Determination of melamine in milk and milk-containing products by capillary zone electrophoresis

For determination of melamine methods of reversed phase and ion-pair high-performance liquid chromatography, and also immune-enzyme analysis are used. The purpose of our work was working out of a technique of determination melamine in milk and lactiferous products method CZE. As a result of researches determination conditions melamine in foodstuff by method CZE (sensitivity from 0.8-1.0 mg/l) are developed, and also conditions of its isolation from objects of research are adapted.     

毛细管区带电泳法测定葡萄酒中金属阳离子

采用高效毛细管区带电泳,在pH4.0的电解液中,以28mmol.L-1乳酸为络合剂,50mmol.L-1咪唑为背景试剂,在20kV、210nm条件下10min内分离测定了八种金属阳离子,并对电泳条件进行优化。八种离子的线性回归方程的相关系数在0.9991～0.9998之间,迁移时间和峰面积的相对标准偏差分别为0.21%～0.97%和1.65%～7.47%。将建立的方法用于葡萄酒中金属阳离子的测定,取得了满意结果,各离子的回收率在92.4%～102.7%。     

Quantification of major camel milk proteins by capillary electrophoresis

Proteins from dromedary camel milk (CM) produced in Europe were separated and quantified by capillary electrophoresis (CE). CE analysis showed that camel milk lacks β-lactoglobulin and consists of high concentration of α-lactalbumin (2.01 ± 0.02 mg mL⁻¹), lactoferrin (1.74 ± 0.06 mg mL⁻¹) and serum albumin (0.46 ± 0.01 mg mL⁻¹). Among caseins, the concentration of β-casein (12.78 ± 0.92 mg mL⁻¹) was found the highest followed by α-casein (2.89 ± 0.29 mg mL⁻¹) while κ-casein represented only minor amount (1.67 ± 0.01 mg mL⁻¹). These results were in agreement with sodium dodecyl sulphate-polyacrylamide gel electrophoresis patterns. Overall, CE offers a quick and reliable method for the determination of major CM proteins, which may be responsible for the many nutritional and health properties of CM.     

高效毛细管电泳测定液态乳中乳糖

针对常用乳糖测定方法存在的局限性和不便性,结合高效毛细管电泳(HPCE)法简单快速、高效低耗的特点,探索出了高效毛细管电泳仪配合紫外检测器测定乳糖的实验条件:熔融石英毛细管(50μm×34 cm);缓冲液为50 mmol/L硼砂/NaOH,pH值为10.0;电泳为10 kV,温度为60℃;检测波长为195 nm;进样为5000 Pa;时间3 s。此方法操作简便、准确度高、精密度好。该方法的测定结果与高效液相色谱法的结果较一致,样品中其他糖类对该方法不存在干扰,克服了莱因-埃农氏法测定乳糖不具专一性的缺点。     

Rapid determination of sodium in milk and milk products by capillary zone electrophoresis

A capillary zone electrophoresis method for the determination of Na in milk and milk products was developed and compared with an International Organization for Standardization/International Dairy Federation standard method that is based on flame atomic absorption spectrometry. The adoption of a background electrolyte consisting of 10 mM imidazole adjusted to pH 3.75 by the addition of oxalic acid allowed baseline separation of Na from other milk cations and from Li ion, which was adopted as an internal standard. Method validation was performed and the results for linearity, precision, limit of detection, limit of quantification, and recovery are presented. The procedure was tested on commercial milk samples differing in fat content (whole, semiskimmed, and skimmed) and processing conditions (pasteurization, UHT sterilization, and microfiltration). The reliability of the method was confirmed for different varieties of cheese and other milk products. The method enables the routine measurement of Na content by a rapid and accurate capillary zone electrophoresis procedure.     

毛细管区带电泳-间接紫外测定食品中木糖醇

目的建立毛细管区带电泳间接紫外测定食品中木糖醇的新方法。方法样品用超纯水提取后离心,过0.45μm膜后上机进样。以未涂敷熔融石英毛细管(50μm×60.2 cm)为毛细管分离柱,以8 mmol/L 3,5-二硝基苯甲酸、10 mmol/L硼砂和0.5 mmol/L十六烷基三甲基溴化铵为分离缓冲溶液。分离电压为-20 k V,检测波长为200 nm,用外标法定量。结果方法检出限为3.00 mg/L(S/N=3),定量限为10.00 mg/L(S/N=9),线性范围为10.00~300.0 mg/L,线性相关系数r为0.9994。在20.00、40.00、80.00 mg/L添加水平下,平均回收率分别为103.2%、103.3%及104.8%,相对标准偏差分别为0.5%、1.2%及0.7%(n=3)。结论该方法简单快速,11 min内即可完成一次样品分析(清洗6 min、分离5 min),试剂及样品消耗量少,适用于食品中木糖醇的检测。     

Determination of iodate in table salt by transient isotachophoresis–capillary zone electrophoresis

A transient isotachophoresis–capillary zone electrophoresis (tITP–CZE) method was first time developed for determining iodate in table salt. Sensitivity enhancement was accomplished by coupling on-capillary tITP with CZE. The interference of sample matrix was overcome by using electrophoretic buffer containing high concentration of sodium chloride. The optimal terminating electrolyte for tITP was 1500 mmol/L phosphate and the separation buffer of capillary zone electrophoresis was 10 g/L sodium chloride (pH 8.0) containing 20 mmol/L cetyltrimethylammonium chloride (CTAC). Calibration graphs based on peak height and peak area showed good linearity. Use of chromate as the internal standard significantly improved the precision of the quantitative results. The wavelength of UV detection for iodate was set at 218 nm with the detection limits of 3.5 μg/L for iodate. The quantitative results of iodate in table salt measured by the tITP–CZE method were compared with those measured by the redox titration and there was no significant difference between the two means. The method developed was sensitive, fast and simple.     

高效毛细管区带电泳-间接紫外法测定食品中三氯蔗糖

目的建立利用毛细管区带电泳-间接紫外法测定食品中三氯蔗糖的方法。方法样品用超纯水提取,离心所得的上清液直接进样,以未涂层熔融石英毛细管(50μm×60.2 cm)为分离柱,3 mmol/L 3,5-二硝基苯甲酸+10 mmol/L磷酸钠+12 mmol/L氢氧化钠(p H=12.58)+0.5 mmol/L十六烷基三甲基溴化铵为分离缓冲液;检测波长200 nm,分离电压-20 k V。采用校正峰面积外标法进行定量。结果方法检出限为10 mg/L,定量限为30 mg/L,线性范围为30~300 mg/L,线性相关系数r=0.999 1。低、中、高3个质量浓度(40、60及80 mg/L)的加标回收率分别为108.1%、102.6%、103.5%,相对标准偏差(RSD)分别为1.3%、1.3%及1.0%,方法精密度为2.0%。结论本研究样品前处理操作简单,20 min之内即可完成三氯蔗糖的含量分析(预清洗6 min,分离13 min),实现了与其结构相似但又同时存在于食品中蔗糖的分离,且试剂及样品消耗量少,适用于实验室对于食品中三氯蔗糖的检测。     

Determination of lactose in sugar-free milk powder by capillary electrophoresis with electrochemical detection

Lactose in three sugar-free milk powder samples were satisfactorily determined by capillary electrophoresis with electrochemical detection using a 300 μm copper disk electrode as the working electrode in 0.1 mol/l NaOH medium. There was acceptable linearity (0.9969) between the peak current and concentration of lactose in the range from 5.0×10⁻⁶ to 5.0×10⁻³ g/ml with the detection limit (S/N=3) of 1×10⁻⁷g/ml. The proposed method was successfully applied to analyze the actual milk powder samples.     

毛细管电泳法测定绿茶酶解液中的还原糖成分

建立了一种利用毛细管电泳测定绿茶酶解液中主要还原糖的方法。针对绿茶浸提液中可能含有的麦芽糖、乳糖、木糖、阿拉伯糖、葡萄糖、鼠李糖、半乳糖、甘露糖、半乳糖醛酸等9种主要还原糖,当被1-甲基-3-苯基-5-吡唑啉酮(PMP)衍生后,在电压21 kV,硼酸浓度200 mmol/L,pH值11.0和柱温25℃的条件下可实现基线分离。对这9种还原糖衍生物作标准曲线,在0.5¹0 mmol/L浓度范围内线性相关度R2为0.993910 mmol/L浓度范围内线性相关度R2为0.9939⁰.9994,最低检测极限范围是0.090.9994,最低检测极限范围是0.09⁰.23μmol/mL,9种还原糖衍生物加标回收率在94.04%0.23μmol/mL,9种还原糖衍生物加标回收率在94.04%¹01.9%。应用该方法测定绿茶酶解液中主要还原糖的组分和含量,得出酶解液中主要含有木糖、阿拉伯糖、葡萄糖、半乳糖和半乳糖醛酸5种,它们的浓度随着复合水解酶的来源不同而不同。     

毛细管电泳法对乳及乳制品中乳源蛋白的研究

采用毛细管电泳方法对原料乳、市售鲜奶、不同厂家的巴氏灭菌乳、不同厂家和产地超高温灭菌乳(UHT)、调味乳、乳酸饮料、复原乳、酸奶、奶粉中蛋白成分进行检测。选择聚乙烯醇涂层毛细管,采用柠檬酸缓冲体系,在紫外检测214nm、分离电压20kV条件下对乳及乳制品中的α一乳白蛋白(α-La)、β一乳球蛋白(β-Lg)、α-酪蛋白(α-CN)、β-酪蛋白(β-CN)和k-酪蛋白(k-CN)进行分离测定。结果表明:五种蛋白的含量在原料乳(巴氏灭菌乳、市售鲜奶)、UHT乳、酸奶、调味乳、乳酸饮料、复原乳中依次降低,而UHT乳含量随保质期的增加而减少,奶粉中蛋白质含量因其适应人群而有差异。乳及乳制品中蛋白质的含量与其存在形式、产地及加工工艺相关。     

毛细管区带电泳-间接紫外检测法测定婴儿配方奶粉中的胆碱

目的建立毛细管区带电泳-间接紫外检测法测定婴儿配方奶粉中胆碱含量的新方法。方法用5 mmol/L乙酸提取婴儿配方奶粉样品中的胆碱,涡旋混匀、9000 r/min离心,上清液经0.45μm醋酸纤维素滤膜过滤后进样。用未涂覆熔融石英毛细管75μm×70 cm(有效长度:60 cm)作为分离柱。以10 mmol/L磷酸二氢钠+20 mmol/L磷酸+7 mmol/L 4-甲基咪唑为分离缓冲体系。分离电压为28 k V,进样压力及时间为0.5 psi、10 s,检测波长为214 nm。结果胆碱的校正峰面积与质量浓度在8.7~86.8 mg/L范围内间线性关系良好,相关系数为0.9997、检出限为2.6 mg/L、定量限为8.7 mg/L,方法的日内和日间精密度分别为1.9%和3.9%(n=7)。3个质量浓度添加水平的平均加标回收率分别为98.8%、95.2%及97.6%,相应RSD分别为0.8%、0.9%及0.6%(n=5)。用本法分析了10件婴儿配方奶粉样品,均获满意结果。结论本方法简单、无需有机溶剂,适用于婴儿配方奶粉中胆碱的常规检测。     

Analysis of cyclopiazonic acid in milk by capillary electrophoresis

A Micellar Electrokinetic Capillary Chromatography (MEKC) method to detect cyclopiazonic acid (CPA) in milk and compare its quantifying efficiency to the Reverse Phase Liquid Chromatography (RPLC) method was evaluated. Alkaline milk samples were defatted, then acidified before being twice liquid–liquid extracted with chloroform. Bare fused-silica capillary-extended light path with 50 μm i.d. and Nova-pak C18-column, were used for the CPA separation in MEKC and RPLC respectively. The analytical response was linear from 40 ppb to 100 ppm CPA in MEKC (correlation coefficient, r=0.99995). Recoveries of spiked CPA in milk were 78–81% over the range of 20 ppb to 500 ppb in MEKC and 71–80% in the range of 50 ppb to 500 ppb in RPLC. The detectable limit of CPA by MEKC was 0.27×10⁻⁰⁷ pg ml⁻¹. Capillary electrophoresis (MEKC) is a better and rapid method for CPA detection in milk.     

Determination of the degree of esterification of alkaline de-esterified pectins by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) was used to determine the correlation between the migration times and alkaline-de-esterified pectins (ADPs) with various degrees (0%, 21%, 47%, 56%, 77% and 93%) of esterification (DEs) using 50 mM phosphate buffer (pH 6.5) as carrier electrolyte. It was observed that pectins with higher DE exhibited shorter migration time, regardless of the capillary length used. Good linearity was obtained with a correlation coefficient (r) as high as 0.994 and 0.998 when a capillary tubing with an effective length of 30 and 60 cm was used, respectively. In addition, separation of pectins was completed in 8 min using a tubing with an effective length of 30 cm. Correlation efficient was also found to be 0.995 when pectin mixture was separated by CZE, suggesting the efficiency and possible utilization of CZE for determination of pectin DE.     

毛细管区带电泳-间接紫外检测法测定饮用水中5种阴离子

目的建立毛细管区带电泳-间接紫外检测法测定饮用水中5种阴离子的新方法。方法样品无需滤膜过滤可直接进样。用未涂覆熔融石英毛细管(75μm×80 cm,有效长度为70 cm)作为分离柱。以20 mmol/L邻苯二甲酸、100 mmol/L二乙醇胺和0.5 mmol/L十六烷基三甲基溴化铵为分离缓冲体系。结果 Cl~-、NO_3~-、SO_4~(2-)、F~-和H_2PO_4~-这5种阴离子的校正峰面积与质量浓度分别在0.5～100.0、0.2～20.0、0.5～100.0、0.2～4.0和0.2～5.0 mg/L范围内呈线性相关,相关系数分别为0.998 8、0.999 9、0.999 7、0.999 7、0.999 8。检出限均为0.05 mg/L,定量限均为0.15 mg/L,方法精密度均小于5%(n=6)。低、中和高质量浓度加标回收率在81.6%～108.6%之间,相对标准偏差在0.6%～3.7%之间(n=6)。用本法分析了7份饮用水样品,并与离子色谱法的结果相比较,除矿泉水中Cl~-结果偏低外,其余基本吻合。结论本方法简单,所用试剂环保,为饮用水中5种阴离子的常规检测提供了一种新方法,但不适合测定水样中低浓度的Cl~-。     

毛细管电泳测定猪肉中克伦特罗的含量

为了建立猪肉中克伦特罗的含量的测定方法,采用高效毛细管电泳法,运行缓冲液为15mmol/L磷酸盐缓冲液(磷酸调pH为6.5);运行电压25kV;柱温25℃;检测波长200nm。克伦特罗线性范围为0.00056～0.01344mg/mL(r=0.9998),加样回收率为99.83%,RSD为1.17%。高效毛细管电泳操作简便、准确,适用于猪肉中克伦特罗的含量的测定     

毛细管电泳法测定不同体细胞数的原料乳的蛋白组成及含量

为明确不同体细胞数(Somatic Cell Count,SCC)数量的原料乳蛋白质组成的变化规律。本研究首先建立了乳蛋白的毛细管电泳分析方法,并采集了不同SCC数量原料乳,分析其乳蛋白成分及含量的差异。结果表明,随着SCC数量的增加,原料乳中酪蛋白的占比显著降低(p<0.05),乳清蛋白比率相对增加;酪蛋白中β-酪蛋白B和β A1-酪蛋白的含量显著下降(p<0.05),水解为新的小片段。毛细管电泳技术能够更准确的分析原料乳蛋白质的组成及变化规律,有利于乳品企业在原料乳收购时进行更深一层的品质分析。     

Detection of buffalo milk adulteration with cow milk by capillary electrophoresis analysis

The addition of cow milk during the production of buffalo mozzarella is a common fraud in dairy industries because of the lower price and greater availability of cow milk throughout the year. The aim of this study was to develop a new, rapid, and robust capillary electrophoresis method for detecting and quantifying cow milk in buffalo milk by exploiting cow α-lactalbumin as a marker of adulteration. In particular, a linear calibration curve was generated, using a training set of calibrators consisting of 7 series of 17 buffalo/bovine whey mixtures, obtained after casein precipitation, with increasing percentages of cow whey. The capillary electrophoresis method showed high linearity (R² = 0.968), repeatability [relative standard deviation (RSD) = 2.11, 3.02, 4.38, and 1.18%, respectively for 5, 10, 20, and 50% of buffalo/bovine whey mixtures], and intermediate precision (RSD = 2.18, 2.49, 5.09, and 3.19%, respectively, for 5, 10, 20, and 50% buffalo/bovine whey mixtures). Moreover, the minimum amount of detectable fraudulent cow milk was 1%, and the limit of quantification was 3.1%.