HPLC测定牛奶中辛硫磷残留的方法研究

试验建立了一种牛奶中痕量辛硫磷的高效液相色谱分析方法(HPLC),比较不同溶剂提取牛奶中辛硫磷的回收率,研究不同净化方法的净化效果。乙腈-水(70/30,V/V)为流动相,检测度长282nm,在ODSC18柱上实现了辛硫磷与杂质的良好分离。方法简单,分析速度快,测定费用低。检测限为0.010μg/mL,回收率为75.7%~81.1%。     

反相高效液相色谱法测定牛奶中土霉素残留

建立了测定牛奶中土霉素残留的RP-HPLC方法.采用草酸甲醇液提取牛奶中的土霉素,离心,用C18色谱柱(5 μm,250 mm×4.6 mm),甲醇 乙腈 0.01 mol/L草酸溶液(20∶ 12∶ 68)为流动相,流速1 mL/min,检测波长360 nm,以HPLC外标法测定牛奶中土霉素的残留量.结果:土霉素峰面积与浓度呈良好的线性关系,其线性范围为50～1 500 μg/L(r=0.999 9),平均回收率为88%.本法简便、准确、快速,是一种较好的测定牛奶中土霉素残留的方法.     

The cell count in milk of goats]

Weekly milk samples were taken from mammary halves from 30 goats from 8 different herds each with from 2 to 5 experimental animals throughout their lactation periods. The physiological variations in the cell counts of goats milk during lactation were investigated by a projection microscope. Only small variations were found in the average cell counts in milk samples from goats in the same herd, but big variations from one herd to another (Table I and Fig. 3.). The curves of the average cell counts in milk samples of 5 herds showed a rise at the beginning of the season at pasture (Fig. 1 and Fig. 2). Also in the housed periods the cell count showed transitory rises. The herd with the lowest average cell count (220,000/ml) was milked by an ordinary bucket milking system, while the herd with the highest average cell count (1,490,000/ml) was milked by a pipeline milking system. Five herds milked by machine had an average cell count of 720,000/ml and three herds milked by hand 540,000/ml. All the herds in the material had an average cell count of 680,000/ml.     

奶及奶粉中4种阿维菌素类药物残留检测高效液相色谱法

建立一种适用于牛奶、羊奶和奶粉中乙酰氨基阿维菌素、阿维菌素、伊维菌素和多拉菌素的残留检测方法。奶及奶粉中的4种阿维菌素类药物用20%乙醇乙腈溶液提取,加水和微量三乙胺稀释后经C18固相萃取柱净化,氮气吹干后,65℃避光衍生化反应15 min。用高效液相色谱—荧光检测法分析,外标法定量。4种药物在0.5~1 000 ng/m L浓度范围内线性关系良好,在牛奶、羊奶中的定量限为0.5μg/kg;在奶粉中的定量限为5μg/kg。一定浓度范围内,4种药物在牛奶、羊奶和奶粉中的平均回收率为89.2%~113%;批内变异系数为0.450%~9.73%,批间变异系数为2.90%~10.6%。该方法操作简单、灵敏度高、准确度和精密度好,适用于牛奶、羊奶及奶粉中阿维菌素类药物的残留检测。     

鲜乳及发酵乳中SOD和T-AOC的活性变化

对10份鲜牛乳以98℃煮沸5 min消毒后用乳酸杆菌发酵制作酸乳,测定了发酵前后乳中SOD的活性和T-AOC的变化.结果发酵前SOD活性和T-AOC分别为54.44 U/mL±10.37 U/mL,4.86 U/mL±2.06 U/mL;发酵后SOD活性和T-AOC分别为:66.96 U/mL±6.45 U/mL,7.97 U/mL±3.51 U/mL.发酵乳SOD活性升高了23%,T-AOC升高了64%(均P《0.01).     

生鲜乳中L-羟脯氧酸测定方法的研究

建立UV法测定生鲜乳中L-羟脯氨酸的量。浓度0-2．0μg／mL L范围呈良好的线性关系,R=0．9998。回收率范围为87．3％～107．9％,批内变异系数≤5．9％,批间变异系数≤5．6％。该方法回收率高,检出限低,工作曲线稳定．重复性好。     

气相色谱法测定骆驼奶中的胆固醇

胆固醇的分析方法主要有比色法、薄层法和酶催化法，在应用于食品的测定中，它们具有操作繁琐、选择性低等缺点，而高效液相色谱法用于分析胆固醇时，除了麦角固醇等具有共扼体系的一部分化合物之外。在紫外区都不具有最大吸收，因而没有可供使用的高灵敏度检测器，此外，它对胆固醇和豆固醇分离效果差。为此，笔者等采用气相色谱法对骆驼奶中的胆固醇进行了测定。     

Physiological basis of high milk production in cattle]

Milk yield is determined by number, size, synthetic and secretory capacity of mammary alveolar cells and low amounts of residual milk after milking. Initial milk yield and persistency of lactation are important. Important factors to achieve high milk yield are: optimal mammary development and preparation to lactation; maintenance and possibly increase in number and of synthetic capacity of alveolar cells during established lactation; sufficient availability of substrates for milk synthesis through high feed intake, readiness to mobilize body reserves (especially depot fat) and increased mammary blood flow; optimal milk let-down; regular and possibly more than twice milking/day. Favorable for a high milk yield are high circulating concentrations of somatotropin, possibly associated with increased production and levels of the insulin-like growth factor I, in the presence of low concentrations of and reduced sensitivity or responsiveness of target organs to insulin, reduced circulating levels of thyroid hormones and possibly enhanced conversion of thyroxine to triiodothyronine in the mammary gland. Enhanced sensitivity of depot fat to lipolytic hormones is favorable for high milk production.     

柱前衍生高效液相色谱法测定乳与乳制品中羟脯氨酸的含量

本实验建立了羟脯氨酸含量的柱前衍生高效液相色谱法(HPLC)测定乳与乳制品中皮革水解蛋白特征性成分。样品经酸水解后采用异硫氰酸苯酯(PITC)衍生后采用高效液相色谱-紫外可见检测器进行测定。采用AgelaVenusil-AA氨基酸分析专用色谱柱(4.6 mm×150 mm,i.d.5μm),柱温40℃,检测波长254 nm,梯度洗脱,流速1.0mL/min,进样量50μL。方法定量限为0.046μg/mL(S/N=10),高中低不同浓度加标回收率为98.2%～99.0%。该法具有样品处理简单,灵敏度高,回收率高,分析时间短等优点,适用于乳及乳制品中羟脯氨酸含量测定。     

链霉素在牛奶中残留的微生物学检测方法

建立了链霉素在牛奶中残留的微生物学检测方法.样品用10%(W/V)三氯乙酸提取,通过冷冻离心使牛奶中残留的链霉素得到分离,再用枯草芽孢杆菌作为检定菌进行含量测定.结果显示,链霉素在0.10～3. 20 μg/mL的浓度范围内具有良好线性关系(r=0.998 1),牛奶中3种添加浓度0.20、0.80、1.60 μg/g的平均回收率为97.6%(n=9),RSD分别为1.6 %、3.7 %、1.2 %(n=3).     

高效液相色谱法检测牛奶中三聚氰胺残留量的方法研究

三聚氰胺（Melamine）是一种三嗪类含氮杂环有机化合物,为重要的氮杂环有机化工原料。分子式C3N6H6（见图1）,分子量126．12,简称三胺,又称2,4,6-三氨基-1,3,5-三嗉、1,3,5-三嗪-2,4,6-三胺、2,4,6-三氨基脲、蜜胺、三聚氰酰胺、氰脲三酰胺。     

Development of rumen fermentation in calves during milk feeding]

The concentration of total volatile fatty acids (VFA) in the rumen fluid were increasing with the age of the animals (Fig. 1). A significant increase in the concentrations of total VFA (P less than 0.01) from 70.93 to 90.71 mmol/l was observed in the age period of 5-7 weeks and a highly significant increase (P less than 0.001) in the age period of 9-11 age. At the average age of seven weeks the lower boundary of the reference value range (80-120 mmol) of the total VFA concentrations in the rumen fluid as mentioned for adult animals was exceeded in the experimental calves. As to this parameter in individual calves, the level of the total VFA concentrations in the rumen fluid of adult animals was not reached in 50% of calves at the age of three weeks, in 80% of calves at the age of five weeks, in 20% of calves at the age of seven weeks and in 10% calves at the age of nine weeks. At the age of 11 weeks the concentrations of total VFA reached the level of adult animals in all experimental animals (Fig. 2). The molar proportion of acetate (Fig 3) decreased from 74.04 mol% at the age of three weeks to 67.54 mol% at the age of 11 weeks, and the propionate proportion increased from 16.73 to 19.53 mol% within the same interval.(ABSTRACT TRUNCATED AT 250 WORDS)