固相萃取-液相色谱-串联质谱法同时测定牛奶中双酚A、双酚F和双酚S

为建立同时测定牛奶中双酚A、双酚F和双酚S含量的液相色谱-串联三重四极杆质谱联用方法,将样品用氨水 ∶ 乙腈溶液(1 ∶ 9,体积比)溶解,超声提取,PRiME HLB固相萃取柱净化,用安捷伦Poroshell 120 PFP色谱柱(100 mm×4.6 mm,2.7 μm)分离,采用负离子多反应监测模式监测,内标法定量。在此优化条件下,牛奶中双酚A、双酚F和双酚S的定量限均为2.0 μg/kg,平均方法回收率在90.4%~103.1%范围,平均相对标准偏差为2.76%~7.34%(n=6)。此方法的准确性和重复性良好,适用于牛奶中双酚A、双酚F和双酚S含量的检测。     

超高效液相色谱-串联质谱法检测牛奶中双酚A

目的通过优化牛奶中双酚A提取纯化和测定条件,建立牛奶中双酚A(bisphenol A,BPA)的超高效液相色谱-串联质谱(ultra performance liquid chromatography-tandem mass spectrometry,UPLC-MS/MS)定量检测方法。方法 采用乙腈作为提取剂和蛋白质沉淀剂,混合型阴离子固相萃取柱净化,采用UPLC-MS/MS在负离子模式下检测,内标法定量。结果该方法在1~100μg/L范围内有良好的线性关系,相关系数r20.990,在空白牛奶基质中,不同添加水平下方法的平均回收率范围为92%~115%,相对标准偏差为3.7%~6.6%;测定低限为1μg/kg。结论 此方法灵敏度高、准确、重现性好,适用于牛奶样品中双酚A的检测。     

液相色谱-串联质谱法测定牛奶和奶粉中6种大环内酯类药物的残留量

建立了液相色谱串联质谱测定牛奶和奶粉中6种大环内酯类药物(螺旋霉素、吡利霉素、竹桃霉素、替米卡星、红霉素和泰乐菌素)残留量的分析方法。采用乙腈提取目标物,OasisHLB固相萃取柱净化提取液,液相色谱-串联质谱测定,外标法定量。牛奶中6种大环内酯类药物的检测低限(LOQ)为1μg/kg,奶粉的LOQ为8μg/kg。6种分析物在0～100μg/L的浓度范围内呈良好线性,线性相关系数>0.992。方法在三个水平的添加回收率在81.5%～96.1%之间,相对标准偏差在3.29%～9.96%之间。方法回收率高、重现性好,适用于牛奶、奶粉等样品中大环内酯类药物残留的定量及确证检测。     

气相色谱-三重四极杆串联质谱法同时测定乳粉中22种邻苯二甲酸酯

建立了气相色谱-三重四极杆串联质谱法测定乳粉中22种邻苯二甲酸酯含量的方法。乳粉样品以水溶解,通过乙腈提取,以氯化钠盐析后,采用气相色谱-三重四极杆串联质谱的多反应监测模式（MRM）进行定量分析。结果表明,采用基质匹配标准曲线,在5~500 ng/mL范围内,22种邻苯二甲酸酯线性关系良好,相关系数(r)均大于0.99,方法检出限在1.0~5.0 μg/kg范围,定量限在3.0~15.0 μg/kg范围。在奶粉基质中3个加标水平下邻苯二甲酸酯的平均回收率在82.4%~111.4%之间,平行测定6次相对标准偏差（RSD）为2.4%~9.5%。该方法高效便捷、灵敏度高、稳定性好,适用于乳粉中22种邻苯二甲酸酯检测。     

气相色谱-质谱法测定婴幼儿配方乳粉及原料中 15 种邻苯二甲酸酯

目的 建立婴幼儿配方乳粉及原料中 15 种邻苯二甲酸酯的气相色谱-质谱检测方法。 方法 样品经乙 腈提取后, 用 GC-MS 检测。采用外标法进行定量分析。结果 15 种邻苯二甲酸酯的线性范围除了邻苯二甲酸 二异壬酯为 0.01~1 mg/L, 其余均为 0.001~1 mg/L, 相关系数大于 0.99。方法检出限(S/N=3)为 0.006~0.2 mg/kg, 定量限(S/N=10)为 0.02～0.7 mg/kg。 在奶粉基质中 3 个加标水平的平均回收率在 88.6%~117.2%, 相对标准偏差 为 1.0%~9.3%。结论 本方法操作简单、精确、快速、廉价、稳定, 适用于奶粉中邻苯二甲酸酯类化合物的检测分析。     

超高效液相色谱串联质谱法测定全蛋粉中的双酚A和双酚S

建立超高效液相色谱-串联质谱测定全蛋粉中双酚A和双酚S的检测方法。全蛋粉经水复溶后经乙腈提取,提取液使用分散系固相萃取-基质增强脂质去除产品进行除脂,使用Oasis PRiME HLB小柱进一步净化,使用超高效液相串联质谱测定,负离子多反应监测(MRM)模式测定,内标法定量。结果显示:双酚A在1~50 μg/kg范围内呈线性,相关系数为0.9991,加标回收率为98.8%~105.0%,日内和日间相对标准偏差分别为3.84%~8.58%和5.65%~8.74%,检出限为0.3 μg/kg,定量限为1.0 μg/kg;双酚S在0.4~20 μg/kg范围内呈线性,相关系数为0.9995,加标回收率为98.5%~102.5%,日内和日间相对标准偏差分别为3.01%~7.86%和3.18%~7.03%,检出限为0.1 μg/kg,定量限为0.3 μg/kg。实际样品测定结果分别为:双酚A 2.4~3.8 μg/kg;双酚S 0.48~0.82 μg/kg。本方法前处理简单、高灵敏度适用于全蛋粉中双酚A和双酚S的日常测定。     

QuEChERS-GC-MS/MS测定饮料中邻苯二甲酸酯

采用QuEChERS-气相色谱/三重四极杆质谱(GC/MS/MS)同时测定饮料中17种邻苯二甲酸酯类塑化剂。样品经正己烷提取,基质分散固相萃取净化,采用气相色谱-质谱/质谱法测定,外标法定量。17种邻苯二甲酸酯在各自的线性范围内(5μg/L~1 000μg/L)线性关系良好,线性相关系数在0.99以上,添加10、50和200μg/kg 3个不同浓度水平,含乳饮料中17种邻苯二甲酸酯的平均回收率在80.9%~108.7%,相对标准偏差在0.2%~14.2%,果汁饮料中17种邻苯二甲酸酯的平均回收率在81.4%~110.2%,相对标准偏差在1.3%~13.0%,检出限和定量下限分别为1.5μg/kg~3.0μg/kg和5.0μg/kg~10.0μg/kg。该方法灵敏度高、重现性好、结果准确可靠,适合饮料中邻苯二甲酸酯类塑化剂的检测。     

同位素内标液相色谱-串联质谱法测定婴儿配方奶粉中雌二醇残留

建立了一种婴儿配方奶粉中雌二醇残留的高效液相色谱-电喷雾串联质谱测定方法。样品经乙腈提取、浓缩、正己烷净化,用高效液相色谱分离后,采用电喷雾串联质谱进行定性和定量检测。线性范围为5~100 ng/mL,线性相关系数r大于0.99,方法的定量检出限为1.0μg/kg(S/N=10),高、中、低3个水平的加标回收率为81.5%~112.4%。     

超高效液相色谱-串联质谱法测定鱼油软胶囊中的双酚A

目的建立超高效液相色谱-串联质谱联用技术测定鱼油软胶囊中双酚A。方法通过优化提取溶剂和提取方式对鱼油软胶囊进行提取并进行超高效液相分析,以乙腈-水为流动相进行梯度洗脱,采用电喷雾离子源及多反应监测模式进行质谱法测定。结果双酚A在0.75~15 ng/mL浓度范围内具有良好的线性关系(r=0.996),在1、5、10 mg/kg 3个不同浓度加标水平下测得回收率为88.7%~96.4%,RSD为1.9%~5.6%(n=6),检出限和定量限分别为0.06μg/kg和0.20μg/kg。结论该方法灵敏度高、抗干扰性强且准确性好,可适用于鱼油软胶囊中双酚A的检测。     

婴幼儿奶粉中邻苯二甲酸酯的迁移残留分析

建立婴幼儿奶粉中邻苯二甲酸酯类化合物的气相色谱质谱检测方法。样品经正己烷振荡萃取,4℃(3 000 r/min)离心后用气相色谱质谱法检测。在本实验条件下,奶粉中十五种邻苯二甲酸酯类化合物质量浓度在0~8.0 mg/L范围内线性良好,最低检出限0.018~0.45 mg/kg,相对标准偏差2.93%~10.23%。该方法能同时检测婴幼儿奶粉中十五种邻苯二甲酸酯类化合物,简单易操作,回收率及精密度均能达到分析要求,结果较满意。     

The perfluoroalkyl substance (PFAS) contamination level in milk and milk products in Poland

Cross-sectional studies concerning the contamination of milk and milk products by perfluoroalkyl substances (PFASs) are presented and the extent of contamination that may occur in food samples, collected in Poland in 2016 is evaluated; not only milk, cottage cheese, natural yoghurt and butter but also previously untested foods, including kefir, sour cream and Camembert-type cheese. Levels of 7 perfluoroalkyl carboxylic acids (PFCAs) and 3 perfluoroalkane sulfonates (PFSAs) were analysed using the QuEChERS extraction method followed by micro-HPLC-MS/MS. All PFASs were detected with an RSD of lower than 10%. The most commonly detected was perfluorooctanoic acid, followed by perfluorobutanoic acid and perfluorohexane sulfonate, on par with perfluorooctane sulfonate. The largest contributor to the total PFAS concentration in the investigated food samples was perfluorobutanoic acid, and its summary concentration within the group was estimated to be 13.34 ng g⁻¹. The results for 43.4% of samples analysed were greater than LOQ (limit of quantification).     

酶联免疫法与乳及乳制品中抗生素残留的检测

对酶联免疫检测技术(ELISA)做了介绍,并对该技术在乳及乳制品抗生素残留检测的应用进行了评述.阐述了该项技术在乳及乳制品抗生素残留检测中的应用前景.     

Heat stability of plasmin (milk proteinase) and plasminogen

The effect of heating on plasmin activity in various media, including phosphate buffer pH 7.0, skim milk, blood plasma, solutions of casein and solutions of whey proteins were investigated. Plots of log residual activity v. heating time were linear at all temperatures from 63 to 143 degrees C. In buffer solutions the presence of casein led to substantial substrate protection, the Arrhenius plots being linear both in the presence and absence of casein. The activation energy, Ea, for the inactivation reaction, was 62.4 kJ/mol in buffer alone and 58.4 kJ/mol with casein present at 25 mg/ml. In skim milk, despite the presence of casein at a similar concentration, plasmin was no more stable to heat than in buffer alone, and a curved Arrhenius plot was obtained indicating a more complex inactivation mechanism. Heating in the presence of proteins having free -SH groups accelerated the inactivation of plasmin. The role of -SH groups was confirmed by experiments with added alpha-lactalbumin, in which no free -SH groups occur, and reduced carboxymethylated beta-lactoglobulin, both of which were without effect. In blood plasma, plasmin was less stable to heat than in buffer (pH 7.0) or in skim milk. Plasminogen behaved very similarly to plasmin either when activated to plasmin with urokinase before heating or when activated afterwards. A hypothesis is presented to describe the heat inactivation and denaturation of plasmin. Technologically important findings are that in skim milk plasmin was largely unaffected by pasteurization conditions and 30-40% of its activity remained even after ultra high temperature processing conditions.     

豆奶、杏仁露、椰子汁等植物蛋白饮料的品质控制

用质量管理体系中的危害性分析方法，对豆奶、杏仁露、椰子汁等植物蛋白饮料的生产工艺进行了分析，对影响产品品质的主要工序进行了分析研究，确定了关键控制点及范围，以提高植物蛋白饮料的质量管理水平，确保产品质量的稳定．     

N-acetyl-beta-D-glucosaminidase (NAGase) levels in bulk herd milk

N-acetyl-beta-D-glucosaminidase ( NAGase ) levels and somatic cell counts (SCC) were determined monthly for 6 months in the bulk milk of 181 suppliers (1063 samples). A highly significant correlation (r = 0.74; P less than 0.001) was found between supplier's bulk herd milk geometric mean NAGase activity and SCC. Monthly trends which grouped suppliers into various categories defined by different NAGase and SCC thresholds showed that a similar overall pattern was obtained with both SCC and NAGase . However, further analysis indicated that 18% of the bulk milk which had SCC less than 500 X 10(3)/ml had NAGase levels greater than 25 units. Also, 34% of samples with SCC greater than 500 X 10(3)/ml had NAGase levels less than 25 units. Overall, 24% of all samples did not have corresponding NAGase and SCC results. When the bulk milk of 2 commercial dairy herds was tested monthly over 12-18 months whilst the infection status of all quarters in the herds was regularly monitored, those herds with low incidence of mastitis (5% quarters infected) had significantly lower bulk milk SCC and NAGase levels than those with a high incidence of mastitis (22% of quarters infected). This suggests that NAGase measurement on bulk herd milk would be a simple means of monitoring infection status of dairy herds and of rapidly classifying a supplier's milk as being of low, medium or high SCC status. The possible combined use of SCC and NAGase levels in bulk milk monitoring schemes is discussed.     

Detection of cows' milk in ewes' milk and cheese by a sandwich enzyme-linked immunosorbent assay (ELISA)

A sandwich enzyme-linked immunosorbent assay (ELISA) has been successfully developed for the detection of defined amounts of cows' milk in ewes' milk and cheese. Polyclonal antibodies were raised in goats against bovine caseins (BC). The resultant antibodies were recovered from the crude antiserum by ammonium sulphate precipitation and further purified by immunoatisorption of the cross-reacting antibodies onto columns containing immobilised ovine, caprine and bovine caseins, followed by elution of the bovine caseins specific antibodies (anti-BC) from the column containing the bovine caseins. The anti-BC bound to the wells of a microtitre plate were used to capture the BC from milk and cheese mixtures. Further immunorecognition of the captured proteins was attained with the same specific antibodies conjugated to biotin. ExtrAvidin-peroxidase was used to detect biotinylated antibodies bound to their specific antigens. Subsequent enzymic conversion of substrate gave clear absorbance differences when assaying mixtures of ewes' milk and cheese containing variable amounts of cows' milk.     

Detection of cows' milk in ewes' milk and cheese by an indirect enzyme-linked immunosorbent assay (ELISA)

An indirect enzyme-linked immunosorbent assay was successfully developed for the detection of defined amounts of cows' milk (1-50%) in sheeps' milk and cheese. The assay used polyclonal antibodies raised in rabbits against bovine caseins (BC). The anti-BC antibodies were recovered from the crude antiserum by immunoadsorption and elution from a column containing BC. The antibodies were biotinylated and rendered cows' milk specific by mixing them with lyophilized ovine and caprine caseins. ExtrAvidin-peroxidase was used to detect the biotinylated anti-BC antibodies bound to BC immobilized on 96-well plates. Subsequent enzymic conversion of substrate gave clear absorbance differences when assaying mixtures of sheeps' milk and cheese containing variable amounts of cows' milk.     

Composition and bioavailability of oxalates in baked taro (Colocasia esculenta var. Schott) leaves eaten with cows milk and cows milk and coconut milk

Taro leaves are an important food in the Pacific Islands but the overall oxalate composition and its nutritional effect has not been investigated. The oxalate contents of taro leaves were determined using chemical and in vitro extraction methods. Maori‐type taro leaves contained 524.2 ± 21.3 mg total oxalates 100 g^?1 fresh weight (FW) and 241.1 ± 20.9 mg soluble oxalates 100 g^?1 FW while the Japanese‐type leaves contained 525.6 ± 19.9 mg total oxalates 100 g^?1 FW and 330.4 ± 28.3 mg soluble oxalates 100 g^?1 FW. Maori‐type taro leaves contained 416.4 ± 1.5 mg gastric soluble oxalates 100 g^?1 FW and 212.4 ± 34.8 mg intestinal soluble oxalates 100 g^?1 FW while the Japanese‐type leaves contained 433.3 ± 9.7 mg gastric soluble oxalates 100 g^?1 FW and 224.2 ± 38.7 mg intestinal soluble oxalates 100 g^?1 FW). Human feeding experiments were conducted to determine the availability of the oxalates in the baked leaves following additions of cows milk and coconut milk. The consumption of a test meal of baked taro leaves resulted in a significant increase (P < 0.001) in the output of urinary oxalate in the following 6 h when compared to the output of oxalate during a reference collection. When the leaves were baked with cows milk or cows milk and coconut milk combined and consumed there was a small non‐significant reduction in urinary oxalate output which suggests that less soluble oxalate was absorbed from these mixtures.