31P NMR spectroscopy in the quality control and authentication of extra-virgin olive oil: a review of recent progress

This review is a brief account on the application of a novel methodology to the quality control and authentication of extra-virgin olive oil. This methodology is based on the derivatization of the labile hydrogens of functional groups, such as hydroxyl and carboxyl groups, of olive oil constituents with the phosphorus reagent 2-chloro-4,4,5,5-tetramethyldioxaphospholane, and the use of the (31)P chemical shifts to identify the phosphitylated compounds. Various experimental aspects such as pertinent instrumentation, sample preparation, acquisition parameters and properties of the phosphorus reagent are reviewed. The strategy to assign the (31)P signals of the phosphitylated model compounds and olive oil constituents by employing 1D and 2D NMR experiments is presented. Finally, the capability of this technique to assess the quality and the genuineness of extra-virgin olive oil and to detect fraud is discussed.     

Identification of compounds from high‐fat and extra virgin olive oil‐supplemented diets in whole mouse liver extracts and isolated mitochondria using mass spectrometry

Nonalcoholic steatohepatitis (NASH) is a fatty liver disorder that could be improved with extra virgin olive oil (EVOO) supplementation in diet. We propose the monitoring, in whole mouse liver extracts and in isolated mitochondria, of the absorption of compounds from three different diets: standard (CT), high‐fat (HFD) and high‐fat supplemented with EVOO (HFSO). Male mice were submitted to one of the following three diets: CT or HFD for 16 weeks or HFD for 8 weeks followed by additional 8 weeks with HFSO. Following this period, liver was extracted for histological evaluation, mitochondria isolation and mass spectrometry analyses. Diets, liver extracts and Percoll‐purified mitochondria were analyzed using ESI‐MS and the lipidomics approach. Morphological, histological and spectrometric results indicated a decrease in NASH severity with EVOO supplementation in comparison with animals maintained with HFD. Spectrometric data also demonstrated that some compounds presented on the diets are absorbed by the mitochondria. EVOO was shown to be a potential therapeutic alternative in food for NASH. Our results are in accordance with the proposition that the major factor that influences different responses to diets is their composition – and not only calories – especially when it comes to studies on obesity. Copyright © 2015 John Wiley & Sons, Ltd.     

固相微萃取-气相色谱/质谱分析栀子花的头香成分

 分别用固相微萃取和动态顶空法分离栀子鲜花的头香成分,用GC/MS技术分析鉴定,并用GC/MS总离子流色谱峰的峰面积进行归一化定量。在固相微萃取方法中,共鉴定了54种化学成分,占总峰面积的99.98%。主要成分(质量分数)依次为金合欢烯（64.86%）、罗勒烯（29.33%）、芳樟醇（2.74%）、惕各酸顺式叶醇酯（1.34%）和苯甲酸甲酯（0.25%）等。经与动态顶空法的分析结果比较发现,固相微萃取法不仅操作简便,而且具有较高的采样灵敏度,获得的化学成分的信息量多于动态顶空法。     

Sensitive determination of amide herbicides in environmental water samples by a combination of solid‐phase extraction and dispersive liquid–liquid microextraction prior to GC–MS

In this paper, solid‐phase extraction (SPE) in combination with dispersive liquid–liquid microextraction (DLLME) has been developed as a sample pretreatment method with high enrichment factors for the sensitive determination of amide herbicides in water samples. In SPE–DLLME, amide herbicides were adsorbed quantitatively from a large volume of aqueous samples (100 mL) onto a multiwalled carbon nanotube adsorbent (100 mg). After elution of the target compounds from the adsorbent with acetone, the DLLME technique was performed on the resulting solution. Finally, the analytes in the extraction solvent were determined by gas chromatography–mass spectrometry. Some important extraction parameters, such as flow rate of sample, breakthrough volume, sample pH, type and volume of the elution solvent, as well as salt addition, were studied and optimized in detail. Under optimum conditions, high enrichment factors ranging from 6593 to 7873 were achieved in less than 10 min. There was linearity over the range of 0.01–10 μg/L with relative standard deviations of 2.6–8.7%. The limits of detection ranged from 0.002 to 0.006 μg/L. The proposed method was used for the analysis of water samples, and satisfactory results were achieved.     

Identification of volatile components in Angelica species using supercritical-CO2 fluid extraction and solid phase microextraction coupled to gas chromatography-mass spectrometry

As a part of our search for environmentally friendly solvents to extract the active components of medicinal plants, two sampling techniques, supercritical fluid extraction (SFE) using CO(2) and solid-phase microextraction (SPME) were compared for their efficacy in the analysis of volatiles rhizome components emitted from the medicinal herbs Angelica gigas NAKAI (Korean danggui), Angelica sinensis (Chinese danggui), and Angelica acutiloba (Japanese danggui). A total of 54 compounds released from all of these varieties of Angelica rhizomes were separated and identified by gas chromatography-mass spectrometry (GC-MS). The composition of supercritical extracts from these plants was very different from the solid-phase microextraction products. More compounds were detected by SPME-GC-MS (41) than by SFE-GC-MS (17). The results of these analyses suggest that SFE may be useful for detecting the main components, decursinol angelate and decursin in Korean danggui, and butylidene dihydro-phthalide in both Chinese and Japanese danggui, whereas the results for SPME did not. The SFE method required specialized instrumentation, required little time to prepare the sample, and had a small sample size and no organic solvent. In sum, these results suggest that SFE is useful for extracting the volatile main components of danggui cultivars. Its simplicity, low cost and speed may allow SPME to increase the recovery of volatile components in general without disturbing the main components of the plant.     

Joint MS‐based platforms for comprehensive comparison of rat plasma and serum metabolic profiling

Metabolomics is a rapidly growing field in the comprehensive understanding of cellular and organism‐specific responses associated with perturbations induced by medicines, chemicals and environment. Blood matrices are frequently used in clinical and biological studies. In this study, we compared metabolic profiling between rat plasma and serum using complementary platforms of gas chromatography–mass spectrometry (GC‐MS) and liquid chromatography–quadruple time‐of‐flight–mass spectrometry (LC‐QTOF‐MS). The sample types that were tested included plasma prepared with K₂EDTA and serum collected using venous blood collection protocols. The results of peak area variation for each detected metabolite/feature in the quality control samples showed a good reproducibility in LC‐QTOF‐MS and better reproducibility in GC‐MS. In GC‐MS analysis: (a) 25.8% of the defined metabolites differed serum from plasma profiling (t‐test, p < 0.05); and (b) serum possessed higher sensitivity than plasma for its generally higher peak intensity in the metabolic profiling. In LC‐QTOF‐MS analysis, 13 (in positive ion mode) and seven (in negative ion mode) important metabolites were identified as mainly contributing to the separation between serum and plasma. Copyright © 2014 John Wiley & Sons, Ltd.     

基于脂肪酸含量分析结合化学计量学的橄榄油等级鉴别方法

建立了一种基于脂肪酸含量分析结合化学计量学技术的橄榄油等级判别方法。以经确认属性的特级初榨橄榄油和精炼橄榄油作为测试集,采用气相色谱法分别测定两类橄榄油中的脂肪酸含量,通过主成分分析（PCA）、聚类分析（HCA）及偏最小二乘判别分析（PLS－DA）法建立橄榄油的等级鉴别模型。结果表明,PCA能成功区分特级初榨橄榄油和精炼橄榄油,HCA也能有效对两种等级橄榄油进行鉴别,最终筛选出VIP值（重要贡献值）大于1的6种特征组分：C23∶0、C18∶2n6t、C24∶0、C18∶1/C18∶2、C20∶1和C18∶1n9c。同时以98个未知属性的橄榄油样品为验证集,对建立的橄榄油等级判别模型进行交叉验证（CV）,模型预测评估值（Q2）及相关系数（R2）均大于0.96,说明所建的橄榄油等级鉴别预测模型较可靠。因此,采用脂肪酸含量分析结合化学计量学技术可用于特级初榨橄榄油和精炼橄榄油的等级鉴别     

非平衡固相微萃取-气相色谱-质谱联用快速监测水中的氯化苄

建立了一种非平衡固相微萃取与气相色谱－质谱联用快速监测水中氯化苄的新方法,整个分析过程只需15min。85μm的聚丙烯酸酯涂层（PA）对水中的氯化苄有较好的萃取效果。方法的线性范围为1－50μg/L,检出限为0．91μg/L,相对标准偏差为9．86％,用于河水中氯化苄的测定,结果满意。     

Electrospray ionization mass spectrometry and partial least squares discriminant analysis applied to the quality control of olive oil

Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)‐MS] is used to obtain fingerprints of aqueous–methanolic extracts of two types of olive oils, extra virgin (EV) and ordinary (OR), as well as of samples of EV olive oil adulterated by the addition of OR olive oil and other edible oils: corn (CO), sunflower (SF), soybean (SO) and canola (CA). The MS data is treated by the partial least squares discriminant analysis (PLS‐DA) protocol aiming at discriminating the above‐mentioned classes formed by the genuine olive oils, EV (1) and OR (2), as well as the EV adulterated samples, i.e. EV/SO (3), EV/CO (4), EV/SF (5), EV/CA (6) and EV/OR (7). The PLS‐DA model employed is built with 190 and 70 samples for the training and test sets, respectively. For all classes (1–7), EV and OR olive oils as well as the adulterated samples (in a proportion varying from 0.5 to 20.0% w/w) are properly classified. The developed methodology required no ions identification and demonstrated to be fast, as each measurement lasted about 3 min including the extraction step and MS analysis, and reliable, because high sensitivities (rate of true positives) and specificities (rate of true negatives) were achieved. Finally, it can be envisaged that this approach has potential to be applied in quality control of EV olive oils. Copyright © 2013 John Wiley & Sons, Ltd.     

Build‐up of carboxylic acids in polyethylene and their relation to off‐flavor and carbonyl index

Oxidation of polyethylene (PE) gives a mixture of degradation products. Carboxylic acids are among the major ones. They are believed to cause off‐flavor in food and beverage packaging. Our previous research has shown that identification and use of indicator products gives earlier detection of oxidation in plastic materials. In the present study, the relation between off‐flavor in water extracts of PE and each of the carboxylic acids in the homologous series from propanoic to nonanoic acid were investigated. Also, a comparison between carbonyl index in solid PE and each of the carboxylic acids in the homologous series from propanoic to decanoic acid were examined. The amount of the carboxylic acids was assessed by head‐space solid‐phase microextraction (HS‐SPME) and gas chromatography–mass spectroscopy (GC‐MS). It was found that the amount of butanoic and hexanoic acid correlated well with the rated off‐flavor intensities in the water extracts. This confirmed earlier results on a linkage between these two carboxylic acids and highly rated off‐flavor intensities. Moreover, a relation between the build‐up of propanoic acid in the solid PE and carbonyl index was found. Hence, propanoic acid could be used as an indicator product for earlier oxidation detection in these PE materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1848–1859, 2007     

固相微萃取法结合GC-MS分析八角茴香中挥发性化合物

采用均相聚合物涂层———自制聚丙烯酸树脂(PA)萃取头,顶空萃取八角茴香中挥发性有机物.对萃取温度、样品量、解吸时间等参数进行了优化,得到了最佳萃取条件.该方法快速、简便,重现性好.通过气相色谱-质谱联用技术定性分析,鉴定了53种成分.同时,与商品多相聚合物涂层CAR/PDMS、DVB/CAR/PDMS分析结果比较,显示自制均相聚丙烯酸树脂萃取头对八角中挥发性有机物的萃取更全面.     

Determination of organic acids in urine by solid-phase microextraction and gas chromatography-ion trap tandem mass spectrometry previous 'in sample' derivatization with trimethyloxonium tetrafluoroborate

A method for the determination of the organic acids directly in the urine employing derivatization with trimethyloxonium tetrafluoroborate as a methylating agent and sequential extraction by head space and direct immersion/solid phase microextraction is reported. Furoic acid, hippuric acid, methylhippuric acid, mandelic acid, phenylglyoxylic acid and trans, trans muconic acid contained in urine and proposed by the American Conference of Governmental Industrial Hygienists as biological exposure indices were determined after a fast and economically convenient preparation step and sensitive gas chromatography-ion trap-mass spectrometry/tandem mass spectrometry analysis. Urine is rather a complex sample and hence the acquisition method required specific GC-MS instrumentation capable of supporting the changeover, fully automated during a single chromatographic separation, from mass to tandem mass spectrometry and both chemical and electron ionization modes. The automation of the analytical method provides a number of advantages, including reduced analysis time for both routine analysis and method development, and greater reproducibility. The equilibrium and kinetics of this substances vs head space/direct immersion-solid phase microextraction were investigated and evaluated theoretically.     

Combined solid‐phase microextraction and high‐performance liquid chromatography with ultroviolet detection for simultaneous analysis of clenbuterol,salbutamol and ractopamine in pig samples

A simple and sensitive method based on the combination of solid‐phase microextraction (SPME) and high‐performance liquid chromatography with ultroviolet detection was developed for the simultaneous determination of clenbuterol, salbutamol and ractopamine in pig samples. Parameters of the SPME procedure affecting extraction efficiency, such as the type of fiber, extraction time, extraction temperature, ion strength, pH of sample and stirring rate, were optimized. The developed method was validated according to the International Conference on Harmonization guidelines. The calibration curves were linear over a range of 0.5–50 µg/L for clenbuterol and ractopamine, and 0.2–20 µg/L for salbutamol. The limits of detection were 0.1 µg/L for clenbuterol, 0.05 µg/L for salbutamol and 0.1μg/L for ractopamine, respectively. The averages of intra‐ and inter‐day accuracy ranged from 79.8 to 92.4%. The intra‐day and inter‐day precision were below 9.6% for the three analytes. This method exhibited the advantages of simplicity, rapidity and low solvent consumption, and was suitable for the monitoring of β₂‐agonists residue in pig samples. Copyright © 2013 John Wiley & Sons, Ltd.