Comparison of sulfuric acid treatment and multi-layer silica gel column chromatography in cleanup methods for determination of PCDDs,PCDFs and dioxin-like PCBs in foods

Two typical cleanup methods, sulfuric acid treatment and multi-layer silica gel column chromatography, for the determination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in seventeen food samples were examined and compared. Vegetables, fruits, cereals, fish, meat and dairy foods were extracted by conventional methods (shaking with acetone/n-hexane or with n-hexane after alkaline treatment). The extracts were cleaned up by sulfuric acid treatment or multi-layer silica gel column chromatography, followed by several column chromatographic steps. Of the samples treated, the vegetable, fruit and cereal samples could be directly applied to the multi-layer silica gel column after extraction. However, the samples containing fats and oils such as fish, meat and dairy foods needed to be treated several times with concentrated sulfuric acid before multi-layer column chromatography, because these samples plugged the column with oily residues. Both cleanup methods gave similar values of isomeric concentrations and showed similar efficiency of purification, and the recoveries ranged from 40 to 120%. These results are considered to provide useful data for the efficient analysis of dioxins in foods which have wide-ranging compositions.     

Analysis of Pesticides in Tomato Combining QuEChERS and Dispersive Liquid–Liquid Microextraction Followed by High-Performance Liquid Chromatography

A new sample preparation procedure combining QuEChERS and dispersive liquid–liquid microextraction (DLLME) was optimized for the determination at trace levels of 13 pesticides from different chemical families (i.e. 2,4-D, acetamiprid, bentazone, cymoxanil, deltamethrin, dicamba, diuron, foramsulfuron, mesotrione, metalaxyl-M, methomyl, pyraclostrobin and tembotrione) in tomato by high-performance liquid chromatography with diode array detection. Target pesticides from tomato samples were isolated by liquid partitioning with acetonitrile and salts and cleaned up by dispersive solid-phase extraction (d-SPE); the analytes were concentrated in trichloromethane by the DLLME procedure. The disperser solvent from DLLME was used at the same time as carrier of analytes form extraction in QuEChERS method. The main factors affecting sample cleanup by d-SPE in QuEChERS and DLLME yield were optimized by means of an experimental design. Under the optimum conditions, good linearity was obtained, the recoveries of pesticides in tomato samples at spiking levels between 0.01 and 1.00 mg/kg ranged from 86 to 116 % (for foramsulfuron and cymoxanil, respectively). Precision was within 15.0 % (RSD) except at the LQ for tembotrione, which was 17.4 %. Limits of quantification achieved (ranging from 0.0058 to 0.15 mg/kg) were below the maximum residue limits established by the European Union.     

Development of a cleanup method for polybrominated diphenyl ether (PBDE) in fish by freezing-lipid filtration

A new cleanup method for the determination of brominated flame retardants with an emphasis on polybrominated diphenyl ethers (PBDEs) has been developed for fish tissue sample. This method effectively reduces the sample pretreatment time, labor and required less solvent quantities relative to conventional methods. Freezing-lipid filtration procedure removes approximately 90 % of the lipids in the extract without any significant loss of the PBDEs. A multilayered silica gel column was used for further cleanup of the extracts after freezing-lipid filtration. Multilayered silica gel column chromatography eliminated most of the co-extracted interferences, such as residual lipids and fatty acids. The extracts were analyzed after cleanup by high-resolution gas chromatography/high-resolution mass spectrometry using the isotope dilution method. Tissue samples with 1.6–8.0 and 8.0–40 ppb of PBDE were analyzed using both the sulfuric acid treatment and freezing-lipid filtration cleanup methods in order to evaluate the method performance. Sulfuric acid treatment did not detect 2,4-DiBDE, whereas freezing-lipid filtration detected 2,4-DiBDE but at 50 % recovery. To compare the method, WMF-01 was analyzed via both the sulfuric acid treatment and freezing-lipid filtration cleanup.     

Cleanup of food samples with pre-packed multi-layer silica gel column for the analysis of PCDDs,PCDFs and dioxin-like PCBs

The cleanup procedure for the determination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs) in food samples using a disposable pre-packed multi-layer silica gel column (multi-layer dioxin tube; D-tube) was evaluated. The blank test showed the need for conditioning of the column with n-hexane. To compare the method with the D-tube and the conventional method for the analyses of actual food samples, seven food samples (spinach, komatsuna, rice, salmon, beef, egg and butter) were extracted by shaking with acetone-n-hexane or n-hexane after alkaline treatment, and then the extracts were cleaned up by use of the D-tube or the prepared conventional column, followed by several column chromatographic steps. Both cleanup procedures gave similar values at each isomeric concentration level and showed similar efficiency with favorable recoveries. The results suggest that the D-tube is applicable to cleanup for the analysis of PCDD/Fs and dioxin-like PCBs in foods.     

加速溶剂提取-凝胶渗透色谱净化-气相色谱测定咸鱼中的敌敌畏

建立咸鱼中敌敌畏残留的气相色谱分析方法。采用加速溶剂萃取(ASE)提取咸鱼样品中的敌敌畏,经凝胶渗透色谱(GPC)净化,浓缩定容后用GC-FPD 检测分析,外标法定量。样品添加水平为2.5 × 10-2mg/kg 和10.0 ×10-2mg/kg 时,敌敌畏的回收率在74.4%～96.8% 之间,方法检出限为5.0 × 10-4mg/kg。本方法准确、自动化程度高、净化效果好,满足残留分析要求。     

Determination of vitamin e in foods — a review

The vitamin E group includes tocopherols and tocotrienols and their isomers, esters, and derivatives. They differ not only in biopotencies as antisterility agents but also in activities in other physiological and chemical relationships. Unlike vitamins A and D, foods (vegetable oils) are among the richest sources of vitamin E, and assay methods for vitamin E include food applications more often than for the former vitamins. Phys‐icochemical methods are replacing bioassays for vitamin E and tocopherol wherever possible because of greater specificity and less variability, time, and, sometimes, expense. Unless careful purifications and isolations are carried out and some of the relative vitamin E activities of components are calculated, bioassays are still required for total vitamin E activity. The vitamin E group is separated by column, paper, thin‐layer, gas‐liquid, and high‐pressure liquid chromatography (HPLC): Gas‐liquid chromatography has been more successfully used for vitamin E than for other fat‐soluble vitamins. Recently developed HPLC methods for vitamin E are sensitive and apparently require less cleanup of extracts and less time than former methods; HPLC may prove to be the most useful technique for vitamin E in foods, especially if other fat‐soluble vitamins can be determined simultaneously on the same sample extract.     

分散固相萃取-气相色谱-串联质谱法测定茉莉花茶中86种农药残留

以QuEChERS（Quick,Easy,Cheap,Effective,Rugged,Safe）法为前处理技术,优化净化吸附剂组合和用量,改进净化方式,并以气相色谱-串联质谱（gas chromatography-tandem mass spectrometry,GC-MS/MS）法为检测手段,建立茉莉花茶中86 种农药残留筛查检测方法。样品用乙腈提取,提取液经饱和的氯化钠溶液萃取,取有机相,转移至装有混合吸附剂和有机滤膜的针筒中完成净化与过滤,GC-MS/MS测定,外标法定量。86 种农药线性范围在5～400 μg/kg之间线性关系良好,相关系数（r2）在0.98以上,方法定量限为0.1～8.0 μg/kg。当添加水平为80 μg/kg时,91.8%的农药平均加标回收率在70.1%～116.0%之间,相对标准偏差为1.9%～11.4%。     

QuEChERS-Based Methods for the Determination of Pesticide Residues in a Dill Using Gas Chromatography with Electron Capture and Nitrogen Phosphorus Detection

In this study, three QuEChERS-based methods of improving sample extract preparation through reduction of unwanted matrix background for pesticide residue analysis in dill (a chlorophyll-containing matrix) were developed and compared. These methods involved the use of (1) dispersive solid-phase extraction (dispersive-SPE), (2) dispersive-SPE combined with liquid–liquid extraction (LLE), and (3) only LLE. Samples were analyzed by gas chromatography with electron capture and nitrogen phosphorus detection (GC-ECD/NPD). The results indicated that cleanup with primary secondary amine (PSA) and graphitized carbon black (GCB) sorbents followed by final solvent exchange from acetonitrile to petroleum ether was the best alternative of the tested methods, resulting in the cleanest extracts. The matrix effect of dill on the most favorable method herein was not significant, and the calibration performed well, with R ²?≥?0.99. The overall recoveries at three spiking levels of 0.01, 0.1, and 1.0 mg kg^?1 fell in the range between 73 and 110 % (95 % on average) with relative standard deviation (RSD) values equal to or lower than 12 % (5 % on average). Uncertainty for the studied pesticides ranged from 7 to 14 % (with the overall average uncertainty of 11 %). Analyses of real samples revealed the presence of pesticides unapproved for use on dill, as well as exceedances of the maximum residue levels (MRLs) for some pesticides. The samples with residue violation results were also confirmed by gas chromatography–tandem mass spectrometry (GC-MS/MS). The proposed method of sample preparation and chromatographic analysis is sufficient and can be applied with all certainty to determine pesticide residues in dill and other plants of high pigment content, i.e., chlorophyll.     

高效液相色谱-串联质谱法测定水产品中7种微囊藻毒素

建立了高效液相色谇串联质谱法同时测定水产品中7种微囊藻毒素（微囊藻毒素-RR、微囊藻毒素-YR、微囊藻毒素-LR、微囊藻毒素-LA、微囊藻毒素-LW、微囊藻毒素-LF、微囊藻毒素．LY）的分析方法。样品用90%醇水（P／g）溶液提取,经离心、固相萃取柱净化后,用C18柱,以0．1％甲酸乙腈．0．1％甲酸溶液为流动相,梯度洗悦分离,使用三重四级杆质谱检测器捡测,以保留时间及特征离子对定性,外标法定量。结果表明,7种微囊藻毒素在线性范围内线性关系良好,相关系数均不低于0．9990,方法的定量限（以信噪比为10计）为0．2-0．5μg／kg,添加水平为1．0-20μg／kg时,回收率为71．5-106％,相对标准偏差（n=6）为312～9．1％。该法前处理简单、回收率高、精密度好,适用于水产品中7种微囊藻毒素的测定。     

高效液相色谱法测定果蔬饮料中的克百威和甲萘威农药残留

建立用HPLC-荧光检测法测定果蔬饮料中克百威、甲萘威残留量的方法。试样用甲醇-二氯甲烷(1:99,V/V)提取,取一定量有机相过氨基柱、浓缩、定容,外标法定量。该方法的检出限为克百威0.002mg/kg、甲萘威0.0008mg/kg,加标回收率在77.1%～94.5%之间,测定的相对标准偏差在1.3%～9.0%之间。     

鱼肉中甲砜霉素残留的分析方法研究

利用固相萃取-气相色谱-质谱联机分析鱼肉中的甲砜霉素残留量。用乙酸乙酯振荡提取鱼肉中的甲砜霉素残留,用硅胶和C18固相萃取柱对乙酸乙酯提取物进行净化和富集。净化后的提取物衍生化和气相色谱-质谱选择离子定量检测(选择离子为409、411、499、501)。通过对提取净化富集条件的优化,建立了鱼肉中甲砜霉素的残留的检测方法。样品加标的回收率为80%～95%,相对标准偏差为3.6%～8.1%,最低检出限为0.3μg/kg。     

Application of GC-HRMS and GC×GC-TOFMS to aid in the understanding of a dioxin assay's performance for soil and sediment samples

There have been numerous attempts to correlate results obtained by gas chromatography-mass spectrometry (GC-MS) to alternative techniques such as immunoassays and bioassays for the analysis of dioxins in environmental samples. In spite of these efforts, uncertainties about the performance of these methods remain. Following a series of performance studies of various dioxin assays, an in-depth evaluation of sample extracts from the Procept Rapid Dioxin Assay was conducted to provide users with a clearer understanding of the differences in the assay's results compared to traditional mass spectrometry. Two powerful analytical techniques [high-resolution mass spectrometry (HRMS) and two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS)] were used to provide a unique perspective about the assay's underlying analytical performance. HRMS analyses demonstrated that the target dioxin and furans were consistently captured in the assay's extracts. TOFMS analyses revealed that interferents in the sample extracts resulting from inconsistencies in the sample preparation process appear to be the primary factor contributing to the assay's imprecision. The conclusion of this research was the assay results cannot be expected to correlate directly with HRMS and should only be utilized as a screening technique (e.g., to identify the relative ranking of contamination, to determine if samples are above/below threshold levels, or to monitor a cleanup) for environmental matrices such as soil and sediment.     

Analysis of multi-pesticide residues in the foods of animal origin by GC–MS coupled with accelerated solvent extraction and gel permeation chromatography cleanup

A new analytical method was developed to simultaneously determine residues of 109 pesticides (including isomers) in the foods of animal origin. Acetonitrile was selected for accelerated solvent extraction (ASE) for effectively extracting the pesticides from the fatty samples. The cleanup was performed with an automated gel permeation chromatography (GPC) cleanup system. The prepared samples were analysed with GC–MS in the selected ion monitoring mode (SIM) using one target and two qualitative ions for each analyte. Chlorpyrifos-d₁₀ was used as an internal standard. The lowest limit of detection was 0.3 μg kg⁻¹ for some pesticides. The recoveries and relative standard deviations (RSDs) were checked by spiking untreated samples with pesticides at 0.05, 0.1 and 0.2 mg kg⁻¹. The average recoveries of most pesticides were from 62.6% to 107.8%. The precision values expressed as RSD were all ?20.5% (n = 6). Good linearity (r ? 0.99) was observed between 0.05 and 1.5 μg mL⁻¹.     

烟草中酰胺类除草剂残留量的测定

研究了烟草中异丙甲草胺、敌草胺和双苯酰草胺残留量的同时多残留测定方法，使用乙酸乙酯和环己烷混合溶剂提取农药残留，水与有机溶剂液／液分配和弗罗里硅土柱层析净化，气相色谱法配氮磷检测器测定。异丙甲草胺、敌草胺和双苯酰草胺的平均回收率分别为90．0％、80．4％和84．8％，检出限均为0．02ug／g。结果令人满意。     

Determination of the cyanobacterial toxin cylindrospermopsin in algal food supplements

For the analysis of blue-green algal food supplements for cylindrospermopsin (CYN), a C18 solid-phase extraction column and a polygraphitized carbon solid-phase extraction column in series was an effective procedure for the clean-up of extracts. Determination of CYN was by liquid chromatography with ultraviolet light detection. At extract spiking levels of CYN equivalent to 25-500 μg g(-1), blue-green algal supplement recoveries were in the range 70-90%. CYN was not detected in ten samples of food supplements and one chocolate product, all containing blue-green algae. The limit of detection for the method was 16 μg g(-1), and the limit of quantification was 52 μg g(-1).     

Determination of Deoxynivalenol and Nivalenol in Wheat by Ultra-Performance Liquid Chromatography/Photodiode-Array Detector and Immunoaffinity Column Cleanup

An ultra-performance liquid chromatography (UPLC®) method has been developed for the simultaneous determination of deoxynivalenol (DON) and nivalenol (NIV) in wheat. Ground sample was extracted with water and the filtered extract was cleaned up through an immunoaffinity column containing a monoclonal antibody specific for DON and NIV. Toxins were separated and quantified by UPLC® with photodiode-array detector (λ?=?220 nm) in less than 3 min. Mean recoveries from blank wheat samples spiked with DON and NIV at levels of 100–2,000 μg/kg (each toxin) ranged from 85 to 95 % for DON and from 81 to 88 % for NIV, with relative standard deviations less than 7 %. Similar recoveries were observed from spiked samples when methanol/water (80:20, v/v) was used as extraction solvent. However, by using a wheat sample naturally contaminated with DON and NIV, the one-way analysis of variance (Student–Newman–Keuls test) between different extraction solvents and modes showed that water extraction provided a significant increase (P?<?0.001) in toxin concentrations (mean values of six replicate analyses) with respect to methanol/water (80:20, v/v). No significant difference was observed between shaking (60 min) and blending (3 min). The limit of detection (LOD) of the method was 30 μg/kg for DON and 20 μg/kg for NIV (signal-to-noise ratio 3:1). The immunoaffinity columns showed saturation of DON/NIV binding sites at levels higher than 2,000 ng in blank wheat extracts spiked with the corresponding amount of mycotoxin, as single mycotoxin or sum of DON and NIV. The range of applicability of the method was from LOD to 4,000 μg/kg, as single mycotoxin or sum of DON and NIV in wheat. The analyses of 20 naturally contaminated wheat samples showed DON contamination in all analyzed samples at level ranging from 30 to 2,700 μg/kg. NIV was detected in two samples at negligible toxin levels (up to 46 μg/kg). This is the first UPLC® method using immunoaffinity column cleanup for the simultaneous and sensitive determination of DON and NIV in wheat.     

多种食品基体中茚虫威残留气相色谱检测

建立了采用气相色谱检测包括毛豆、青梗菜、柚子、姜、木耳、笋、茶叶、猪肉、鱼肉及鸡肉等多种食品基体中茚虫威残留的方法。采用丙酮 正已烷混合溶剂提取试样中茚虫威残留,ENVI-CARB固相萃取小柱净化植物源性产品、Florisil PR固相萃取小柱净化动物源性产品。对于气相色谱分析,定量限(LOQ)为0.005mg/kg,在添加浓度0.005～0.04mg/kg时,回收率及相对标准偏差分别为74.9%～106.4%及1.9%～11.5%。     

Blood plasma sample preparation method for the assessment of thyroid hormone-disrupting potency in effect-directed analysis

A sample preparation method combining solid-phase extraction (SPE) and liquid-liquid extraction (LLE) was developed to be used in Effect-Directed Analysis (EDA) of blood plasma. Until now such a method was not available. It can be used for extraction of a broad range of thyroid hormone (TH)-disruptors from plasma with high recoveries. Validation of the method using spiked cow plasma showed good recoveries for hydroxylated polybrominated diphenyl ethers (OH-PBDEs; 93.8 ± 19.5%), hydroxylated polychlorinated biphenyls (OH-PCBs; 93.8 ± 15.5%), other halogenated phenols (OHPs; 107 ± 8.1%), and for short-chain (<8 C-atoms) perfluoroalkyl substances (PFASs; 85.2 ± 24.6%). In the same extracts, the potency of the compound classes spiked to the cow plasma to competitively bind to transthyretin (TTR) was recovered by 84.9 ± 8.8%. Furthermore, the SPE-LLE method efficiently removed endogenous THs from the extracts, thereby eliminating their possible contribution to the binding assay response. The SPE-LLE method was applied to polar bear plasma samples to investigate its applicability in future EDA studies focusing on TH-disrupting compounds in this top predator species that is exposed to relatively high levels of bioaccumulating pollutants. A first screening revealed TTR-binding potency in the polar bear plasma extracts, which could be explained for 60-85% by the presence of OH-PCBs.     

番茄、辣椒、茄子中甲基毒死蜱残留量测定

采用高效液相色谱-二极管阵列检测器对番茄、辣椒和茄子中甲基毒死蜱残留量进行测定。样品用乙腈提取后,经Carb/NH2固相萃取小柱净化,用C8液相色谱柱、二极管阵列检测器,对甲基毒死蜱残留量的测定可取得满意的结果。该方法样品平均加标回收率为80.7%～92.4%,相对标准偏差为1.1%～4.6%;蔬菜中甲基毒死蜱检出下限为0.02mg/kg。     

分散固相萃取净化-高效液相色谱-串联质谱法测定鱼体中地克珠利残留量

建立分散固相萃取净化-高效液相色谱-串联质谱法测定鱼体中地克珠利残留量的分析方法。样品经无水硫酸钠脱水,乙腈超声提取并减压浓缩,正己烷去脂,基质分散固相萃取净化,以电喷雾离子源负离子扫描模式进行质谱分析,内标法定量。结果表明,地克珠利在1～100 μg/L范围内线性关系良好,相关系数R2大于0.999。地克珠利添加水平为1.00～50.0 μg/kg时,平均回收率在95.4%～108%之间,批内和批间变异系数均小于15%。地克珠利的检出限为0.50 μg/kg。本方法灵敏、高效、简单、重复性好,能满足鱼体中地克珠利残留量的检测要求。