Method for simultaneous analysis of eight vitamin E isomers in various foods by high performance liquid chromatography and fluorescence detection

The objective of this study was to optimize a method to investigate the occurrence and to quantify the full isomeric composition of vitamin E (α-, β-, γ- and δ-tocopherols and tocotrienols) in 6 vegetables (raw and cooked), 3 herbs/spices, raw and cooked eggs, vegetable oils (canola, olive and soybean), flaxseed and sorghum (flour and seeds) and soy (flour) by HPLC with fluorescence detection. Different conditions of extraction and analysis were tested. The optimized method consisted of direct extraction with solvent (hexane:ethyl acetate, 85:15, v/v). For analysis normal phase column was used with mobile phase consisting of hexane:isopropanol:acetic acid (98.9:0.6:0.5) with isocratic elution and fluorescence detection. Excellent separation of all isomers was obtained along with adequate quantification in the foods analyzed. Recovery rates of standards ranged from 91.3 to 99.4%. The linearity range for each isomer varied from 2.5 to 137.5 ng/mL (R2 greater than 0.995 in all cases). Detection limits ranged from 21.0 to 48.0 ng/mL for tocopherols and from 56.0 to 67.0 ng/mL for tocotrienols, while quantification limits ranged from 105.0 to 240.0 ng/mL for tocopherols and from 280.0 to 335.0 ng/mL for tocotrienols. The optimized method was considered simple, fast and reliable, and also preserved vitamin E isomers when compared to validated methods involving saponification.     

超高效液相色谱-电喷雾质谱法结合同位素稀释技术检测动物源性食品中的六溴环十二烷异构体

建立了使用超高效液相色谱-电喷雾四极杆质谱(UPLC-ESI-MS)结合同位素稀释技术准确测定动物源性食品中六溴环十二烷(HBCD)的3种非对映异构体的方法。试样在加入同位素内标13C-HBCD后进行索氏提取,提取液去除脂肪后经硅胶固相萃取柱浓缩、净化后,通过Waters ACQUITY UPLCTM BEH C18色谱柱分离,以甲醇-乙腈混合液和水为流动相进行梯度洗脱。在UPLC-MS分析过程中以保留时间和母离子信息进行定性,选择离子记录(SIR)方式定量。该法对于所测试的鲜奶、鱼肉等样品,检出限为0.1～0.4 ng/g,定量限为0.4～1.2 ng/g。对于加标鱼肉样品,添加水平为0.6,2.0和6.0 ng/g时,3种被测物的加标回收率为92.9%～99.3%,相对标准偏差为3.1%～8.0%。     

Determination of phthalate esters in cow milk samples using dispersive liquid-liquid microextraction coupled with gas chromatography followed by flame ionization and mass spectrometric detection

A simple and economic method for the analysis of phthalate esters, dimethyl phthalate, diethyl phthalate, di-iso-butyl phthalate, di-n-butyl phthalate, and di-2-ethylhexyl phthalate in cow milk samples by means of gas chromatography-flame ionization detection and gas chromatography-mass spectrometry has been developed. In this work, NaCl and ACN were added to 5 mL of the milk sample as the salting out agent and extraction solvent, respectively. After manual shaking, the mixture was centrifuged. In the presence of NaCl, a two-phase system was formed: upper phase - acetonitrile containing phthalate esters -and lower phase - aqueous phase containing soluble compounds and the precipitated proteins. After the extraction of phthalate esters from milk, a portion of supernatant phase (acetonitrile) was removed, mixed with 1,2-dibromoethane at microliter level and injected by syringe into NaCl solution. After the extraction of the selected phthalate esters into 1,2-dibromoethane, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. Under the optimum extraction conditions, low limits of detection and quantification between 1.5-3 and 2.5-11 ng/mL, respectively was observed. Enrichment factors were in the range of 397-499. The relative standard deviations for the extraction of 100 ng/mL of each phthalate ester were in the range of 3-4% (n = 6). Finally, some milk samples were successfully analyzed using the proposed method and two analytes, di-n-butyl phthalate and di-2-ethylhyxel phthalate, were determined in them in nanogram per milliliter level.     

Simultaneous determination of five phthalate esters and bisphenol A in milk by packed‐nanofiber solid‐phase extraction coupled with gas chromatography and mass spectrometry

A novel polystyrene/pyridine composite nanofiber was synthesized and utilized as the sorbent material for the solid‐phase extraction of bisphenol A and five common phthalate esters in milk. The method of extraction integrated extraction and preconcentration of target analytes into a single step. Bisphenol A and five common phthalate esters were selected as target compounds for the development and evaluation of the method. The effects of operating parameters for nanofiber‐based solid‐phase extraction, such as selection and amount of sorbent, the volume fraction of perchlorate (precipitate protein), desorption solvent, volume of desorption solvent, and effect of salt addition were optimized. Under optimal conditions, higher extraction recoveries (89.6–118.0%) of the six compounds in milk spiked at three levels were obtained, and the satisfied relative standard deviation were ranged from 0.6 to 10.9%. The detection limits and quantification limits of the method ranged from 0.01 to 0.06 μg/L and 0.05 to 0.53 μg/L, respectively. Matrix effects were also verified and well controlled in the range of 91.3–109.3%. The new method gave better performance metrics than Chinese standard method and other published methods. Thus, the proposed method may be applied to the analysis of the phthalate esters and bisphenol A in complex matrixes.     

Magnetic solid‐phase extraction of polycyclic aromatic hydrocarbons in water samples by Fe3O4@polypyrrole/carbon nanotubes

A magnetic solid‐phase extraction method coupled with gas chromatography was proposed for the determination of polycyclic aromatic hydrocarbons in the environmental water samples. The magnetic adsorbent was prepared by incorporating Fe₃O₄ nanoparticles, multi‐walled carbon nanotubes, and polypyrrole. The main factors affecting the extraction efficiency including the amount of the sorbents, desorption conditions, extraction time, salt concentration, and sample solution pH were investigated and optimized. Under the optimum conditions, good linearity was obtained within the range of 0.03?100 ng/mL for all analytes, with correlation coefficients ranging from 0.9942 to 0.9973. The method detection limits (S/N = 3) were in the range of 0.01–0.04 ng/mL and the limits of quantification (S/N = 10) were 0.03–0.1 ng/mL. Repeatability of the method was assessed through five consecutive extractions of independently prepared solutions at concentrations of 0.1, 10, and 100 ng/mL of the compounds. The observed repeatability ranged 3.4–10.9% depending of the compound considered. The proposed method was successfully applied in the analysis of PAHs in environmental samples (tap, well, river, and wastewater). The recoveries of the method ranged between 93.4 and 99.0%. The procedure proved to be efficient and environmentally friendly.     

Organochlorine residue analysis of commercial milks by capillary gas chromatography

The determination of organochlorine pesticides and polychlorinated biphenyls in milks requires the use of efficient extraction methods. A rapid procedure has been developed, based on extraction of organochlorine residues from milk on to octadecylsilica solid phase extraction cartridges and elution with hexane. The addition of different organic solvents to the milk before solid phase extraction has been studied. The use of methanol to disrupt the fat globules enables almost complete recovery of the residues with minimum extraction of fatty substances. Recovery experiments were performed for eighteen compounds present at ppb levels in whole, two per cent, and skimmed milks. The average recoveries of the compounds from two per cent and skimmed milks were 73–84%; values for whole milk were lower. The residues were determined by gas chromatography using two kinds of capillary column (non-polar and semi-polar) and electron capture detection. The procedure shows low lipid carry over, and extraneous interferences are minimal. The method has been applied to the detection of organochlorine pesticides and nine individual polychlorinated biphenyls in commercial milks. The results obtained demonstrated the presence of very low levels of organochlorine residues in the commercial milks analyzed.     

New application of chitosan‐grafted polyaniline in dispersive solid‐phase extraction for the separation and determination of phthalate esters in milk using high‐performance liquid chromatography

Chitosan‐grafted polyaniline was synthesized and applied as a sorbent for the preconcentration of phthalate esters in dispersive solid‐phase extraction. By coupling dispersive solid‐phase extraction with high‐performance liquid chromatography and response surface methodology (central composite design), a reliable, sensitive, and cost‐effective method for simultaneous determination of phthalate esters including dimethyl phthalate, di‐n‐butyl phthalate, and di(2‐ethylhexyl)phthalate was developed. The morphology of sorbent had been studied by scanning electron microscopy and its chemical structure confirmed by Fourier transform infrared spectroscopy. Under optimum condition, good linearity was observed in the range of 5.0–5000.0 ng/mL. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were 0.1–0.3 and 0.3–1 ng/mL, respectively. The relative standard deviations were less than 8.8%. Finally, this procedure was employed for extraction of trace amounts of phthalic acid esters in milk samples, the relative recoveries ranged from 82 to 103%.     

Simultaneous determination of three organophosphorus pesticides in different food commodities by gas chromatography with mass spectrometry

A sensitive and selective gas chromatography with mass spectrometry method was developed for the simultaneous determination of three organophosphorus pesticides, namely, chlorpyrifos, malathion, and diazinon in three different food commodities (milk, apples, and drinking water) employing solid‐phase extraction for sample pretreatment. Pesticide extraction from different sample matrices was carried out on Chromabond C₁₈ cartridges using 3.0 mL of methanol and 3.0 mL of a mixture of dichloromethane/acetonitrile (1:1 v/v) as the eluting solvent. Analysis was carried out by gas chromatography coupled with mass spectrometry using selected‐ion monitoring mode. Good linear relationships were obtained in the range of 0.1–50 μg/L for chlorpyrifos, and 0.05–50 μg/L for both malathion and diazinon pesticides. Good repeatability and recoveries were obtained in the range of 78.54–86.73% for three pesticides under the optimized experimental conditions. The limit of detection ranged from 0.02 to 0.03 μg/L, and the limit of quantification ranged from 0.05 to 0.1 μg/L for all three pesticides. Finally, the developed method was successfully applied for the determination of three targeted pesticides in milk, apples, and drinking water samples each in triplicate. No pesticide was found in apple and milk samples, but chlorpyrifos was found in one drinking water sample below the quantification level.     

超高效液相色谱-串联质谱同时检测血液中29种农药

本文采用超高效液相色谱-串联质谱法(UPLC-MS/MS)和固相萃取法(SPE)建立了血液中29种农药同时筛查、定性、定量分析的方法,血液经4%磷酸水溶液稀释后,震荡10min,以8000r·min-1转速离心10min,取上清液过3mL甲醇和3mL水活化好的Oasis Prime HLB(3cc,60mg)固相萃取小柱,使用3mL5%甲醇水淋洗,3mL乙腈甲醇混合溶剂(90:10)洗脱,接收洗脱液后在40℃条件下氮吹仪吹干,使用0.5mL初始流动相复溶,震荡10s后,过0.22μm水膜,装液质小瓶后进样分析。采用ACQUITY UPLC HSS C18色谱柱(150 mm×2.1mm,1.8μm)分离,流动相为0.1%甲酸乙腈-水/甲酸/甲酸铵(5mmol,pH=3),梯度洗脱,电喷雾电离正离子模式(ESI+),多反应选择离子监测模式(MRM)检测。29种农药的检出限为0.1 ng·mL^-1~5 ng·mL^-1,定量限为0.5 ng·mL^-1~10 ng·mL^-1,回收率为62.4%~97.4%,基质效应为82.8%~109%,相对标准偏差小于10.3%,相关系数均大于0.99,线性关系良好范围为10 ng·mL^-1~1000ng·mL^-1。本文方法灵敏度高,可以对血液中29种农药成分进行筛查、定性、定量分析,能够满足实际血液样品中农药成分检测的需求。     

Validation of the Method of Selected Polychlorinated Biphenyls Determination in Human Milk Samples

A method for determination of trace concentrations of individual PCB congeners in human milk was validated. The analytical procedure included the following steps: acetone : hexane extraction, clean-up of extracts with concentrated sulfuric acid and solid phase extraction (SPE) on Florisil. The identification and quantification of analytes in purified extracts were carried out by high-resolution gas chromatography (HRGC) with electron capture detection (ECD) and/or with low-resolution mass spectrometry (LRMS). Recoveries of 14 PCB congeners from spiked cow milk samples, based on HRGC-ECD were between 87.3 and 93.6%. The precision of analyte determination was established as close to or less than 10%. The detection limits ranged between 0.14 and 0.26 ng/g fat and the quantification limits between 0.57 and 0.86 ng/g fat. The method was linear and characterized by good correlation coefficients (>0.99) for most of the compounds studied. The quality of the method under validation was verified by the analysis of Standard Reference Material (CRM-450) and interlaboratory exercise.     

Self‐assembly of poly(ionic liquid) functionalized mesoporous magnetic microspheres for the solid‐phase extraction of preservatives from milk samples

In this work, a novel, rapid, and simple analytical method was proposed for the detection of parabens in milk sample by gas chromatography coupled with mass spectrometry. At the same time, milk sample was pretreated by magnetic solid phase extraction, which detected up to five parabens. A series of important parameters of magnetic solid phase extraction were investigated and optimized, such as pH value of loading buffer, amount of material, adsorption time, ionic strength, eluting solvents, and eluting time. Under the optimized conditions, the corresponding values were more than 0.9991, limits of detection and the limit of quantification were 0.1 and 0.5 ng/mL, respectively. In addition, the recoveries were achieved in range of 95–105%, the liner range were within 0.1–600 ng/mL, and the relative standard deviations were even lower than 5%.     

Extraction of quinolones from milk samples using bentonite/magnetite nanoparticles before determination by high‐performance liquid chromatography with fluorimetric detection

In this work, bentonite magnetic nanoparticles synthesized by a typical coprecipitation method were used as the adsorbent for the magnetic solid‐phase extraction of six quinolones (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin, sarafloxacin, and lomefloxacin) from milk samples followed by high‐performance liquid chromatography with fluorimetric detection. Under the optimized conditions, the linear quantitation range for the six quinolones was 0.3–200 ng/mL, and the correlation coefficients of the calibration curves ranged from 0.9994 to 0.9999. The detection limit of the method was 0.1 ng/mL. Recoveries of quinolones from pure and low‐fat spiked milk samples varied from 80.4 to 92.7% and from 81.3 to 93.5%, respectively. These results demonstrated that the proposed method for the determination of six quinolones in milk samples was rapid, reliable, and efficient.     

Simultaneous determination of selected estrogenic endocrine disrupting chemicals and bisphenol A residues in whole milk using fabric phase sorptive extraction coupled to HPLC‐UV detection and LC‐MS/MS

A simple and sensitive analytical methodology is developed for rapid screening and quantification of selected estrogenic endocrine disrupting chemicals and bisphenol A from intact milk using fabric phase sorptive extraction in combination with high‐performance liquid chromatography coupled to ultraviolet detection/tandem mass spectrometry. The new approach eliminates protein precipitation and defatting step from the sample preparation workflow. In addition, the error prone and time‐consuming solvent evaporation and sample reconstitution step used as the sample post‐treatment has been eliminated. Parameters with most significant impact on the extraction efficiency of fabric phase sorptive extraction including sorbent chemistry, sample volume, extraction time have been thoroughly studied and optimized. Separation of the selected estrogenic endocrine disrupting chemicals including α‐estradiol, hexestrol, estrone, 17α‐ethinyl estradiol, diethylstilboestrol, and bisphenol A were achieved using a Zorbax Extend‐C18 high‐performance liquid chromatography column (15 cm × 4.6 mm, 5 μm particle size). The limit of detection values obtained in fabric phase sorptive extraction with high‐performance liquid chromatography with ultraviolet detection ranged from 25.0 to 50.0 ng/mL. The method repeatability values were 3.6–13.9 (relative standard deviation, %) and intermediate precision values were 4.6–12.7 (relative standard deviation, %). The fabric phase sorptive extraction method was also coupled to liquid chromatography with tandem mass spectrometry for identifying each endocrine disrupting chemical at 10 ng/mL.     

High performance liquid chromatographic determination of diazinon, permethrin, DEET (N, N-diethyl-m-toluamide), and their metabolites in rat plasma and urine

A rapid method was developed for the analysis of the insecticide (A) diazinon (O,O-diethyl O-2-isopropyl-6-methylpyridimidinyl) phosphorothioate, its metabolites (B) diazoxon (O,O-diethyl O-2-isopropyl-6-methylpyridimidinyl) phosphate, and (C) 2-isopropyl-6-methyl-4-pyrimidinol, the insecticide (D) permethrin [3-(2,2-dichloro-ethenyl)-2,2-dimethylcyclopropanecarboxylic acid (3-phenoxyphenyl)methylester], its metabolites (E) m-phenoxybenzyl alcohol, and (F) m-phenoxybenzoic acid, the insect repellent (G) DEET (N,N-diethyl-m-toluamide), and its metabolites (H) m-toluamide and (I) m-toluic acid in rat plasma and urine. The method is based on using C18 Sep-Pak cartridges (Waters Corporation, Milford, Mass., U.S.A.) for solid phase extraction and high performance liquid chromatography with a reversed phase C18 column, and absorbance detection at 230 nm for compounds A, B, and C, and at 210 nm for compounds D-I. The compounds were separated using a gradient from 1% to 99% acetonitrile in water (pH 3.0) at a flow rate ranging between 1 and 1.7 mL/min in a period of 17 min. The limits of detection were ranged between 20 and 100 ng/mL, while limits of quantification were 80-200 ng/mL. The relationship between peak areas and concentration was linear over a range of 100-1000 ng/mL. This method was applied to determine the above insecticides and their metabolites following dermal administration in rats.     

Rapid analysis of three β‐agonist residues in food of animal origin by automated on‐line solid‐phase extraction coupled to liquid chromatography and tandem mass spectrometry

An automated online solid‐phase extraction with liquid chromatography and tandem mass spectrometry method was developed and validated for the detection of clenbuterol, salbutamol, and ractopamine in food of animal origin. The samples from the food matrix were pretreated with an online solid‐phase extraction cartridge by Oasis MCX for <5 min after acid hydrolysis for 30 min. The peak focusing mode was used to elute the target compounds directly onto a C₁₈ column. Chromatographic separation was achieved under gradient conditions using a mobile phase composed of acetonitrile/0.1% formic acid in aqueous solution. Each analyte was detected in two multiple reaction monitoring transitions via an electrospray ionization source in a positive mode. The relative standard deviations ranged from 2.6 to 10.5%, and recovery was between 76.7 and 107.2% at all quality control levels. The limits of quantification of three β‐agonists were in the range of 0.024–0.29 μg/kg in pork, sausage, and milk powder, respectively. This newly developed method offers high sensitivity and minimum sample pretreatment for the high‐throughput analysis of β‐agonist residues.     

Direct immersion solid‐phase microextraction with gas chromatography and mass spectrometry for the determination of specific biomarkers of human sweat in melted snow

To provide a reliable tool for investigating diffusion processes of the specific components of the human odor 3‐hydroxy‐3‐methylhexanoic acid and 3‐methyl‐3‐sulfanylhexan‐1‐ol through the snowpack, we developed and optimized an analytical method based on direct immersion solid‐phase microextraction followed by gas chromatography with mass spectrometry. Direct immersion solid‐phase microextraction was performed using polyacrylate fibers placed in aqueous solutions containing 3‐hydroxy‐3‐methylhexanoic acid and 3‐methyl‐3‐sulfanylhexan‐1‐ol. After optimization, absorption times of 120 min provided a good balance to shorten the analysis time and to obtain suitable amounts of extractable analytes. The extraction efficiency was improved by increasing the ionic strength of the solution. Although the absolute extraction efficiency ranged between 10 and 12% for 3‐hydroxy‐3‐methylhexanoic acid and 2–3% for 3‐methyl‐3‐sulfanylhexan‐1‐ol, this method was suitable for analyzing 3‐hydroxy‐3‐methylhexanoic acid and 3‐methyl‐3‐sulfanylhexan‐1‐ol concentrations of at least 0.04 and 0.20 ng/mL, respectively. The precision of the direct immersion solid‐phase microextraction method ranged between 8 and 16%. The variability within a batch of six fibers was 10–18%. The accuracy of the method provided values of 88–95 and 86–101% for 3‐hydroxy‐3‐methylhexanoic acid and 3‐methyl‐3‐sulfanylhexan‐1‐ol, respectively. The limit of detection (and quantification) was 0.01 ng/mL (0.04 ng/mL) for 3‐hydroxy‐3‐methylhexanoic acid and 0.06 ng/mL (0.20 ng/mL) for 3‐methyl‐3‐sulfanylhexan‐1‐ol. The signal versus concentration was linear for both compounds (r² = 0.973–0.979). The stability of these two compounds showed that 3‐hydroxy‐3‐methylhexanoic acid was more stable in water than 3‐methyl‐3‐sulfanylhexan‐1‐ol. We applied the method to environmental samples in correspondence with an olfactory target buried previously.     

Molecularly imprinted polymer surfaces as solid-phase extraction sorbents for the extraction of 2-nitrophenol and isomers from environmental water

The novel surface molecularly imprinted polymer (MIP) with 2‐nitrophenol (2‐NP) as the template has been prepared and used as the adsorbent for the solid‐phase extraction (SPE). The selectivity of the polymer was checked toward several selected nitrophenols (NPs) such as 2‐NP, 3‐nitrophenol (3‐NP), 4‐nitrophenol (4‐NP) and 2,4,6‐trichlorophenol (2,4,6‐TCP). Under the optimized conditions, high sensitivity (detection limits: 0.07–0.12 ng/mL) and good reproducibility of analytes (2.3–4.8% for four cycles) were achieved. Then, the method was applied for the analysis of selected phenols in spiked tap, lake and river water samples. High recoveries (>83.3%) for nitrophenols (NPs) were obtained, but lower recoveries (<63.4%) were achieved for 2,4,6‐TCP. The method was found to be linear in the range of 1–300 ng/mL with correlation coefficients (R²) greater than 0.99 and repeatability relative standard deviation (RSD) below 7.2% in all cases. For analysis of 120 mL water samples, the method detection limits (LODs) ranged from 0.10 to 0.22 ng/mL and the limit of quantification (LOQs) from 0.33 to 0.72 ng/mL. These results showed the suitability of the MIP‐SPE method for the selective extraction of a group of structurally related isomeric compounds.     

Development and Validation of a Chiral Liquid Chromatographic Assay for Enantiomeric Separation and Quantification of Verapamil in Rat Plasma: Stereoselective Pharmacokinetic Application

A novel, fast and sensitive enantioselective HPLC assay with a new core–shell isopropyl carbamate cyclofructan 6 (superficially porous particle, SPP) chiral column (LarihcShell-P, LSP) was developed and validated for the enantiomeric separation and quantification of verapamil (VER) in rat plasma. The polar organic mobile phase composed of acetonitrile/methanol/trifluoroacetic acid/triethylamine (98:2:0.05: 0.025, v/v/v/v) and a flow rate of 0.5 mL/min was applied. Fluorescence detection set at excitation/emission wavelengths 280/313 nm was used and the whole analysis process was within 3.5 min, which is 10-fold lower than the previous reported HPLC methods in the literature. Propranolol was selected as the internal standard. The S-(−)- and R-(+)-VER enantiomers with the IS were extracted from rat plasma by utilizing Waters Oasis HLB C18 solid phase extraction cartridges without interference from endogenous compounds. The developed assay was validated following the US-FDA guidelines over the concentration range of 1–450 ng/mL (r² ≥ 0.997) for each enantiomer (plasma) and the lower limit of quantification was 1 ng/mL for both isomers. The intra- and inter-day precisions were not more than 11.6% and the recoveries of S-(−)- and R-(+)-VER at all quality control levels ranged from 92.3% to 98.2%. The developed approach was successfully applied to the stereoselective pharmacokinetic study of VER enantiomers after oral administration of 10 mg/kg racemic VER to Wistar rats. It was found that S-(−)-VER established higher C_max and area under the concentration-time curve (AUC) values than the R-(+)-enantiomer. The newly developed approach is the first chiral HPLC for the enantiomeric separation and quantification of verapamil utilizing a core–shell isopropyl carbamate cyclofructan 6 chiral column in rat plasma within 3.5 min after solid phase extraction (SPE).     

亚临界水萃取及气相色谱-串联质谱法检测红茶中多种农药残留

建立了亚临界水萃取及气相色谱-串联质谱(GC-MS/MS)检测红茶中21种有机氯和拟除虫菊酯农药残留的方法。在萃取压力为5 MPa条件下,样品经150 ℃的亚临界水提取15 min后,将目标物转移至丙酮-正己烷(1:1, v/v)中,经ENVI-Carb固相萃取净化小柱净化,DB-5毛细管气相色谱柱分离,在多反应监测(MRM)模式下进行MS/MS检测,基质匹配溶液内标法定量。各目标物在5.0～320.0 μg/L范围内线性关系良好,相关系数均大于0.99,其定量限(信噪比(S/N)＞10)为50 ng/g,检出限(S/N＞3)为10 ng/g。茶叶基质中添加50、100和200 ng/g的标准品时,21种农药的回收率为70.18%～119.98%,相对标准偏差(RSD)为5.01%～11.76%。该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求,适用于红茶中有机氯和拟除虫菊酯农药残留的检测。     

Determination of Ginsenoside Rg2 in Rat Plasma by High‐Performance Liquid Chromatography–Mass Spectrometry after Solid‐Phase Extraction

Abstract

A sensitive liquid chromatography‐mass spectrometric (LC/MS) method for the quantification of ginsenoside Rg2 (Rg2) in rat plasma was developed after solid‐phase extraction (SPE). Chromatographic separation was achieved on a reversed‐phase Kromasil C₁₈ column with the mobile phase of acetonitrile‐ammonium chloride (500 µM/L) and step gradient elution resulted in a total run time of about 9 min. The analytes were detected using electrospray negative ionization mass spectrometry in the selected ion monitoring (SIM) mode. A good linear relationship was obtained in the concentration range (5–2500 ng/mL) (r=0.9999). Limit of quantification (LOQ) was 5 ng/mL and the limit of detection (LOD) was 2 ng/mL using 100 µL plasma sample. Average recoveries ranged from 72.43–84.73% in plasma at the concentrations of 20, 200, and 2000 ng/mL. Intra‐ and interday coefficients of variation for the assay were 4.93–10.87% and 4.06–7.84%, respectively. The method was successfully applied to the analysis of ginsenoside Rg2 in rat plasma. The applicability of this assay was examined in a preliminary pharmacokinetic study of ginsenoside Rg2 in rats.