Analysis of Local Anesthetics in Biological Samples via Kinetically Calibrated Liquid-Phase Solvent Bar Micro-Extraction Combined with HPLC

In this study, a liquid-phase solvent bar micro-extraction technique was used to investigate both the extraction and back-extraction processes of the target analyte. A novel concentration curve method and a classic time curve method, used under the same experimental conditions, verified the symmetry between the extraction process (target analyte moves from sample matrix to the organic solvent-based extraction phase) and the back-extraction process (target analyte moves from organic solvent to the sample matrix), providing the basis to use the target analyte in the back-extraction process to calibrate its extraction process. A quantitative calibration can be achieved using back extraction on the target analyte from the blank sample matrix in the organic solvent. Information from the process of back extraction of the target analyte, such as the time constant a, can be directly used to calculate the initial concentration of the target analyte in the sample matrix. This new kinetic calibration method employs a liquid-phase solvent bar micro-extraction technique combined with high-performance liquid chromatography with a diode array detector (HPLC-DAD) and was successfully used to analyze three local anesthetics in biological samples; it extends the application of the kinetic calibration to HPLC-DAD and establishes a novel, simple and accurate method to determine the concentration of the free drug in biological samples and its protein-binding ratio.     

Headspace liquid phase microextraction for quantitation of hexanal in potato crisps by gas chromatography

A simple and rapid method using headspace liquid-phase microextraction (HS-LPME) was developed for the determination of hexanal at low levels in potato crisp samples. Parameters such as extraction solvent, agitation of the sample, salt addition, organic drop volume, exposure time, and extraction time were controlled and optimised. The developed protocol was found to yield a linear calibration curve in the concentration range from 0.001 to 2 mg/L and a limit of detection of 0.1 microg/L with a good enrichment factor of > 107 for the analyte. The repeatability of the method was satisfactory (4%). The results demonstrate that HS-LPME is a rapid, accurate, and effective preparation method and could be successfully used for the determination of hexanal in potato crisp samples.     

中空纤维液相微萃取-高效液相色谱法测定纺织品中10种含氯苯酚类化合物

建立了中空纤维液相微萃取-高效液相色谱法测定纺织品中10种含氯苯酚类化合物的方法。系统地优化了影响萃取效率的因素,得到的最佳萃取条件为：萃取溶剂为正己烷,接受相NaOH溶液的浓度为0.10 mol/L,萃取时间为60 min,搅拌速度为600 r/min。在最佳萃取条件下,10种含氯苯酚在0.01～1.00 mg/L范围内线性关系良好（r>0.999）,10种含氯苯酚的检出限（信噪比为3）为0.01 mg/kg,富集倍数为95～101。在空白样品中添加0.01、0.05和0.1 mg/kg 3个不同水平的10种含氯苯酚类化合物,其平均回收率为78.8%～105.1%,相对标准偏差为0.3%～7.3%。研究结果表明该方法灵敏度高、简便、准确,可用于纺织品中含氯苯酚类化合物的测定。     

Advances in sample preparation in chromatography for organic environmental pollutants analyses

Many pollutants are present at trace level in our environment, which are beyond the scope of the detection by advance instruments too. Therefore, there is urgent need to develop advance sample preparation methods to determine the concentrations of the pollutants even at trace levels. Keeping this into consideration, many extraction techniques have been developed and applied for the analysis of organic pollutants in environmental samples. This review presents the sate-of-the-art of sample preparation methods in environmental samples. The extraction techniques discussed are headspace, liquid based extraction, supported liquid, homogeneous liquid–liquid, homogeneous liquid–liquid, single drop micro-extraction, membrane assisted solvent, solid-phase, molecularly imprinted solid-phase, monolithic spin column, matrix solid-phase, dispersive solid-phase, disposable pipette, magnetic solid-phase, solid-phase micro-extraction, micro-extraction by packed sorbent and stir bar sorptive. The article will be highly useful for environmental chromatographers.     

兽药残留分析中样品前处理技术研究进展

样品前处理是兽药残留分析中的关键步骤,直接影响检测的结果.近年来,出现了一些新的样品前处理技术,如固相萃取、基质固相分散萃取、固相微萃取、搅拌棒吸附萃取、膜萃取、液相微萃取、超临界流体萃取、加速溶剂萃取、分子印迹、微波辅助萃取.这些技术能够有效地减少分析过程中由样品前处理过程带来的误差,具有前处理快速、简便的优点,同时可与分析仪器联用,实现分析的自动化.本文对这些新技术的基本原理、特点及在兽药残留分析中的应用进行了综述,并对样品前处理的前景进行了展望.     

高效液相色谱-二极管阵列检测法及高效液相色谱-电喷雾串联质谱法测定植物源性蛋白中残留的三聚氰胺

建立了高效液相色谱-二极管阵列检测器(HPLC-DAD)及HPLC-电喷雾串联质谱(ESI-MS/MS)测定植物源性蛋白中残留的三聚氰胺的方法。利用HPLC-DAD进行样品中三聚氰胺的初筛,利用HPLC-MS/MS进行确证。采用三氯乙酸溶液沉淀样品中的蛋白,同时提取目标分析物,质谱检测时样品再经强阳离子固相萃取柱富集净化。HPLC-DAD的检测低限为10 mg/kg,HPLC-MS/MS的检测低限为0.5 mg/kg;HPLC-DA的添加回收率为76%～88%,HPLC-MS/MS的添加回收率为72%～82%(基质匹配曲线校正),两种方法的添加回收率的相对标准偏差(RSD)为3.4%～6.4%。     

Analysis of organochlorine pesticides in wine by solvent bar microextraction coupled with gas chromatography with tandem mass spectrometry detection

A solvent bar microextraction (SBME) technique combined with gas chromatography/tandem mass spectrometry (GC/MS/MS), for the determination of selected organochlorine pesticides (OCPs) in wine samples, is described. In this work the OCPs were extracted and dissolved in a 2-microL aliquot of organic extraction solvent (n-tetradecane) confined within a 1.7-cm length of hollow fiber. Both ends of the hollow fiber (solvent bar) were sealed, and it was placed in an aqueous sample solution for extraction. The effects of solvent selection, sample agitation, extraction time, extraction temperature, and salt concentration on the SBME performance were optimized. The influence of aqueous sample/organic solvent phase ratio was further investigated in detail. High enrichments (1900-7100-fold) could be obtained at an aqueous sample/organic solvent volume ratio of 20 mL/2 microL in this study. Good extraction reproducibility was obtained with relative standard deviation (RSD) values below 12.6%. Comparisons of sensitivity and precision between SBME and dynamic hollow-fiber liquid-phase microextraction were also investigated.     

Application of liquid-phase microextraction for the determination of phoxim in water samples by high performance liquid chromatography with diode array detector

A new method, which involves liquid-phase microextraction (LPME) followed by high performance liquid chromatography (HPLC) with diode array detector (DAD), was developed to determine phoxim in water sample. Experimental parameters affecting the extraction efficiency, such as extraction solvent, solvent volume, agitation speed of the sample and extraction time were investigated. Under the optimal extraction conditions, phoxim was found to yield a good linear calibration curve in the concentration range from 0.01 to 5 μg mL⁻¹. The limit of detection (LOD) is 10 ng mL⁻¹, and relative standard deviation (RSD) at the 100 ng mL⁻¹ levels is 8.4%. Lake water and tap water samples were successfully analyzed using the proposed method.     

LC Determination of Chloramphenicol in Honey Using Dispersive Liquid–Liquid Microextraction

A novel method, dispersive liquid–liquid microextraction coupled with liquid chromatography-variable wavelength detector (LC-VWD), has been developed for the determination of chloramphenicol (CAP) in honey. A mixture of extraction solvent (30 μL 1,1,2,2-tetrachloroethane) and dispersive solvent (1.00 mL acetonitrile) were rapidly injected by syringe into a 5.0 mL real sample for the formation of cloudy solution, the analyte in the sample was extracted into the fine droplets of C₂H₂Cl₄. After extraction, phase separation was performed by centrifugation and the enriched analyte in the sedimented phase was determined by LC-VWD. Some important parameters, such as the kind and volume of extraction solvent and dispersive solvent, extraction time, sample solution pH, sample volume and salt effect were investigated and optimized. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 3 to 2,000 μg kg^?1 for target analyte. The enrichment factor for CAP was 68.2, and the limit of detection (S/N = 3) were 0.6 μg kg^?1. The relative standard deviation (RSD) for the extraction of 10 μg kg^?1 of CAP was 4.3% (n = 6). The main advantages of method are high speed, high enrichment factor, high recovery, good repeatability and extraction solvent volume at μL level. Honey samples were successfully analyzed using the proposed method.     

Micro-extraction techniques in analytical toxicology: short review

This paper discusses new developments in plasma micro-extraction techniques in the context of established micro-extraction and protein precipitation methodology. Simple liquid-liquid solvent extraction (LLE) of plasma with direct GC or HPLC analysis of the resulting extract has been used for many years. Butyl acetate and methyl t-butyl ether (MTBE) give efficient extraction of many drugs and metabolites from small volumes of plasma or whole blood at an appropriate pH, and form the upper layer, thus simplifying extract removal. Butyl acetate does not interfere with NPD, ECD or MS in GC, whilst MTBE has a relatively low UV cutoff (220 nm). Thus, HPLC eluents that use a high proportion of an organic component allow MTBE extracts to be analysed directly. 'Salting-out' and extractive derivatization using acetic anhydride or phenylboronic acid can be used with appropriate analytes. As regards protein precipitation, an important consideration is lowering the pH, although this is not feasible with acid-labile analytes. More recent developments include sold-phase micro-extraction (SPME) and liquid-phase micro-extraction (LPME). This latter technique especially may prove invaluable as analytes that cannot easily be extracted with LLE can be isolated simply at low cost with a minimum of apparatus.     

Ultrasonication followed by single-drop microextraction combined with GC/MS for rapid determination of organochlorine pesticides from fish

A novel, rapid and simple sample pretreatment technique termed ultrasonication followed by single-drop micro-extraction (U-SDME) has been developed and combined with GC/MS for the determination of organochlorine pesticides (OCPs) in fish. In the present work, the lengthy procedures generally used in the conventional methods like, Soxhlet extraction, supercritical fluid extraction, pressurized liquid extraction and microwave assisted solvent extraction for extraction of OCPs from fish tissues are minimized by the use of two simple extraction procedures. Firstly, OCPs from fish were extracted in organic solvent with ultrasonication and then subsequently preconcentrated by single-drop micro-extraction (SDME). Extraction parameters of ultrasonication and SDME were optimized in spiked sample solution in order to obtain efficient extraction of OCPs from fish tissues. The calibration curves for OCPs were found to be linear between 10-1000 ng/g with correlation of estimations in the range 0.990-0.994. The recoveries obtained in blank fish tissues were ranged from 82.1 to 95.3%. The LOD and RSD for determination of OCPs in fish were 0.5 ng/g and 9.4-10.0%, respectively. The proposed method was applied for the determination of bioconcentration factor in fish after exposure to different concentrations of OCPs in cultured water. The present method avoids the co-extraction of lipids, long extraction steps (>12 h) and large amount of organic solvent for the separation of OCPs. The main advantages of the present method are rapid, selective, sensitive and low cost for the determination of OCPs in fish.     

Temperature-assisted ionic liquid dispersive liquid-liquid microextraction combined with high performance liquid chromatography for the determination of anthraquinones in Radix et Rhizoma Rhei samples

In this article, a novel method termed as temperature-assisted ionic liquid dispersive liquid-liquid microextraction (TA IL-DLLME) combining high performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the determination of anthraquinones in Radix et Rhizoma Rhei samples. The ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) was used to replace volatile organic solvent as an extraction solvent for the extraction of anthraquinones (aloe-emodin, rhein, emodin, chrysophanol and physcion) from Radix et Rhizoma Rhei. Several important parameters influencing the extraction efficiency of TA IL-DLLME such as the type and volume of extraction solvent and disperser solvent, sample pH, extraction time, extraction temperature, centrifugation time as well as salting-out effects were optimized. Under the optimal conditions, the spiked recovery for each analyte was in the range of 95.2-108.5%. The precisions of the proposed method were varied from 1.1% to 4.4% (RSD). All the analytes exhibited good linearity with correlation coefficients (r²) ranging from 0.9986 to 0.9996. The limits of detection for all target analytes were ranged from 0.50 to 2.02 μg L⁻¹ (S/N = 3). The experimental results indicated that the proposed method was successfully applied to the analysis of anthraquinones in Radix et Rhizoma Rhei.     

Determination of chlorophenols in environmental water samples using directly suspended droplet liquid-liquid-liquid phase microextraction prior to high-performance liquid chromatography

A new sample preparation method named directly suspended droplet liquid-liquid-liquid phase microextraction was used in this research for determination of three chlorophenols in environmental water samples. The analytes (2-chlorophenol, 3-chlorophenol and 4-chlorophenol) were extracted from 4.5?mL acidic donor phase, (pH 2, P1) into an organic phase, 350?µL?of benzene/1-octanol (90?:?10 v/v, P2) and then were back-extracted into a 7?µL droplet of an basic (pH 13) aqueous solution (acceptor phase, P3). In this method, contrary to the ordinary single drop liquid-phase microextraction technique, an aqueous large droplet is freely suspended on the surface of the organic solvent, without using a microsyringe as supporting device. This aqueous microdroplet is delivered at the top-centre position of an immiscible organic solvent which is laid over the aqueous donor sample solution while the solution is being agitated. Then, the acceptor phase containing chlorophenols was withdrawn back into a HPLC microsyringe and neutralised by adding of 7?µL HCl 0.1?M. The total amount was eventually injected into the HPLC system with UV detection at 225?nm for further analysis. Parameters such as the organic solvent, phases volumes, extraction and back-extraction times, stirring rate and pH values were optimised. The calibration graphs are linear in the range of 10–2000?µg?L^?1 with r?≥?0.9973. The enrichment factors were ranged from 115 to 170, and the limit of detection (LOD, n?=?7) varied from 5 to 10?µg?L^?1. The relative standard deviations (RSDs, n?=?5) were found 6.8 to 7.4 at S/N?=?3. All experiments were carried out at room temperature, (22?±?0.5°C).     

Coupling of air-assisted liquid–liquid microextraction method with partial least squares for simultaneous spectrophotometric determination of some preservatives

An air-assisted liquid–liquid microextraction method coupled with a multivariate calibration method, namely partial least squares (PLS), was developed for the extraction and simultaneous determination of benzoic acid (BA) and sorbic acid (SA) via a spectrophotometric approach. In this work, a two-step microextraction method was used. In the first step, analytes were extracted from acidic aqueous solution into octanol, as an organic solvent, and in the second step, the analytes were simultaneously back-extracted into an alkaline aqueous solution. The high absorption signal of octanol was the main reason to perform this back-extraction step. The effects of different parameters on the method efficiency were investigated; the parameters included extraction solvent volume, ionic strength of aqueous solution, pH, number of extraction cycles, and aqueous sample volume. Under optimum conditions, calibration graphs were seen to be linear over the range of 0.1–2.0 µg mL^?1 for the both analytes. Other analytical parameters were obtained as follows: Enrichment factors (EFs) were found to be 14.98 and 13.03, and limits of detection were determined to be 0.03 and 0.04 µg mL^?1 for BA and SA, respectively. As the last step, binary mixtures of the analytes were prepared and simultaneously extracted using the proposed method. Finally, PLS modeling was used for multivariate calibration of spectrophotometric data. It was successfully utilized for the analysis of the target analytes in real samples.     

Hollow fibre liquid-phase microextraction of parabens from environmental waters

Parabens (alkyl-p-hydroxybenzoates) are antimicrobial preservatives widely used in cosmetics, toiletries, pharmaceuticals, and food. Nowadays, they are considered emerging pollutants and their determination is becoming increasingly important since they are continuously released into the environment. In this work, a hollow fibre liquid-phase microextraction method has been developed for the extraction of parabens from environmental waters. The parameters affecting the extraction of parabens (organic solvent used as liquid membrane; pH of both sample and acceptor solution; salting-out effect; extraction time and stirring speed) were carefully optimized in order to reach high recoveries for all tested analytes. Under optimum conditions, parabens were extracted from river, reservoir and sea water samples with recoveries ranging from 16.7 to 68.6% depending upon the analyte and the sample analyzed, leading to detection limits lower than 0.2?ng?mL^?1 using a simple HPLC-UV instrument.     

Hydrodistillation–liquid-phase microextraction for infrared analysis of food

A combination of hydrodistillation (HD) and liquid-phase microextraction (LPME) has been successfully developed to improve sensitivity and selectivity in attenuated total reflection (ATR) infrared determination of semivolatile organic compounds from high water content plant and food matrices contributing to solve extraction efficiency drawbacks. The HD sampling facilitates the extraction of the semivolatile analytes from the sample matrix compared to headspace sampling, while the liquid-phase microextraction using a water immiscible solvent allows analyte preconcentration prior to ATR analysis. Experimental conditions regarding temperature and time of extraction, water effect and number of consecutive extractions have been deeply studied. The qualitative and quantitative capability of the developed methodology has been evaluated through the identification of the main semivolatile substances in plant and food matrices like spices and citrus peels and the effect of different drying treatments on the volatile composition of rosemary samples was studied through the quantification of camphor and eucalyptol.     

Determination of steroid sex hormones in urine matrix by stir bar sorptive extraction based on monolithic material and liquid chromatography with diode array detection

A simple, rapid and sensitive method for simultaneous determination of six steroid sex hormones in urine matrix was developed by the combination of stir bar sorptive extraction (SBSE) with high performance liquid chromatography (HPLC) and diode array detection (DAD). A poly (methacrylic acid stearyl ester-ethylene dimethacrylate) was synthesized and selected as SBSE extraction medium. To achieve the optimum extraction performance, several parameters, including agitation speed, desorption solvent, extraction and desorption time, pH value, inorganic salt and organic solvent content of the sample matrix were investigated. Under the optimized experimental conditions, low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target compounds were achieved within the range of 0.062-0.38 and 0.20-1.20 ng/mL, respectively from spiked urine, respectively. The calibration curves of six steroid sex hormones showed good linearity ranging from 1.0 to 200 ng/mL with linear coefficient R2 values above 0.990. Good method reproducibilities presented as intra- and inter-day precisions were also found with the R.S.D.s less than 9.2 and 10.0%, respectively. Finally, the proposed method was successfully applied to the determination of the target compounds in a urine sample from a pregnant woman.     

Headspace Single Drop Microextraction for the Analysis of Fire Accelerants in Fire Debris Samples

Fire accelerants such as gasoline, kerosene, and diesel have commonly been used in arson cases. Improved analytical methods involving the extraction of fire accelerants are necessary to increase sample yield and to reduce the number of uncertain findings. In this study, an analytical method based on headspace single drop microextraction (HS-SDME) followed by gas chromatography–flame ionization detection (GC-FID) has been developed for the analysis of simulated fire debris samples. Curtain fabric was used as the sample matrix. The optimized conditions were 2.5 μL benzyl alcohol microdrop exposed for 20 min to the headspace of a 10 mL aqueous sample containing accelerants placed in 15-mL sample vial and stirred at 1500 rpm. The extraction method was compared with the solvent extraction method using n-hexane for the determination of fire accelerants. The HS-SDME process is driven by the concentration difference of analytes between the aqueous phases containing the analyte and the organic phase constituting the microdrop of a solvent. The limit of detection of HS-SDME for kerosene was 1.5 μL. Overall, the HS-SDME coupled with GC-FID proved to be rapid, simple and sensitive and a good alternative method for the analysis of accelerants in fire debris samples.     

Fast extraction of amphenicols residues from raw milk using novel fabric phase sorptive extraction followed by high-performance liquid chromatography-diode array detection

A simple, sensitive, reliable, and fast analytical method was developed for the simultaneous determination of amphenicols residues in raw milk by combining fabric phase sorptive extraction (FPSE) and high-performance liquid chromatography-diode array detection. FPSE, a new generation green sample preparation technique, efficiently incorporates the advanced and tunable material properties of sol–gel derived microextraction sorbents with the rich surface chemistry of a cellulose fabric substrate, resulting in a flexible, highly sensitive, and fast microextraction device capable of extracting target analytes directly from complicated sample matrices. Due to the strong chemical bonding between the sol–gel sorbent and substrate, the microextraction device demonstrates a very high chemical and solvent stability. Therefore, any organic solvent/solvent mixture can be used as the eluent/back-extraction solvent.     

Non‐hydrolytic Sol‐gel Methodology to Prepare a Molecularly Imprinted,Organic‐silica Hybrid‐based Stir Bar for Recognition of Sulfonylurea Herbicides

Based on a molecularly imprinted organic‐silica hybrid‐based stir bar, a pre‐treatment methodology was developed for enrichment of nicosulfuron in aqueous samples. The molecularly imprinted organic‐silica hybrid‐based coating on the outer surface of a glass stir bar was prepared by in‐situ polymerization using nicosulfuron as a template molecule, α‐methacrylic acid as a functional monomer, methacryloxypropytrimethoxysilane as a cross‐linker in the mixture of acetonitrile and trichloromethane (V/V, 7.5:1). To achieve the selective extraction of the target analyte from aqueous samples, several main parameters, including extraction time, pH value and contents of inorganic salt in the sample matrix were investigated. Evidence was also presented by the scanning electronic microscopic images of the imprinted and non‐imprinted stir bars. Then, the extraction efficiency of the stir bar was tested with separate experiments and competitive sorption experiments. These results showed that using six sulfonylureas as substrates the molecularly imprinted organic‐silica hybrid‐based stir bar gave high selectivity for the template, nicosulfuron compared to the non‐imprinted organic‐silica hybrid‐based stir bar. This sorption extraction was coupled to liquid chromatography ultraviolet detection allowing the determination of nicosulfuron from tap water. The method showed good recoveries and precision, 96.0% (RSD 2.7%, n=3) for tap water spiked with 0.125 nmol (25.00 mL sample), suggesting that the stir bar can be successfully applied to the pre‐concentration of nicosulfuron in real aqueous samples.