Folin-Ciocalteu比色法测定库拉索芦荟花中多酚

建立Folin-Ciocalteu比色法测定库拉索芦荟花中多酚含量的方法。利用多功能微孔板分光光度计对Folin-Ciocalteu法检测库拉索芦荟花多酚的显色反应条件进行优化，再用紫外可见分光光度计对其方法稳定性、重现性及准确性进行验证。结果表明，向库拉索芦荟花样品溶液中加入Folin-Ciocalteu试剂1.0 mL、50 g/L碳酸钠溶液2.0 mL，用水定容至10 mL，于40℃避光显色60 min，测定反应体系在765 nm处的吸光度，多酚质量浓度在6.3～62.6μg/mL范围内与吸光度具有良好的线性关系，线性相关系数为0.999 6。样品测定值的相对标准偏差为1.42%(n=6)，测定方法的平均回收率为95.52%。该方法适用于库拉索芦荟花中多酚含量的测定。     

红外分光光度法测定工作场所空气中矿物油雾浓度

以玻璃纤维滤膜采集工作场所空气中矿物油雾,用四氯化碳浸提,采用红外分光光度法测定矿物油雾含量.对采样方法、玻璃纤维滤膜处理方法进行了探讨.矿物油雾浓度在0.0～252.0μg/mL范围内与吸光度呈良好的线性关系,相关系数r=0.9995,加标回收率为98.7％～102.3％,方法检出限为2.0 μg/mL,测定结果的相对标准偏差为0.80％～ 1.39％(n=6).该方法适用于工作场所空气中矿物油雾浓度的测定.     

沉淀分离-气相色谱法测定聚氯乙烯塑料制品中的磷酸甲苯酯类增塑剂

建立了沉淀分离前处理技术结合气相色谱法测定聚氯乙烯塑料制品中磷酸甲苯酯类增塑剂含量的分析方法.采用四氢呋喃作溶剂将聚氯乙烯塑料溶解,以甲醇为沉淀剂,有效地将增塑剂从聚合物中分离出来,再采用气相色谱-火焰光度检测器进行分析.磷酸甲苯酯的3种异构体在0.1～2.0 mg/L范围内线性关系良好,相关系数大于0.999,方法平均回收率在82.9％～99.1％之间,测定结果的相对标准偏差为0.8％～5.9％,方法的检出限为50 mg/kg.本方法操作简便,准确性好,适用于聚氯乙烯塑料中磷酸甲苯酯类增塑剂含量的测定.     

用电导滴定法快速测定钾盐中的钾含量

用四苯硼钠溶液电导滴定法确定终点,测定钾的含量。适宜测定的ｐＨ＞９,在此范围内氨的存在不干扰测定。测定高含量钾和中含量钾回收率分别在９９．８％～１００．２％和９９．２％～１００．８％。该法简便,测定周期仅需１０ｍｉｎ左右,所需试剂种类和用量少,准确度与四苯硼钾重量法接近,适用于钾盐、卤水和复混肥和钾肥中钾的测定     

化妆品中二噁烷的气相色谱-质谱分析

建立气相色谱串联质谱法鉴别并测定化妆品中二噁烷含量的方法.采用顶空进样,并建立标准曲线,计算化妆品中二噁烷的含量.方法的最低检出限为1.3 ng/g,定量限为4.3 ng/g;当标准工作液在0.026～10.35 mg/L的范围内线性良好;当加标质量浓度在0.104～1.035 mg/L的范围内,化妆品中二噁烷的回收率为89.4％～109.6％,相对标准偏差为5.7％.建立的方法能满足相关法规要求,研究结果为化妆品中二噁烷的含量测定提供了参考依据.     

柱前衍生-反相高效液相色谱法测定荔枝果蒂中的氨基酸

建立了AccQ· Tag柱前衍生-高效液相色谱法测定荔枝果蒂中氨基酸含量的方法.荔枝果蒂样品在120℃下真空水解22 h,再与AQC衍生剂进行衍生,并采用反相液相色谱法-荧光检测器进行分析,外标法计算样品中17种氨基酸的含量.17种氨基酸在35 min内可完全分离,荔枝果蒂中氨基酸的含量在2.5～25 μmol/L范围内与色谱峰面积呈良好的线性关系,相关系数不小于0.999.方法的加标回收率在71.2％～92.0％之间,测定结果的相对标准偏差为3.16％～9.94％(n=6),方法的检出限(S/N=3)在0.000 5～0.0012 mg/L之间.     

油茶籽油中角鲨烯含量的气相色谱法测定

建立了油茶籽油中角鲨烯含量测定的气相色谱检测方法.油茶籽油样品经氢氧化钾-乙醇溶液皂化,石油醚萃取净化,经HP -5色谱柱分离,气相色谱仪(GC-FID)检测,外标法定量.在5～ 200g/L线性范围内线性良好,在1.0～3.0g/kg添标水平,平均回收率在93.7％ ～ 101.3％,相对标准偏差在1.7％～6.8％...     

槟榔提取物中多酚含量的测定

考察了福林酚试液用量、Na_2CO_3溶液用量、反应时间等因素对槟榔提取物中多酚测定的影响,确定了多酚测定条件,建立了测定槟榔提取物中多酚的方法.结果表明,在选定的测定条件下,没食子酸浓度在2.0～10.0 mg/L之间与吸光度成良好线性关系.线性方程为:y=0.103 8x-0.067 6;相关系数r=0.999 5;检测限为0.026 mg/L.该方法具有仪器简单、操作简便,准确度高等特点,用于槟榔提取物中多酚的测定,结果满意.     

微柱高效液相色谱和质谱法测定烟草样品中的多酚

植物多酚是烟草中一类重要物质,它们在烟草中的含量对烟草质量有重要影响,因而研究烟草及其制品中的植物多酚具有重要意义。高效液相色谱法是测定其常用的一种方法。和常规高效液相色谱相比,微柱高效液相色谱由于具有流动相消耗小,分析时间短,可不分流直接和质谱连用等特点,近几年来得到了迅速发展。我们研究了用WatersXterraTMRP18(1.0×50mm,2.5μm)微柱为固定相液相色谱法测定烟草中的多酚,烟草中的主要多酚在4.0min内可达到基线分离,和常规液相色谱相比大大节约了分析时间。并用大气压电离质谱和二次质谱技术对未购到标样的绿原酸异构体作了辅助定性,方法用于烟草样品中多酚的分析,回收率在97％-103％之间,RSD在1.4％～1.9％之间,结果令人满意。     

湿消解-电感耦合等离子体发射光谱法测定药用胶囊中的铬含量

以硝酸作为消解液,采用湿消解-电感耦合等离子体发射光谱法(ICP-AES)测定药用胶囊中的铬含量.在0～80 ng/mL范围内,铬的浓度与发射光强度呈良好的线性关系,相关系数r=0.999 98,检出限为1.42 ng/mL.对3个浓度水平的铬标准溶液进行平行测定,测定结果的相对标准偏差为1.43％～1.79％(n=6),加标回收率为93.1％ ～110.0％.该方法可以用于药用胶囊中铬的日常检测.     

Innovative Combination of Dispersive Solid Phase Extraction Followed by NIR-Detection and Multivariate Data Analysis for Prediction of Total Polyphenolic Content

Recently polyphenols attracted great interest in the field of food and nutrition as well as in the pharmaceutical and cosmetics industries due to their health benefits through antioxidative behavior in the human body. However, because of the high number of compounds characterized as phenols and their structural diversity, quantification of polyphenols turns out to be a highly complex task. Although, a wide variety of analytical methods are used for the determination of total polyphenolic content, they are all found to be lacking in a variety of different tasks, such as their limits of detection and quantification, repeatability, accuracy and specificity. For this reason, a novel approach combining the advantages of solid phase purification, near infrared analysis and multivariate data analysis was investigated for the prediction of total polyphenolic content, suitable for a wide range of sample matrices. Dispersive solid phase extraction was performed and optimized using polyvinylpyrrolidone as sorbent, known to selectively bind polyphenols. Near-infrared detection of adsorbed polyphenols was carried out subsequently. Furthermore, the method was in-house validated, examining selectivity, repeatability and accuracy, working range, as well as multivariate limit of detection and limit of quantification, comparing it with two routinely used methods—namely, Folin–Ciocalteu photometric assay and Löwenthal titration. The novel established method was applied for the prediction of total polyphenolic content in tea and wine samples.     

茶叶中的茶多酚荧光检测方法

以石墨烯量子点为荧光探针,基于二氧化锰纳米片与石墨烯量子点之间发生有效的荧光共振能量转移,构建了一种茶叶中茶多酚含量的荧光检测新方法。MnO2纳米片使石墨烯量子点的荧光淬灭,而茶多酚能与MnO2发生氧化还原反应,将其还原成Mn^2+,使体系荧光恢复。茶多酚含量与荧光强度增量在20~750μg/mL范围内成线性相关,线性方程为F=1.0574c-114.9,线性相关系数为R=0.9936。将该方法用于茶叶中茶多酚含量的检测,结果与国标法接近。方法有望应用于食品中其它抗氧化物质的实时检测。     

Ultrasound-assisted extraction, HPLC analysis, and antioxidant activity of polyphenols from unripe apple

The polyphenols were extracted from the unripe apple assisted by a highly efficient and simple method of the ultrasound. Response surface methodology was used to investigate the effects of processing parameters, including ultrasound power, extraction time, temperature, and ethanol concentration on total polyphenols yield and polyphenols composition was analyzed by HPLC. Antioxidant activity of the polyphenols was evaluated as 2, 2-diphenyl-1-picrylhydracyl scavenging activity and inhibition activity of lipid peroxidation. The results showed that 10-100 times higher total polyphenols yield was obtained from the unripe apple than those from the reported apple pomace. The optimum extraction conditions were ultrasonic power of 519.39 W, extraction time of 30 min, extraction temperature 50°C, ethanol concentration of 50% gave the total polyphenols yield of 13.26 ± 0.56 mg GAE/g. HPLC analysis indicated that (-)-epicatechin, procyanidin B2, chlorogenic acid, and procyanidin B1 were the predominant polyphenols in unripe apple, which contributed to the higher antioxidant activity to 2, 2-diphenyl-1-picrylhydracyl of unripe apple polyphenols than other apple polyphenols. The extracted polyphenols had higher ability to inhibit lipid peroxidation than butylated hydroxy toluene, which demonstrated that the unripe apple polyphenols have the potential to be used as a substitute of some synthetic antioxidants.     

Determination of polyphenols in wines by reaction with 4-aminoantipyrine and photometric flow-injection analysis

A new flow-injection analytical procedure is proposed for the determination of the total amount of polyphenols in wines; the method is based on the formation of a colored complex between 4-aminoantipyrine and phenols, in the presence of an oxidizing reagent. The oxidizing agents hexacyanoferrate(III), peroxodisulfate, and tetroxoiodate(VII) were tested. Batch trials were first performed to select appropriate oxidizing agents, pH, and concentration ratios of reagents, on the basis of their effect on the stability of the colored complex. Conditions selected as a result of these trials were implemented in a flow-injection analytical system in which the influence of injection volume, flow rate, and reaction-coil length, was evaluated. Under the optimum conditions the total amount of polyphenols, expressed as gallic acid, could be determined within a concentration range of 36 to 544 mg L(-1), and with a sensitivity of 344 L mol(-1) cm(-1) and an RSD <1.1%. The reproducibility of analytical readings was indicative of standard deviations <2%. Interference from sugars, tartaric acid, ascorbic acid, methanol, ammonium sulfate, and potassium chloride was negligible. The proposed system was applied to the determination of total polyphenols in red wines, and enabled analysis of approximately 55 samples h(-1). Results were usually precise and accurate; the RSD was <3.9% and relative errors, by the Folin-Ciocalteu method, <5.1%.     

Immobilised tyrosinase-based biosensor for the detection of tea polyphenols

An amperometric principle-based biosensor containing immobilized enzyme tyrosinase has been used for detection of polyphenols in tea. The immobilized tyrosinase-based biosensor could detect tea polyphenols in the concentration range 10–80 mmol L⁻¹. Immobilization of the enzyme by the crosslinking method gave good stable response to tea polyphenols. The biosensor response reached the steady state within 5 min. The voltage response was found to have a direct linear relationship with the concentration of polyphenols in black tea samples. Enzyme membrane fouling was observed with number of analyses with a single immobilised enzyme membrane. The tyrosinase-based biosensor gave maximum response to tea polyphenols at 30°C. The optimum pH was 7.0. This biosensor system can be applied for analysis of tea polyphenols. Variation in the biosensor response to black tea infusions gave an indication of the different amounts of theaflavins in the samples, which is an important parameter in evaluating tea quality. A comparative study of the quality attributes of a variety of commercially available brands of tea were performed using the biosensor and conventional analytical techniques such as spectrophotometry.     

Evaluation of the Chemiluminometric Method for Determination of Polyphenols in Wine

The Pholasin chemiluminometric method for determination of polyphenols in wine was evaluated by comparison with liquid chromatography with mass-spectrometric detection. The results were also compared with the conventional Singleton-Rossi spectrophotometric method for determination of total polyphenols.

A total of 141 wine samples were examined using all three methods and the results indicated a good agreement between the chemiluminometric and the Singleton-Rossi methods; however, the chromatographic data correlated reasonably well with the chemiluminometric data only for gallic acid, but less well or not at all with other determined phenolic antioxidants: trans-resveratrol, (+)-catechin, (?)-epicatechin, quercetin, vanillic-, caffeic-, caftaric-, p-coumaric-, 3,4-dihydroxybenzoic-, ellagic-, sinapic-, ferullic-, and ellagic acid.     

Dispersive solid-phase extraction of alkaloids and polyphenols using borate hypercrosslinked polymers

In this study, a borate hyper-crosslinked polymer was synthesized by crosslinking 1-naphthalene boric acid and dimethoxymethane via the Friedel-Crafts reaction. The prepared polymer exhibits excellent adsorption performance toward alkaloids and polyphenols with maximum adsorption capacities ranging from 25.07 to 39.60 mg/g. Adsorption kinetics and isotherms model results indicated the adsorption was a monolayer and chemical process. Under the optimal extraction conditions, a sensitive method was established for the simultaneous quantification of alkaloids and polyphenols in green tea and Coptis chinensis by coupling with the proposed sorbent and ultra-high performance liquid chromatography detection. The proposed method exhibited a wide linear range of 5.0–5000.0 ng/ml with R² ≥ 0.99, a low limit of detection (0.66–11.25 ng/ml), and satisfactory recoveries (81.2%–117.4%). This work provides a simple and convenient candidate for the sensitive determination of alkaloids and polyphenols in green tea and complex herbal products.     

Optimization and method validation of determining polyphenolic compounds by UFLC-DAD system using two biphenyl and pentafluorophenylpropyl columns

The development of efficient analytical methods for the identification and quantification of polyphenols in natural products is needed. The present study was aimed to optimize the polyphenols by UFLC using two different Ascentis express columns. Chromatographic separation was performed using UFLC-DAD connected with Ascentis Express Biphenyl column (system I) and Ascentis Express F5 pentafluorophenylpropyl (PFP) column (system II). Multistep gradient elution program was used in both analytical instruments to detect 34 compounds of different classes (phenolic acids, flavonoids, isoflavones, flavanols, flavonols and flavanones). The detection wavelength, linear calibration range, theoretical plate, tailing factor, limits of detection and of quantification were determined. The results were validated and the optimized method was proven to be precise, revealing good separation in the UFLC system II using Ascentis Express F5 PFP column. In conclusion, this study shows analytical preciseness and is useful in determining polyphenols in natural products.     

Determination of total polyphenol index in wines employing a voltammetric electronic tongue

This work reports the application of a voltammetric electronic tongue system (ET) made from an array of modified graphite-epoxy composites plus a gold microelectrode in the qualitative and quantitative analysis of polyphenols found in wine. Wine samples were analyzed using cyclic voltammetry without any sample pretreatment. The obtained responses were preprocessed employing discrete wavelet transform (DWT) in order to compress and extract significant features from the voltammetric signals, and the obtained approximation coefficients fed a multivariate calibration method (artificial neural network-ANN-or partial least squares-PLS-) which accomplished the quantification of total polyphenol content. External test subset samples results were compared with the ones obtained with the Folin–Ciocalteu (FC) method and UV absorbance polyphenol index (I₂₈₀) as reference values, with highly significant correlation coefficients of 0.979 and 0.963 in the range from 50 to 2400 mg L⁻¹ gallic acid equivalents, respectively. In a separate experiment, qualitative discrimination of different polyphenols found in wine was also assessed by principal component analysis (PCA).