Determination of Traces of Chromium in Foods by Solvent Extraction Flame Atomic Absorption Spectrometry

ABSTRACT

A simple methodology for Cr(III) determination in foods was developed through flame atomic absorption spectrometry with air/acetylene after a fast oxidation of Cr(III) with KM_nO₄ and pre-concentration of Cr(VI) in MIK as C_rO₂CI₂. A limit of detection and limit of quantification (LOQ), respectively, of 4 μg/Kg and 13 μg/Kg Cr(III) were obtained in commercialized foods in São Paulo, Brazil. Two certificated samples as well as some food samples were analyzed with good results. A study of sample treatment showed that the dry ash method is the best.     

富硒酵母的研究开发与应用

介绍了硒的生理功能、人体对硒的需求、富硒酵母的开发以及作为功能性食品基料在各方面的应用。     

近红外光谱通用模型在农产品及食品检测中的研究进展

我国人口基数大,农产品和食品的需求量多。农产品和食品的质量与安全与人们的日常生活息息相关。如何实现使用无损、快速、环境友好型、高通量的检测方法对农产品和食品的品质进行检测,是当代社会的发展需要。传统的检测分析方法存在着耗时耗力、检测的样品不能再次出售、产生次品漏检的现象等缺点。近红外光谱分析技术作为一种快速无损的检测手段,逐渐被一些学者以及相关行业人员所重视。然而,近红外光谱分析方法大多数只针对于单一物料建立数学模型。对于数量庞大且种类众多的农产品和食品而言,如不同地域、不同年份、不同温度、不同加工方法、不同成分组成甚至是不同品种,这种相对传统的近红外分析方法无疑会增加建模的工作量。随着计算机技术、光谱仪硬件、化学计量学以及互联网技术的发展,相关学者已经开始着手于近红外光谱通用模型的研究与开发来解决这一问题,即建立一个近红外通用模型,能够对多种物料的同一指标或多种指标进行检测。相比于传统的近红外光谱模型,通用模型具有建模成本低、工作量小等优点,特别使近红外光谱技术在农产品和食品领域中应用以及推广方面具有重要的意义。针对近红外光谱通用模型在农产品和食品检测中的研究进行综述,通过比较传统模型建模方法与通用模型建模方法,分别就建立通用模型过程中样品信息的获取、模型的建立以及样品信息的预测三大建模步骤中使用的方法进行总结,并归纳了近红外光谱通用模型在建模步骤中的要点。近红外光谱通用型模型在农产品以及食品品质检测方面的研究尚处于发展阶段。也提出对于通用模型开发与研究的一些建议,并就近红外光谱通用模型预测方法在检测领域的发展趋势进行了进一步展望。     

示波极谱法测定某些食品对亚硝酸根的阻断率

在高氯酸底液中，当有硫氰酸盐作催化剂时，亚硝酸根能迅速与二苯胺定量生成Ｎ－亚硝基二苯胺，并产生灵敏的催化电流。峰电位Ｅｐ＝－０．６１Ｖ（ｖｓ．ＳＥＣ），检测限２×１０＾－８ｍｏｌ／Ｌ，线性范围０～３×１０＾－５ｍｏｌ／ Ｌ，测定了茶叶等几种称范匝窍跛岣淖瓒下剩晃诹瑁梗梗保ィ滩瑁福常矗ィ笏猓矗担担ィ保罚矗ィ劢梗福ィ胛南妆ǖ老辔呛希刖浞椒ㄏ啾龋痉ň哂屑虮悖槊艉妥既     

From thermal analysis to safety science

The approach of thermal analysis and explosion in relation to safety science is based on investigation methods in the mining and chemical industries. Once adapted to the particularities of foods, these methods correspond well to the needs of the food industry. Thus, thermal analysis and explosion simulation techniques as part of safety science (or loss prevention) participate to a large extent in the prevention of incidents and accidents by helping to take preventive measures.The author gratefully acknowledges P. Lambelet for many helpful discussions and I. Horman for reviewing this text.     

Analytical performances of validated chemiluminescent enzyme immunoassays to detect N-methylcarbamate pesticides

In the present work, enzyme-linked immunosorbent assays (ELISAs) with chemiluminescent detection for the determination of carbofuran, carbaryl and methiocarb were developed and the analytical parameters of these assays were compared with those of ELISAs with colorimetric detection. Both were conjugate-coated formats based on identical monoclonal antibodies and homologous protein conjugates. In comparison with colorimetric ELISA, the ability of the chemiluminescent reagents to detect lower concentrations of horseradish peroxidase allowed to decrease the optimal antibody and conjugate concentrations and to reach better analytical parameters. The experimental comparison of the analytical performance of the ELISAs was carried out by analysing extracts of apple-strawberry baby food and simply diluted fruit juices, both spiked at different concentration levels with the above mentioned pesticides. Recovery values for both ELISAs were around 100% and no matrix effects were observed when fruit juices were diluted 1:20 or more. Results obtained by ELISAs correlated well, both in terms of accuracy and precision, with those obtained by a liquid chromatography-electrospray mass spectrometry (LC/ESI/MS/MS) analysis, used as reference method to validate the immunoassays results. The limits of detection reached by using the chemiluminescent assay were 0.03, 0.007 and 0.004 ng ml⁻¹ for carbofuran, carbaryl and methiocarb, respectively.     

Determination of chloropropanols in foods by one-step extraction and derivatization using pressurized liquid extraction and gas chromatography-mass spectrometry

3-Chloropropane-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) were determined for the first time in bakery foods using pressurized liquid extraction (PLE) combined with in situ derivatization and GC-MS analysis. This one-step protocol uses N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as silylation reagent. Initially, screening experimental design was applied to evaluate the effects of the variables potentially affecting the extraction process, namely extraction time (min) and temperature (°C), number of cycles, dispersant reagent (diatomaceous earth in powder form and as particulate matter with high pore volume Extrelut NT) and percent of flush ethyl acetate volume (%). To reduce the time of analysis and improve the sensitivity, derivatization of the compounds was performed in the cell extraction. Conditions, such as the volume of BSTFA, temperature and time for the in situ derivatization of analytes using PLE, were optimized by a screening design followed to a Doehlert response surface design. The effect of the in-cell dispersants/adsorbents with diatomaceous earth, Florisil and sodium sulfate anhydrous was investigated using a Box-Behnken design. Using the final best conditions, 1 g of sample dispersed with 0.1 g of sodium sulfate anhydrous and 2.5 g diatomaceous earth was extracted with ethyl acetate. 1 g of Florisil, as clean-up adsorbent, and 70 μL of BSTFA were used for 3 min at 70°C. Under the optimum conditions, the calibration curves showed good linearity (R(2)>0.9994) and precision (relative standard deviation, RSD≤2.4%) within the tested ranges. The limits of quantification for 1,3-DCP and 3-MCDP, 1.6 and 1.7 μg kg(-1), respectively, are far below the established limits in the European and American legislations. The accuracy, precision, linearity, and limits of quantification provided make this analytical method suitable for routine control. The method was applied to the analysis of several toasted bread, snacks, cookies and cereal samples, none of which contained chloropropanols at concentrations above the legislation levels.     

Non-chromatographic screening procedure for arsenic speciation analysis in fish-based baby foods by using electrothermal atomic absorption spectrometry

A procedure for the speciation analysis of arsenic in fish-based baby foods is presented. Inorganic arsenic, methylarsonic acid (MA), dimethylarsinic acid (DMA) and arsenobetaine (AB) were determined by electrothermal atomic absorption spectrometry (ETAAS) using suspensions prepared in a 0.01 mol L⁻¹ tetramethylammonium hydroxide (TMAH) solution. Speciation is based on the use of three different chemically modified ETAAS atomizers to obtain the analytical signals. Using a palladium salt as the chemical modifier, the signal corresponding to the total arsenic concentration is obtained. When palladium is replaced by Ce(IV), the signal is solely due to inorganic arsenic (III and V) + MA. If no signal is obtained in this latter case, it is possible to distinguish between DMA and AB using a zirconium coated atomizer. The signal obtained in this way is due solely to DMA, and the concentration of AB can be obtained by the difference with the total arsenic content. Determinations by ETAAS require the use of the standard additions method. The limits of detection for the determination of AB, DMA and inorganic arsenic (+MA) are 15, 25 and 50 ng g⁻¹ expressed as arsenic, respectively. These detection limits are good enough for the procedure to be appropriate for the rapid determination of these compounds, avoiding extraction processes and/or chromatographic separations. Data for commercial samples, as well as for four standard reference materials, are given.     

Liquid chromatographic/electrospray ionization mass spectrometric studies of proanthocyanidins in foods

The proanthocyanidins in three foods (pinto beans, plums and cinnamon) were studied with electrospray ionization (ESI) mass spectrometry (MS) in the negative mode following separation by normal-phase high-performance liquid chromatography. The MS/MS analysis demonstrated that the major ions derived from heterocyclic ring fission and retro-Diels-Alder reaction of flavan-3-ol provided information about the hydroxylation pattern and type of interflavan bond. The connection sequence of the oligomers was identified through diagnostic ions derived from quinone methide (QM) cleavage of the interflavan bond. Novel heterogeneous B-type proanthocyanidins containing (epi)afzelechin as subunits were identified in pinto beans. Proanthocyanidins with interestingly different A-type linkages were identified in plums and cinnamon. In efforts aimed at extending the identification capacity of ESI-MS to polymers, we found that the polymeric procyanidins fragmented readily instead of forming multiply charged ions in the negative ESI mode. Fragmentation patterns were proposed based on our data obtained by ESI-MS/MS and ESI time-of-flight MS.     

食品中角鲨烯样品前处理与检测方法研究进展

角鲨烯是一种存在于动物、植物、微生物体内的小分子功能活性脂质,由于具有抗氧化、防癌抗癌、抗辐射、携氧、皮肤保湿和抑制微生物生长等多种生物活性功能,被广泛应用于功能食品、医药产品和化妆品的开发。因此,不同食品中角鲨烯含量的分析技术一直是国内外学者研究的热点与重点。该文综述了不同食品中角鲨烯的样品前处理方法,包括超临界二氧化碳萃取法、固相萃取法、固相微萃取法、皂化法、有机溶剂提取法和分步结晶法等以及气相色谱法、液相色谱法和气相色谱-质谱联用法等检测方法在角鲨烯分析中的应用,并对其发展趋势进行了展望,为食品中角鲨烯的分析提供参考与借鉴。