Optimization of QuEChERS Procedure Coupled to GC-ECD for Organochlorine Pesticide Determination in Carrot Samples

An optimised version of the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for simultaneous determination of 14 organochlorine pesticides in carrots was developed using gas chromatography coupled with electron-capture detector (GC-ECD) and confirmation by gas chromatography tandem mass spectrometry (GC-MS/MS). A citrate-buffered version of QuEChERS was applied for the extraction of the organochlorine pesticides, and for the extract clean-up, primary secondary amine, octadecyl-bonded silica (C18), magnesium sulphate (MgSO₄) and graphitized carbon black were used as sorbents. The GC-ECD determination of the target compounds was achieved in less than 20 min. The limits of detection were below the EU maximum residue limits (MRLs) for carrots, 10–50 μg kg^?1, while the limit of quantification did exceed 10 μg kg^?1 for hexachlorobenzene (HCB). The introduction of a sonication step was shown to improve the recoveries. The overall average recoveries in carrots, at the four tested levels (60, 80, 100 and 140 μg kg^?1), ranged from 66 to 111 % with relative standard deviations in the range of 2–15 % (n?=?3) for all analytes, with the exception of HCB. The method has been applied to the analysis of 21 carrot samples from different Portuguese regions, and β-HCH was the pesticide most frequently found, with concentrations oscillating between less than the limit of quantification to 14.6 μg kg^?1. Only one sample had a pesticide residue (β-HCH) above the MRL, 14.6 μg kg^?1. This methodology combines the advantages of both QuEChERS and GC-ECD, producing a very rapid, sensitive and reliable procedure which can be applied in routine analytical laboratories.     

顶空固相微萃取联合气相色谱-质谱检测葡萄酒中2,4,6-三氯苯甲醚

利用响应面法优化采用顶空固相微萃取联合气相色谱-质谱技术检测葡萄酒中2,4,6-三氯苯甲醚（2,4,6-trichloroanisole,TCA）。对萃取头进行了选择,并优化固相微萃取参数：样品体积、萃取温度、平衡时间和萃取时间等对TCA萃取效果的影响。结果表明,用聚二甲基硅氧烷/二乙烯基苯（65 μm）萃取头进行TCA萃取的最佳条件：样品9.8 mL、2 g NaCl、33 ℃平衡10 min、萃取90 min进行气相色谱-质谱分析,以TCA-d5为内标物进行定量。该方法的相关系数R2为0.999 9,重复性的相对标准偏差为1.03%,加标回收率范围在95.7%～106.1%之间,检出限和定量限分别为0.3 ng/L和1 ng/L。检测7 种市售葡萄酒产品的TCA含量在0～7.6 ng/L之间,干白葡萄酒中TCA含量低于干红葡萄酒。该方法操作简单、可靠,适用于葡萄酒中TCA的测定。     

Vortex-Assisted Ionic Liquid Dispersive Liquid-Liquid Microextraction Coupled with High-Performance Liquid Chromatography for the Determination of Triazole Fungicides in Fruit Juices

A rapid, efficient, and environmentally friendly method using vortex-assisted ionic liquid dispersive liquid-liquid microextraction (VA-IL-DLLME) prior to high-performance liquid chromatography coupled with photodiode array detection (HPLC-PDA) has been developed for the determination of six triazole fungicides (triazolone, triadimenol, epoxiconazole, flusilazole, tebuconazole, and diniconazole) in various fruit juices. 1-Hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) and acetonitrile were used as extraction and dispersive solvents, respectively. A single factor experiment was selected to obtain the significant variables from the several related parameters that could affect the extraction efficiencies, such as the volume of IL and acetonitrile, extraction time, centrifugation time, and salt addition. Under the optimum conditions, an excellent linearity with correlation coefficients higher than 0.997 was obtained. Enrichment factors and average recoveries in three concentration levels ranged from 51 to 72, and 71.0 to 104.5 %, respectively, and the relative standard deviations (RSDs) from 1.4 to 11.8 %. The limits of detection (LODs) (S/N?=?3) for the six triazole fungicides were between 0.4 and 6.7 μg L^?1. The proposed method was successfully applied for the determination of trace amounts of triazole fungicides in various fruit juices including peach, apple, and orange juices.     

Graphene Oxide-Reinforced Hollow Fiber Solid-Phase Microextraction Coupled with High-Performance Liquid Chromatography for the Determination of Cephalosporins in Milk Samples

An effective and sensitive method to determine six cephalosporins (cefadroxil, cephapirin sodium, cefixime, cefuroxime sodium, cefoxitin sodium, and ceftiofur hydrochloride) in milk samples was developed using graphene oxide-reinforced hollow fiber solid-phase microextraction (GO-HF-SPME). After extraction, analytes were desorbed and analyzed using high-performance liquid chromatography-photodiode array detection (HPLC-PDA). The graphene oxide (GO) was dispersed in N,N-dimethyl formamide by ultrasonication and then immobilized into the pores of a hollow fiber (HF). Several factors of GO-HF-SPME experiment, such as the pH of the sample solution, type of organic desorption solvent, pH of the desorption solvent, extraction time, and desorption time, were optimized to achieve the highest extraction efficiency. Under the optimized extraction conditions, the method showed good linear ranges (0.05–10 μg/mL) with correlation coefficients higher than 0.9950, low limits of determination (LODs, 0.01–0.02 μg/mL), and good recoveries (71–108 %) at three different spiked levels. The results demonstrated that GO-HF-SPME would be a promising method for the enrichment of cephalosporins in dairy products.     

Determination of Triazole Fungicides in Liquid Samples Using Ultrasound-Assisted Emulsification Microextraction with Solidification of Floating Organic Droplet Followed by High-Performance Liquid Chromatography

An ultrasound-assisted emulsification microextraction with solidification of organic droplet method followed by high-performance liquid chromatography with diode array detection for six triazole fungicide determination (diniconazole, fluquinconazole, flusilazole, myclobutanil, tebuconazole, and tetraconazole) was developed. After some preliminary experiments, undecanol was chosen as extracting solvent using 50 μL for 10 mL of liquid sample. A central composite design was performed to obtain the best experimental conditions for the following variables NaCl concentration (250 g L^?1), extraction time (18 min), and temperature (30 °C) in ultrasonic bath. After the ultrasound-assisted extraction, two steps considering centrifugation (4,200 rpm, 10 min) and solidification (5 min, 3 °C) were done. Following these conditions, the method showed linearity higher than 0.9930 with the concentration ranged from 20 to 890 μg L^?1. The limits of detection obtained using calibration curves were from 10.9 to 17.2 μg L^?1 and the intra- and inter-day repeatability at two levels showed RSD values between 1.9 and 10.6 %. The enrichment factors for the studied triazoles were between 226 (flusilazole) and 255 (tebuconazole). Recovery studies at two spiked levels in apple and grape juices gave values from 64 to 112 %.     

Solid-Phase Microextraction Coupled to Fast Gas Chromatography for the Determination of Migrants from Polystyrene-Packaging Materials into Yoghurt

In view of the importance of a rapid determination of migrants in food, a headspace solid-phase microextraction coupled with fast high-resolution capillary gas chromatography (HS-SPME/fast GC) method has been developed for the rapid determination of styrene and ethylbenzene in polystyrene-packaged yoghurt. The method accuracy is satisfactory with recoveries ranging from 97% to 105%. The developed method was applied to the study of the variation in migrant content during the shelf-life of commercial-packaged yoghurts. Compared with conventional SPME/GC, the employment of a SPME/fast GC method led to reduction of both the SPME equilibration and analyte separation time; the method allowed the determination of styrene and ethylbenzene in about 15 min (including sampling, extraction and analysis). At the same time, several volatile organic compounds belonging to the key aroma compounds of the fermented milks were identified. The coefficient of variation in terms of peak area and retention time was included between 3% and 4% for all the components identified. Styrene and ethylbenzene have been quantified using the standard addition method. Calibration curves were linear for both the compounds in the range from 1 to 10 ng g⁻¹ for ethybenzene and from 2 to 25 ng g⁻¹ for styrene. Detection limits ranged from 0.5 to 0.6 ng g⁻¹ and quantification limits from 1.0 to 2.2 ng g⁻¹.     

固相微萃取-高效液相色谱-荧光检测法分析苹果汁中的多菌灵和噻菌灵

目的应用固相微萃取(SPME)-高效液相色谱(HPLC)技术建立苹果汁中多菌灵(MBC)和噻菌灵(TBZ)的新分析方法.方法采用固相微萃取和液相色谱联用.经过优化,本实验选用60 μm PDMS/DVB萃取纤维在室温下直接萃取50 min,磁力搅拌速度为1 100 r/min,然后萃取纤维在解吸室内静态解吸8 min后进行HPLC分析.结果多菌灵和噻菌灵在0.05～1.5 mg/L范围内具有良好的线性关系(R＞0.99),检出限分别为20 μg/L和10μg/L,加标回收率在88.5%～96.9%(n=5)之间,相对平均标准偏差(RSD)在3.5%～6.7%之间.结论该方法快速、简便,无需使用有机溶剂,适于苹果汁中多菌灵和噻菌灵的残留分析.     

Determination of Vanillin and Ethyl-Vanillin in Milk Powder by Headspace Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry

A method for determination of vanillin and ethyl-vanillin in milk powder by auto headspace solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was established. Vanillins in sample were extracted with SPME through a fused-silica fiber coated with divinylbenzene/polydimethylsiloxane. The analytes were desorbed by GC at 260 °C for 5 min and separated on a DB-5MS capillary column and detected by MS with EI source by selected ion monitoring mode (EI-SIM). As a result, the limit of detection of vanillin and ethyl-vanillin was 0.1 and 0.05 mg/kg. The spiked recovery was between 90.0 and 100 %, and the RSD ranged from 1.9 to 5.1 % (n?=?6). This method eliminated the interferences from complicated matrix effectively. The method was successfully applied for quick determination of vanillin and ethyl-vanillin content in milk powder samples.     

固相微萃取-气相色谱-质谱联用法测定传统酸肉发酵过程中特征挥发性成分

通过固相微萃取-气相色谱-质谱联用仪对鲜肉及发酵10、30、50?d酸肉的挥发性物质进行鉴定,探究传统发酵酸肉中挥发性成分种类及含量变化.结果表明:4个时期的肉样中共检出106种挥发性物质,其中酯类32种、酸类2种、醇类11种、醛类16种、酮类3种、碳氢化合物29种及其他类化合物13种;采用主成分分析、偏最小二乘判别分...     

Analytical Method for Determination of Organochlorine Pesticides in Tea Brews using Single-Drop Microextraction with GC-ECD

The single drop microextraction method was developed for the determination of ten organochlorine pesticides in tea brews using gas chromatograph-electron capture detector. The optimized parameters for effective extraction required a 2 μL drop of n-hexane at the tip of a microsyringe immersed in 5 mL of a diluted tea brew sample for 25 min and stirred at 600 rpm. The limit of detection in the range of 0.01 to 0.025 μg/L, with relative standard deviation of repeatability and reproducibility, was in the range of 1–10 and 8–24%. The relationship of the measured signal was a linear function (>0.9863) of concentration and the recovery method ranged from 92–116%. The single drop microextraction method showed the advantage of being easy to operate, low consumption of organic solvent, and high extraction efficiency.     

Fully Automated Vortex-Assisted Liquid-Liquid Microextraction Coupled to Gas Chromatography-Mass Spectrometry for the Determination of Trace Levels of Phthalate Esters in Liquor Samples

A fully automated vortex-assisted liquid-liquid microextraction (VALLME) system coupled to gas chromatography-mass spectrometry (GC/MS) was developed for the determination of phthalate esters (PAEs) in liquor samples. The whole analytical procedure, including spiking, extraction, phase separation, extractant collection, and GC/MS quantification, were automatically carried out. The use of a commercially available sample vial and a multipurpose sampler equipped with a highly efficient orbital vortex shaker facilitated the accessibility and automation of the method. Key factors, such as type and volume of the extractant, time and speed for VALLME, agitation speed and time required for phase separation, sample pH, salt effects, and matrix effects, were thoroughly investigated. Under the optimum conditions, linearity was in the range 0.05 to 120 μg L^?1. Limits of detection ranged from 0.003 to 0.006 μg L^?1. Enrichment factors were in the range 211 to 304. Reproducibility and recoveries were assessed by testing a series of liquor samples spiked with different concentrations of phthalate esters. This work provided an innovative way to automate the VALLME method and couple it on-line with GC/MS.     

分散液相微萃取-液相色谱联用测定番茄中8种氨基甲酸酯农药残留

采用分散液相微萃取与液相色谱-荧光检测联用技术建立了测定番茄样品中氨基甲酸酯农药残留的新方法。对影响萃取和富集效率的因素进行了优化。萃取条件选定为在10mL带塞离心试管中加入5.0mL番茄样品溶液（ph7）,并快速注入2.2mL丙酮（分散剂2ml）/二氯甲烷（萃取剂200μL）混合溶液,振荡摇匀后以8000r/min离心5min,然后将上层清液吸干至试管底部萃取剂沉积相,用微量移液器准确移取100μL入自动进样瓶内胆进样分析。在优化的实验条件下,8种氨基甲酸酯农药的富集倍数可达20.4～24.3倍;检出限在8.0～20.0μg/kg（S/N=3：1）范围内。测定8种氨基甲酸酯农药残留的线性范围为50.0～500.0μg/kg,线性相关系数在0.9977～0.9998范围内。本方法已成功应用于番茄样品中8种氨基甲酸酯农药残留的测定,平均加标回收率在79.1%～98.6%范围内;相对标准偏差在3.5%～8.5之间,结果令人满意。     

Solid-Phase Extraction and Procedure for Determination of Phenolic Compounds in Maple Syrup

A solid phase extraction procedure was developed for the extraction of phenolic compounds from maple syrup. The list of targeted chemicals contains phenolic acids as well as aldehydes, flavanols and others such as coniferyl alcohol and 5-hydroxymethyl furfural. The procedure consists in passing a small quantity of maple syrup, 1 g diluted in 2 ml deionized water, through an Oasis HLB cartridge of 200 mg. The cleanest extracts were obtained by rinsing the cartridge load with formic acid 2 %/methanol (9:1). The analytes eluted with methanol were passed in an high-performance liquid chromatography (HPLC)-DAD system for analysis. The method performances show good recoveries; excluding gallic acid measured at 49 %, the chemical recoveries ranged from 81 to 119 %. Moreover, the method repeatability is less than 12 % (RSD) relative standard deviation for all chemicals except for epicatechin (20 %). The analysis method was applied for the determination of phenolic compounds in maple syrups from different color classes (Extra Light to Amber). Results show that concentrations of phenolic compounds vary among syrup classes and the greatest concentration was observed for the Amber syrups.     

Rapid and Selective Determination of Trace Benzimidazole Fungicides in Fruit Juices by Magnetic Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography-Fluorescence Detection

In this paper, a new method was established for the determination of benzimidazole fungicides in fruit juices by magnetic solid-phase extraction coupled with high-performance liquid chromatography-fluorescence detection. The extraction adsorbent was synthesized to form a core–shell Fe₃O₄@SiO₂ structure surface functionalized with benzenesulfonic acid. The negative charges of the benzenesulfonic acid groups can promote strong electrostatic interaction with positively charged analytes to exhibit efficient and selective extractive ability. After the extraction, the magnetic adsorbent can be rapidly isolated from the matrix by an external magnet. Main factors influencing the extraction efficiency including amount of adsorbent, solution pH, extraction time, and volume of desorption solution were studied and optimized. Under the optimal conditions, recoveries of the spiked samples ranged from 83 to 96 % with the relative standard deviations lower than 10 %. The limits of detection were 0.55 and 0.14 μg?kg^?1 for carbendazim and thiabendazole, respectively. The proposed method was successfully applied for selective and efficient determination of benzimidazole fungicides in various juice samples.     

Solid-Phase Microextraction Method for the Determination of Volatile Compounds in Hydrolysates of Alaska Pollock Frame

The volatile compounds in Alaska pollock frame and Alaska pollock frame hydrolysates were analyzed by solid-phase microextraction and gas chromatography-mass spectrometry for identifying and comparing their flavor characteristics. The optimized SPME extraction conditions were 75 μm carboxen/polydimethyl siloxane fiber, adsorption time of 40 min, and extraction temperature of 65°C. Compared to Alaska pollock frame, Alaska pollock frame hydrolysates have more aromas detected and identified. Numerous volatile compounds were responsible for the overall aroma of Alaska pollock frame hydrolysates, such as 1-penten-3-ol, 2-penten-1-ol, ethyl acetate, methacrolein, 3-methylbutanal, hexanal, octanal, nonanal, 6-methyl-5-hepten-2-one, and so on. However, only a relatively small proportion showed similar composition. Although Alaska pollock frame hydrolysates was prepared by the same raw material, each Alaska pollock frame hydrolysate exhibited its individual flavor characteristics. Thus, the type of enzyme was probably one of the important factors affecting the differences of volatile compound composition and Alaska pollock frame hydrolysate flavor. Compared to other Alaska pollock frame hydrolysates, FPH5 (hydrolysates prepared by mixed enzymes for animal proteolysis) exhibited less fishy odor. It can be used as an effective approach to improve product quality.     

顶空固相微萃取分析啤酒花的挥发性组分

研究了采用顶空固相微萃取技术分析酒花中挥发性香气组分的方法。组分的分离与鉴定主要依靠GC-MS,使用DB-WAXETR毛细管色谱柱定性了23种化合物,其中的11个组分峰用作定量测定,分析了30个酒花样品,采用统计分析成功地对它们作了类型区分。     

SPME-GC-MS法测定小鳄龟肉中关键风味化合物的响应面法优化

以小鳄龟肉为原料,通过单因素试验及响应面分析优化小鳄龟肉中挥发性风味化合物的萃取条件,采用顶空固相微萃取(solid-phase microextraction,SPME)和气相色谱-质谱联用(gas chromatography-mass spectrometry,GC-MS)技术检测并分析小鳄龟肉中的挥发性风味物质,同时结合化合物的感觉阈值,利用相对气味活度值(relative odor activity value,ROAV)法确定关键风味化合物。结果表明:小鳄龟肉中挥发性风味化合物的最佳萃取条件为萃取时间25 min、萃取温度60℃、样品添加量1.0 g。在此萃取条件下,从去皮及带皮小鳄龟肌肉中分别检测出33种和37种挥发性风味物质,且关键风味化合物种类基本相同,主要是D-柠檬烯、壬醛、3-甲基丁醛、3-甲硫基丙醛、(Z)-4-庚烯醛、苯乙醛、庚醛、己醛、1-辛烯-3-醇、二甲基硫醚及2-乙基呋喃等化合物,它们共同决定了小鳄龟肌肉的整体风味。     

Nanoporous Carbon as the Solid-Phase Extraction Adsorbent for the Extraction of Endocrine Disrupting Chemicals from Juice Samples

A nanoporous carbon prepared from metal?organic frameworks through high temperature treatment has been examined for the extraction of some endocrine disrupting chemicals (bisphenol A, 4-tert-octylphenol, nonylphenol, and 4-nonylphenol) from bottled juice samples. To obtain an optimum extraction performance, the main experimental parameters for the extraction including the type and volume of the eluent, and the pH and volume of sample solution were investigated. Under the optimized extraction conditions, a linear response for the analytes was obtained in the range of 0.15–100.0 ng mL^?1 with correlation coefficients larger than 0.9900 for juice samples. The method detection limit (MDL) and method quantification limit (MQL) for the analytes were 0.04 and 0.13 ng mL^?1 for the juice samples. The intra-day and inter-day RSDs were lower than 8.9%. The method was successfully applied for the analysis of juice samples with recoveries from 91.0 to 96.6% for bisphenol A, 91.6 to 99.6% for 4-tert-octylphenol, 86.0 to 96.3% for nonylphenol, and 89.4 to 99.6% for 4-nonylphenol.     

顶空固相微萃取分析苹果酯类香气

酯类是苹果香气成分中的重要组成之一。应用顶空固相微萃取、气相色谱和质谱联用技术分析了苹果酯类香气成分的组成。对HS-SPME的萃取条件如萃取头的选择、萃取时间、萃取温度进行了优化,建立了适合苹果酯类香气成分萃取的最优组合-采用纤维头65μm PDMS/DVB在50℃下吸附30 min。使用该方法在成熟金冠苹果中鉴定出18种酯类香气成分。