Micellar electrokinetic chromatography estimation of size and composition of procyanidins after thiolysis with cysteine

This paper describes the characterization of procyanidin mixtures by acid depolymerization in the presence of cysteine (thiolysis with cysteine) and micellar electrokinetic chromatography (MEKC). Reversed-phase liquid chromatography (RP-HPLC) and MEKC were investigated for the separation of the major components of the depolymerized mixtures (catechins and their cysteinyl derivatives). The solutes could only be effectively separated using MEKC. Two background electrolytes (BGEs) are recommended: (i) 50 mM phosphate at pH 7, containing 40 mM sodium cholate (SC) and 10 mM sodium dodecyl sulfate (SDS); (ii) a BGE with the same composition but containing only 50 mM SDS. The MEKC procedures here reported, are cheap, reliable and fast, and their potential in the determination of the size and composition in procyanidin mixtures has been shown. The proposed MEKC methods were validated by comparison with our intralaboratory reference RP-HPLC method using cysteamine as thiol donor.     

Simultaneous spectrophotometric determination of three food dyes by using the first derivative of ratio spectra

Ternary mixtures of colorants E-123 (Amaranth), E-124 (Ponceau 4R) and E-120 (Carminic acid) are resolved by using the first derivative ratio spectrum-zero crossing method without the need for any separation step. Calibration graphs were linear up to 64 mg l⁻¹ of carminic acid, 32 mg l⁻¹ of Amaranth and 32 mg l⁻¹ of Ponceau 4R. The method was applied to different commercial food products and results concordant with high performance liquid chromatography were obtained.     

A new democratic phase coherent data-scatter technique for calibration, measurement, fingerprinting and rapid archival identification of ultraviolet-visible multi-component food spectra

The new theory of democratic phase coherent data-scatter (DPCD-S) is introduced. Basics of UV-visible spectrometry theory and error propagation have been presented. The qualitative spectral analysis provided is point-by-point over the complete data set and not just limited to Lambda-maxima. Equal weightings of the ‘voting’ data scattering algorithm are employed in the analysis of both the calibration and food colour data and this is consequently the democratic algorithm. The paper shows how the technique can be used with UV-visible standards to analyse the wavelength and photometric calibration of a spectrophotometer. The main results relate to the analysis of a series of spectra taken on complex mixtures of three important food dyes and their quantitative analysis using the phase coherent data-scatter technique. This method is shown to offer new possibilities for identifying and archiving UV-visible spectra from a single point in a transform space. Complex spectra can therefore be represented by a single point in this transform space, which is weighted by the ‘votes’ of all the data points in the complex data set. The software allows the user to interrogate the scatter results and locate the scatter point to the specific spectral positions. A new mathematical operator has been introduced to resolve any possible coincidence of two spectral projection points. Analysis of two close spectra from very-different admixtures of food colours shows powerfully the utility of this operator. Error propagation severely limits the accuracy of the usual UV-method of simultaneous equation secondary mixtures analysis.     

Solid-phase ultraviolet sensing system for determination of methylxanthines

In this study the use of a single continuous-flow solid-phase UV spectrophotometric sensing system for determination of methylxanthines was evaluated. Two methods were developed to determine caffeine (CF) and theophylline (TP) in pharmaceuticals and CF and theobromine (TB) in food and beverages. The sensor is based on transient and sequential retention of the analytes on a hydrophobic sensing solid zone (octadecyl silane C₁₈ gel) and detection of their intrinsic UV absorbance. Temporary sequencing of the arrival of the analytes at the sensing zone is achieved by on-line separation of one of the analytes using a pre-column of the same particulate material, placed just before the flow cell. After TB or TP had been carried toward the sensing zone (by the appropriate carrier solution), produced its transitory signal, and been eluted by the carrier, an appropriate eluting solution (25% MeOH) was used to elute CF, which was strongly retained on the minicolumn, so that its transient signal could be recorded. The sensing zone was completely regenerated with this eluting solution, and so was ready for analysis of another sample. After selecting the most suitable conditions, the sensing system was calibrated in the range 1–16 and 1–12 mg L^–1 for CF and TP–TB, respectively, giving detection limits below 0.1 mg L^–1 with RSD values less than 3%. The usefulness of this approach has been evaluated by applying it to the determination of caffeine, theobromine, and theophylline in different samples of food, beverages, and pharmaceutical formulations. The results were in satisfactory agreement with those obtained by use of an HPLC reference method.     

Enzymatic probe sonication extraction of Se in animal-based food samples: a new perspective on sample preparation for total and Se speciation analysis

This paper describes a fast, simple and novel extraction method for total selenium and selenium species determination in food samples. Parameters influencing extraction, such as sonication time, extracting media, temperature, sample mass, ultrasound amplitude and sample/enzyme mass ratio were investigated. The enzymatic hydrolysis proposed, enhanced by probe sonication, allowed the quantitative extraction of selenium in chicken muscle, liver, kidney and feed (97, 93, 95 and 102%, respectively) in 2 min, maintaining the original Se-species integrity. Total Se content of the samples was determined using inductively coupled plasma mass spectrometry. Se-species were identified and quantified using high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry. Chromatographic analyses were carried out under two chromatographic conditions and led to the identification of SeMet in all samples. The accuracy of the proposed method was assessed using certified reference materials as well as microwave digestion. Potential advantages of the proposed method over traditional hydrolysis are speed, simplicity and safety of the procedure.     

食品安全与健康——深圳市卫生部门食品安全保障体系

回顾了国际国内的食品安全问题以及管理现状,着重介绍了深圳市卫生部门食品安全保障工作.近几年,深圳市有效运行了食品污染物监测网络,基本掌握了食品安全存在的问题,通过对问题食品的追溯,从根本上着手解决问题,控制了污染食品进入餐桌;以风险评估作为科学手段,做好重点食品污染物的监测预警;引导和提醒消费者提高自我保护意识,为政府制定相关决策提供了依据,从而显著地减少了食源性疾病的发生,有效地保障了公众的身体健康.     

The potential of mass spectrometry to study iron-containing proteins used in clinical diagnosis

Many proteins contain iron as metal ion either within their own structures or bound to their active sites. These iron-containing proteins are involved in numerous biological processes and some of them serve as biomarkers of clinical pathologies, not only related to iron homeostasis but also to other physiological disorders. Thus, a variety of analytical strategies have been developed over the last years in order to conduct studies on Fe-containing proteins. Among them, mass spectrometric (MS) methods still remain as preferred tools since they provide the capabilities of structure elucidation together with quantitative possibilities. Therefore, in this work we have tried to summarize the most recent applications of elemental and molecular mass spectrometric-based methods for the characterization (mostly qualitative but quantitative in some cases) of the high abundant Fe-containing proteins used for clinical diagnosis.     

Detection of Phakopsora pachyrhizi by polymerase chain reaction (PCR) and use of germination test and DNA comet assay after e-beam processing in soybean

Soybean harvest is the main agribusiness in Brazil, which is the second largest exporter in the world and has a revenue of billions of dollars. Asian dust is caused by the fungus Phakopsora pachyrhizi and its dissemination is difficult to control, since it occurs through wind dispersion. Actually P. pachyrhizi is found in different parts of the world. Electron beam treatment could be an alternative process to minimize these losses, especially for the grains exportation industry. Besides the possibility of being disconnected when not in use, this source does not need to be reloaded, is easily available and, streamlines the process and reduces logistics costs. The present work aims to identify, by the polymerase chain reaction technique (PCR), the P. pachyrhizi fungus presence in the irradiated soybeans and the possibility to use radiation treatment as a sanitary alternative. Doses 0, 1.0, 2.0, 5.0, 6.0, 7.0, 8.0, 9.0 and 10.0 kGy (IPEN-CNEN/SP Electron Accelerator) were applied and two fast-screening methods were performed: DNA comet assay (for the detection of DNA damage) and germination test (for the measurement of roots inhibition). These tests are very easy to carry out and measure damage response depending on radiation dose.     

近红外光谱检测技术在农业和食品分析上的应用

近红外光谱是 2 0世纪 90年代以来发展最快、最引人注目的光谱分析技术。阐述了近红外光谱的原理、技术特点 ,介绍了近红外光谱仪、光谱预处理方法以及化学计量学研究的发展过程 ,重点列举了近红外光谱在农业和食品分析中的成功应用实例。资料表明 ,近红外光谱以其速度快、不破坏样品、操作简单、稳定性好、效率高等特点 ,已广泛应用于各个领域。特别是在欧美及日本等发达国家 ,很多近红外光谱分析法被列为标准方法。而我国近红外光谱的应用研究起步较晚 ,虽然某些方面已具国际领先水平 ,但就总体来看与国际水平还有大的差距。文章首次提出了集中优势资源 ,包括人力资源和设备资源 ,利用现代网络技术 ,建立终端用户和中心数据库资源共享的模式 ,以推动近红外光谱技术在我国农业科技和生产中的应用。     

钯盐作为改进剂在微波消化-石墨炉原子吸收法测量食品中微量元素的应用

本文研究了钯盐作为改进剂在微波消化-石墨炉原子吸收法测量食品中微量元素As、Cd、Cr、Ni、Pb、Sb、Se、Sn的作用。实验发现钯盐的改进剂作用远好于其他情况。氯化钯加抗坏血酸对上述元素测量具有较好的改进作用,但受硝酸浓度影响很大。硝酸钯加硝酸镁在测量铬、镉、锡时效果较好,且受硝酸影响小。