学生作业本中VBL的检测与分析

以16种中小学生作业本为检测对象,首先以白度颜色测定仪进行荧光白度检测,其次以水为溶剂对其中V B L荧光增白剂进行提取,采用紫外分光光度计进行V B L含量分析。同时,以V B L为标样添加到纸页中,抄造含有不同V B L含量的纸张样品。对实验所制备的样品经白度颜色测试仪以及紫外分光光度计测试,验证荧光白度与紫外分光光度计的分析吻合程度,也佐证学生作业本中V B L含量的检验结果。结果表明,荧光白度与紫外分光光度分析方法均可测定纸页中VB L的含量。16种试样中全部含有VB L荧光增白剂,VB L含量最高为0.23%,最少为0.05%;荧光白度最大为14.47%,最小为5.32%。     

硫酸钡比浊法测定食盐中钡含量的优化

目的优化硫酸钡比浊法测定食盐中钡含量的分析方法。方法采用紫外分光光度计对样品悬浊液进行光度测试,分别探讨了测定波长、稳定剂加入量、静置时间对硫酸钡悬浊液体系的影响。结果优化后的方法为:待测溶液加入5 mL甘油-乙醇稳定剂静置10 min后,在波长420 nm处进行测定,标准曲线在钡含量0～3mg范围,相关系数r~2达到0.99915,线性良好,实际检测样品的相对标准偏差在0.71%～4.3%之间,回收率大于90%。结论用分光光度法测定食盐中的钡含量解决了GB5009.42-2016比浊法无法定量测定的缺陷,对进一步监测食盐中的钡提供了帮助,该检测方法可满足食盐中钡含量的定量测定要求。     

水洗脱除生物柴油中甘油的工艺研究

甘油是生物柴油生产过程中的主要副产物。生物柴油中甘油含量多少是评价生物柴油质量好坏的重要指标之一。通过水洗可以很容易去除粗生物柴油中的游离甘油,采用单因素试验研究影响水洗脱除甘油的因素,再用正交法优化工艺条件。结果表明：水洗脱除甘油的最优条件为：水洗温度40℃、水洗次数4次、搅拌时间25min、搅拌速度250r/min,此时的甘油脱出率85.49%。生物柴油经最佳工艺条件水洗,其甘油残留量为0.0065%,符合美国ASTMD6751-02的标准规定。     

紫外分光光度法测定保健食品中总蒽醌的含量

目的建立测定保健食品中总蒽醌含量的紫外分光光度法。方法通过对仪器条件、呈色稳定性、提取方式、萃取溶剂及水解酸选择等条件的试验研究,优化紫外分光光度计测定总蒽醌含量的方法。结果样品以混合酸为提取剂,直火加热回流30 min,用乙醚萃取,用混合碱显色,以518 nm为检测波长。试验平均回收率为97.08%,相对标准偏差为3.96%(n=9),1,8-二羟基蒽醌在0.0020~0.0252 mg/m L浓度范围内呈良好线性关系(r~2=0.9996)。样品可于40~75 min内测定且稳定性良好。结论本方法操作简便、稳定性好且仪器设备成本较低,适用于保健食品中总蒽醌含量的测定。     

紫外分光光度法测定红曲中酸式Lovastatin的含量

研究紫外分光光度计测定红曲中酸式Lovastatin的方法。将内酯型Lovastatin全部转化为酸式形式后用硅胶柱层析进行分离，再用双波长紫外分光光度法测定样品中总Lovastatin（以酸式存在）含量，同时用本室报道的实验方法测定内酯型Lovastatin的含量，二之差为红曲样品中酸式Lovastatin的含量。实验探索了样品中Lovastatin转化和洗脱的最佳条件，对总Lovastatin测定方法的准确度、精密度及最低检测限进行了研究，并且运用这一方法实测了五种红曲样品中酸式Lovastatin的含量。结果表明该方法具有良好的实用性，适用于中小企业对Lovastatin产品的科研开发及质量控制。     

利用分光光度计测定羽绒耗氧量的探讨

羽绒耗氧量的测定易受滴定速度、空白样品中标准高锰酸钾体积、杂质及试验人员主观判断等影响,为获得数据精确、重现性良好且与其他试验样品具有可比性的试验结果,探讨了利用分光光度计测定耗氧量的可行性。该方法利用分光光度计在波长525 nm处测得试验样品的吸光度,对照标准高锰酸钾工作曲线,得到其残留的高锰酸钾体积,计算耗氧量。通过与滴定法进行比对试验,结果表明分光光度计法在测定羽绒耗氧量时是一种高效便捷且测量精度和精密度都较高的试验方法。     

一种测定口香糖中V_C的方法

针对目前国标没有口香糖中VC含量的检测方法,结合已有国标VC测定方法的基础上进行改良试验。对口香糖样品进行快速溶解,使样品中的VC溶解进入含有乙酸的溶液中,与固蓝盐B反应生成黄色的草酰肼-2-羟基丁酰内酯衍生物。在其最大吸收波长420 nm处,用紫外可见分光光度计测定其含量。本方法的线性范围1μg/mL~20μg/mL,检出限为1μg/mL,样品加标回收率在90.9%~98.6%,相对标准偏差为1.57%。     

胶原蛋白水解物中L-羟脯氨酸两种检测法对比分析

应用紫外分光光度计和氨基酸自动分析仪检测胶原蛋白水解物中L-羟脯氨酸含量,分析了两种方法的适用性。结果显示,紫外分光光度计法和氨基酸分析仪法在0~2.95 mg/L范围内,L-羟脯氨酸的浓度分别和吸光度、峰面积的线性良好,相关系数R2分别为0.999 3和0.999 8,RSD分别为0.96%和0.73%(n=6)。紫外分光光度计法样品处理简便且重复性好,适合基层大量检测使用;氨基酸分析仪法操作简便且不受其他氨基酸干扰,适合精密和研究检测使用。     

生物柴油中游离甘油和总甘油测定方法研究

该文对生物柴油中游离甘油和总甘油含量的分析测试方法进行研究,通过原理设计和实验验证,该方法具有可行性,而且与气相色谱法相比,通用性更强。     

紫外分光光度法快速测定调味品中脱氢乙酸含量

目的:本实验建立了紫外分光光度法测定调味品中脱氢乙酸的含量。方法:样品中脱氢乙酸在酸性条件下经水蒸气蒸馏和有机溶剂萃取后,用紫外分光光度计在308nm波长处测定吸光度,与标准比较定量。结果:紫外分光光度法测定调味品中脱氢乙酸加标回收率在94.1%~103.7%之间,RSD为0.4%~4.7%。结论:该方法快速、成本低、操作简便,准确度和精密度高,可应用于生抽酱油、老抽酱油、米醋、蚝油、烧烤汁、甜辣酱等调味品中脱氢乙酸的快速测定。     

现代光度分析法测定食品中痕量铅的研究与应用

对现代光度分析法,主要是普通光度法、胶束增溶分光光度法、固相光度法、催化光度法、流动注射光度法、荧光光度法等测定食品中痕量铅的研究进展作一综述。     

Gravimetric determination of tannins and their correlations with chemical and protein precipitation methods

Abstract. A method for gravimetric determination of tannins based on binding with insoluble polyvinylpyrrolidone (PVP) is presented. The gravimetric method gives the absolute amount of tannins and avoids problems of standards associated with spectrophotometric methods. The method was applied to nine browse and tree leaves. The values obtained correlate significantly with tannins determined spectrophotometrically, protein precipitation capacities and protein precipitable phenotics. This method together with other tannin assays will be useful in nutritional studies. The present study also demonstrates the different behaviour of tannic acids from different commercial sources towards PVP suggesting the presence of different moieties in tannic acids from different commercial sources and even among batches from the same source thereby affecting the results obtained using the spectrophotometric methods. Use of well-defined tannic acid as a standard in spectrophotometric methods is suggested which will allow meaningful comparison of values obtained from different laboratories.     

一种测定油脂中微量游离甘油的方法

介绍了一种可以准确测定油脂中微量甘油的方法,它基于游离的甘油可被高碘酸氧化生成甲醛,甲醛与乙酰丙酮反应生成的衍生物在410 nm的波长下具有最大吸光度,可以用分光光度计测定。在测定的含量线性范围内,回收率为96.70%~99.43%,变异系数为0.73%~2.06%。此种方法定量准确,简便快捷,是一种理想的测定油脂中微量游离甘油的方法。     

Performance evaluation of an enzymatic spectrophotometric method for milk urea nitrogen

Our objective was to determine the within and between laboratory performance of an enzymatic spectrophotometric method for milk urea nitrogen (MUN) determination. This method first uses urease to hydrolyze urea into ammonia and carbon dioxide. Next, ammonia (as ammonium ions) reacts with 2-oxoglutarate, in the presence of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) and the enzyme glutamate dehydrogenase (GlDH), to form l-glutamic acid, water, and NADP⁺. The change in light absorption at 340 nm due to the conversion of NADPH to NADP+ is stoichiometrically a function of the MUN content of a milk sample. The relative within (RSD_r) and between (RSD_R) laboratory method performance values for the MUN enzymatic spectrophotometric method were 0.57% and 0.85%, respectively, when testing individual farm milks. The spectrophotometric MUN method demonstrated better within and between laboratory performance than the International Dairy Federation differential pH MUN method with a much lower RSD_r (0.57 vs. 1.40%) and RSD_R (0.85 vs. 4.64%). The spectrophotometric MUN method also had similar method performance statistics as other AOAC International official validated chemical methods for primary milk component determinations, with the average of all RSD_r and RSD_R values being <1%. An official collaborative study of the enzymatic spectrophotometric MUN method is needed to achieve International Dairy Federation, AOAC International, and International Organization for Standardization official method status.     

Intrinsic significance of molecular aggregation in sucrose-surfactant separation by dialysis

Aqueous sucrose-surfactant mixtures were dialysed and the diffusates examined quantitatively for sucrose at intervals by spectrophotometric analysis. The effect of surfactants (lecithin and glycerol monostearate) on the dialysability of sucrose from these solutions was also investigated and the amount of sucrose dialysed was found to increase steadily only up to about 2h with lecithin slowing down the rate of sucrose dialysis much more than GMS. These variations in the dialysability of sucrose from the mixtures are explained in terms of molecular aggregation and these are confirmed by freezing point depression measurements. The results are discussed in terms of the significance of molecular aggregation on the gustatory qualities of sapid molecules.     

DETERMINATION OF DIACETYL IN BEER USING DIFFERENTIAL-PULSE POLAROGRAPHY

A Polarographie method is proposed for the determination of diacetyl and other vicinal diketones in beer. Similar to the EBC official spectrophotometric method, diacetyl is derivatised with o-phenylene-diamine, producing 2,3-dlmethylquinoxaline, a polarographically active compound . The Polarographic method allows discrimination between diacetyl and methylglyoxal and a detection limit ten times lower than the EBC method is obtained. In addition, problems of erratic results for diacetyl may be avoided and data are in good agreement with those obtained by gas chromatography with electron capture detection and headspace sampling . It is suggested that high results obtained with the spectrophotometric method may be attributed to an erroneous procedure used in the spectrophotometric calculations. An alternative procedure is proposed, with which lower values for diacetyl in beer are obtained, similar to those found with other methods. These low diacetyl values are near the detection limit of the spectrophotometric method .     

Rapid determination of esterified glycerol and glycerides in triglyceride fats and oils by means of periodate method after transesterification

This paper describes an accurate method to determine esterified glycerol in the glycerides of edible fats and oils and, in general, in all triglyceride fat or oil. Esterified glycerol is released by means of a transesterification reaction with potassium hydroxide in methanol, which simultaneously produces fatty acid methyl esters. Free glycerol is oxidized selectively to formic acid and without any interference in the same environment in which the transesterification reaction occurs by the addition of periodate.     

Multielement stable isotope ratio analysis of glycerol to determine its origin in wine

 The adulteration of wine with glycerol is considered to be a problem in European wine-producing countries. The latest control methods are mainly based on the detection of impurities from commercial products, but suffer from the raising efficiency of the purification processes. As there is little chance of being able to identify glycerol from different sources on the basis of a method which uses only one isotope, a multielement approach was tested. Glycerol from wine showed the lowest relative enrichment with D, mainly in position C-2, a relatively high ¹⁸O content, and very negative δ¹³C values, which significantly correlated with those of ethanol from the same wines. The isotopic data of glycerol samples from different sources were in agreement with those given by indices of origin (impurities). These data allowed us to identify the origin of these glycerol samples, i.e. whether they were produced industrially or synthesised by animals or plants. Glycerol of plant origin was most similar to glycerol found in wine. The combination of several isotopic data by discriminance analysis yielded clusters of data obtained from glycerol samples of similar origin. Taking into account the characteristics of possible mixtures, proof that wine has been adulterated depends on the origin and isotope levels of the added compound. This study showed that it is possible to prove that wine has been adulterated with glycerol from other sources when the latter is present at a concentration of 15% of the total glycerol content. Received: 27 October 1997 / Revised version: 12 February 1998     

Effects of a humidity-stabilizing sheet on the color and K value of beef stored at cold temperatures

The effects of a humidity-stabilizing sheet containing glycerol, on the color and K value of beef stored at cold temperatures were investigated in this study. A drip-absorbing sheet seems to be effective for the preservation of meat quality, while a humidity-stabilizing sheet containing glycerol prevents the increase of metmyoglobin in cold stored beef. Maintaining samples wrapped in humidity-stabilizing sheets containing glycerol at low temperature for 7days was a functional method for conserving the concentration of inosine monophosphate. Beef samples wrapped in sheets containing glycerol had lower K values than samples wrapped in sheets not containing glycerol. When the surface of the meat starts to desiccate, the humidity-stabilizing sheet releases moisture that has been absorbed from the beef in the early stages of storage. Thus, glycerol could potentially play a role as a humidity-stabilizing controller and color preservative. This research suggests that a humidity-stabilizing sheet containing glycerol is a useful moisture controller and prevents deterioration of meat quality, discoloration, and desiccation.     

非贵金属盐催化开环反应制备脂肪酸单甘酯的研究

月桂酸缩水甘油酯在非贵金属无机盐的催化作用下,经水解开环、冷却结晶纯化,可获得高纯度的月桂酸单甘酯产品。优化月桂酸单甘酯的合成反应条件,得出最佳条件为:反应溶剂乙腈,催化剂氯化铜,催化剂用量为月桂酸缩水甘油酯摩尔量的8%,反应时间24 h。将该合成及纯化方法应用于棕榈酸单甘酯和硬脂酸单甘酯的制备,并对纯化后的产品进行了傅里叶变换红外光谱和电喷雾电离质谱表征,结果表明该制备方法具有一定的普适性。