2种微生物试剂盒法快速检测乳粉中叶酸含量

目的 对2种商业化试剂盒法检测婴幼儿配斱乳粉中叶酸含量的结果迚行对比研究。方法 通过制作标准曲线,加标回收试验及样品重复性试验对2种试剂盒迚行比对。结果 研究表明2种试剂盒的叶酸标准曲线相关系数均在0.999以上;样品加标回收试验的加标回收率均在90%～100%之间,符合试剂盒加标回收要求;样品重复性试验结果相对标准偏差均小于5%。结论 2种商业化叶酸试剂盒具有操作简单、实验周期短、重复性较好等特点,可快速检测婴幼儿配斱乳粉中叶酸的含量。     

Determination of selected mycotoxins in mould cheeses with liquid chromatography coupled to tandem with mass spectrometry

A simple and feasible method is described for analysing nine mycotoxins in cheese matrix. The method involves liquid extraction followed by high performance liquid chromatographic separation and mass spectrometric detection of the analytes, and allows the determination of aflatoxins B1, B2, G1, G2 and M1, ochratoxin A, mycophenolic acid, penicillic acid and roquefortine C simultaneously. Average recoveries of the mycotoxins from spiked samples at concentration levels of 5-200 µg kg^-1 ranged from 96-143%. Within-day relative standard deviations at these concentration levels varied from 2.3-12.1%. The limit of quantification for aflatoxin M1 was 0.6 µg kg^-1 and for the other compounds 5 µg kg^-1. The method developed was applied for analysing these mycotoxins in blue and white mould cheeses purchased from Finnish supermarkets. Roquefortine C was detected in all of the blue mould cheese samples in concentrations of 0.8-12 mg kg^-1. One blue cheese contained also 0.3 mg kg^-1 mycophenolic acid. The other investigated mycotoxins were absent in the samples.     

涡旋振荡提取-高效液相色谱-紫外检测法测定铁叶酸片中的叶酸含量

摘要：目的建立涡旋振荡提取-高效液相色谱-紫外检测法（high performance liquid chromatography-ultraviolet, HPLC-UV）快速测定保健食品铁叶酸片中叶酸含量的分析方法。方法样品研磨成粉后,取样0.1 g, 加入0.3%的氨溶液25 mL,之后立即在旋涡混合器中涡旋振荡提取3 min。静置3 min后取上清液,滤膜过滤后,结合HPLC-UV方法进行含量检测。结果改进后的涡旋振荡提取法相比于常规的超声及加热提取法,前处理时间更短,提取效率更高,而且能够良好的避免基质中亚铁离子对含量测定的影响。叶酸在0.0054~0.2143 mg/mL浓度范围内线性良好（r2=0.9999）,实际样品平均回收率为98.18%~99.88%,相对标准偏差为0.89%~1.12%（n=6）。结论此改进后的方法准确、高效、简便、重现性良好,适用于保健食品铁叶酸片中叶酸含量的测定。     

微生物法测定乳清蛋白粉类样品中的叶酸含量

目的 建立微生物法测定乳清蛋白粉类样品中叶酸含量的分析方法。方法 利用叶酸标准品制作叶酸标准曲线。将样品进行超声处理得到样品溶液。向试管中加入等体积的培养基和不同体积的样液,稀释至10mL,得到样品待测液。样品待测液和叶酸标准曲线溶液灭菌后,加入鼠李糖乳杆菌(Lactobacillus casei spp.rhamnosus)CICC 6224菌悬液进行培养,将培养物混匀后测其吸光度值,根据标准曲线计算相应的叶酸含量,并进行方法的空白试验、检出限、精密度、重复性、稳定性及回收率试验。结果 在0.1010~1.0103ng/mL范围内,叶酸标准曲线呈现良好的线性,相关系数R_²=0.99373,符合GB/T27404-2008《实验室质量控制规范》的要求,该方法的相对标准偏差(relative standard deviation,RSD)为3.8%(n=6),平均回收率为102.5%(n=9)。结论 该方法稳定准确,适合用于测定乳清蛋白粉类样品中的叶酸含量。     

A precise method to measure the total fat content of spreadable fats

A simple gravimetric solvent-extraction method was developed to determine the total fat content of a wide range of spreadable fats having fat contents in the range 23–82 g 100 g⁻¹. Operating parameters affecting the yield of lipid were optimised. The available evidence indicated that full recovery of mono- and diglycerides and sterols was obtained. The method was compared with the Schmid–Bondzynski–Ratzlaff (SBR) method, which was shown to have a much poorer repeatability and to co-extract non-lipid matter. Precision estimates obtained from a pilot collaborative study, involving six laboratories and 10 different spreadable fats, were 0.27 g 100 g⁻¹ and 0.44 g 100 g⁻¹ for repeatability (2.83s_r) and reproducibility (2.83s_R) respectively. These estimates were constant over the fat range tested and thus did not depend on the composition of the products. The relative repeatability standard deviations (RSD_r) and the relative reproducibility standard deviations (RSD_R) for total fat were very low with ranges of 0.10–0.32% and 0.15–0.95%, respectively. The method has fewer health and safety risks than the Röse Gottlieb and SBR methods and is deemed sufficiently precise to be used for checking the fat content of spreadable fats against legislative specifications.     

高效液相色谱法测定烟草中的水杨酸

建立了用三氯乙酸溶液提取,三氯甲烷反萃取,甲醇和磷酸溶液为流动相,高效液相色谱法测定烟草中水杨酸含量的方法.结果表明,水杨酸的回收率为88％～90％,相对标准偏差为3.3％～5.4％.采用该方法检测了10个烤烟烟叶样品,水杨酸含量在1.43～6.22 μg/g之间.     

Determination of the mycotoxin fumonisin B1 in maize by reversed-phase thin-layer chromatography: a collaborative study

A simple and cost-effective method using thin-layer chromatography for the determination of the mycotoxin fumonisin B₁ in maize is described. The analytical method consisted of the extraction of ground maize by shaking with methanol/water (75:25) for 60 min and clean-up of the resultant extract by means of strong anion exchange solid-phase extraction. The purified residue, formed by evaporation of the elution solvent, was reacted with fluorescamine and the fumonisin B₁-derivative was separated by reversed-phase thin-layer chromatography using a developing solution of methanol/aqueous 4% potassium chloride (70:30). The derivatized FB₁ was readily visualized as a greenish-yellow spot under long wavelength ultraviolet light and quantified by visual comparison with a set of similarly derivatized standards in the range 20-300 ng FB₁ spotted on plate. Based on visual comparison, levels down to 0.5 mg kg^-1 were successfully estimated. The method was collaboratively studied in 14 laboratories using four duplicate maize meal samples (including a blank) and a spiked sample for determination of recovery. No significant difference was observed between mean FB₁ levels by high-performance liquid chromatography or thin-layer chromatography. Based on within-laboratory relative standard deviations of 27.1-41.7% and between-laboratory relative standard deviations of 35.0-63.3%, the method can be considered semiquantitative. The mean recovery achieved by participants at a spiking level of 2.00 mg kg^-1 was 74.5%.     

A simple and efficient ultrasonic-assisted extraction procedure combined with UV-Vis spectrophotometry for the pre-concentration and determination of folic acid (vitamin B9) in various sample matrices

A simple and efficient ultrasonic-assisted extraction (UAE) procedure has been proposed for the pre-concentration of (2S)-2-[(4-{[(2-amino-4-hydroxypteridin-yl)methyl]amino}phenyl)formamido]pentanedioic acid (folic acid) in vegetables, pharmaceuticals and foods prior to determination at 540 nm using UV-Vis spectrophotometry. The method is based on hydrophobic ternary complex formation of folic acid with silver ions in the presence of cetyltrimethylammonium bromide (CTAB) as a sensitivity enhancer counter ion at pH 7.0, and then extraction into a micellar phase of polyethylene glycol monoalkyl ether (Genapol X-080). The impacts on the extraction efficiency and complex formation of analytical parameters such as sample pH, concentration of silver, concentration of surfactants and extraction time, ultrasonic time and sample volume, were investigated and optimised in detail. The matrix effect on the pre-concentration and determination of folic acid was investigated, and it was observed that the proposed method was highly selective against possible matrix co-extractives. Under optimised conditions, a good linear relationship between the analytical signal and folic acid concentration was obtained in the range of 0.6–180 μg l^?1 with a detection limit of 0.19 μg l^?1 and quantification limit of 0.63 μg l^?1. The applicability was evaluated using samples fortified at different concentration levels, and recoveries higher than 94.1% were obtained. The precision as the percent relative standard deviation (RSD%) was in range of 2.5–3.8% (10 and 40 μg l^?1, n = 5). The proposed method was validated by analysis of two standard reference materials (SRMs) and various real samples, and satisfactory results were obtained.     

乳清蛋白粉营养成分分析研究

目的分析不同批次乳清蛋白粉蛋白、脂肪、乳糖、维生素、矿物质及其他功能性营养素的含量及波动情况。方法依照国标方法对乳清蛋白粉营养成分进行检测,并对检测数据进行汇总,分析不同批次间乳清蛋白粉营养素指标的波动范围及相对标准偏差。结果不同批次间乳清蛋白粉营养素波动不大,部分维生素(维生素B12、叶酸、泛酸、维生素C)、矿物质(锌、镁)、功能性营养成分(α-亚麻酸、胆碱、左旋肉碱)相对标准偏差在15%以上,波动较大。结论乳清蛋白粉营养成分含量整体比较稳定。     

自动电位滴定仪测定饼干中酸价和过氧化值的应用研究

目的建立自动电位滴定仪法测定饼干食品中酸价和过氧化值的检测方法。方法通过石油醚超声浸提提取饼干样品中的油脂,分别用自动电位滴定仪法和人工滴定法测定样品中的酸价和过氧化值。结果取15份饼干样品分别用自动电位滴定仪和人工滴定测定酸价和过氧化值,将结果进行配对t检验,方法无显著差异(P>0.05),人工滴定法测定时高、低酸价值样品相对标准偏差分别为0.34%和6.74%,自动电位滴定仪法测定时对应的相对标准偏差分别为0.27%和1.87%;人工滴定法测定时高、低过氧化值样品相对标准偏差分别为0.13%和0.96%,自动电位滴定仪法测定时对应的相对标准偏差分别为0.08%和0.21%。结论自动电位滴定法测定饼干中酸价和过氧化值所得结果精密度均优于人工滴定法,稳定性好,安全且便于操作。     

高效液相色谱法测定食品中番泻苷A和番泻苷B的含量

建立高效液相色谱法测定食品中番泻苷A和番泻苷B的方法。样品经过0.2%碳酸氢钠溶液超声提取,采用Agilent ZORBAX SB-C₈(4.6 mm×150 mm,5.0 μm)色谱柱分离,以四氢呋喃-水-乙酸为流动相洗脱,DAD检测器,检测波长:340 nm。番泻苷A、番泻苷B在1～100 μg/mL范围线性关系良好,相关系数均大于0.999,检出限(S/N=3)为15 mg/kg,定量限(S/N≥10)为50 mg/kg。以空白样品进行添加回收试验,番泻苷A的回收率为80.88%～96.34%,相对标准偏差(Relative Standard Deviation)为3.07%～7.73%,番泻苷B的回收率为81.32%～102.2%,相对标准偏差(RSD)为2.62%～9.62%。该方法前处理简单、灵敏度高、操作简便、准确性良好。在市售的果冻类食品中,检出阳性样品。     

Aflatoxins in ginseng roots

Ginseng roots can be infected by molds during growth, harvest and storage and result in contamination with mycotoxins. In this study, an analytical method for the determination of aflatoxins B₁, B₂, G₁ and G₂, a group of structurally similar mycotoxins, in ginseng root was developed. Test samples were extracted with methanol-water (8 + 2), diluted and passed through an immunoaffinity column packed with antibodies specific for aflatoxins. The purified extract was then derivatized with a mixture of water, trifluoroacetic acid and acetic acid. Aflatoxins were then separated and quantified by reverse phase liquid chromatography (LC) with fluorescence detection. Recoveries of total aflatoxins at 2, 4, 8 and 16 ng/g added to toxin-free 4 to 5-year old dried sliced Wisconsin ginseng were 92, 77, 91 and 83% respectively; and relative standard deviations were 3.6, 8.0, 6.9 and 2.0% respectively. A total of 11 wild simulated and 12 cultivated ginseng root samples were analysed for aflatoxins. All cultivated roots were found to be free of aflatoxin contamination. Two of the wild simulated roots contained total aflatoxins B₁, B₂, G₁ and G₂ at 15.1 and 15.2 ng/g. One moldy ginseng root purchased from a grocery store was found to be contaminated with aflatoxins at 16 ng/g.     

Occurrence of aflatoxin M1 in domestic milk in Japan during the winter season

A total of 208 samples of commercial pasteurized milk gathered from retail outlets across Japan during the winter season were analysed for aflatoxin M₁ (AFM₁). Japan was divided into 11 regions from north to south, and nine to 45 milk samples from each region were randomly purchased between December 2001 and February 2002. Each milk sample was cleaned up by an immunoaffinity column, and AFM₁ was quantified by liquid chromatography with fluorescence detection in four independent laboratories. The limit of detection of the method was 0.001 μg kg^-1. The identity of the putative AFM₁ in milk sample was confirmed by the formation of AFM₁ hemi-acetal with trifluoroacetic acid. Based on the results obtained with spiked samples (0.05 μg AFM₁ kg^-1), the mean recovery was 91.4%, the relative standard deviation for repeatability was 4.6%, and the relative standard deviation for reproducibility was 8.0% among four independent laboratories. AFM₁ was detected in 207 (99.5%) of 208 milk samples at 0.001-0.029 μg kg^-1, with a mean of 0.009 μg kg^-1 and a 90th percentile of 0.014 μg kg^-1. No significant difference of the level of AFM₁ contamination was observed among the regions.     

Determination of folic acid by ion-pair RP-HPLC in vitamin-fortified fruit juices after solid-phase extraction

A sensitive and reliable method was developed for the determination of folic acid (FA) in vitamin-fortified fruit juices and fruit drinks. After solid-phase extraction clean-up with strong-anion-exchange material, FA was determined by ion-pair reversed phase high-performance liquid chromatography (RP-HPLC). Limits of detection (LOD) and quantitation (LOQ) were 0.04 and 0.06 mg/l, respectively. Average recoveries at two fortified levels (0.5 and 1.0 mg/l) were 97% in 0.1 M acetate buffer (pH 4.9) and ranged from 78 to 93% in spiked blackcurrant nectar, apple juice, and cherry nectar, with standard deviations less than 2.3%. The method was used to analyze nine commercial fruit juices and fruit drinks containing FA in the range of 0.30–1.40 mg/l. In two samples significantly less FA was found than specified.     

Quantification of staphylococcal enterotoxin type A in cow milk by using a stable isotope-labelled peptide via liquid chromatography–tandem mass spectrometry

ABSTRACT

In this study, the staphylococcal enterotoxin type A (SEA) contaminant was quantified in cow milk by liquid chromatography–tandem mass spectrometry (LC–MS/MS) with the use of a stable isotope-labelled peptide of SEA as an internal standard. SEA was cleaned up in a two-step process that included pH control and trichloroacetic acid (TCA) precipitation. The pH control phase eliminated other proteins. TCA precipitation cleaned up SEA without special equipment. An appropriate enzyme-to-protein ratio maximised tryptic digestion. A desalting process guaranteed the stable retention of SEA-digested peptides. The coverage of amino-acid sequences (>10%) clearly identified the toxin’s presence. SEA was accurately quantified using LC-MS/MS based on a multiple-reaction monitoring mode. The developed method was validated based on spiked recovery tests at 50 and 100 µg kg^?1 conducted with two samples collected on a daily basis for five days based on Japanese validation guidelines. The new method exhibited good accuracy which ranged from 80% to 82%. The relative standard deviations of repeatability were 13–14% and the relative standard deviations of within-laboratory reproducibility were 13–18%. These standard deviations satisfied the criteria of the Japanese validation guidelines. The quantification limit was estimated to be 10 µg kg^?1.     

气相色谱-串联质谱法测定食糖中18种邻苯二甲酸酯

研究建立了气相色谱-串联质谱(GC-MS/MS)测定食糖中18种邻苯二甲酸酯的方法.食糖样品经甲醇超声提取,浓缩后正己烷复溶,采用气相色谱-串联质谱进行测定,多反应监测模式(MRM)扫描,外标法定量.结果表明,18种邻苯二甲酸酯在0.01～0.2 mg/L范围内线性良好(r2>0.997),检出限为0.0003～0.0...     

高效液相色谱法测定保健食品多维康胶囊中叶酸的含量

目的建立高效液相色谱法(high performance liquid chromatography,HPLC)测定多维康胶囊中叶酸含量的方法。方法采用C₁₈(150mm×4.6mm,5μm)色谱柱,以磷酸二氢钾-甲醇溶液为流动相,流速0.8 mL/min,检测波长254 nm,柱温30℃,进样体积10μL。结果叶酸的线性关系良好,相关系数为1.000;方法检出限为0.034μg/mL,定量限为0.091μg/mL;方法平均加标回收率为98.80%~104.17%,平均相对标准偏差为0.02%。结论该方法操作简单,灵敏度高,可作为保健食品多维康胶囊中叶酸的测定方法。     

高效液相色谱法同时测定工夫红茶中10种内含物成分

建立高效液相色谱法同时测定工夫红茶中咖啡碱、儿茶素、表儿茶素、表没食子儿茶素、表儿茶素没食子酸酯、表没食子儿茶素没食子酸酯、茶黄素、茶黄素-3-没食子酸酯、茶黄素-3’-没食子酸酯、茶黄素双没食子酸酯10 种内含物成分含量的方法。通过色谱条件优化,确定出工夫红茶中10 种内含物成分含量测定的最佳色谱条件为：色谱柱为Whatman Partisphere C18液相色谱柱（4.6 mm×125 mm,5 μm）、柱温32 ℃、流动相为0.035%三氟乙酸-5%乙腈溶液和0.025%三氟乙酸-50%乙腈溶液、流速1 mL/min、进样量10 μL、检测波长205 nm。在此条件下,上述10 种内含物成分得到很好的分离和测定。各种内含物的线性范围为0.05～500 μg/mL,标准曲线相关系数均在0.999 8以上,精密度检测相对标准偏差为0.72%～3.32%（n=5）,重复性检测相对标准偏差为1.87%～4.43%（n=5）,回收率在94.73%～102.38%之间。该方法简单、快捷、准确、重复性好,可应用于工夫红茶中10 种内含物质的同时快速测定。     

毛细管柱气相色谱法测定月饼中脱氢乙酸的含量

目的建立一种快速、准确测定月饼中脱氢乙酸含量的气相色谱法,并应用于昆明市中秋月饼中脱氢乙酸含量专项监测工作中。方法样品经酸化后,用乙醚提取,浓缩后,用丙酮溶解残渣并定容,用气相色谱-FID测定,色谱柱为HP-5石英毛细管柱(30m×0.25mm×0.25μm)。结果脱氢乙酸在10～500μg/ml的范围,峰面积与浓度呈良好的线性关系。加标回收率为85.3%～99.8%。精密度3.13%～4.73%。结论本方法快速、准确、分析成本低,能满足月饼中脱氢乙酸含量的快速分析。     

A spectrophotometric method for the detection of carboxymyoglobin in beef drip

A spectrophotometric method, based on the electronic absorption and second‐derivative spectra of beef drip, has been developed to detect the amount of carbon monoxide bound to myoglobin in treated beef samples. The method has been validated following the criteria reported in the Eurachem guides. The limit of detection, equal to 0.14 μm , has been evaluated analysing ten blank samples, taking into account the mean concentration and the resulting standard deviations. The accuracy of the method has been studied in terms of trueness and precision; the first is expressed as per cent recovery (always exceeding 90%) and the second as relative standard deviation. The method is easy, rapid and allows one to determine qualitatively and quantitatively the CO concentration in the meat drip, by simply measuring in the UV–Vis spectrum of an unknown sample the absorbance values at three specific wavelengths: 423, 429 and 434 nm.