A simple colorimetric method for the determination of sugars in fruit and vegetables

A rapid, manual colorimetric method for determining glucose, fructose and sucrose in fruit and vegetables is described. The method is based on the determination of reducing sugars before and after invertase digestion using p-hydroxybenzoic acid hydrazide (PAHBAH). Total fructose (fructose plus fructose in sucrose) is determined using 2-thiobarbituric acid and the component sugars calculated. Addition of sugars to fruit extracts gave good recoveries (97.4–101.8%) for glucose, fructose and sucrose.     

A simple and rapid colorimetric method for lactose determination in milk

A simple and rapid technique for the estimation of lactose in fluid milk and whey, utilizing trichloroacetic acid (TCA) as a precipitating agent, is outlined. The color development is based on the reaction of picric acid with lactose in the presence of phenol, sodium hydroxide and sodium bisulfate. This method can be completed within 10 min. There is no significant difference (p ≤ 0·05) between the results obtained by the proposed method and those obtained by the IDF method.     

Re-evaluation of simple colorimetric method for damaged starch determination

The appropriateness of a simple colorimetric method for damaged starch determination in wheat flour was tested in relation to the possibility of use of this method to predict farinograph absorption. The investigation of the influence of damaged starch and protein on farinograph absorption showed dominant influence of thus determined damaged starch on absorption, especially in samples having a small range of protein content. Consequently, partial regression equations for prediction of farinograph absorption on the basis of damaged starch content for high-protein and low-protein samples were calculated. Predicted absorption agreed well (r = 0.979***) with actual absorption, what proved that simple method to be good enough for determination of damaged starch in flour and prediction of farinograph absorption.     

A non-diazotization-coupling reaction-based colorimetric determination of nitrite in tap water and milk

A non-diazotization-coupling reaction-based colorimetric method was developed and validated for the determination of nitrite in tap water and milk samples. Under acidic condition, nitrite could selectively react with pyrrole, resulting in the emerging of a new absorption peak at 509 nm and a distinct color change from clear to red, with which the concentration of nitrite can be determined indirectly. Excellent linear range was achieved from 0.72 to 40.0 μmol L^?1 with a detection limit of 0.22 μmol L^?1. The detection limit was lower than or comparable to most of the recently published methods. The experimental conditions were optimized, and effects of coexisting substances were evaluated, and the results showed excellent priority since a certain amount of other anions, including SO₃ ^?, SeO₃ ^? and other acid radicals, would not interfere with the measurement. We highlighted the simplicity and efficiency of this method as no diazotization-coupling procedure and toxic aniline were involved. Determination of nitrite in tap water and milk samples was performed.     

测定磷脂中氨基氮的新方法

建立了甲醛法测定磷脂中氨基氮的新方法,实验结果表明,此法操作简便、快速,有良好的重现性和精密度。用该法测定浓缩大豆磷脂和酰化磷脂中氨基氮,浓缩磷脂和酰化磷脂浓度分别在10~60g/L和20~100g/L范围内与测定结果呈良好的线性关系,精密度分别为1.24%和1.98%,回收率分别为98.3%和97.8%。     

A collaborative study on the determination of free amino acids in blood plasma

Collaborative work to determine the amino acid, taurine, urea and ammonia contents of a standard mixture of amino acids and of blood plasma from a preruminant and a ruminant calf was carried out at four laboratories to assess the accuracy of the ion-exchange column chromatographic technique. Samples of blood plasma were deproteinised by the organising laboratory and by the collaborating laboratories using their own methods. For the standard amino acid mixture the mean absolute deviation was 0.036 of the true concentration. This compared favourably with results from previous collaborative trials on protein hydrolysates. The mean absolute deviations were 0.192 for preruminant calf blood deproteinised by the organising laboratory and 0.159 for blood deproteinised by the collaborating laboratories. Comparable values for ruminant calf blood were 0.149 and 0.117, respectively. These results were much poorer than those obtained for protein hydrolysates and possible explanations are put forward for these different degrees of precision.     

分光比色法测定水浮莲类黄酮含量的研究

为进一步开发水浮莲资源,更准确地测定水浮莲类黄酮的含量,本实验对水浮莲类黄酮的测定方法进行了研究。实验结果表明:最大吸收波长为502nm,回归方程为y=19.42x-0.0079,标准工作曲线的r=0.9990,平均加标回收率为99.7%,RSD为2.9%。该方法简单方便,准确可靠,可用来测定水浮莲中类黄酮的含量。     

An automated colorimetric method for the determination of free nicotinic ccid in minced meat

Summary An automated method for the determination of free nicotinic acid in minced meat with the Technicon AutoAnalyzer is described. The method is based on the extraction of free nicotinic acid into water and a subsequent reaction with cyanogen chloride after dialysation, after which the absorbante of the reaction product is measured at 470 nm. The reaction takes place in an aceton/water medium of such a water/aceton ratio that, at the given wavelength, an amount of nicotinamide equal to nicotinic acid gives only 5-6% of the absorbante caused by nicotinic acid. The recovery is 96.7-103.3% at a range of 6-60 mg nicotinic acid added to 100 g of meat with a mean recovery of 100.5%. The lowest detection limit is 0.1 g/ml. The coefficient of variation is 1.2% at 5 g/ml.

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Zusammenfassung Es wird eine automatische Methode zur Bestimmung freier Nicotinsäure im Hackfleisch mit dem Technicon AutoAnalyzer beschrieben. Nach Extraktion der freien Nicotinsäure mit Wasser, wird dialysiert und nach Reaktion mit Chlorcyan erfolgt die Colorimetrische Messung bei 470 nm. Die Reaktion erfolgt in einem Aceton/Wasser-Milieu einer derartigen Zusammensetzung, daß bei der gegebenen Wellenlänge Nicotinamid nur 5-6% der Absorption gibt wie eine gleiche Menge Nicotinsäure. Die Zurückgewinnung ist bei 6–60 mg zugegebener Nicotinsäure pro 100 g Fleisch 96,7–103,3% mit einem Mittelwert von 100,5%. Die Meßgrenze ist 0,1 g/ml. Die relative Standardabweichung wurde für 5 g/ml zu 1,2% bestimmt.

     

同时测定饮料中20种游离氨基酸含量

利用氨基酸分析仪生理体液法测定了茶饮料、凉茶和代茶饮料中的牛磺酸、茶氨酸、天冬氨酸、苏氨酸、丝氨酸、谷氨酸、甘氨酸、丙氨酸、缬氨酸、胱氨酸、蛋氨酸、异亮氨酸、亮氨酸、酪氨酸、苯丙氨酸、赖氨酸、组氨酸、精氨酸、脯氨酸、γ-氨基丁酸共20种游离氨基酸的含量。其中牛磺酸、茶氨酸、γ-氨基丁酸的样品加标平均回收率(n=5)在93.95%～104.20%之间;方法的精密度(RSD,n=5)范围为0.44%～0.93%;脯氨酸的检出限为10nmol/mL,其他氨基酸的检出限均为2nmol/mL。该方法适用于同时测定饮料中的多种氨基酸含量。     

A colorimetric method for the determination of glycerides

The quantitative determination of lipids is a universal and repeating problem of analytical chemistry in different fields, for example food- or biochemistry. Important criterions to value methods are the time needed for analysis, reproducibility and detection limit. The determination of glycerides can be performed by classical methods, for instance by the Weibull-Stoldt method [1] or by extraction. HPLC and GLC can be used successfully, too. All these methods are expensive of time or equipment. In this paper a colorimetric method is reported characterized by good reproducibility, great sensitivity and little time needed to perform. The determination, first time reported by Fletcher [2] is based on the oxidation of glycerol after saponification of the lipid with periodate. The formaldehyde produced is determined by coupling a dye in a Hantzsch condensation with ammonium ions and 2,4-pentadione. The 3,5-diacetyl-1,4-dihydrolutidin formed is measured in a photometer at 410 nm.     

茶游离氨基酸总量测定方法的改进

对国家标准GB/T8314—2002中茶游离氨基酸总量测定方法存在的问题进行探讨,并针对存在问题从方法的原理、标准工作液配制、反应体系缓冲液的选择、加样量、样品分析中参比的选择等方面进行研究并提出改进措施。改进的游离氨基酸总量测定程序为:取茶汤或标准工作液1.0mL于25mL容量瓶中,分别加入pH6.81的1/15mol/L磷酸氢二钠-磷酸二氢钾缓冲液0.5mL和20g/L茚三酮溶液0.5mL,在沸水浴中加热15min,冷却后加水定容至25mL,放置10min后,在570nm处测定吸光度。标准曲线测定以水代替标准工作液按同样操作作为参比,样品分析以水代替茚三酮溶液按同样操作作为参比。改进的方法在谷氨酸浓度为0.1～0.3mg/mL范围内呈现良好线性,精密度高、重复性好。     

水溶性维纶纤维的水溶解性能研究

研究了水处理温度、水处理时间及升温过程对水溶性维纶水溶解度的影响。研究结果表明，在温度一定时，增加水处理时间，水溶性维纶纤维的水溶解度增加；当时间一定时，升高水处理温度，水溶性维纶的水溶解度增加。采用水溶性维纶纤维试样与水浴同步升温的工艺，水溶性维纶在80℃完全溶解并且所用时间短。     

大豆水溶性蛋白含量测定的不确定度评定

建立大豆水溶性蛋白含量测定(NY/T 1205—2006)不确定度评定的数学模型,对检测过程中带来的各个不确定度分量进行识别和量化,提出应用该方法检测的不确定度评定结果。     

小麦粉自由巯基(-SH)测定方法的对比研究

小麦粉自由巯基的含量直接影响小麦粉的加工品质,从而影响小麦粉的用途。对比研究了3种自由巯基检测方法在巯基的提取、显色反应等方面的优劣,并分别以低筋粉、中筋粉和高筋粉面粉加工厂原粉及市售饺子粉(低筋粉)、标准粉(中筋粉)和面包粉(高筋粉)为原料,并分析了几种方法对不同原料的检测适用性。结果表明:从加标回收率的角度看,方法一、方法二均可用于市售低筋粉和中筋粉的自由巯基含量的检测,几种方法均不适于测定市售高筋粉的巯基含量;3种方法均可用于小麦原粉巯基含量的检测。总体来讲,方法一是适用性和方便性最佳的检测小麦粉自由巯基的方法。     

全自动氨基酸分析仪测定酱油中游离氨基酸的不确定度评定

该实验评定了全自动氨基酸分析仪测定酱油中游离氨基酸的不确定度。参考 CNAS-GL 006—2019《化学分析中不确定度的评估指南》和JJF 1059.1—2012《测量不确定度评定与表示》中的规定与要求,分析游离氨基酸在测定过程中的各种不确定度来源。在包含因子k=2时,酱油中游离氨基酸的扩展不确定度范围为0.02～0.60 g/100 g。结果表明,影响不确定度的主要因素是仪器本身的不确定度和酱油重复性测量的不确定度。     

茶中游离氨基酸测定标样的选择

茶中游离氨基酸测定中,国家标准没有对标准样品谷氨酸和茶氨酸加以区别,造成这一指标测定结果的混乱。运用统计学成对比较t检验方法,将2种标样的2个吸光度、按2种标样算出的样品的2种氨基酸含量以及文献中2种标样下游离氨基酸的2种含量分别一一配对,进行样本差数方差分析,结果表明,谷氨酸的吸光度高于茶氨酸,达到极显著水平,且差异随着氨基酸量的增加而增大;样品游离氨基酸含量谷氨酸标样测定结果普遍低于茶氨酸测定结果,差异达到极显著或显著水平。根据茶中各种氨基酸各自的含量和分子量,用加权法计算出混合氨基酸的相对平均分子量为147~150u,与谷氨酸分子量147.1u接近,偏离茶氨酸分子量174.2u;此外,谷氨酸吸光值高,测定更加灵敏。为此,认为茶中游离氨基酸测定的国家标准应该保留谷氨酸做标样,取消茶氨酸作标样。     

蚕蛹蛋白水解液中游离氨基酸测定方法初探

水解蚕蛹提取氨基酸,制备氨基酸系列产品是开发我国丰富蚕蛹资源最有效的途径之一。在蚕蛹水解过程中,需要对水解液游离氨基酸含量进行检测,以实现工艺控制。常见的游离氨基酸总量及各种游离酸含量检验的方法包括双指示剂甲醛滴定法、电位滴定法、氨基酸自动分析仪法、高效液相色谱法二极管阵列-荧光检测器联用技术等。     

亚硝酸盐-紫外吸收光谱法测定水中的游离氯

目的 研究亚硝酸盐-紫外光谱法测定生活饮用水中游离氯含量的分析方法.方法 向含游离氯的水样管中加入1.0 ml亚硝酸钠溶液(ρ=5 g/L)作用30 min,依次加入1.0 ml氨基磺酸溶液(ρ=10 g/L)和1.0 ml盐酸(c=1.0 mol/L)制备样品溶液,以硝酸盐氮标准溶液制备标准溶液,在220 nm波长下同时测定样品管和标准管的吸光度值,并以此计算出水样中游离氯的含量.结果 亚硝酸钠将水中的游离氯定量地还原成了硝酸盐,其生成的量与游离氯的含量成正比(r=0.999 8),并呈等摩尔关系.方法中加入的氨基磺酸消除了过量的亚硝酸盐对测定结果的影响.在室温下,可直接取澄清水样按本法检测水中游离氯的含量.本法灵敏度为:0.05 mg/L,RSD为1.43％～10.00％,回收率为94.23％～103.20％.结论 本法可用于测定生活饮用水中的游离氯的含量.     

一种食用油质量的快速检测方法

本研究建立了一种可视化检测食用油质量的快速检测方法,制备了由聚二烯丙基二甲基氯化铵(PDDA)和环状糊精(a或β或γ,或混合)同时修饰的纳米金复合探针溶液。当探针溶液与劣质油等体积混合时,劣质油中的杂质(如游离脂肪酸,氢过氧化物,醛类,酮类等)与其有特异性的非共价作用,使得纳米金探针从水相转至上层油时产生颜色变化,颜色变化的程度跟劣质油的含量成正比,通过肉眼观察颜色变化和两相分层情况即可定性的判断食用油的质量。结合紫外光谱630 nm处的扫描结果可定量的判断食用油的质量。研究发现:该方法的最低检测限可达食用油中勾兑比率为3.0%劣质油,勾兑比率大于5.0%的劣质油可准确测定出来。将上述方法分别应用于实际样品的检测,总准确率达到97%。因此,这种方法非常适用于市场的快速监督检验和基层的推广应用。