Determination of seven preservatives in cosmetic products by micellar electrokinetic chromatography

A micellar electrokinetic chromatography method using cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, coupled with UV–Vis detection, was developed for the simultaneous determination of seven preservatives, including methyl‐, ethyl‐, propyl‐ and butyl‐paraben and phenol, phenoxyethanol and resorcinol. The method involved optimizing the pH of the phosphate buffer and concentrations of CTAB, ethanol and 2‐hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD). The preservatives were well separated using optimum conditions and separated within 10 min at a separation voltage of ?12.5 kV with the 1.0 mM phosphate buffer (pH 7.0) containing 90 mM CTAB, 25 mM HP‐β‐CD and 10% (v/v) ethanol. Satisfactory recoveries (84.1–103.0%), migration time (RSD < 3.1%) and peak area (RSD < 4.5%) repeatabilities were achieved. Detection limits of the preservatives were between 0.31 and 1.52 μg mL^?1 (S/N = 3, n = 5). The optimized method was successfully applied to the simultaneous determination of these preservatives in 10 commercial cosmetic products.     

发酵食品中多种防腐剂检测方法的建立

该实验建立了高效液相色谱法同时测定苯乳酸、苯甲酸、山梨酸的方法。在以C18柱为分离柱,流动相为甲醇-0.020 mol/L乙酸铵（20∶80,V/V）,色谱柱温为25 ℃,流速为1.0 mL/min,检测波长为220 nm条件下,12 min内可实现苯乳酸、苯甲酸、山梨酸的分离。该方法在0.25～50.00 mg/L范围内具有良好的线性关系（相关系数R2＞0.998）,检出限（LOD）＜50.00 ng/mL,回收率为96.93%～118.42%,精密度试验结果相对标准偏差（RSD）为0.39%～6.21%。该方法操作简便、结果准确度高,可用于发酵食品中苯乳酸、苯甲酸和山梨酸的同时分析检测。     

PCR-DGGE指纹分析技术在食品微生物检测中的应用

多聚酶链式反应结合变性梯度凝胶电泳指纹分析技术(PCR-DGGE)常用于分析自然环境中微生物群体的遗传多样性,具有可重复和容易操作且不需要进行微生物培养等特点,近年来该技术开始作为食品微生物的研究手段。本文概述了PCR-DGGE指纹分析技术在国外发酵食品及相关生态环境的研究中的应用现状与前景。     

Determination of phenolic antioxidants by micellar electrokinetic capillary chromatography with electrochemical detection

A new and efficient method for the determination of synthetic phenolic antioxidants (SPAs) has been developed by using micellar electrokinetic capillary chromatography (MECC) with electrochemical detection. Under the optimum conditions, all analytes were successfully separated within 13 min at the separation voltage of 18 kV in a 20 mmol/L borate running buffer (pH 7.4) containing 25 mmol/L sodium dodecyl sulfate. The excellent linearity was obtained in the concentration range from 5.0 × 10⁻⁴ to 2.0 × 10⁻⁶ mol/L and the detection limits (S/N = 3) of propyl gallate (PG), tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) range from 2.9 × 10⁻⁷ to 2.7 × 10⁻⁶ mol/L. This method has been proved to be effective and successfully applied for the determination of SPA in food products, providing a promising and convenient entry to monitor the superscale use of phenolic antioxidants.     

PCR及其改进技术在食品检测中的应用

在介绍传统PCR的基础上,简介实时定量PCR、多重PCR、PCR—DGGE等几种常用的PCR改进技术在食品检测方面的应用。     

紫杉醇的薄层层析显色反应与应用

为了进行抗癌药物紫杉醇产生菌株的快速筛选,建立了紫杉醇检测的薄层层析(TLC)方法。研究结果表明,应用薄层层析技术对内生真菌的发酵产物进行检测比高效液相色谱(HPLC)方法更加高效,能够简便、准确的筛选到紫杉醇产生菌株,并且可以初步推测菌株的紫杉醇产生能力。     

实时荧光定量技术在食品微生物检测和研究中的应用

实时荧光定量PCR技术是通过检测PCR产物中荧光讯号强度来达到定量的目的,不仅实现了对核酸信息量的分析比较,而且与常规PCR相比,它具有特异性更强、能有效解决PCR污染问题、自动化程度高等特点。文章概述了实时荧光定量PCR技术的原理、优缺点及其在食品微生物检测中的应用与研究进展,并探讨了它的技术发展和应用前景。     

The detection short chain fatty acids in foods by gas-liquid chromatography method

On the basis of gas-liquid chromatography (GLC) technique of quantitative determination in food, and biologically active additives (BAA) to food short-chain fatty acids: acetic, propionic, butyric, isobutyric, valeric and isovaleric. For this purpose, we used the method of GLC with a plasma-ionization detection, which allowed us to determine the amount of these acids in dietary supplements, prepared on the basis of bacterial.     

Simultaneous determination of nine kinds of preservatives in foods by HPLC

A simple and rapid HPLC method was developed for the simultaneous determination of nine kinds of preservatives, benzoic acid (BA), sorbic acid (SOA), dehydroacetic acid (DHA), methyl p-hydroxybenzoate (PHBA-Me), ethyl p-hydroxybenzoate (PHBA-Et), isopropyl p-hydroxybenzoate (PHBA-isoPu), propyl p-hydroxybenzoate (PHBA-Pu), isobutyl p-hydroxybenzoate (PHBA-isoBu) and butyl p-hydroxybenzoate (PHBA-Bu), in foods. For solid foods, the preservatives were extracted with methanol. After addition of 5 mmol/L citrate buffer to the extract, the extract solution was cleaned up on an Oasis HLB cartridge. The cartridge was washed with 5 mmol/L citrate buffer and methanol-5 mmol/L citrate buffer (4:6). Then, nine kinds of preservatives were eluted with methanol. The eluent was used for BA, SOA and DHA determination by HPLC. Furthermore, a part of the eluent was cleaned up on a Bond Elut PSA cartridge for p-hydroxybenzoate esters determination by HPLC. Liquid foods were cleaned up after addition of 5 mmol/L citrate buffer without the extraction process, and the subsequent procedure was the same as for solid foods. The recoveries of p-hydroxybenzoate esters from ten kinds of foods fortified at levels of 0.01 and 0.10 g/kg each were 91.5 to 107.4%, and those of BA, SOA and DHA were 76.4 to 104.8%. The quantitation limits of the preservatives in foods were 0.005 g/kg. (Received March 20, 2006)     

Application of real-time PCR for tree nut allergen detection in processed foods

Abstract

Currently, food allergies are an important health concern worldwide. The presence of undeclared allergenic ingredients or the presence of traces of allergens due to accidental contamination during food processing poses a great health risk to sensitized individuals. Therefore, reliable analytical methods are required to detect and identify allergenic ingredients in food products. Real-time PCR allowed a specific and accurate amplification of allergen sequences. Some processing methods could induce the fragmentation and/or degradation of genomic DNA and some studies have been performed to analyze the effect of processing on the detection of different targets, as thermal treatment, with and without applying pressure. In this review, we give an updated overview of the applications of real-time PCR for the detection of allergens of tree nut in processed food products. The different variables that contribute to the performance of PCR methodology for allergen detection are also review and discussed.     

Residue analysis of melamine in milk products by micellar electrokinetic capillary chromatography with amperometric detection

A high-performance micellar electrokinetic capillary chromatography with amperometric detection (MECC–AD) method for the fast determination of melamine (MM), occasionally used to increase the apparent protein content of milk products, has been developed. Method development involved optimisation of the working electrode, the running buffer system and acidity, the concentration of sodium dodecyl sulphate (SDS), the separation voltage, the applied potential and the sample injection time. Under the optimum conditions, MM can be well separated from its co-existing interferences in real-world samples within 9 min at the separation voltage of 20 kV in a 8 mmol/L SDS/20 mmol/L H₃BO₃–Na₂B₄O₇ running buffer (pH 7.4). Satisfactory recovery (83.3–105.5%), repeatability of the peak current (3.2%) and migration time (3.8%), and the limit of detection (2.1 × 10⁻⁶ g/mL) for the method were achieved. This proposed procedure has been successfully used for the determination of MM in milk products.     

气相色谱内标法测定食品中多种常见防腐剂的含量

采用乙醚提取,进入GC-FID,采用内标(十一烷酸)法对食品中11种防腐剂进行定量测定,该方法线性良好,检出限为0.84～5.01mg/kg,精密度为2.0%～3.6%,回收率在90.6%～98.8%,此方法操作简便,抗基质干扰、结果可靠,适合食品中多种防腐剂含量的准确测定。     

Analysis of coumarin in various foods using liquid chromatography with tandem mass spectrometric detection

Recently authorities and the media have published reports of increased coumarin levels in Christmas biscuits, gingerbread, cinnamon cookies and other foods. The maximum tolerance limits for coumarin in food are set out in EC Directive 88/388/ECC. Since the standard use of analytical techniques, such as HPLC–UV, are only limitedly suitable for verifying compliance with the regulatory limit of 2 mg/kg for coumarin in food, a selective, sensitive isotope dilution LC–MS/MS method for determining coumarin content in foods was developed, tested and validated, and the results then compared to the HPLC–UV method. This LC–MS/MS method increased selectivity and raised sensitivity by a factor of 100 compared to the HPLC–UV technique. The respective limits of determination and quantification for the method were 0.03 and 0.05 mg/kg, respectively, with an RSD of 1–8% and a linearity range of 0.1–500 ng/mL (corresponding to 0.05–250 mg/kg in food). In addition, a selection of around 500 food samples was also tested for coumarin content using the LC−MS/MS technique.     

A bio-sensing strategy for the detection of prions in foods

An affinity based bio-sensing technique was developed using an anti-transmissible spongiform encephalopathy monoclonal antibody to detect prion in 0.1 mol/l sodium phosphate buffer. Fluoresein iso-thio-cyanate (FITC) labeled with a prion epitope (QYQRES) was used as a decoy for prions. Lowest detectable prion concentration was 8 nmol/l in phosphate buffer. The bio-sensing scheme was used to probe the presence of prions in gelatin and baby-formula. The gelatin interfered with the binding and the displacement reaction of antibody, decoy and prion. Addition of sodium dodecyl sulfate (SDS) at 0.3 mg/ml to gelatin samples facilitated prion detection in gelatin. The lowest detectable concentration of prion in gelatin was 0.5 nmol/l at 0.4 mg/ml gelatin. The baby formula samples produced light scattering and the intrinsic peak of baby formula interfered with the dye peak. Serial dilutions of baby formula were done to reduce the interference. Addition of Triton-X-100 at 0.454 mg/ml to the baby formula samples facilitated the prion detection. The lowest detectable concentration of prion was 2 nmol/l for baby formula.     

A medium for the impedimetric detection of yeasts in foods

A mycological medium, CBAS, was developed for the detection of yeasts in foods using polarization capacitance (Cpol) measurements. The signal obtained due to the growth of yeasts in CBAS provided earlier detections and stronger responses than the signals produced by these yeasts in other common media. Of several impedance components evaluated, Cpol provided the most useful signal for yeasts in CBAS. Further investigation showed that pH change was responsible for approximately 50% of the Cpol signal. Cpol detection times correlated highly with plate counts of a yeast isolated from orange juice when tested in CBAS (r = ?0·99) and in a 1:10 dilution of orange juice in CBAS (r = ?0.94). A concentration of 10² yeast cfu ml⁺¹ in a 1:10 dilution of orange juice in CBAS was detected within 26 h by Cpol in contrast with a 3 to 5 day plate count.     

色谱技术在检测牛奶中激素类药物残留的应用

牛奶中激素类药物残留的检测是保证人们放心食用安全牛奶的重要环节,检测技术是解决此问题的关键。本文分别介绍了色谱技术在检测牛奶中五类激素类药物残留的应用情况,分析不同色谱技术的优缺点,并对牛奶中激素类药物残留检测技术的发展趋势进了展望。      

程序变波长-高效液相色谱法同时测定果蔬中9种防腐剂

建立了柑橘、黄瓜、白菜、西红柿四种果蔬中9种防腐剂（对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯、对羟基苯甲酸异丙酯、对羟基苯甲酸异丁酯、乙萘酚、乙氧基喹、4-苯基苯酚）的程序变波长-高效液相色谱同时测定方法。样品采用乙醚提取,液-液萃取净化,以甲醇-水为流动相进行梯度洗脱,经Agilent Eclipse XDB-C18色谱柱（150mm×4.6mm,3.5μm）分离,程序化变波长检测,外标法定量。结果表明,9种防腐剂在0.5¹00.0mg/L范围内线性关系良好（r≥0.9991）;在50、200、500μg/kg三个添加水平下平均回收率为70.7%¹19.5%,相对标准偏差（RSD）为0.9%⁹.9%。该方法简便快速、准确可靠,适用于果蔬中多种防腐剂残留的同时测定。