Tryptophan determination of food proteins by h.p.l.c. after alkaline hydrolysis

The alkaline hydrolysis of proteins prior to tryptophan analysis has been evaluated, and a method for the measurement of tryptophan by reverse phase h.p.l.c. after alkaline hydrolysis has been proposed and compared with published methods. Hydrolysis with either LiOH or NaOH gave similar results. Tryptophan values and the recovery of added 5-methyltryptophan were similar when hydrolysis was made under tap-water vacuum (1500 Pa) or at high vacuum (2 Pa). Partially-hydrolysed starch reduced the losses of tryptophan during hydrolysis better than thiodiglycol. High levels of indolyl-3-propionic acid or 5-methyltryptophan did not further improve tryptophan recovery. 5-Methyltryptophan is the preferred internal standard; its recovery after hydrolysis more closely resembled that of protein-bound tritiated tryptophan from goat casein than did the recoveries of α-methyltryptophan or free ¹⁴C-tryptophan. Under some conditions, the recovery of protein bound tryptophan was lower than the recovery of free tryptophan. The stability of tryptophan in hydrolysates was improved by using a phosphate buffer pH 7.0 containing 0.02% sodium azide.     

An h.p.l.c. method for the quantitative determination of asulam, acetylasulam and sulphanilamide in peaches

An analytical method has been developed for the determination of the herbicide, asulam [methyl(4-aminobenzenesulphonyl)carbamate] and two metabolites, sulphanilamide and acetylasulam individually, in peaches. Asulam and acetylasulam were partitioned from an aqueous phase with ethyl ether, leaving behind more polar components which interfered with the analysis of these compounds. The sulphanilamide was next partitioned from the aqueous phase into ethyl acetate. Each fraction was then chromatographed on its own neutral alumina column, activity grade 1, and analysed by high performance liquid chromatography (h.p.l.c.) using a C-18 reverse phase column. From peach samples fortified at the 0.10 p.p.m. level, recoveries averaged 72% (asulam), 100% (acetylasulam) and 90% (sulphanilamide). No residues of these compounds were found in two studies of peaches harvested 0, 5, 10, 15 and 20 days following asulam treatment at 0-7.50 kg/ha.     

Determination of sugars in tropical root crops using 13C N.m.r. spectroscopy: Comparison with the h.p.l.c. method

The ¹³C nuclear magnetic resonance (n.m.r.) spectrum of sugars normally present in foods, viz. glucose, fructose, sucrose, maltose and raffinose contains resonances that are diagnostic of each sugar. The quantity of each sugar is determined by measurement of the ratios of the peak heights of the sugar resonances compared with peak height of an internal standard, present at constant concentration in all solutions. A linear calibration relationship between the peak height ratio and concentration is established for single resonances of glucose and fructose and for two resonances of each of sucrose, maltose and raffinose. Samples of sweet potato and taro flour dried at 40°C, were blended with 80% ethanol, the sugars were extracted and analysed by ¹³C n.m.r. and h.p.l.c. Both methods gave similar results and have similar degrees of reproducibility. The n.m.r. method is useful for quantitation of sugars and identification of other molecules extracted from the food, but requires more material than does h.p.l.c. Drying at 40°C causes a decrease in sucrose content and increases in glucose, fructose and maltose which partly compensate for the loss in sucrose. There is considerable variability of the sugar content between different sweet potato tubers and between different taro corms of the same cultivar as well as across different cultivars. For sweet potato the total sugar content is 0.6-3.6% fresh weight, with considerably more sucrose present than glucose, fructose and maltose. With taro total sugar content is 0.2-0.8% fresh weight. Raffinose is present in one sample only.     

高效液相色谱法测定车厘子中果糖、葡萄糖及蔗糖含量

采用高效液相色谱法(HPLC)测定车厘子中果糖、葡萄糖及蔗糖的含量。测定方法：Shodex SUGAR系列KS-801(钠型)色谱柱(8 mm×300 mm,6 μm)、流动相为超纯水,流速0.8 mL/min,柱温80 ℃,示差折光检测器(RID)温度30 ℃,进样量20 μL,外标法定量。该法对果糖、葡萄糖和蔗糖测定的平均回收率分别为99.96%、100.30%、99.26%,相对标准偏差(RSD)分别为1.54%、0.49%、0.48%,检出限分别为3.50 μg/mL、4.88 μg/mL、7.50 μg/mL,果糖、葡萄糖和蔗糖的标准曲线相关系数均在0.999以上(n=5)。该法可快速准确的对果糖、葡萄糖和蔗糖定性、定量分析。结果表明,车厘子果肉中果糖、葡萄糖、蔗糖的含量分别为5.69%、5.83%、0.24%。     

Assessment of a procedure for fractionating organic phosphates in soil and organic materials using gel filtration and h.p.l.c

A method for extracting and fractionating organic phosphates is described. In the fractions, inositol hexaphosphate (IHP) was determined with a carbon detector after high pressure liquid chromatography (h.p.l.c). Sample preparation consisted of a single mild extraction with 0.1M EDTA in 0.3M-NaOH and a preseparation by gel filtration. Adenosine-5-triphosphate (ATP) could also be separated and determined in this way. With a number of samples, clean-up by gel filtration could not prevent deterioration of the anion exchange column, used in the h.p.l.c. determination. IHP was then determined as total P after isolation by two consecutive gel filtrations. Limits of detection were 5-50 μg P/g when determining IHP by h.p.l.c. and 0.05-0.5 μg P/g when determining IHP as total P after isolation by gel filtration. Limits of detection when determining ATP by h.p.l.c. were 5-50 ng P/g. Results of applying the method to soil and various organic materials are given and discussed.     

A rapid h.p.l.c. method for the determination of methionine hydroxy analogue free acid in supplemented feeds

Two methods are described for determining methionine hydroxy analogue free acid (HMB) in supplemented poultry feeds. The procedure is based on extraction of analogue from the feed, followed by high-pressure liquid chromatographic measurement of the HMB directly after extraction or, more rigorously, after extraction and hydrolysis of oligomers to monomer. Recoveries of HMB over the supplementation range 0.08–0.25% (by wt) are 98% with coefficients of variation of 5.4% in commercial poultry feeds. A 98% correlation coefficient is obtained when the analyses are compared with the gas chromatographic method.     

H.p.l.c. Determination of trace levels of succinic acid in orange juice from Freeze-damaged and undamaged fruit

Succinic acid was determined by high-performance liquid chromatography (h.p.l.c.) in juice from oranges subjected to freeze damage on the tree and by storage at below freezing temperatures. Succinic acid levels did not change in fruit subjected to freezing temperatures while on the tree or in storage. In order to measure succinic acid at these low levels (5–180 mg litre^?1 juice) an earlier h.p.l.c. procedure was modified.     

离子色谱法测定苦瓜茶中的半乳糖、葡萄糖、甘露糖和果糖

建立了离子色谱法同时分离测定苦瓜茶中的半乳糖、葡萄糖、甘露糖和果糖的分析方法。用METROSEP CARB1(150mm×4.0mm)阴离子交换分离柱和脉冲安培检测器,对淋洗分离条件进行优化。选择了8mmol/L NaOH为淋洗液,淋洗液流速为1.0mL/min,总分析时间为25min。半乳糖、葡萄糖、甘露糖和果糖的检出限分别为0.105、0.126、0.152、0.587mg/L(进样体积20μL)。混标溶液连续8次进样,峰高的相对标准偏差为2.12%~5.43%,保留时间的相对标准偏差为2.06%~3.28%。样品测定的回收率为94.2%~99.8%。该方法具有样品前处理简单,灵敏度高,快速有效等优点。结果满意。为苦瓜茶中糖分的检测提供了一个简单有效的方法。     

离子交换色谱法测定10种热带水果中的葡萄糖、蔗糖和果糖

建立了高效阴离子交换-脉冲安培检测（High performance anion exchange-pulsed amperometric detection,HPAE-PAD）测定火龙果、莲雾、牛油果等10种热带水果中葡萄糖、蔗糖和果糖的检测方法。热带水果中的多糖经超声萃取后,用METROSEP CARB 1（150 mm×4.0 mm）色谱柱进行分离,以30.0 mmol/L Na OH为流动相,等度洗脱,用安培检测器检测,18 min可完成对样品多糖的分离和定量分析。经测定,葡萄糖和蔗糖的检出限分别为0.1209μg/m L和0.2827μg/m L,线性范围为1.0⁷0.0μg/m L;果糖的检出限为0.5501μg/m L,线性范围为5.0⁸0.0μg/m L。样品溶液连续5次进样,3种糖的相对标准偏差为0.67%⁷.04%,平均回收率为78.70%¹17.75%。该方法前处理简单、选择性好、灵敏度高,可用于热带水果中可溶性糖的测定。      

HPLC-ELSD法测定微胶囊中阿拉伯糖、果糖、葡萄糖、蔗糖、麦芽糖、乳糖含量

建立高效液相色谱-蒸发光散射法(High performance liquid chromatography with evaporative light-scattering detection,HPLC-ELSD)同时测定微胶囊中阿拉伯糖、果糖、葡萄糖、蔗糖、麦芽糖、乳糖含量的高效液相色谱方法。样品经乙腈水超声波浸取,采用Waters Amide色谱柱(4.6×250mm3.5μm)分离,以1%氨水和乙腈为流动相,使用蒸发光散射检测器进行检测。结果表明,阿拉伯糖:0.44~7.06mg/mL、果糖:0.30~4.74mg/mL、葡萄糖:0.40~6.45mg/mL、蔗糖:0.32~5.04mg/mL、麦芽糖:0.40~6.47mg/mL及乳糖:0.41~6.61mg/mL范围内线性关系良好;方法检出限为0.02~0.03mg/mL;回收率为95.31%~105.33%,6种糖含量相对标准偏差在2.30%~3.50%之间。该方法前处理简单、灵敏度高和检测速度快,适用于微胶囊中阿拉伯糖、果糖、葡萄糖、蔗糖、麦芽糖、乳糖的定量检测。     

高效液相色谱法检测乳制品中果糖、葡萄糖、蔗糖和乳糖的含量

建立用高效液相色谱法同时测定乳制品中果糖、葡萄糖、蔗糖和乳糖含量的方法。以乙腈-水(体积比75:25)为流动相,通过氨基柱分离和示差折光检测器测定四种糖的含量。在2～20mg/mL范围内线性良好,果糖、葡萄糖、蔗糖和乳糖精密度分别为2.90%、1.41%、1.40%和2.79%,相应的回收率分别为94.96%、104.61%、104.56%和97.87%,此法具有快速准确的特点。     

Prof. Dr. Dr. h. c. Dr. h. c. Bruno Huber

Ohne Zusammenfassung     

Dr. h. c. Dr. h.c. Friedrich Georgi vollendete 65. Lebensjahr

Ohne Zusammenfassung     

HPLC示差折光分析法测定饮料中果糖、葡萄糖、蔗糖含量

本文利用高效液相示差折光分析法测定饮料中果糖、葡萄糖、蔗糖含量。方法采用Agilent Car-bohydrate柱，流动相为乙腈＋水（75：25），流速0．6mL／min．检测器池温度：35℃，柱温25℃，进样量15μL。方法的检出限0．5％，加标回收率92．0％～110．0％．相对标准偏差为4．13％。该法具有样品预处理简单，灵敏度高，分析时间短等优点，可用于饮料样品的直接测定。     

Non-enzymatic glycosylation of dietary proteins by glucose and fructose]

Preliminary evaluation of glucose and fructose as glycosylation agents of some animal and vegetable food proteins has been presented. The study was conducted using the method of radioactive indicators. It has been shown that fructose binds proteins to a higher degree than glucose, and it can make for increasing glucose glycosylating activity in their combination in the product.     

HPLC-CAD法测定乳制品中果糖、葡萄糖、蔗糖、乳糖、半乳糖和麦芽糖含量的不确定度评定

目的采用高效液相色谱(HPLC)串联电喷雾检测器(CAD)法同时测定乳制品中果糖、葡萄糖、蔗糖、乳糖、半乳糖和麦芽糖的含量,分析果糖、葡萄糖、蔗糖、乳糖、半乳糖和麦芽糖不确定度。方法通过HPLC-CAD法测定乳制品中果糖、葡萄糖、蔗糖、乳糖、半乳糖和麦芽糖的含量方法建立数学模型,对各个不确定度因素进行评估、计算,由此计算合成不确定度,最终给出测量结果在95%置信区间下的扩展不确定度。结果本次实验含量测定结果为果糖2.15±0.009(g/100g)葡萄糖7.7490±0.010(g/100g)蔗糖24.5571±0.014(g/100g)乳糖19.8333±0.021(g/100g)半乳糖1.0168±0.026(g/100g)麦芽糖1.8727±0.019(g/100g)。结论所建方法可行,适用于乳制品中果糖、葡萄糖、蔗糖、乳糖、半乳糖和麦芽糖含量的测定。     

A simplified procedure for quantification of potato glycoalkaloids in tuber extracts by H.p.l.c.; comparison with ELISA and a colorimetric method

An improved high-performance liquid chromatography (h.p.l.c.) procedure for determination of glycoalkaloid levels in potato tubers has been developed in which Sep-Pak cartridges replace the commonly used alkaline precipitation for clean-up of tuber extracts. Glycoalkaloids are extracted from fresh tuber tissue into an aqueous medium, the extract is submitted to clean-up and α-solanine and α-chaconine are quantitatively separated on a reversed phase column with ethanolamine modifier added to the mobile phase. Potato tubers were comparatively analysed for their glycoalkaloid content by this and two other methods: a recently developed immunoassay (ELISA) and a colorimetric procedure representing the traditional chemical approach. Agreement between the h.p.l.c. and the other methods was good.     

毛细管气相色谱法测定烟草中葡萄糖、果糖、蔗糖的含量

建立了一种用毛细管气相色谱法测定不同烟草样品中水溶性葡萄糖、果糖、蔗糖含量的方法。以80%(v/v)乙醇提取烟样中水溶性糖,糖液利用三甲基氯硅烷进行硅醚化反应后,进行毛细管气相色谱分析。结果表明葡萄糖、果糖和蔗糖的含量与其峰面积具良好的线性(相关系数在0.9995~0.9998),重复性好(RSD< 1.39%),加标回收率在96.19%~99.16%,可以实现对烟草中单糖的分离鉴定。