Solid-phase extraction of soy isoflavones

An automated method using solid-phase extraction (SPE) for the concentration and clean-up of soy isoflavone extracts is proposed in this work. Using a standardized sample (0.1 g of a freeze dried soybean extract/25 mL of water); eight SPE cartridges with a wide range of sorbents (C18, divinylbenzene and modified divinylbenzene) from different suppliers were evaluated and compared. A large variation on SPE cartridges performance was observed, especially regarding retention and breakthrough volume of isoflavones during sample load and washing steps. The most effective cartridges were the divinylbenzene based cartridges, especially Strata X (from Phenomenex) and HLB oasis (from Waters). Using Strata X cartridges, several extraction parameters, such as sample loading flow (5-15 mL min(-1)), extracting solvent volume (2-6 mL of methanol), pH of the extracting solvent and the necessity of drying the sorbent before elution, were evaluated to provide a fast, specific, quantitative and reproducible SPE method. The optimized method consists of conditioning the cartridge with 10 mL of methanol and 10 mL of water (10 mL min(-1)), loading 25 mL of the standardized extract onto the cartridges (5 mL min(-1)), washing the cartridge with 10 mL of water (10 mL min(-1)) and finally eluting with 4 mL of methanol (10 mL min(-1)). Mean isoflavones recovery was 99.37% and mean intra- and inter-day reproducibility was higher than 98%. The developed sample clean-up/concentration (6.25:1) method takes less than 10 min and can be used in the analysis of isoflavones from soy extracts.     

Liquid chromatographic analysis of cinchona alkaloids in beverages

A method for the determination of Cinchona extract (whose main components are the alkaloids cinchonine, cinchonidine, quinidine, and quinine) in beverages by liquid chromatography was developed. A beverage with an alcohol content of more than 10% was loaded onto an OASIS HLB solid-phase extraction cartridge, after it was adjusted to pH 10 with 28% ammonium hydroxide. Other beverages were centrifuged at 4000 rpm for 5 min, and the supernatant was loaded onto the cartridge. The cartridge was washed with water followed by 15% methanol, and the Cinchona alkaloids were eluted with methanol. The Cinchona alkaloids in the eluate were chromatographed on an L-column ODS (4.6 mm id x 150 mm) with methanol and 20 mmol/L potassium dihydrogen phosphate (3 + 7) as the mobile phase. Cinchona alkaloids were monitored with an ultraviolet (UV) detector at 230 nm, and with a fluorescence detector at 405 nm for cinchonine and cinchonidine and 450 nm for quinidine and quinine (excitation at 235 nm). The calibration curves for Cinchona alkaloids with the UV detector showed good linearity in the range of 2-400 microg/mL. The detection limit of each Cinchona alkaloid, taken to be the concentration at which the absorption spectrum could be identified, was 2 microg/mL. The recovery of Cinchona alkaloids added at a level of 100 microg/g to various kinds of beverages was 87.6-96.5%, and the coefficients of variation were less than 3.3%. A number of beverage samples, some labeled to contain bitter substances, were analyzed by the proposed method. Quinine was detected in 2 samples of carbonated beverage.     

固相萃取-气相色谱/质谱法同时测定涂料中的8种有机锡

建立了一种固相萃取（SPE）前处理、气相色谱-质谱（GC-MS）法同时测定涂料中8种有机锡的方法。样品采用阳离子交换固相萃取小柱净化,最佳固相萃取条件为：固相萃取小柱分别用5mL甲醇、7mL洗脱液（氯化铵、甲醇、冰乙酸的混合溶液）预洗,10mL甲醇活化;将用甲醇稀释的涂料样品上样后,用5mL甲醇淋洗,抽干2min,7mL乙酸-氯化铵甲醇溶液（10：90,V／V）洗脱溶液洗脱。洗脱液用四乙基硼化钠溶液衍生后,气相色谱-质谱法进行定性定量分析。结果表明：以标准加入法计算回收率,在1.68％-16.84%添加范围内,平均回收率在85％-105％之间,相对标准偏差均小于12％。     

固相萃取-液相色谱／串联质谱法测定黄酒中的甜蜜素

建立了黄酒中甜蜜素残留的固相萃取-液相色谱／串联质谱法（SPE—LC／MS／MS）测定方法。黄酒样品用水稀释后,弱阴离子（WAX）固相萃取小柱净化,氨化甲醇洗脱。采用HypersilGold C18色谱柱（150mm×2．1mm,5μm）,乙腈-0．1％甲酸水溶液为流动相,以电喷雾离子源负离子模式（MRM）定性、定量测定甜蜜素。甜蜜素在10～500μg／L范围内峰面积与质量浓度呈线性关系,相关系数为0．9995。取有代表性的阴性样品进行添加回收试验,在0．5—5．0mg／L范围内,回收率为81．1％-88．2％,相对标准偏差为3．65％～5．21％,方法的定量检测限为0．5mg／L。该方法净化效果好,检测灵敏度高,能同时完成黄酒中甜蜜素的定量和定性分析。     

固相萃取-高效液相色谱法测定环境水样中的三嗪类化合物

建立了固相萃取-高效液相色谱法(SPE-HPLC)测定地表水中三嗪类化合物的方法。考察了4种不同固相萃取柱对三嗪类化合物的吸附效果,最终选择ENVI-18固相萃取柱用于萃取地表水中的三嗪类化合物;系统研究了环境水样中三嗪类化合物的最佳固相萃取条件,选择洗脱溶剂为甲醇,洗脱溶剂用量5 mL,水样在萃取前不需要添加甲醇,不调节pH值。测定了方法的检测限,结果表明,扑草净、莠去津、西玛津、脱乙基莠去津、羟基化莠去津和脱异丙基莠去津的最低检测限依次为0.14 μg/L,0.12 μg/L,0.08 μg/L,0.08 μg/L,0.10 μg/L和0.18 μg/L。将该法应用于实际环境水样的分析测定,结果表明某湖水中扑草净的含量为（9.33±0.27） μg/L,某江水中莠去津和扑草净的含量分别为（5.28±0.43） μg/L和（7.12±0.54） μg/L。     

Determination of cyclamate in foods by ultraperformance liquid chromatography/tandem mass spectrometry

A highly sensitive and selective method that requires minimal sample preparation was developed for the confirmation and quantitation of cyclamate in a variety of foods by high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). Sample preparation consisted of homogenization followed by extraction and dilution of cyclamate with water. HPLC separation was achieved using a bridged ethyl hybrid C18 high-pressure column with a mobile phase consisting of 0.15% acetic acid and methanol. Under electrospray ionization negative conditions, quantitation was achieved by monitoring the fragment m/z = 79.7 while also collecting parent ion m/z = 177.9. Two food matrixes, diet soda and jelly, were subjected to a validation procedure in order to evaluate the applicability of the method. The cyclamate limit of detection for both matrixes was determined to be 0.050 microg/g with a limit of quantitation of 0.150 microg/g. The correlation coefficient of the calibration curves was >0.9998 from 0.0005 to 0.100 microg/mL. The method has been used for the determination of cyclamate in several foods and the results are presented.     

Determination of 4-methylpiperaine-1-carbodithioc acid 3-cyano-3,3-diphenylpropyl ester hydrochloride in rats' plasma by online-SPE-HPLC-DAD: application to a pharmacokinetic study

A specific, simple, and fast online-solid-phase extraction-high performance liquid chromatography-diode array detector (SPE-HPLC-DAD) method was developed and validated to quantify 4-methylpiperaine-1-carbodithioc acid 3-cyano-3,3-diphenylpropyl ester hydrochloride (TM208) in small volume samples of rats' plasma for the first time. In this method, the 50-μL plasma sample was taken to perform protein precipitation with 75 μL methanol, and then 50 μL supernatant containing the target analytes was injected and concentrated automatically in a C18 solid-phase extraction (SPE) cartridge. After that the sample was separated on a C18 RP analytical column and analyzed by DAD. The run cycle time is 6.0 min for each sample, and the calibration curve over the range of 0.03 to 25.00 μg/mL has a good linear relationship (r > 0.9998). The recoveries of the quality control samples were all greater than 90%. The limit of detection and the lowest limit of quantification were 0.01 and 0.03 μg/mL, respectively. Finally, this method was successfully applied to a pharmacokinetic study of TM208 in rats.     

Dialysis-solid-phase extraction combined on-line with non-aqueous capillary electrophoresis for improved detectability of tricyclic antidepressants in biological samples

Dialysis-solid-phase extraction (SPE) sample pretreatment is combined on-line with non-aqueous capillary electrophoresis for the determination of tricyclic antidepressants in urine and serum. After clean-up and enrichment, the water is removed from the sample matrix and the analytes are eluted from the cartridge by means of an organic solvent. Next, the eluate is transported to the capillary and the injection is performed electrokinetically. This injection, which does not suffer from an adverse sample matrix effect because of the SPE step, results in further analyte concentration. The detection limits are in the 0.02-0.1 microg/ml range and the day-to-day repeatabilities are between 2.5 and 9.5%, which is quite satisfactory.     

禽蛋中头孢噻肟残留的高效液相色谱-串联质谱法测定

建立了高效液相色谱-串联质谱(LC-MS/MS)测定禽蛋中头孢噻肟药物残留的方法。禽蛋样品中的头孢噻肟用纯水提取,乙腈沉淀蛋白,Oasis HLB(500 mg,6 mL)固相萃取柱净化,8 mL甲醇洗脱。采用Zorbax XDB-C18(2.1 mm×50 mm,3.5μm)色谱柱,以0.2%甲酸水-乙腈为流动相,0.3 mL/min梯度洗脱,经高效液相色谱分离后,采用电喷雾质谱正离子模式电离,多反应选择离子检测(MRM)模式测定。检测离子对为m/z456.1/396.1、m/z456.1/324.1,其中m/z456.1/396.1为定量离子对。在1.35~135μg/L范围内标准曲线的线性关系良好,相关系数为0.999 3;在1.0、50.0、100μg/kg3个添加水平的平均加标回收率为87%~99%,相对标准偏差为1.9%~3.9%;方法检出限为0.3μg/kg,定量下限为1.0μg/kg。该方法简便、灵敏、准确、可靠,适用于禽蛋中头孢噻肟药物残留的分析。     

Combined use of supported liquid membrane and solid-phase extraction to enhance selectivity and sensitivity in capillary electrophoresis for the determination of ochratoxin A in wine

This paper proposes a novel strategy to enhance selectivity and sensitivity in CE, using supported liquid membrane (SLM) and off-line SPE simultaneously. The determination of ochratoxin A (OA) in wine has been used to demonstrate the potential of this methodology. In the SLM step, the donor phase (either a 20 mL volume of a standard solution at pH 1 or a wine sample at pH 8) was placed in a vial, where a micromembrane extraction unit accommodating the acceptor phase (1 mL water, pH 11) in its lumen was immersed. The SLM was constructed by impregnating a porous Fluoropore Teflon (PTFE) membrane with a water-immiscible organic solvent (octanol). In the off-line SPE step, the nonpolar sorbent (C-18, 4 mg) selectively retained the target ochratoxin, enabling small volumes of acceptor phase (1 mL) to be introduced. The captured analytes were eluted in a small volume of methanol (0.1 mL). This procedure resulted in sample cleanup and concentration enhancement. The method was evaluated for accuracy and precision, and its RSD found to be 5%. The LODs for OA in the standard solutions and wine samples were 0.5 and 30 microg/L, respectively. The results obtained demonstrate that SLM combined with off-line is a good alternative to the use of immunoaffinity columns prior to CE analysis.     

Development of a solid-phase extraction method for determination of pheophorbide a and pyropheophorbide a in health foods by liquid chromatography

A simple solid-phase extraction (SPE) method was developed for the liquid chromatography (LC) determination of pheophorbide (Phor) a and pyropheophorbide (Pyro) a in health foods such as chlorella, spirulina, etc. The food sample was extracted with 85% (v/v) acetone. The extract was acidified with hydrochloric acid and loaded on a C18 cartridge. After washing with water, Phor a and Pyro a were eluted with the LC mobile phase. Phor a and Pyro a were separated by isocratic reversed-phase LC and quantitated by fluorescence detection. The recoveries for spiked samples of chlorella and the extract were 87.1-102.0%. Commercial health foods (chlorella, spirulina, aloe, kale, Jews mallow, and green tea leaves) were analyzed using the SPE method. The values found for Phor a and Pyro a ranged from 2 to 788 microg/g and from <1 to 24 microg/g, respectively. There was no significant difference between the SPE method and the official method in Japan (spectrophotometry after liquid-liquid extraction). The advantages of the SPE method are the short extraction times, lack of emulsions, and reduced consumption of organic solvents compared with the official method in Japan. The SPE method is considered to be useful for the screening of Phor a and Pyro a in health foods.     

反相离子对高效液相色谱法快速分离和定量测定食品中的甜蜜素

采用反相离子对高效液相色谱法快速分离和测定食品中的甜蜜素。在ODS柱上,以V（甲醇）：V（水,含离子对试剂）=30：70的溶液为流动相进行分离,分别考察了流动相中离子对试剂和甲醇浓度对甜蜜素保留行为的影响。检测波长为205nm;采用外标法定量,测得甜蜜素在0．5～2．5g／L范围内具有良好的线性关系;回收率在96．9％～101．7％之间;检测限为0．05g／L。     

固相萃取-离子色谱法测定饮用水中的痕量卤代乙酸

建立了固相萃取-离子色谱(SPE-IC)测定饮用水中痕量卤代乙酸(HAAs)(包括一氯乙酸、二氯乙酸、三氯乙酸、一溴乙酸和二溴乙酸)的方法。固相萃取采用LiChrolut EN SPE柱来进行痕量待测物的预浓缩（25倍）和基体杂质的消除,用NaOH(10 mmol/L)洗脱;色谱分离采用亲水性、高容量、氢氧化物选择型阴离子交换柱Dionex IonPac AS16(250 mm×4 mm i.d.),以NaOH为流动相进行浓度梯度淋洗,淋洗速度为0.8 mL/min,电导检测,进样量为500 μL。结果表明,用SPE-IC法测定HAAs,一溴乙酸的检测限为12.5 μg/L,其余4种HAAs的检测限为0.38~1.69　μg/L。该法可实现对饮用水中痕量卤代乙酸的测定。     

超高效液相色谱/串联质谱法分析水中的微囊藻毒素

建立了超高效液相色谱/质谱快速、准确、高灵敏度地测定水体中痕量微囊藻毒素（MCYST）的分析方法,并用于实 际样品的分析。采用固相萃取法富集净化样品。该法在5 min内即可完成4种MCYST（LR、RR、LW、LF）的分离及检测;LR 、RR、LW、LF的定量检测限、回收率分别为1.3～6.0 ng/L、91.1%～111%;工作曲线的线性相关系数大于0.99,线性范 围达3个数量级。实际样品分析表明,在所测定的水库水样中均检出了LR和RR,其质量浓度分别为0.0447～2.73 μg/L和0.0208～1.36 μg/L;而在所有的检测样品中均未检出LW和LF。     

新型毛细管内固相萃取-气相色谱法检测纺织品中烷基酚类物质

建立了毛细管内固相萃取(SPE)-气相色谱(GC)检测纺织品中壬基酚和辛基酚含量的分析方法。通过比较4种性质不同固相萃取剂的萃取效果,筛选出对烷基酚(APs)类物质萃取效果最佳的固相萃取剂,将其作为填充物质制作毛细管内固相萃取柱,将毛细管内固相萃取法与气相色谱联用进行分析检测。最佳固相萃取剂为Abselut NEXUS,毛细管内固相萃取最佳条件为:1.2 μL甲醇和1.2 μL超纯水活化,1.2 μL甲醇洗脱,上样速率是0.4 μL/min。该法在较低浓度范围内呈现良好的线性相关性,对烷基酚的富集倍数约为100倍,对辛基酚和壬基酚的检出限分别为3.7 μg/L和4.5 μg/L,加标回收率分别为85.6%~98.2%和83.8%~95.7%,结果表明,此法能够简捷、迅速、有效地检测出纺织品中残留的烷基酚类物质。     

Evaluation of graphene as an advantageous adsorbent for solid-phase extraction with chlorophenols as model analytes

Graphene, a novel class of carbon nanostructures, possesses an ultrahigh specific surface area, and thus has great potentials for the use as sorbent materials. We herein demonstrate the use of graphene as a novel adsorbent for solid-phase extraction (SPE). Eight chlorophenols (CPs) as model analytes were extracted on a graphene-packed SPE cartridge, and then eluted with alkaline methanol. The concentrations in the eluate were determined by HPLC with multi-wavelength UV detection. Under the optimized conditions, high sensitivity (detection limits 0.1-0.4 ng/mL) and good reproducibility of CPs (RSDs 2.2-7.7% for run-to-run assays) were achieved. Comparative studies showed that graphene was superior to other adsorbents including C18 silica, graphitic carbon, single- and multi-walled carbon nanotubes for the extraction of CPs. Some other advantages of graphene as SPE adsorbent, such as good compatibility with various organic solvents, good reusability and no impact of sorbent drying, have also been demonstrated. The proposed method was successfully applied to the analysis of tap and river water samples with recoveries ranging from 77.2 to 116.6%. This work not only proposes a useful method for environmental water sample pretreatment, but also reveals great potentials of graphene as an excellent sorbent material in analytical processes.     

On-line automatic SPE-CE coupling for the determination of biological markers in urine

Automatic SPE has been coupled on-line to CE by a transfer tube and the replenishment system of the CE instrument. The approach allows the target analytes (viz. creatinine, creatine, xanthine, hypoxanthine, uric acid, p-aminohippuric acid and ascorbic acid in urine samples) to be removed from the sample matrix, cleaned up, preconcentrated and injected into the capillary. The detection limits range between 0.14 and 4.50 microg/mL, the quantification limits between 0.45 and 15.0 microg/mL, and linear dynamic ranges - which include the reference healthy human values - from the quantification limits to 1332 microg/mL. The precision, expressed as RSD, ranges between 0.38 and 2.22% for repeatability and between 1.79 and 7.61% for within-laboratory reproducibility. The errors, expressed as RSD for all compounds, range between 0.20 and 6.90%. The time for automatic SPE and that necessary for the individual separation-detection of the target analytes are 13 and 12 min, respectively; the analysis frequency is 5 h(-1). The accuracy of the method and potential matrix effects were studied by using spiked samples and recoveries between 96.00 and 103.07 % were obtained. The proposed method was applied to samples from healthy young students.     

Liquid chromatography-electrospray ionization isotope dilution mass spectrometry analysis of paraquat and diquat using conventional and multilayer solid-phase extraction cartridges

The performance of alkyl-silica sorbent packed solid-phase extraction (SPE) cartridges and a mixed-mode, polymeric sorbent packed SPE cartridge (resin SPE cartridge) were evaluated for the sample preparation of paraquat and diquat in environmental water and vegetation matrices. Also the recoveries of the native and 2H-labeled paraquat and diquat were correlated to validate that the 2H-labeled species can be used for the isotopic dilution mass spectrometry (IDMS) analysis of paraquat and diquat. The results show that the extraction efficiency of alkyl-silica SPE is dependent on the carbon loading of the sorbent and deteriorates with an increasing sample pH. The resin SPE cartridge required no pH adjustment and showed excellent correlation between the native and 2H-labeled species, therefore, allowing us to develop the first liquid chromatography-electrospray ionization IDMS analytical method for the analysis of paraquat and diquat in environmental water and vegetation matrices. Method detection limits derived using standard EPA protocol were 0.2 and 0.1 microg/l for paraquat and diquat in water matrices, and 0.02 and 0.01 microg/g in vegetation matrices, respectively.     

超高效液相色谱-串联质谱法同时测定水体中莠去津和呋喃丹的含量

水样中莠去津和呋喃丹通过C18固相萃取柱使之分离并富集。用氮气将固相萃取柱吹干后,用二氯甲烷淋洗使被测组分洗脱,所得洗脱液用氮气吹至尽干,用混合溶剂[甲醇与甲酸-水(0.1+99.9)溶液按40比60的比例混合]1 mL溶解残渣,所得溶液供超高效液相色谱-串联质谱法(UPLC-MS/MS)分析用。用Waters BEH C18色谱柱作分离柱,用不同比例的甲醇和甲酸-水(0.1+99.9)溶液的混合液作流动相进行梯度淋洗,使上述两种农药分离后进行串联质谱测定,所用质谱条件为电喷雾离子源,正离子扫描和多反应监测模式。两种农药质量浓度均在0.10~10.00μg.L-1范围内与相应的峰面积值呈线性关系,检出限(3S/N)均为0.15 ng.L-1。在3个浓度水平上(0.10,0.50,5.00μg.L-1)加入两种农药的标准溶液进行回收试验,测得其平均回收率在77.0%~102.2%之间,相对标准偏差(n=5)在2.9%~7.6%之间。     

Solid Phase Extraction of Sulfonamides Using Cyclobond-I Cartridges

Abstract

The use of cyclobond-I solid phase extraction (SPE) cartridges in the analysis of sulfonamides was investigated. an aqueous solution of sulfonamides in 0.1 M potassium phosphate buffer (pH 4.0) was passed through the SPE cartridge. the sulfonamides which were retained on the cartridge by formation of inclusion complexes between the sulfonamides and B-cyclodextrin were eluted with 50% aqueous methanol. the eluate was directly analysed by High Performance Liquid Chromatograph with UV detection at 265nm.