Rapid sample preparation procedure for As speciation in food samples by LC-ICP-MS

This paper describes a rapid method for arsenic (As) speciation by LC-ICP-MS in several types of food samples. Prior to analysis, samples were milled and the As species extracted from biological tissues by sonication in only 2?min with a solution containing MeOH (10%, v/v) plus HNO₃ (2%, v/v). As species were separated by LC using an anion exchange column. Method detection limits for AsB, As³⁺, DMA, MMA and As⁵⁺ were 1.3, 0.9, 0.6, 0.7 and 0.8?ng?g^?1, respectively. Method accuracy and precision were traceable to Certified Reference Materials SRM1577 bovine liver from the National Institute of Standards and Technology, CE278 mussel tissue from the Institute of Reference Materials and Measurements and DOLT-3 dogfish liver tissue and DORM-3 fish protein from the National Research Council of Canada. Finally, the method was applied to speciate As in food samples (egg, fish muscle, beef and chicken) purchased in Brazilian markets.     

Improvement of a sample preparation procedure for multi-elemental determination in Brazil nuts by ICP-OES

Various sample preparation procedures, such as common wet digestions and alternatives based on solubilisation in aqua regia or tetramethyl ammonium hydroxide, were compared for the determination of the total Ba, Ca, Cr, Cd, Cu, Fe, Mg, Mn, Ni, P, Pb, Se, Sr and Zn contents in Brazil nuts using inductively coupled plasma optical emission spectrometry (ICP-OES). For measurement of Se, a hydride generation technique was used. The performance of these procedures was measured in terms of precision, accuracy and limits of detection of the elements. It was found that solubilisation in aqua regia gave the best results, i.e. limits of detection from 0.60 to 41.9 ng ml^?1, precision of 1.0–3.9% and accuracy better than 5%. External calibration with simple standard solutions could be applied for the analysis. The proposed procedure is simple, reduces sample handling, and minimises the time and reagent consumption. Thus, this can be a vital alternative to traditional sample treatment approaches based on the total digestion with concentrated reagents. A phenomenon resulting from levels of Ba, Se and Sr in Brazil nuts was also discussed.     

食品分析中样品制备新技术概况

介绍了六种食品分析中样品制备新技术:超临界萃取技术,微波协助萃取技术,固相萃取技术,固相微萃取技术,顶空技术和流动注射分析技术。综述了他们在食品分析中的应用及未来发展趋势。     

环介导等温扩增技术快速检测食品中变形杆菌的研究

采用环介导等温扩增(LAMP)技术,快速检测食品中的变形杆菌。以变形杆菌(CMCC49027)的atpD基因作为靶序列,设计内、外引物,通过肉眼观察白色沉淀,判断检测结果。共对11株致病菌进行特异性实验。结果表明,变形杆菌为阳性,其他10株菌为阴性。采用FTA滤膜制备模板进行LAMP反应,其方法的灵敏度为6.4×102CFU/mL。利用LAMP技术直接检测人工污染的肉制品中的变形杆菌,其检出限为3.6×103CFU/g。本实验所建立的快速检测变形杆菌的LAMP检测方法具有较高的特异性和敏感性,能够满足变形杆菌快速检测的需要。     

Rapid screening of roundup ready soybean in food samples by a hand-held PCR device

Food Science and Biotechnology - Insulated isothermal PCR (iiPCR) method was recently available for rapid on-site detection of roundup ready soybean (RRS; event GTS40-3-2) in food materials and...     

食品采样、制备、样品管理研究中遇到的问题及对策

随着食品安全意识的提升,人们对食品检验提出了更高的要求,其通常包括食品采样、食品制备、样品管理等关键环节.食品采样要保证所采样品具有代表性、时效性、完整性;食品制备要保证制备工具清洁、干燥,不与所制样品发生任何化学反应;样品管理要保证样品存放环境符合相应标准,不同样品按不同储存环境进行存放,其中任何一个环节出现问题,都...     

Cloud point extraction for speciation of iron in beer samples by spectrophotometry

A new method based on the cloud point extraction (CPE) separation and spectrophotometric detection was proposed for the determination of iron species. In this method, Fe(II) reacts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in the presence of EDTA yielding a hydrophobic complex, which then is extracted into surfactant-rich phase. Total iron was determined after the reduction of Fe(III) to Fe(II) by using ascorbic acid as reducing agent. Variable parameters affecting the CPE efficiency were evaluated and optimised. The calibration graph was linear in the range of 5.0–112 μg/L (at 742 nm) for both species. Under the optimised conditions, the detection limits of 0.8 μg/L and 1.0 μg/L and the relative standard deviations of 2.0% and 2.6% (C_Fe(II) = C_Fe(III) = 10 μg/L, n = 5) for Fe(II) and Fe(III) were found, respectively. The proposed method has been applied to the speciation of iron in beer samples with satisfactory results.     

Improved PCR detection of Campylobacter jejuni from chicken rinses by a simple sample preparation procedure

Many food samples and enrichment media are inhibitory to the PCR, thereby lowering its detection capacity. A simple sample preparation method based on buoyant density centrifugation was examined for its application in PCR detection of Campylobacter jejuni from chicken rinse samples. Bacterial cells were spiked at different levels in a mixture of Preston broth and chicken rinse (4:1 ratio) and 0.9 ml of these mixtures were layered over 0.6 ml of gradient medium made from Percoll. PCR sensitivity for bacterial samples treated with this procedure was approximately 10-100 times higher than for samples without treatment. This sample preparation method allowed for the detection of C. jejuni from 26 of 31 naturally contaminated chicken samples after a 20-24-h enrichment period in Preston broth, compared with only 14 positives for untreated samples. In addition, the effect of Oxyrase on the growth and PCR detection of C. jejuni was examined. While Oxyrase significantly enhanced the growth and the PCR signals of C. jejuni in pure culture, it appeared not to improve the PCR detection of C. jejuni in naturally contaminated chickens.     

Applications of sample preparation techniques in the analysis of pesticides and PCBs in food

Pesticides and polychlorinated biphenyls (PCBs) are found in various parts of the environment in quite small concentrations, but they accumulate and thus become a threat to human health and life. A review is focused on the application of some popular techniques for sample preparation in analysis of these compounds in food. Even with the emergence of advanced techniques of final analysis, complex matrices, such as food, require extensive sample extraction and purification. Traditional sample preparation techniques are time consuming and require large amount of solvents, which are expensive, generate considerable waste, contaminate the sample and can enrich it for analytes. There have been many sample preparation techniques proposed to meet the requirements connected with the multiplicity of food. Optimal sample preparation can reduce analysis time, sources of error, enhance sensitivity and enable unequivocal identification and quantification. Sample extraction and purification techniques are discussed and their most recent applications in food analysis are provided. This review pointed out that sample preparation is the critical step.     

The preparation of food and environmental samples for residue analysis of pesticides and PCBs by continuous steam distillation]

The treatment of water, soil and food samples was tested with a modified equipment of glass for simultaneous steam distillation/solvent extraction. Spiked samples with 22 pesticides (most of them contained halogen) and PCB yielded good or very good recoveries after 1.5 h for water samples and after 5 h for soil and plant food samples, respectively. This method is ecologically beneficial, and because it needs only a small amount of solvent (less than 10 ml) it is not expensive and may be used as a quick screening in several fields.     

食品添加剂中重金属元素前处理与检测方法研究进展

本文主要对食品添加剂中重金属检测的前处理方法以及检测方法进行综述。目前,重金属前处理方法主要包括干法灰化、湿法消解、微波消解、液液萃取等,其中干法消解、湿法消解作为常用的前处理方法,耗时较长且容易造成损失,而微波消解具有方便、快速、干扰小等特点,逐渐得到认同与推广。重金属检测方法主要包括:快速显色法、原子吸收分光光度法、原子荧光分光光度法、电感耦合等离子体检测法等,后者以其较好的准确度与精密度,受到越来越多学者的追捧。     

Rapid screening for pesticides using automated online sample preparation with a high-resolution benchtop Orbitrap mass spectrometer

For pesticide analysis in food products a common approach is to develop a fast multi-residue method that is capable of identifying and quantifying a large number of analytes in various matrices. This study demonstrates rapid screening and accurate mass confirmation of 116 pesticides in oranges and hazelnuts using an automated online sample preparation method with turbulent-flow chromatography technology coupled to a high-resolution benchtop Orbitrap? mass spectrometer. The limits of quantification (LOQs) for the majority of analytes are well below the maximum residue limit (MRL) set by the European Union and the Japanese government. The recoveries were in the range of 70-120% for over 75% of analytes in both matrices. The present methodology is suitable for routine pesticides analysis in food safety laboratories.     

Muscle sample preparation for scanning electron microscopy

Scanning electron microscopy has a number of features which make it more suited to studying the relationships between muscle structure and the rheological properties of meat than either light microscopy or transmission electron microscopy. One of these features is the ability to examine large samples at high magnifications without the need to section the material. A simple tissue preparation procedure is presented which allows this feature of SEM to be fully utilized and consistently produces high quality results.     

Rapid detection of bacterial proliferation in food samples using microchannel impedance measurements at multiple frequencies

We present a novel method for detecting viable bacteria in suspensions such as milk and apple juice. Underlying the technique is the fact that bacteria in aqueous suspensions can store a large amount of charge, and thus act like (non-ideal) capacitors. Thus increased numbers of bacteria due to proliferation increases the capacitance of the bulk of the suspension. However, this increase cannot be directly measured since the capacitance of the solid–liquid interface (“double layer”) in effect “screens” the latter. We present a method (derived from an earlier one) that is able to discern such changes with high sensitivity and robustness. We also demonstrate its ability to monitor food quality/safety by detecting bacterial proliferation in “real world” liquid food samples like milk and apple juice. We are able to detect ~ 1, 10, 100, and 1000 CFU/mL of E. coli in milk in about 4.5, 3, 2, and 0.5 h, respectively. For the same initial loads, the corresponding times to detection (TTDs) for Lactobacillus in apple juice are approximately 8, 6, 4, and 1 h. These represent a greater than 4-fold reduction in TTD when compared to automated systems on the market such as RABIT, Bactometer etc. We can achieve such low TTDs for low initial loads since, due to the much greater effective charge holding capacity of bacterial cells (compared to surrounding media), we are able to detect a change in the overall bulk capacitance of the suspension as the bacterial numbers cross a threshold of around 500 CFU/mL.     

Automated DNA preparation from maize tissues and food samples suitable for real-time PCR detection of native genes

There is an increasing need for high-throughput analyses of plants and food samples for the presence of specific DNA sequences, e.g. transgenic contaminations. We developed and optimized conditions for the automated isolation of DNA from several maize tissues and various edibles containing maize using the MagNA Pure LC system (Roche Applied Science). Our results show that the system provided is capable of isolating DNA from any tested source. Quantification of an endogenous gene by LightCycler real-time PCR revealed that the DNA is suitable in quality and quantity for multiple PCR analyses.     

In situ sample cleanup during immunoassay: a simple method for rapid detection of aflatoxin B, in food samples

A strategy for rapid in situ elimination of interfering substances that are present in extracts of food samples during assay is described in this article. The novel feature of this method is that the sample purification is carried out as a part of the assay, and a separate sample cleanup step is not required. The assay procedure involves the sequential addition of standard or sample, cleaning solutions, and aflatoxin B1-horseradish peroxidase conjugate (AFB1-HRP) over antibody-spotted zones of a membrane, and 3,3'-diaminobenzidine was used as the substrate for visualization. We have determined that trifluoroacetic acid and propionic acids at concentrations of 100 mM are highly effective for cleaning groundnut, wheat, corn, and poultry feed samples and that NaHCO3 (100 mM) is successful in cleaning processed soybean. In all cases, subsequent washing was performed with phosphate-buffered saline solution to facilitate the removal of traces of adhering interfering substances. A batch of 12 samples can be analyzed within 8 min either by visual comparison of the color intensity (inversely related to the analyte concentration) of a sample spot with those of reference standards or, more precisely, by densitometry. The method was tested for the analysis of AFB1 in groundnut, wheat, corn, processed soybean, chili, and poultry feed. The detection limit obtained was 5 microg/kg, except for chili, where it was 10 microg/kg. The average recoveries from different noninfected food samples spiked with AFB1 at concentrations of 5 to 100 microg/kg were between 99 and 105%. The values obtained for infected corn and groundnut samples correlated well with the estimates obtained by high-pressure liquid chromatography. The absence of a sample extraction step reduces the cost and labor involved in the assay. The method may be potentially applicable to the assay of other mycotoxins and environmental pollutants.     

主成分分析法用于食品样品分类研究

利用化学模式识别技术的主成分分析(PCA)法对取自江西不同地区的谷物、蔬菜、水果的24个样品进行分类研究,所涉及的变量包括金属离子K、Na、Ca、Mg、Mn、Fe、Zn、Cu、Cr、Pb和有机物蛋白质、碳水化合物、脂肪、VB1、VB2。结果表明,运用PCA法可获得大量样品的统计特征,对变量进行适当的选择能够有效地分辨不同的样品。     

超高效液相色谱法快速测定保健食品中洛伐他汀

建立超高效液相色谱(UPLC)检测保健食品中的洛伐他汀。采用乙醇超声提取食品中的洛伐他汀,Acquity UPLC BEH C18柱分离,甲醇+0.1%磷酸(70:30)洗脱,流速0.4mL/min,用UPLC二极管阵列检测器(UPDA)在238nm波长下检测。测定结果显示,在1.06～21.2mg/L范围内,标准曲线呈良好的线性关系(r=0.99996),加样回收率为94.4%~103%,精密度(n=6)为0.88%。该方法4分钟完成一次进样分析,节省时间和溶剂,具有操作简便、快速准确等优点。     

ELISA法在检测食品中镉的研究进展

简述了酶联免疫吸附法的原理、镉抗原及其特异性单克隆抗体的制备、方法的选择.作为一种新型的检测方法,具有灵敏度高、特异性强、省时、省力、操作简单、便于携带等特点,最主要是能实现大量筛选.分析研究了该法在实际检测中的应用,探讨了酶联免疫吸附法在检测中存在的不足以及应用前景.     

Optimization of nanocapsules preparation by the emulsion-diffusion method for food applications

The aim of this work was to establish the conditions to obtain polymeric nanocapsules containing food ingredients by the emulsification-diffusion method. The Response Surface Methodology was used to optimize the process. The variables studied were shear rate (3070-18,920 s⁻¹), polymer-wall concentration: poly-?-caprolactone (PCL, 100-300 mg), and stabilizer concentration: polyvinyl alcohol (PVAL, 25-100 g/L). The analyzed responses were particle size (PS), polydispersion index (PDI), density (ρ_nc), and zeta potential (ζ). The results of ρ_nc and micrographs confirmed the presence of capsular structures. The most efficient conditions to obtain nanocapsules were 10,917 s⁻¹, 50 g/L of PVAL and 256 mg of PCL, predicting a response of PS = 250 nm, ρ_nc = 1.021 g/cm³, PDI = 0.045, and ζ = −20.02. It was concluded that keeping the same preparation conditions, the formation of nanocapsules is also possible from other food oily materials with similar characteristics (predicting values PS ≈ 300 nm and ζ ≈ −25). The proposed nanocapsules may have application in food preservation and storage.