Xiupin Wang

Simultaneous determination of 13 phytohormones in oilseed rape tissues by liquid chromatography‐electrospray tandem mass spectrometry and the evaluation of the matrix effect

In the experiment, a high-performance liquid chromatography and electrospray ionization-tandem mass spectrometry with selected reaction monitoring was used to simultaneously determine various classes of phytohormones, including indole-3-acetic acid, α-naphthaleneacetic acid, 2-chlorobenzoic acid, 4-chlorobenzoic acid, indole-3-butyric acid, gibberellic acid, 2,4-dichlorophenoxyacetic acid, 2-naphthoxyacetic acid, abscisic acid, 2,3,5-triiodobenzoic acid, uniconazole, paclobutrazol and 2,4-epibassinolide in rape tissues. The analyses were separated by an HPLC equipped with a reversed-phase column using a binary solvent system composed of methanol and water, both containing 0.1% of formic acid. The matrix effect was also considered and determined. The technology was applied to analyze rape tissues, including roots, stems, leaves, flowers, immature pods and rape seeds. The rape tissues were subjected to ultrasound-assisted extraction and purified by dispersive solid-phase extraction, and then transferred into the liquid chromatography system. The detection limit for each plant hormone was defined by the ratio of signal/background noise (S/N) of 3. The results showed perfect linearity (R(2) values of 0.9987-1.0000) and reproducibility of elution times (relative standard deviations, RSDs,<1%) and peak areas (RSDs,<7%) for all target compounds.

Classification and Adulteration Detection of Vegetable Oils Based on Fatty Acid Profiles

The detection of adulteration of high priced oils is a particular concern in food quality and safety. Therefore, it is necessary to develop authenticity detection method for protecting the health of customers. In this study, fatty acid profiles of five edible oils were established by gas chromatography coupled with mass spectrometry (GC/MS) in selected ion monitoring mode. Using mass spectral characteristics of selected ions and equivalent chain length (ECL), 28 fatty acids were identified and employed to classify five kinds of edible oils by using unsupervised (principal component analysis and hierarchical clustering analysis), supervised (random forests) multivariate statistical methods. The results indicated that fatty acid profiles of these edible oils could classify five kinds of edible vegetable oils into five groups and are therefore employed to authenticity assessment. Moreover, adulterated oils were simulated by Monte Carlo method to establish simultaneous adulteration detection model for five kinds of edible oils by random forests. As a result, this model could identify five kinds of edible oils and sensitively detect adulteration of edible oil with other vegetable oils about the level of 10%.

Graphene oxide: an adsorbent for the extraction and quantification of aflatoxins in peanuts by high-performance liquid chromatography.

In this paper, graphene oxide (GO) was synthesized and specifically selected by centrifugation to extract four aflatoxins (B1, B2, G1, and G2) as an effective adsorbent. Then, the amount of aflatoxins was quantitatively measured by high-performance liquid chromatography (HPLC). The GO was characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and ultraviolet (UV) spectrophotometer. Several parameters that could affect the extraction efficiency, including the GO amount, methanol concentration in the extraction solvent, spiked amount, extraction time, and elution cycle, were also investigated and optimized in this work. Under optimal conditions, good linear relationships were achieved with the correlation coefficient (r) ranging from 0.99217 to 0.99995. The detection limit of this method for the four aflatoxins ranged from 0.08 to 0.65ng/g. Finally, the proposed method has been successfully applied to determine aflatoxins in peanut samples. The results show that the recoveries of the four aflatoxins range from 85.1% to 100.8% with the relative standard deviations between 2.1% and 7.9%.

Characterization of volatile components in four vegetable oils by headspace two-dimensional comprehensive chromatography time-of-flight mass spectrometry

Edible oil adulteration is the biggest source of food fraud all over the world. Since characteristic aroma is an important quality criterion for edible oils, we analyzed volatile organic compounds (VOCs) in four edible vegetable oils (soybean, peanut, rapeseed, and sunflower seed oils) by headspace comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (Headspace-GC×GC-TOFMS) in this study. After qualitative and quantitative analysis of VOCs, we used unsupervised (PCA) and supervised (Random forests) multivariate statistical methods to build a classification model for the four edible oils. The results indicated that the four edible oils had their own characteristic VOCs, which could be used as markers to completely classify these four edible oils into four groups.

Rapid screening of mycotoxins in liquid milk and milk powder by automated size-exclusion SPE-UPLC–MS/MS and quantification of matrix effects over the whole chromatographic run

An automated, size-exclusion solid phase extraction (SPE)-UPLC-MS/MS protocol without pre-treatment of samples was developed to screen for four mycotoxins (OTA, ZEN, AFB1, and AFM1) in liquid milk and milk powder. Firstly, a mixed macropore-silica gel cartridge was established as a size-exclusion SPE column. The proposed methodology could be a candidate in green analytical chemistry because it saves on manpower and organic solvent. Permanent post-column infusion of mycotoxin standards was used to quantify matrix effects throughout the chromatographic run. Matrix-matched calibration could effectively compensate for matrix effects, which may be caused by liquid milk or milk powder matrix. Recovery of the four mycotoxins in fortified liquid milk was in the range 89-120% and RSD 2-9%. The LOD for the four mycotoxins in liquid milk and milk powder were 0.05-2 ng L(-1) and 0.25-10 ng kg(-1), respectively. The LOQ for the four mycotoxins in liquid milk and milk powder were 0.1-5 ng L(-1) and 0.5-25 ng kg(-1), respectively.

Screening for pesticide residues in oil seeds using solid‐phase dispersion extraction and comprehensive two‐dimensional gas chromatography time‐of‐flight mass spectrometry

In this paper, we describe the development of an oil-absorbing matrix solid-phase dispersion extraction with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry suitable for screening of 68 pesticide residues (PRs) in peanut, soybean, rape seed, sesame, and sunflower seed. The 68 PRs include 27 kinds of organophosphorus, 23 organic chlorines, 11 synthetic pyrethroids, and 7 carbamates. Heptachlor epoxide was used as the internal standard. Aminopropyl silica was chosen as the dispersion sorbent of the oil-absorbing matrix solid-phase dispersion extraction and was applied to capture hydrophobic components from high oil samples. A 35-min orthogonal separation was performed by using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry with a nonpolar-polar column set. Identification of 68 PRs in the extract was finished by using the time-of-flight mass spectrometry in the assistance of an automated peak-find and spectral deconvolution software. A screening based on control design was introduced and explained. This screening method considerably reduced the cost for the quantitative and confirmatory analyses. The quality of present screening method was evaluated by the Document No. SANCO/10684/2009. The false positive rate and false negative rate provide a useful tool for the evaluation of screening performance.

Simultaneous determination of isoflavones and resveratrols for adulteration detection of soybean and peanut oils by mixed-mode SPE LC-MS/MS.

To ensure authenticity of vegetable oils, isoflavones (genistein, genistin, daidzein and daidzin) and resveratrols (cis-resveratrol and trans-resveratrol) were selected as the putative markers for adulteration of soybean and peanut oils. Firstly, mixed mode solid-phase extraction coupled with liquid chromatography tandem mass spectrometry (mixed-mode SPE LC-MS/MS) method was developed to analyze isoflavones and resveratrols in vegetable oils. The concentration of marker compounds in vegetable oils were 0.08-1.47mgkg(-1) for daidzein, ND-78.9μgkg(-1) for daidzin, 0.40-5.89mgkg(-1) for genistein, 1.2-114.9μgkg(-1) for genistin, 3.1-85.0μgkg(-1) for trans-resveratrol and 1.9-51.0μgkg(-1) for cis-resveratrol, which are compatible with the raw materials for oil press. Additionally, the applicability of this method has been successfully tested in thirteen vegetable oils from the market. Mixed-mode SPE LC-MS/MS method can simultaneously detect isoflavones and resveratrols in vegetable oils and assess adulteration and quality of soybean and peanut oils.

Untargeted fatty acid profiles based on the selected ion monitoring mode.

Fatty acids are potential biomarkers of some diseases and also key markers and quality parameters of different dietary fats and related products. Thus, untargeted fatty acid profiles are important in the study of dietary fat quality and fat-related diseases, as well as in other fields such as bioenergy. In addition, accurate identification of unknown components is a technological breakthrough for the selected ion monitoring (SIM) mode for untargeted profiles. In this study, we developed untargeted fatty acid profiles based on SIM. We also investigated mass spectral characteristics and equivalent chain lengths (ECL) to eliminate the influence of non-FAMEs for identifying fatty acids in samples. As an application example, fatty acid profiles were used to classify three edible vegetable oils. The results indicated that SIM-based untargeted fatty acid profiles could yield accurate qualitative and quantitative results for more fatty acids and benefit related studies of metabolite profiles.

Rapid adulteration detection for flaxseed oil using ion mobility spectrometry and chemometric methods

To prevent the potential adulteration of flaxseed oil with high amounts of nutritional components, a simple and rapid adulteration detection method was proposed based on ion mobility spectrometry (IMS). After dilution in n-hexane, the edible oil sample was analyzed by IMS for 20 s. Subsequently, the multivariate statistical methods, including principal component analysis (PCA) and recursive support vector machine (R-SVM), were employed to establish a discriminant model for authentic and adulterated flaxseed oils. The cross validation results indicated that the R-SVM model could identify adulterated flaxseed oil samples (≥5%) with a high accuracy of 93.1%. Therefore, IMS could be used as an important tool to protect customers from adulterated flaxseed oil.

Aflatoxin Measurement and Analysis

Aflatoxin is a group of secondary metabolites produced by fungi Aspergillus species, such as A. flavus and A. parasiticus; in particular, A. flavus is common in agriculture. A. bombycis, A. ochraceoroseus, A. nomius, and A. pseudotamari are also aflatoxin-producing species, but they are encountered much less frequently (Bennett and Klich, 2003). Aflatoxin contamination can be occurred very widely. They can be found in over a hundred kinds of agro-products and foods,such as peanut, corn, rice, soy sauce, vinegar, plant oil, pistachio, tea, Chinese medicinal herb, egg, milk, feed etc,. Also some of them in animal organism can be detected. Besides these, aflatoxin can spread and accumulated in environment, for example, river and agricultural field. Aflatoxins are highly toxic, mutagenic, teratogenic, and carcinogenic compounds, a group of difuranocoumarin derivatives, consisted of a coumarin and a double-furan-ring of molecule usually. Aflatoxin B1, for example, its toxicity is ten times of potassium cyanide, 68 times of arsenic and 416 times of melamine. Furthermore, their carcinogenicity is over 70 times than that of dimethylnitrosamine and 10000 times of Benzene Hexachloride (BHC). And International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) accepted that aflatoxin should be classified as a Group 1 carcinogen in 1987, and then AFB1 is classified as Group 1 (carcinogenic to humans) by the WHO– IARC in 1993 (Li, Zhang & Zhang, 2009). According to the nearest researches by University of Pittsburgh, aflatoxin may play a causative role in 4.6–28.2% of all global HCC cases (Liu and Wu, 2010). To protect agricultural environment, estimate quality of commercials of agro-products and food, and safeguard safety of consumers’ health and lives, over seventy countries setup maximum limits in agro-products, and analytical methods for determination of aflatoxin, play a great role for monitoring and estimation of the contaminants. There are a variety of well established methodologies reported for analysing aflatoxins in many different foodstuffs, such as thin layer chromatography, high-performance liquid chromatography, ultra-pressured layer chromatography, immunoaffinity chromatographyhigh-performance liquid chromatography, near infrared spectroscopy and immunoassay