Analysis of brandy aroma by solid‐phase microextraction and liquid–liquid extraction

Headspace solid‐phase microextraction (SPME) and continuous liquid–liquid extraction (LLX) with Freon were used to extract and analyse aroma volatiles in brandy. In general, SPME using a non‐polar polydimethylsiloxane coating was more selective for esters and acids than was LLX. LLX using Freon 11 extracted the higher alcohols more efficiently than SPME. Relative differences in volatiles between brandies made from Vitis vinifera L cv Colombard and Vitis vinifera L cv Ugni blanc were observed, particularly for hexanol, 3‐methylbutylacetate, 3‐methylbutanol and 3‐methylbutyloctanoate. In addition, a combination of SPME with GC–olfactometry was used to provide more detailed information on sensory characteristics of varietal brandies. © 2000 Society of Chemical Industry     

Analysis of tea catechins in vegetable oils by high‐performance liquid chromatography combined with liquid–liquid extraction

In this study, a method was developed for the determination of various tea catechins in vegetable oils. Firstly, vegetable oils including tea seed oil, sunflower seed oil and soya bean oil were extracted by methanol/water (40:60, v/v), and then, a high‐performance liquid chromatography (HPLC) method was developed for the simultaneous determination of GA, caffeine, EGC, EGCG, EC, ECG, GC, GCG, C and CG. For the compounds detected in tested vegetable oils, LODs were in the range of 0.05–1.65 ng, both intraday and interday relative standard deviations (RSDs) were <5.0%, and the recovery rates were in the range of 96.2–100.5% with RSD <3.7%. The results showed in vegetable oils which declared to had added tea catechins in, the concentrations of tea catechins were less than that showed in package label, and the content of EGCG was the highest in all samples. Therefore, the advancement made in our study will facilitate studies of tea catechins in oil industry.     

Development of a liquid–liquid extraction method for the determination of pyrimethanil,metalaxyl, dichlofluanid and penconazol during the fermentative process of must by GC‐NPD

BACKGROUND: A rapid, selective and sensitive gas chromatographic method is described for the analysis of four fungicides—pyrimethanil, metalaxyl, penconazol and dichlofluanid, widely used in vineyards—in must and wine, as well as samples during alcoholic fermentation. The effect of alcoholic fermentation on pyrimethanil concentration in synthetic and real musts was studied. RESULTS: The proposed method was based on liquid–liquid extraction followed by gas chromatography with nitrogen–phosphorus detector. n‐Hexane was the most appropriate solvent for extracting the target fungicides in synthetic and real samples. Quality parameters of the proposed method presented good recovery (ca 78.3% for almost all compounds) and precision (between 1.4% and 6.1%), and quantification limits lower than maximum residue limits. However, for dichlofluanid recovery levels of well over 100% were found. CONCLUSIONS: There was no matrix effect in the analysis of pyrimethanil, metalaxyl or penconazol, but this effect was observed for dichlofluanid in synthetic and real matrices. The application of the fermentative process on pyrimethanil fungicide caused a high decrease in the concentration of this compound, and no product appeared in degradation. The decrease of pyrimethanil in fermented samples was similar in both synthetic and real samples. Copyright © 2009 Society of Chemical Industry     

分散式固相萃取结合高效液相色谱法快速测定 油脂中三种抗氧化剂含量

目的 采用分散式固相萃取技术结合高效液相色谱(HPLC),建立了食用油脂中叔丁基羟基茴香醚(BHA)、2,6-二叔丁基对甲酚(BHT)、特丁基对苯二酚(TBHQ)残留的快速检测方法。方法 采用中性氧化铝作为吸附剂, 以整合了吸附剂活化、目标物提取和样品净化等步骤的“一步式”前处理方式净化样品, 最后用高效液相色谱二极管阵列检测器(DAD)对三种抗氧化剂含量进行测定。结果 在优化实验条件下, 方法的线性范围为0.2 ~200 mg/L,线性相关系数R₂≥0. 9993,对BHA、BHT、TBHQ的检出限(S/N=3)均为0.5mg/kg,回收率为85.5% ~ 95.4%,峰面积的相对标准偏差为2.10% ~ 3.53% 。结论 本文所建立的方法较液液萃取、固相萃取、凝胶渗透色谱等传统的方法更为简便快速,高效环保,成本低廉,可满足油脂中BHA、BHT、TBHQ含量检测需求;整个样品前处理过程仅需10 ~ 15分钟,适合BHA、BHT、TBHQ含量检测的批量实验。     

Determination of cyprodinil and fludioxonil in the fermentative process of must by high‐performance liquid chromatography–diode array detection

BACKGROUND: A quantitative, selective and sensitive high‐performance liquid chromatographic method is described for the analysis of new fungicides cyprodinil, fludioxonil and their commercial formulation Switch in model solutions of must and wine, as well as samples during alcoholic fermentation. A study of the dissipation of residues was carried out. RESULTS: The proposed method is based on liquid–liquid extraction (LLE) followed by high‐performance liquid chromatography and diode array detection. Dichloromethane was the most appropriate solvent for extracting cyprodinil and fludioxonil in samples. Quality parameters of the proposed method presented good recovery (ca. 97% for almost all compounds) and precision (between 4.8% and 5.4%), and limits of quantification were lower than maximum residue limits (MRLs) in grapes. CONCLUSIONS: There is no matrix effect in the analysis of cyprodinil and fludioxonil. The application of the fermentative process on cyprodinil and fludioxonil fungicides causes a decrease in the concentrations of these compounds. This decrease is slightly higher, the higher the initial concentration, without observing the appearance of any product in degradation. Fludioxonil shows a higher reduction when the compounds are presented together in Switch. Copyright © 2008 Society of Chemical Industry     

Determination of sunset yellow (E110) in foodstuffs and pharmaceuticals after separation and preconcentration via solid‐phase extraction method

The two novel preconcentration and separation methods based on adsorption onto Amberlite XAD‐1180 and Amberlite XAD‐16 polymeric resins for spectrophotometric determination of sunset yellow dye were developed. The parameters, affecting the quantitative recovery, including pH, sample and eluent flow rates, eluent type, sample volume, were investigated and optimised. The interference effects of some cations, anions and widely used dye were also studied. At the optimum conditions, detection limits of the methods were found as 2.0 and 1.6 μg L^?1 for Amberlite XAD‐1180 and Amberlite XAD‐16 resins, respectively. Linear dynamic ranges of the methods were obtained in the range of 0.2–50.0 and 0.2–20.0 μg mL^?1 for Amberlite XAD‐1180 and Amberlite XAD‐16 resins, respectively. The relative standard deviations were below than 7% and 5% for Amberlite XAD‐1180 and Amberlite XAD‐16 resins, respectively. The determination of dye was performed at 483.0 nm using spectrophotometry. Validations of the methods were performed comparatively with determination of the sunset yellow content of some foodstuffs and pharmaceuticals.     

Influence of pressurised liquid extraction and solid–liquid extraction methods on the phenolic content and antioxidant activities of Irish macroalgae

The efficiencies of pressurised liquid extraction (PLE) and a traditional solid–liquid extraction (SLE) at extracting antioxidant polyphenols from Irish macroalgae Ascophyllum nodosum, Pelvetia canaliculata, Fucus spiralis and Ulva intestinalis were compared. PLE was more effective for extracting polyphenols with acetone/water (80:20); however, when food‐friendly solvents of ethanol/water (80:20) and water were employed, SLE resulted in higher phenolic content in brown macroalgal extracts. For example, the Fucus spiralis SLE water and ethanol/water extracts displayed total phenolic contents (TPCs) of 130.58 ± 2.78 and 142.81 ± 1.77 μg phloroglucinol equivalents (PGE) mg^?1 sample, respectively, compared with TPCs of 90.79 ± 1.16 and 124 ± 6.54 μg PGE mg^?1 sample for the corresponding PLE extracts. All SLE aqueous ethanolic macroalgal extracts possessed higher DPPH radical scavenging abilities (RSA) and ferric reducing antioxidant power (FRAP) than their PLE equivalents . This study indicates that the application of high extraction temperatures (50–200 °C) and pressures (500–3000 psi) used in PLE does not enhance the antioxidant activities of macroalgal extracts relative to SLE extraction. The ability to produce antioxidant food‐friendly macroalgal extracts using SLE could represent significant cost reductions on an industrial scale further enhancing the potential of macroalgal polyphenols to be used in functional food preparations.     

Optimization of solid‐phase microextraction methods for GC‐MS determination of terpenes in wine

Solid‐phase microextraction using a 100 µm poly(dimethylsiloxane) fiber, followed by gas chromatography–mass spectrometry determination, has been optimized for the analysis of some terpenes in wine samples. The best results were obtained by direct immersion of the fiber using a sampling period of 15 min with constant magnetic stirring (1100 rpm) and an extraction temperature of 20 °C. The sample volume was 7 ml with 25% NaCl, in a 15 ml capped vial. Desorption was performed directly in the gas chromatograph injector port over 5 min at 250 °C using the splitless mode. The method is sensitive, with detection limits between 11 and 25 µg l^?1, precise, with variation coefficients in the range 1.28–3.71%, and linear over more than one order of magnitude. The related conditions were used for wine sample analyses with recoveries between 71.8 and 90.9%. Solid‐phase microextraction remains an attractive alternative technique due to its rapidity and because it is a solvent‐free extraction. Copyright © 2005 Society of Chemical Industry     

全自动分子印迹固相萃取高效液相色谱法测定食用油中10种多环芳烃

为快速测定食用油中的多环芳烃,建立全自动分子印迹固相萃取高效液相色谱法测定食用油中10种多环芳烃的分析方法。将样品用正己烷溶解,以2 mL正己烷为淋洗液,二氯甲烷为洗脱剂,经全自动分子印迹固相萃取柱净化,氮吹后定容进高效液相色谱仪(配荧光检测器)检测。结果表明：所建方法线性关系良好,检出限为0.1～1.3μg/kg,定量限为0.3～4.0μg/kg;方法的准确度良好,精密度高,10种多环芳烃在玉米油和花生油基质中的加标回收率为79.2%～114.3%,相对标准偏差为0.4%～5.7%,将该方法应用于实际食用油样品中苯并[a]芘的测定,所测样品中苯并[a]芘含量均未超出国标限量。所建方法前处理简单快速,可实现固相萃取柱的自动化处理,减少有机溶剂的消耗,适合食用油中多环芳烃的快速测定。     

基质分散固相萃取-高效液相色谱-可变波长检测法测定新鲜牛奶中8种抗生素

摘要：目的 建立基于基质分散固相萃取-高效液相色谱的新鲜牛奶中氯霉素、呋喃唑酮、甲硝唑、磺胺嘧啶、磺胺吡啶、磺胺-5-甲氧嘧啶、磺胺甲基异恶唑、磺胺二甲氧嘧啶8种抗生素的分析方法。方法 采用0.5%乙酸乙腈对新鲜牛奶中的8种抗生素进行提取,提取液用C18粉末和乙二胺-N-丙基甲硅烷(primary secondary amine, PSA)粉末基质分散固相萃取,以乙酸酸化的乙腈溶液(pH=3.0)和0.05 mol/L磷酸二氢钾溶液(pH=3.0)为流动相,Eclipse XDB-C18(4.6 mm×150 mm, 5 μm)色谱柱,梯度淋洗分离,多波长检测定量。结果 8种抗生素在1.0~100.0 μg/kg浓度范围内线性关系良好,相关系数为0.99904~1.00000;对新鲜牛奶进行3个水平(5、20、50 μg/kg)的加标回收实验,其回收率为84%~101%,相对标准偏差为2.4%~10.7%;检出限为0.18~0.41 μg/kg,定量限为0.63~1.23 μg/kg。结论 本方法适用于新鲜牛奶或液态奶中抗生素的检测,其前处理方法简便、回收率高、灵敏度高,能够满足实验要求。