牛奶中拟除虫菊酯类农药残留检测——QuEChERS-气相色谱分析方法的研究与建立

目前,牛奶中拟除虫菊酯类农药残留分析方法普遍存在前处理操作繁琐的问题,不适于大批量样品的检测。建立一种快速、简便、环保、高效,可用于大量牛奶及其制品中拟除虫菊酯类农药残留的检测方法是非常必要的。本研究采用改进的QuEChERS法进行样品前处理,以气相色谱-ECD检测器作为检测手段,建立了牛奶中8种拟除虫菊酯类农药的分析方法。试验结果表明,使用该方法检测牛奶中8种拟除虫菊酯农药,最低检出限在0.001～0.008mg/kg之间,样品加标回收率为65.09%～100.02%,RSD为2.96%～11.64%,符合食品中农药残留检测的要求。本方法准确、简便、快速、安全,可用于牛奶样品中拟除虫菊酯农药残留的快速定量检测。     

牛奶和羊肉中铅含量测定前处理法的改进与微波消解法的应用

采用微波消解法对牛奶和羊肉样品进行前处理，再用石墨炉原子吸收分光光度法测定其中铅的含量。该法测定的线性范围在0～40ng／mL，相关系数r=0．9997。羊肉和牛奶样品添加回收率为91％～94％。该法不仅准确，可靠，减少了操作带来的误差，而且大大提高了检测效率。     

牛奶中环丙沙星残留的微生物学检测方法研究

以藤黄微球菌(标准号28001)为工作菌,用圆滤纸片法测定环丙沙星在牛奶中的残留.结果表明,环丙沙星在牛奶中的最低检测限为 0.08 μg/mL.该方法精密度良好,变异系数小于15%,操作简便,不需特殊设备,样品用量少,易于推广,适用于环丙沙星的半定量分析.     

湿法消解-原子荧光法测定牛奶中的微量硒

采用湿法消解牛奶样品,应用氢化物发生-原子荧光光度法对3种不同品牌牛奶中的微量硒进行测定。研究发现样品消解时混酸(HNO3∶HClO4)比例为4∶1、温度在150～170℃时测得牛奶中的硒方法准确。在0～20μg/L浓度范围之间呈良好的线性关系,R=0.99912,加标回收率为96.5%～104%,相对标准偏差均小于5%。结果表明,该消解法适用于牛奶中硒含量的测定。     

离子色谱法测定牛奶中硫氰酸根离子

液态奶样品沉淀蛋白、去除脂肪后,用离子色谱法分析,电导检测器检测,外标法定量。使用了戴安公司的"离子色谱法测定牛奶中硫氰酸根"方法,该方法使用戴安公司离子色谱仪和AS16离子色谱柱进行检测。该检测方法结果准确,重复性良好,检测限低,相关系数r=0.999 9,回收率99%～100%。结论:方法灵敏,结果准确,适用于牛奶中硫氰酸根的快速测定。     

离子色谱法测定牛奶中硫氰酸根

液态奶样品沉淀蛋白、去除脂肪后,用离子色谱法分析,电导检测器检测。以丙酮碳酸钠、碳酸氢钠、丙酮为流动相测定牛奶中硫氰酸根,该方法使用万通公司离子色谱仪883和iColumns智能柱进行检测。该检测方法结果准确,重复性良好,检测限低,相关系数r=0.999984,回收率90%～110%。结论:方法灵敏,结果准确,适用于牛奶中硫氰酸根的快速测定。     

牛奶和牛血浆中头孢喹肟HPLC-MS/MS检测方法的建立

建立了头孢喹肟在牛奶和牛血浆中的高效液相色谱-串联质谱(HPLC-MS/MS)检测方法。牛奶样品用10%三氯乙酸沉淀蛋白,两次提取后过Strata-X-C固相萃取柱,30%乙腈洗脱后供HPLC-MS/MS检测。血浆样品用乙腈沉淀蛋白,高速离心后吸取0.2 mL上清液,与0.8 mL水混合后直接检测。以0.1%甲酸水-乙腈为流动相梯度洗脱,流速0.25 mL/min,进样量5!L。头孢喹肟在牛奶中的回收率在76.70%～87.02%之间,定量限为5 ng/mL。牛血浆中的回收率在89.41%～98.25%之间,定量限为2 ng/mL。结果表明,该方法简单快速、灵敏度高,适用于头孢喹肟在奶牛乳和血浆中的残留检测。     

固相萃取-高效液相色谱法测定牛奶中的三聚氰胺

本文建立了牛奶中三聚氰胺的固相萃取-高效液相色谱检测方法,经阳离子交换固相萃取柱净化后的样品采用高效液相色谱法测定。结果表明,三聚氰胺的标准曲线为y=44771.2x+4563.8,相关系数r=0.9995,检测限为0.05mg/kg。回收率为97.6%～100.4%。该方法操作简单,精密度和回收率高,可满足奶粉中三聚氰胺的准确定性和定量测定要求。     

牛奶中氯唑西林残留量的高效液相色谱法测定

为建立高效液相色谱法测定牛奶中氯唑西林残留的方法,牛奶样品用乙腈沉淀蛋白,三氯甲烷反萃取,有机相旋干用流动相溶解,正己烷除脂。0.02mol/L磷酸二氢钾溶液(pH 5.0)-乙腈(68∶32)比例为流动相,C18反相色谱柱分离,紫外检测。结果氯唑西林在15μg/kg～1 000μg/kg范围内呈现良好的线性关系,相关系数大于0.999 0;在15、30、60μg/kg三个添加水平,氯唑西林在牛奶中的平均回收率为70.25%～94.38%,批内变异系数小于8.34%,批间变异系数小于3.52%。方法检出限为5μg/kg,定量限为15μg/kg。表明该检测方法简单、灵敏、可靠,适用于牛奶中氯唑西林残留的分析检测。     

酶联免疫吸附法测定牛奶中青霉素残留的试验报告

用酶联免疫吸附法对牛奶中残留的青霉素进行了检测,结果得出该方法的最低检出限为2.0μg/L。本方法对牛奶中添加青霉素浓度为2.0～6.0μg/L的检测回收率在65.0%～115.0%范围内,批内变异系数≤14%,批间变异系数小于≤15%。表明该方法可用于青霉素残留量的筛选检测。     

超高效液相色谱法测定原料乳中羟脯氨酸

本试验旨在研究利用超高效液相色谱测定原料乳中羟脯氨酸（Hyp）含量的方法。在原料乳中羟脯氨酸测定过程中各种条件对测定结果的影响,并获得了较好的测定条件。结果发现本方法的回收率在94.7%～98.6%之间,在1.0～16.0 μg/mL标准曲线的回归方程为y=3286.5x+87.943,R²=0.9999,相对标准偏差（RSD）小于2.36%;最低检出限为1 mg/kg。该方法操作简便、色谱分离速度快、准确度高、精密度好,可用于原料乳中羟脯氨酸的定量测定,从而判定是否在原料乳中添加动物水解蛋白。     

高效液相色谱法测定牛奶中糠氨酸含量

检测牛奶中的糠氨酸含量可以评价牛奶的热处理强度。本文建立高效液相色谱法,在波长280 nm下测定牛奶中糠氨酸的含量。试验结果表明：采用外标法定量,当浓度为0.06~4.00 mg/L,吸光度与糠氨酸质量浓度线性关系良好,相关系数R²=0.999 7;糠氨酸在5 mg/L、10 mg/L、15 mg/L、30 mg/L添加水平的回收率在91.48%~91.73%之间,RSD值在0.13%~0.37% 之间;方法的检出限为1.5 mg/100 g蛋白质,测得结果与第三方机构检测结果偏差小于1.00%,适用于乳品企业对糠氨酸的日常检测。     

电感耦合等离子体质谱仪测定乳粉中铅的检出限方法优化

对电感耦合等离子体质谱法检测铅的检出限进行研究,通过对实验过程中所用器皿、试剂等因素进行分?析,建立超声清洗处理方式,有效降低空白值,使电感耦合等离子体质谱仪法测定乳粉中铅的检出限由0.02 mg/kg降?低到0.005 mg/kg。当铅的添加水平为0.005～0.015 mg/kg时,样品的加标回收率为86.9%～119.0%,相对标准偏差为?3.1%～12.3%,满足方法学验证要求,说明了整体方案的可行性。降低检出限后的方法适用于乳粉中铅的检测。     

高效离子色谱法测定乳及乳制品中低聚果糖含量

建立离子色谱法定量测定乳及乳制品中低聚果糖的方法,应用CarboPacTMPA1(4mm×250mm)阴离子交换柱、氢氧化钠和醋酸钠淋洗液梯度淋洗、脉冲安培检测器检测。6次测定液态奶中低聚果糖的含量,相对标准偏差小于9%,3种糖的加标回收率在94.8%～103.6%之间。本方法简单快捷,适用于乳及乳制品中低聚果糖含量的检测。     

Near infrared spectroscopy for biomonitoring: cow milk composition measurement in a spectral region from 1,100 to 2,400 nanometers

The potential of near infrared spectroscopy (NIRS; 1,100 to 2,400 nm) to measure fat, total protein, and lactose content of nonhomogenized milk during milking and the influence of individual characteristics of each cow's milk on the accuracy of determination were studied. Milk fractions were taken during milking, twice per month, for 6 mo. Samples were taken every 2nd and 4th wk at the morning and the evening milkings. Teatcups were removed at each 3 L of milk yield as determined with a fractional sampling milk meter. A total of 260 milk samples were collected and analyzed with an NIRSystem 6500 spectrophotometer with 1-mm sample thickness. Partial least squares (PLS) regression was used to develop calibration models for the examined milk components. The comparison with the reference method was based on standard error of cross validation (SECV). The obtained SECV varied from .107 to .138% for fat content, from .092 to .125% for total protein, and from .066 to .096% for lactose content, and the accuracy of the reference method (AOAC, 1990, method No 972.16) was .05% for all measured milk components. The obtained models had lower SECV when an individual cow's spectral data were used for calibration. The reduction of SECV for each cow's individual calibration, when compared with SECV for the set of all samples, differed with the different constituents. For fat content determination, the reduction reached 22.46%, for protein 26.40%, and for lactose 31.25%. This phenomena was investigated and explained by principle component analysis (PCA) and by comparing loading of PLS factors that account for the most spectral variations for each cow and the measured milk components, respectively. The results of this study indicated that NIRS (1,100 to 2,500 nm, 1-mm sample thickness) was satisfactory for nonhomogenized milk compositional analysis of milk fractions taken in the process of milking.     

Mastitis detection in dairy cows by application of neural networks

The aim of the present research was to investigate the usefulness of neural networks (NN) in the early detection and control of mastitis in cows milked in an automatic milking system. A data set of 403,537 milkings involving 478 cows was used. Mastitis was determined according to two different definitions: udder treatment or somatic cell counts (SCC) over 100,000/ml (1) and udder treatment or SCC over 400,000/ml (2). Mastitis alerts were generated by an NN model using electrical conductivity, milk production rate, milk flow rate and days in milk as input data. To develop and verify the model, the data set was randomly divided into training and test data subsets. The evaluation of the model was carried out according to block-sensitivity, specificity and error rate. When the block-sensitivity was set to be at least 80%, the specificities were 51.1% and 74.9% and the error rates were 51.3% and 80.5% for mastitis definitions 1 and 2, respectively. Additionally, the average number of true positive cows per day ranged from 1.2 to 6.4, and the average number of false negative positive cows per day ranged from 5.2 to 6.8 in an average herd size of 24 cows per day for the test data. The results for the test data verified those for the training data, indicating that the model could be generalized. The performance of the NN was not satisfactory. A decrease in the error rate might be achieved by means of more informative parameters.     

蒽酮-硫酸比色法测定天然鸽乳中可利用糖含量的研究

采用蒽酮-硫酸比色法测定玉米中的可利用糖含量以确定试验测定的最佳条件,并以此条件为对照测定天然鸽乳中可利用糖含量.玉米及天然鸽乳可利用糖溶液经乙醚去脂,高峰氏糖化酶水解,乙醇提取,饱和乙酸铅脱色后制得.结果表明,葡萄糖标准溶液的测定量在0.1～0.6 mg/mL的浓度范围内有良好的线性关系,其回归方程为y=1.6771x 0.0737,相关系数R=0.9987.测定不同的天然鸽乳样品,试验精密度高,重复性好,其可利用糖含量,0～3日龄天然鸽乳为7.45%～7.64%,4～6日龄天然鸽乳为32.08～60.28 %.     

液相色谱-飞行时间质谱法快速筛查生乳中29 种兽药残留的研究

本文研究了用液相色谱串联飞行时间质谱建立生乳中29 种兽药残留的快速检测方法。生乳样品采用0.2%甲酸乙腈溶液提取上清液,采用Dikma ProElut QuECHERS净化管净化后测定。目标化合物通过Waters ACQUITY UPLC HSS T3色谱柱分离,以乙腈和1.0%甲酸水溶液为洗脱剂进行程序洗脱,正离子扫描模式检测。结果表明,通过对数据进行靶向分析,20.0 min内生乳中29 种兽药残留能够同时被检测出来,其中Mass Error在±2.0 mg/kg之内,Library Score得分均在90 分以上,准确性高,操作简便。     

Incidence of foreign substances in raw and pasteurized milk

In 1980 to 1982, the occurrence of inhibiting substances, herbicides and chemical elements contaminating raw farm and bulk milk and pasteurized milk in different stages of technological processing was studied in the input regions of 19 dairies of the Lacrum Brno concern corporation. Residues of inhibiting substances were demonstrated by the thin-layer microbiological diffusion disk method using the testing strain of B. stearothermophilus var. calidolactis, to be present in raw milk (9.1% out of 143 samples) as well as in pasteurized milk (2.0% out of 151 samples). Chromatographic method (sensitivity 0.01-0.05 mg.kg-1 milk) was used for examining 135 raw milk samples for the occurrence of herbicides based on diazines and triazines. Herbicides were demonstrated to get into milk; residues were found in 45 samples (33.3%). Atomic absorption spectrophotometry was used for examining 143 raw milk samples for the contents of zinc, copper, iron and manganese. As to zinc content, 100% of the samples met the standard, as to iron content 99%, and as to the content of copper, 89% (Ministry of Health Directives, No. 50, 1978). The content of manganese remained within the range up to 0.1 mg.kg-1 milk in 60% of the samples. Out of the 135 milk samples (101 raw, 34 pasteurized milk ones) examined for the content of lead, four samples (3%) failed to meet the limit of the highest admissible level.