15 amide herbicides in rice.

Select

Determination of eight antifungal drugs in mutton by QuEChERS coupled with ultra-performance liquid chromatography-tandem mass spectrometry ZHANG Kai, QIN Yu, BIAN Hua, CAO Hui, LIU Tianyi, GE Yu 2018, 36 (10):  999-1004.  DOI: 10.3724/SP.J.1123.2018.05028 Abstract ( 328 )   [Full Text(HTML)] () PDF (1638KB) ( 87 )   A method for the simultaneous determination of eight antifungal drugs in mutton was developed using QuEChERS combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were shaken with acetonitrile containing 2.0% (v/v) formic acid, and then subjected to QuEChERS purification. The residual targets were analyzed on an Atiantis® T3 column (100 mm×2.1 mm, 3 μm) with gradient elution using acetonitrile-0.1% (v/v) formic acid aqueous solution as the mobile phase. All the analytes were effectively separated and cleaned up within 9 min, and were finally detected by UPLC-MS/MS with ESI+ ionization in multiple reaction monitoring (MRM) mode. All the eight antifungal drugs showed a good linear trend in the range of 0.2-50 μg/L, with the correlation coefficient (R2) greater than 0.99. The limits of detection (LODs) and limits of quantification (LOQs) were 0.3-3.0 μg/kg and 1.0-10.0 μg/kg, respectively. The calibration curves were used in the analysis to reduce the negative influence of matrix effects. The average recoveries at different levels (low, medium, and high) for all the analytes ranged from 70.3% to 118.4%, with the relative standard deviations of 0.4%-4.3% (n=6). The developed method shows excellent recovery and stable repeatability, and is suitable for the determination of the antifungal drugs in mutton.

Select

Qualitative analysis of illegally adulterated sildenafil and related compounds in dietary supplements by ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry YU Hong, HU Qing, SUN Jian, FENG Rui, ZHANG Su, ZHANG Jingxian, MAO Xiuhong, JI Shen 2018, 36 (10):  1005-1017.  DOI: 10.3724/SP.J.1123.2018.04031 Abstract ( 297 )   [Full Text(HTML)] () PDF (10270KB) ( 93 )   The presence of illegally adulterated sildenafil and related compounds in dietary supplements was qualitatively analyzed by employing ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Samples were extracted by ultrasonic method using methanol. The analysis was performed on an Agilent Poroshell 120 SB-C18 column (75 mm×3.0 mm, 2.7 μm) using gradient elution with a mixture of aqueous formic acid solution (0.1%, v/v) and acetonitrile as the mobile phase at a flow rate of 0.4 mL/min. Q-TOF-MS equipped with ESI ion source was operated in a positive ionization mode. Qualitative analysis was based on the retention time and the accurate relative molecular mass of elemental compositions of the precursor ion and product ions. The limits of detection (LODs) of sildenafil and other 99 compounds were found to be 0.1-50 mg/kg or 0.1~50 mg/L in 10 different matrices. In this manuscript, the fragmentation behavior of 98 phosphodiesterase-5 inhibitors are categorically summarized, which can provide information for referencing and identification of suspicious compounds. The method was successfully applied to the analysis of actual samples, of which 19 compounds combated the illegal adulteration behavior effectively.

Select

Rapid determination of ultra-trace levels of atrazine in surface water by on line solid phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry SHEN Fei, XU Yanjuan, SONG Ting, CHEN Jing, WANG Ye 2018, 36 (10):  1018-1021.  DOI: 10.3724/SP.J.1123.2018.06031 Abstract ( 272 )   [Full Text(HTML)] () PDF (834KB) ( 79 )   A method for the determination of ultra-trace atrazine in surface water was developed based on on line solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry (on line SPE-UPLC-MS/MS). The water sample was directly injected into an on line SPE system after filtering using a 0.22 μm filter membrane. An HLB Direct Connect HP column was used for the enrichment and purification of the water sample and eluted using a methanol solution. The analyte was separated on an Acquity BEH 130 column, and then detected by tandem mass spectrometry. The analyte was quantified with external standard method. There was a good linear relationship in the range of 1.0-5000 ng/L. The correlation coefficient (r) was 0.9989. The method detection limit was 0.2 ng/L. The recoveries of atrazine ranged from 83.0% to 105.1%. The relative standard deviation was 1.6%-5.3% (n=7), which met the requirements of trace analysis. The method is sensitive, fast and effective, and it is suitable for the determination of atrazine in surface water. It is important to ensure the safety of the water environment, provide timely pollution information, and effectively respond to environmental emergencies.

Select

Determination of short-chain chloroparaffins in synthetic surfacing layers used in sports and diluents by solid-phase extraction coupled with gas chromatography-negative chemical ionization-mass spectrometry HUANG Shaojun, DU Ping, LIU Chunxia, YANG Jun, YANG Chaofen, SUN Hui, HUANG Qiuling 2018, 36 (10):  1022-1027.  DOI: 10.3724/SP.J.1123.2018.05002 Abstract ( 288 )   [Full Text(HTML)] () PDF (1743KB) ( 110 )   A new method was established to determine short-chain chloroparaffins (SCCPs) in synthetic surfacing layers used in sports and diluents by solid-phase extraction (SPE) coupled with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The analysis conditions for gas chromatography and mass spectrometry were optimized. Then, the samples were extracted by ultrasonication, purified on a Florisil SPE column, monitored in the selective ion monitoring (SIM) scanning mode, and quantified by the external standard method. With this method, a good linear relationship was found over a wide mass concentration range from 0.0501 to 100.17 mg/L, with a linear correlation coefficient (R2) of 0.9995. The detection limit for SCCPs by this method was found to be as low as 0.50 μg/g (i. e. 0.000050%) and the average recoveries for SCCPs spiked in the blank samples varied from 83.2% to 96.3% with relative standard deviations (RSDs) of 1.56%-6.02%. Ten batches of samples were tested and the contents of SCCPs detected in each batch were in the range from 0.016% to 0.55%, which agrees well the European Union limitation requirement for SCCPs. Thus, this method is suitable for qualitative and quantitative analyses of SCCPs in synthetic surfacing layers used in sports and diluents.

Select

Determination of 18 polychlorinated biphenyls in tea by gas chromatography-mass spectrometry coupled with dispersive solid-phase extraction LIU Tengfei, YANG Daifeng, ZHANG Xueming, MAO Jian, DONG Minghui 2018, 36 (10):  1028-1037.  DOI: 10.3724/SP.J.1123.2018.07014 Abstract ( 320 )   [Full Text(HTML)] () PDF (9678KB) ( 89 )   A method for the rapid determination of 18 polychlorinated biphenyls (PCBs) in tea by gas chromatography-mass spectrometry (GC-MS) coupled with dispersive solid-phase extraction (dSPE) was developed and evaluated. Carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) and primary secondary amine (PSA) were used as sorbents in pretreatment process. PCBs were ultrasonically extracted from tea samples with hexane-acetone (1:1, v/v), and purified with the mixed sorbents of MWCNTs-COOH and PSA after replacing hexane-acetone by toluene. The PCBs were determined by an electron impact ionization source and selected ion monitoring mode. The analytes were qualitatively confirmed from the retention time and relative abundance ratio of characteristic ions, and quantified by a matrix-matched standard solution. The chromatographic and MS parameters influencing separation and sensitivity were optimized, and major factors affecting the extraction and cleanup efficiency including type and volume of extraction solvent, extraction time, type and amount of cleanup sorbent, and clean-up time were investigated. The performance of the method was evaluated. Under optimum conditions, satisfactory linear relationship was observed with the content of PCBs ranging from 5 to 500 μg/kg, with correlation coefficients (r) no less than 0.9998. The 18 PCBs in three kinds of tea matrices including Biluochun tea, Tieguanyin tea and Pu'er tea were spiked at 5, 10 and 100 μg/kg to evaluate recoveries, which ranged from 90.7% to 115.2% with relative standard deviations (n=5) between 0.3% and 10.9%. The limits of detection and the limits of quantification were 0.3-1.7 μg/kg and 5 μg/kg for each PCB, respectively. The method is simple, rapid, accurate, sensitive and effective, and is suitable for the determination of the 18 PCBs in different kinds of tea.

Select

Determination of organochlorine and organophosphorus pesticides in soil by gas chromatography-tandem mass spectrometry with accelerated solvent extraction SONG Xiaojuan, HE Xinran, YIN Mingming, WAN Yanyan 2018, 36 (10):  1038-1044.  DOI: 10.3724/SP.J.1123.2018.05012 Abstract ( 379 )   [Full Text(HTML)] () PDF (1673KB) ( 114 )   A method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) coupled with accelerated solvent extraction (ASE) was developed for the determination of eight organochlorine pesticides (OCPs) and five organophosphorus pesticides (OPPs) in soils. The soil samples were grinded after freeze-drying. Particles with diameters lower than 250 μm were chosen by ion-sieving. After this, 10.0 g soil mixed with 2.0 g diaomite was extracted with hexane-acetone (1:1, v/v). The extracts were dehydrated with anhydrous sodium sulfate and concentrated with a termovap sample concentrator. The concentrated solutions were further cleaned up with Si SPE columns and eluted with hexane-acetone (1:1, v/v). The purified solutions were then isolated by HP-5MS column (30 m×0.25 mm×0.25 μm) and detected using the multiple reaction monitoring mode at the electron impact source. It is observed that this method has good linearities in the range of 1.00-100 μg/L for the 13 compounds, and the correlation coefficients (R) were greater than 0.995. The spiked recoveries of the 13 compounds were in the range of 66.8%-88.4%, and the relative standard deviations were less than 10%. With 10.0 g of sampling weight, the method detection limits ranged from 0.02 to 0.04 μg/kg for the eight OCPs and from 0.06 to 0.12 μg/kg for the five OPPs. This method is suitable for the determination of trace OCPs and OPPs in soils.

Select

Separation of alkaloids using radial chromatography and its separation efficiency ZHANG Mengting, GONG Dandan, SUN Wanyang, SUN Guoxiang 2018, 36 (10):  1045-1052.  DOI: 10.3724/SP.J.1123.2018.05016 Abstract ( 411 )   [Full Text(HTML)] () PDF (1457KB) ( 180 )   The radial thin layer chromatography (RTLC) is a chromatographic method for the simple, rapid and efficient separation of samples from the center along the radial direction. Simple device was assembled to separate the alkaloids contented in Zhusha Anshen Pills (ZSASP). Based on the theory of thin layer chromatography, the test was designed to compare the separation efficiency of radial chromatography and general thin layer chromatography. The RTLC is faster, more efficient, more economical, and more suitable for the separation of high polar samples like alkaloids as proved. The theoretical root of the high separation efficiency of radial thin layer method was explored, which also provided new methods and ideas for theoretical innovation.

Select

An analytical method for alkaloids of Coptis chinensis based on mixed-mode surface electrostatic exclusion/reversed-phase chromatography ZHANG Huarong, GUO Zhimou, YU Wei, YAN Jingyu, JIN Gaowa, WANG Lianzhi 2018, 36 (10):  1053-1060.  DOI: 10.3724/SP.J.1123.2018.06006 Abstract ( 347 )   [Full Text(HTML)] () PDF (1138KB) ( 137 )   A mixed-mode chromatographic method based on surface electrostatic exclusion and reversed-phase chromatography was established for the determination of alkaloids present in Coptis chinensis. The effects of two mobile phase additives, formic acid and acetic acid, on retention, peak shape and selectivity of the alkaloids in Coptis chinensis were investigated using the self-made C18HCE column. Acetic acid (0.1%, v/v) used as the additive was found to be optimum for effective separation of the main alkaloids present in Coptis chinensis. The main chromatographic peaks of Coptis chinensis were recognized by the established method and references, which were coptisine, epiberberine, columbamine, jatrorrhizine, berberine and palmatine, respectively. With reference to the content determination method of Coptis chinensis in the 2015 edition of pharmacopoeia, the linear relationship of berberine in the range of 0.5-100 mg/L was good, the correlation coefficient was 0.9996, and the average recovery was 93.74%. The contents of alkaloids in Coptis chinensis in different batches of Hubei and Chongqing were determined. The method is simple, reliable and accurate, and can be used as reference for separation and analysis of other basic compounds.

Select

Separation and purification of iopamidol using preparative high-performance liquid chromatography LI Huajun, CHEN Qian 2018, 36 (10):  1061-1066.  DOI: 10.3724/SP.J.1123.2018.06001 Abstract ( 392 )   [Full Text(HTML)] () PDF (1264KB) ( 132 )   The development and optimization of separation and purification methods for high-purity iopamidol were performed based on preparative high-performance liquid chromatography (prep-HPLC). In this study, a reversed-phase separation method for the analysis of iopamidol was developed first. The effects of chromatographic parameters, including two kinds of stationary phase with different bonded amounts, column temperature, and sample loading capacity, on the retention, resolution, and peak shape of iopamidol were investigated. The results showed that good retention and resolution of iopamidol were realized on a C18-1 column (250 mm×4.6 mm, 10 μm) of which the bonded amount was 13.7%. Retention of iopamidol was weakened with increasing column temperature, resulting in a low resolution between iopamidol and impurities. Thus, the column temperature was adjusted to 20-30℃. Meanwhile, the increasing of loading capacities was also detrimental to retention of iopamidol or removal of impurities. Prep-HPLC was performed on the C18-1 column (270 mm×50 mm, 10 μm) with the mobile phase of water-methanol at a column temperature of 20℃. After preparation, the chromatographic purity of the iopamidol sample was 98.97% with recovery of 93.44%, and its related substances all met limited requirements. This method can reduce the impurity level effectively with a high recovery rate, which is helpful for the development of separation and purification of iopamide.

Select

Solvent with switchable hydrophilicity used in liquid-liquid microextraction combined with gas chromatography-mass spectrometry for the determination of diclazepam in urine XU Fangmin, LI Haibo, WEI Wanli, LIU Lingyun, LI Qiang 2018, 36 (10):  1067-1072.  DOI: 10.3724/SP.J.1123.2018.05022 Abstract ( 294 )   [Full Text(HTML)] () PDF (1126KB) ( 91 )   A simple, fast, and sensitive method was developed for the determination of diclazepam in urine using a solvent with switchable hydrophilicity in liquid-liquid microextraction followed by gas chromatography-mass spectrometry. N,N-Dimethylcyclohexylamine was used as the extraction solvent with switchable hydrophilicity, because it can be made miscible or immiscible with aqueous phase by adding hydrochloric acid and sodium hydroxide. Experimental parameters affecting the extraction efficiency, such as the volume of hydrochloric acid, the type and volume of the solvent with switchable hydrophilicity, the volume of sodium hydroxide, and the extraction time, were investigated. Under the optimal conditions, the intraday and interday recoveries ranged from 76.5% to 90.3% with relative standard deviations between 3.3% and 6.5% (n=6). The linear range was found to be 0.025-2.5 mg/L, with r2 greater than 0.99 and limit of detection of 0.007 mg/L. This method provided excellent linearity, precision, and recovery, and thus, can be applied to the analysis of diclazepam in urine due to its simplicity, accuracy, and practicality.