Determination of bisphenol A in milk and dairy products by high-performance liquid chromatography with fluorescence detection

This study was conducted to develop a selective and sensitive method for the determination of bisphenol A (BPA) levels in milk and dairy products. A method based on solvent extraction with acetonitrile and solid-phase extraction (SPE) was developed for the analysis of BPA in milk, yogurt, cream, butter, pudding, condensed milk, and flavored milk, and a method using two SPE cartridges (OASIS HLB and Florisil cartridge) for skim milk was also developed. The developed methods showed good recovery levels (77 to 102%) together with low detection limits (1 microg/liter for milk, yogurt, pudding, condensed milk, flavored milk, and skim milk and 3 microg/liter for cream and butter). These methods are simple, sensitive, and suitable for the analysis of BPA in milk and dairy products. When 40 milk and dairy products were analyzed by the proposed methods, BPA was not identified in noncanned products, but its levels ranged from 21 to 43 microg/kg in canned products, levels that were 60- to 140-fold lower than the migration limits in the European Union and Japan.     

高效液相色谱法测定奶粉及其他乳制品中的L-羟脯氨酸

建立了柱前衍生反相高效液相色谱法测定奶粉及其他乳制品中L-羟脯氨酸的方法.采用酸水解样品,经6-氨基喹啉基-N-羟基琥珀酰亚氨基甲酸酯(AQC试剂)衍生水解样品中的L-羟脯氨酸,以磷酸盐缓冲溶液、乙腈、水梯度洗脱,流速1.0ml/min,通过symmetry C18柱将L-羟脯氨酸与其他18种氨基酸分离.紫外检测器在248nm波长下检测.测定结果显示,在0～2.05mmol/L范围内,标准曲线呈良好的线性关系(r=0.9991),加样回收率为95.1%～101%,方法精密度RsD(n=7)为1.3%.该方法具有简单、稳定、灵敏度高、准确等优点.     

Determination of polycyclic aromatic hydrocarbons in Italian milk by HPLC with fluorescence detection

The presence of polycyclic aromatic hydrocarbons (PAHs) in Italian commercial milk samples is reported. The study was carried out on lactating (cow and goat) and plant (rice, soya, oat) milk. The quantitative determination involved liquid–liquid extraction of PAHs, a pre-concentration and determination by HPLC using a fluorescence detector. The recovery of analytes was in the range of 70–115%. The precision of the method was found to be between 6% and 24%. The detection limit ranged from 0.66 to 33.3 µg l^–1 corresponding to 0.03–1.66 µg kg^–1 milk (wet weight), at a signal-to-noise ratio of 3, depending on the compound. By this procedure, the levels of more volatile PAHs (two to three aromatic rings) were confirmed in 34 commercial milk and three plant milk samples, whereas benzo[a]pyrene was found only in five pasteurised milk samples at a mean concentration of 0.17 µg kg^–1 milk. These results provide evidence that PAH levels are influenced by heat treatments and skimming processes of milk production.     

高效液相色谱-蒸发光散射检测器测定脂肪酸和甘油酯的含量

建立了一种利用反相高效液相色谱-蒸发光散射检测、通过梯度洗脱测定油脂中脂肪酸、单甘酯、二甘酯与三甘酯含量的方法,色谱柱是C18反相柱,流动相为乙腈(0.05%醋酸V/V)-二氯甲烷,流速1.0 mL/min;蒸发光散射检测器漂移管温度70℃,载气流速1.7L/min.各物质色谱峰面积的自然对数与浓度的自然对数呈良好的线性关系,精密度RSD为0.43%～2.75%,最低检测限为0.02～0.04μg,回收率测定值为93.2%～104.5%.该方法不仅可以准确、快速地定量、定性分析各类混合脂肪酸甘油酯和游离脂肪酸,而且还可以分离具有立体异构的单甘酯和二甘酯.     

液相色谱双检测器串联法测定农产品中农药残留

建立了采用高效液相色谱-紫外-荧光检测器串联法测定农产品中12种农药残留的方法。采用乙腈提取,使用氨基固相萃取小柱净化,通过液相色谱柱及变换波长等各种色谱条件优化,紫外检测器检测吡虫啉、多菌灵、除虫脲、灭幼脲、辛硫磷,荧光检测器测定经柱后衍生的氨基甲酸酯类农药残留。12种农药在0.05～4mg/kg范围内线性良好,平均回收率在73.0%～108%之间,RSD为0.2%～7.1%,检出限为0.001～0.03mg/kg。方法快速、经济,为农产品中农药残留检测增加一种新思路。     

HPLC法测定乳制品中的结合型羟甲基糠醛

5-羟甲基糠醛来源于食品的热处理加工过程,分游离型和结合型两种。通过对Amadori产物水解和还原糖异构化可获得该化合物,它可作为一种评估食品中蛋白质发生质量损伤程度的有效标志物。采用三氯乙酸沉淀法对婴幼儿配方食品进行蛋白质沉淀,通过对获得的Amadori产物酸水解,最终测定发生于美拉德反应过程中的羟甲基糠醛含量。结果表明:Amadori产物水解的最优条件为:草酸浓度1.07 mol/L;22.22 mL草酸/g蛋白质;水解240 min。该方法的检出限为0.045μg/mL,变异系数为7.9%,回收率为92.2%。通过对市售样品分析发现,蛋白质质量热损伤程度不同的乳制品中B-HMF差别较显著。     

花椒游离脂肪酸的微波快速提取与衍生化HPLC荧光检测方法研究

建立了花椒中游离脂肪酸的微波快速提取技术,并采用苯并[b]吖啶酮-5-乙基对甲苯磺酸酯（BAETS）作为柱前衍生试剂,建立了19种长链饱和与不饱和游离脂肪酸的衍生化HPLC荧光检测分析方法。微波提取功率700W,溶剂为体积比1∶1的氯仿/甲醇,70℃提取10min,可达近100%提取率。采用色谱柱Eclipse XDB-C8（4.6mm×150mm,5μm）,酸性乙腈/水流动相进行梯度洗脱,HPLC荧光激发和发射波长分别为273nm和505nm。同时进行在线质谱辅助鉴定（APCI-MS）,更提高了HPLC荧光定量的准确度。结果表明,微波提取快速高效,分析方法线性良好,线性范围14.286～0.0139μmol/L,最低检出限为0.636nmol/L,回收率在87.60%～106.59%之间。本方法快速、准确、高灵敏,可作为花椒相关样品的标准化检测方法。      

Dietary enrichment of milk and dairy products with n-3 fatty acids: A review

Milk and dairy products are important sources of nutrients in the human diet; however, they are also the main sources of saturated fatty acids (FAs) that can cause an increase in the risk of cardiometabolic and cardiovascular disease. Unfortunately, the n-3 FAs that are known for their health benefits are found in small amounts in normal ruminant milk fat and dairy products. Dietary supplementation with vegetable seeds or oils rich in α-linolenic acid (ALA) and grass-based feeding can enhance the content of n-3 FAs, particularly ALA, in milk and dairy products. Alternatively, ruminants are often supplemented with fish meal, fish oil and microalgae that are rich in the long-chain n−3 FAs eicosapentaenoic acid and docosahexaenoic acid. In this paper, the latest scientific studies regarding n−3 FA enrichment in milk and dairy products are reviewed, giving an overview of the effectiveness of the different supplementation approaches.     

高效液相色谱法测定乳制品中核苷酸的含量

建立乳制品中五种核苷酸的含量测定方法。通过对实验前处理条件、色谱柱、流动相等条件的选择,确定了乳制品中核苷酸的检测分离条件为:SUPELCOSIL LC-18-T色谱柱;检测波长:254 nm、278nm;流动相为含0.75 mL四丁基氢氧化铵溶液的磷酸二氢钾水溶液(pH 4.5)和甲醇。实验表明:五种核苷酸在1～20μg/mL的范围内均呈线性,且相关系数均在0.9999以上;三个水平的加标回收率均在98～107%之间,且RSD均小于4%。     

A developed pre-column derivatization method for the determination of free fatty acids in edible oils by reversed-phase HPLC with fluorescence detection and its application to Lycium barbarum seed oil

Free fatty acids (FFAs) in edible oils are one of the most frequently determined quality indices during production, storage, and marketing. In this study, a simple, stable and sensitive method for the simultaneous determination of saturated and unsaturated FFAs from edible oils using 2-(11H-benzo[a]carbazol-11-yl)-ethyl-4-methylbenzenesulphonate (BCETS) as labelling reagent with fluorescence detection has been established. FFAs are derivatized by BCETS and separated on a reversed-phase Eclipse XDB-C₈ column with a gradient elution. The results indicated that all FFAs were found to be given an excellent linear response with correlation coefficients of >0.9994. The detection limits at a signal-to-noise ratio of 3 were in the range of 0.22–1.06 ng/mL. When applied to Lycium barbarum seed oils, the developed method showed good reproducibility. The effect of extraction methods including supercritical CO₂ and organic solvent extraction on the FFAs composition has also been investigated. Meanwhile, this method exhibits powerful potential for the trace analysis of short- and long-chain free fatty acids from edible oils, foodstuff and other complex samples.     

Determination of individual free fatty acids in milk by strong anion-exchange resin and gas chromatography

A quantitative method for determination of free fatty acids in milk is described. Free fatty acids and some glycerides were extracted from milk in acetonitrile in the presence of sulfuric acid and anhydrous sodium sulfate. The filtered extract was evaporated to dryness. With use of strong anion-exchange resin as heterogeneous basic catalysts, the free fatty acids were methylated directly. The free fatty acids were separated by gas chromatography with a 2000 mm X 2-mm inner diameter glass column packed with 10% SP-2330 on 100/120 mesh Chromosorb W.     

Determination of underivated fatty acids by HPLC

Inclusion of high-quality vegetable oils is of great importance for a scientifically balanced diet. Hence, there is a need for analytical techniques that can be used in the control of the purity and authenticity of such oils. Therefore, three reversed-phase HPLC methods were devised for the qualitative and quantitative measurement of fatty acids. These methods were applied to various vegetable oils and are an alternative to often-used gas chromatographic techniques. In the first step, the vegetable oil is hydrolysed, then the free fatty acids obtained are analysed by HPLC without any further derivatization. Omission of the hydrolysis step allows the determination of the amount of free fatty acids in the oils with the proposed methods. The iodine value and the acid number can be calculated from the chromatographic data.     

Free fatty acids quantification in dairy products

Free fatty acids (FFA) in dairy products have experienced a resurgence of interest in recent years due to their associated health benefits, flavour potential and antimicrobial activity, as a direct cause of hydrolytic rancidity, and also because of the importance of accurate determination for quality, research and legislative purposes. Gas chromatographic analysis remains the technique of choice for FFA analysis; however, little advancements in method development have occurred over the last twenty years. The purpose of this review is to provide an overview of the methodology used to quantify FFA in dairy products by gas chromatography since its inception, to highlight some of the challenges experienced, to suggest aspects that could be improved to increase accuracy and throughput and reduce labour costs and solvent usage and to widen applications.     

乳及乳制品中L-羟脯氨酸的测定

采用比色法对乳及乳制品中的L-羟脯氨酸质量分数进行测定.结果表明,本方法的检出限为2.1 μg/g,回收率为91.6%～101.3%.RSD为1.71%～2.45%,可用于判定乳及乳制品中是否添加动物胶原水解蛋白或者舍有游离L-羟脯氨酸.     

乳制品中游离甘氨酸的测定

建立了高效液相色谱法测定乳制品中甘氨酸质量浓度的方法。采用色谱柱为waters氨基酸色谱柱,流动相缓冲液A和缓冲液B,流速为0．4mL／min,激发波长338nm,发射波长425nm。结果表明,甘氨酸的最低检出限为0．03mg／L,回收率为99．88％,变异系数（CV％）为0．42。     

柱前衍生高效液相色谱法测定乳制品中甘氨酸的含量

采用单磺酰氯柱前衍生高效液相色谱法测定乳制品中甘氨酸的含量.应用单磺酰氯作为柱前衍生试剂,55℃温度下,反应15min.衍生产物用C18柱(3.9mm×150mm,5μm)分离,0.1mol/L醋酸钠(pH7.2):乙腈75 : 25为流动相进行洗脱,流速1.0mL/min,在330nm的波长下,能准确检测出乳制品中游离甘氨酸.方法回收率在98.2%102%之间,在0205mg/L范围内,线性方程相关系数为0.99994,相对标准偏差RSD为0.87%.该方法衍生反应简单,时间短.衍生产物在330nm具有较强的紫外吸收,且产物单一稳定,冰箱中存放可稳定一星期以上,分析速度快,7min内可与其他峰完全分离.本方法具有操作简单﹑结果重复性好﹑准确等优点.     

乳脂肪分析仪检测乳及乳制品中脂肪含量

目的采用乳脂肪分析仪测定乳与乳制品中脂肪的含量,并与国家标准方法比对。方法以国家标准GB5009.6-2016的第三法碱水解法为依据,对样品进行在线碱水解,再用无水乙醚和石油醚抽提样品的水解液,通过蒸馏去除溶剂,最后测定溶于溶剂中的抽提物的质量,用乳脂肪分析仪测定乳及乳制品中脂肪的含量。结果本方法可检测不同食品中脂肪含量,平均回收率为97.5%,其重复性相对标准偏差(relative standard deviation, RSD)值(n=6)分布在0.08%～1.24%之间。用仪器法和国标法同时检测质控样品,其回收率和RSD结果显示仪器法优于国标法。结论乳脂肪分析仪集在线恒温水解、搅拌、分层、抽提于一体,操作简便快捷,结果准确,适用于乳与乳制品中脂肪的测定。     

葡萄酒中游离氨基酸的HPLC测定方法

近年来,人民饮食消费水平日益提高,营养保健意识也不断增强,要求饮食能促进身体健康,吃要注意三低一高食品,喝酒要选择三低三丰富的酒种。所谓三丰富中有丰富的氨基酸一项,而好的葡萄酒中就含有丰富的氨基酸,因此如何准确快速测定葡萄酒中的氨基酸就显得十分重要。氨基酸的分析方法很多,仅液相色谱法就有柱前衍生法,柱后衍生法两种。柱后衍生法需用离子交换柱及多种试剂,且分析时间长,费用较高。本实验采用柱前衍生法进行。该法具有快速、准确、费用低、易于操作等优点。1 材料与方法1.1 仪器及材料仪器:日本岛津LC-6A高效液相色谱仪,SP…     

微波消解-原子荧光光谱法测定乳和乳制品中的锑

研究了原子荧光光谱法测定乳和乳制品中锑的方法,对AP5-2202E型原子荧光先度计的工作条件及实验条件进行优化.采用微波消解处理试样,在选定的最佳测定条件下,检出限为0.05 μg/L,回收率为92.0%～102%,相对标准偏差为1.8%.本方法快速、简单,检出限低,灵敏度高,仪器价格低廉,适合用于分析乳和乳制品中锑的含量.     

浅析乳制品中脂肪酸类营养强化剂检测方法

本文将乳制品经酸水解后,利用乙醇-乙醚-石油醚提取脂肪酸,在碱性条件下进行甲基化反应,用气相色谱-质谱法测定出添加的7种脂肪酸类营养强化剂。本检测方法前处理简单快捷,易于操作,方法重现性良好,其RSD可达0.82%～1.78%;回收率可达89.9%～103.6%;灵敏度高,检测限为0.1 mg/kg。