催化动力学光度法测定茶叶和中药中的单宁

在盐酸介质中,微量单宁对碘酸钾氧化丙基红的褪色反应有显著的催化作用,据此建立了催化动力学光度法测定微量单宁的新方法。方法的线性范围为0．1～3．0／μg／mL,检出限为0．04／μg／mL。本法简便、快速、灵敏度高和选择性较好,用于茶叶和中药五倍子、诃子中单宁含量的测定,结果满意。     

Simultaneous Kinetic Spectrophotometric Determination of Ascorbic Acid and L-Cysteine by H-Point Standard Addition Method

The H-point standard addition method (HPSAM) is applied to kinetic data for the simultaneous determination of ascorbic acid (AA) and L-cysteine (Cys). If present in excess amounts, iron(III) is quantitatively reduced to iron(II) by AA or Cys which in turn, in the presence of phenanthroline (phen), produces a colored iron(II)-phen complex showing maximum absorbance at 510nm. HPSAM is based on the difference of the reaction rates between AA and Cys with Fe(III). The linear dynamic ranges for the two analytes AA and Cys are 0.50–4.00ppm and 1.00–8.00ppm, respectively. The RSD% for 6 replications of AA and Cys at 3.00ppm is 2.30 and 2.70, respectively. The predictability of the method is checked by determining the two analytes in real samples. The various effects of several similar reducing agents are investigated.     

Kinetic Spectrophotometric Determination of Ascorbic Acid in Pharmaceutical Samples by Oxidation of Ponceau 4R by Hydrogen Peroxide

A new sensitive and simple kinetic method is developed for determination of traces of ascorbic acid based on its activated effect on oxidation of trisodium‐2‐hydroxy‐1‐(4‐sulphonato‐1‐naphthylazo)naphthalene‐6,8‐disulphonato (red artificial color Ponceau 4R) by hydrogen peroxide, in the presence of Cu(II) as catalyst, in borate buffer. The reaction is followed spectrophotometrically by tracing the oxidation product at 478.4 nm within 1 min after addition of H₂O₂. The optimum reaction conditions are: borate buffer (pH = 11.00), Ponceau 4R (9.6·10^?6 mol/L), H₂O₂ (2·10^?2 mol/L), Cu(II) (8·10^?7 mol/L) at 22 °C. Following this procedure, ascorbic acid can be determined with a linear calibration graph up to 1.76 ng/mL and a detection limit of 0.28, based on 3S criterion. The relative error ranges between 6.77‐1.66% for the concentration interval of ascorbic acid 1.76‐17.61 ng/mL. The effects of certain foreign ions upon the reaction rate were determined for an assessment of the selectivity of the method. The method was applied for determination of ascorbic acid in pharmaceutical samples, and spectrophotometric method was used like an comparative method.     

KIO_4－NTA－二苯胺磺酸钠体系催化光度法测定痕量锰（Ⅱ）

本文研究了Ｍｎ（Ⅱ）催化ＫＩＯ＿４氧化二苯胺磺酸钠的显色反应。在ＮａＡｃ－ＨＣｌ介质中，以氨三乙酸作活化剂，当测定波长为５１０ｎｍ时，锰浓度在０～１５０ｎｇ／２５ｍＬ范围内与吸光度呈线性关系。该法已用于测定茶叶、莲子、黄豆等样品中的痕量锰，结果个人满意。     

磷钼钨三元杂多酸光度法测定药物中的抗坏血酸

研究了抗坏血酸与磷钼钨三元杂多酸的显色反应,提出了借磷钼钨杂多蓝测定抗坏血酸的分光光度法.最大吸收波长为730nm,抗坏血酸在0.08～10mg/L范围内线性良好.回归方程为A=1.05×10⁴C+0.017,线性相关系数γ=0.9995,表观摩尔吸光系数ξ₇₃₀=1.05×10⁴L·mol^-1·cm^-1,方法检出限为0.04mg/L,回收率为94～102%,相对标准偏差≤1.5%(n=8).本方法由于钨钼的混合配位增强了氧化能力,较之二元杂多酸的方法,省去了水浴加热等操作,只需在室温下反应30min,吸光值至少可稳定6h.过量的黄色杂多酸可加入适量的氢氧化钠溶液分解,从而获得色泽纯正的高灵敏度显色体系.     

光谱电化学法测定水果中抗坏血酸的研究

本文采用平行入射式光谱电化学装置，对水果中的抗坏血酸进行测定并寻找了最佳的测定条件。方法简便快捷，可消除背景干扰。线性范围１．０×１０＾－５－１．０×１０＾－４ｍｏｌ／Ｌ，检测下降为４．０×１０＾－６ｍｏｌ／Ｌ，回收率高，结果满意。     

磷钼钨三元杂多酸光度法测定药物中的抗坏血酸

研究了抗坏血酸与磷钼钨三元杂多酸的显色反应，提出了借磷钼钨杂多蓝测定抗坏血酸的分光光度法。最大吸收波长为７３０ｎｍ，抗坏血酸在０．０８～１０ｍｇ／Ｌ范围内线性良好。回归方程为Ａ＝１．０５×１０４Ｃ＋０．０１７，线性相关系数γ＝０．９９９５，表观摩尔吸光系数ξ７３０＝１．０５×１０４Ｌ·ｍｏｌ－１·ｃｍ－１，方法检出限为０．０４ｍｇ／Ｌ，回收率为９４～１０２％，相对标准偏差≤１．５％（ｎ＝８）。本方法由于钨钼的混合配位增强了氧化能力，较之二元杂多酸的方法，省去了水浴加热等操作，只需在室温下反应３０ｍｉｎ，吸光值至少可稳定６ｈ。过量的黄色杂多酸可加入适量的氢氧化钠溶液分解，从而获得色泽纯正的高灵敏度显色体系。     

动力学光度法测定痕量镉的研究

本研究了氨水介质中，痕量镉阻抑过氧化氢氧化偶氮胂１褪色的新指示反应及其动力学条件，建立了动力学光度法测定痕量镉的新方法，方法检出限为２．７×１０＾－１２ｇＣｄ＾２＋／ｍｌ，测定范围为０－１．０μｇＣｄ＾２＋／２５ｍｌ。     

Kinetic and Spectrophotometric Determination of Thioctic Acid in Bulk and Pharmaceutical Formulations

Three simple and sensitive spectrophotometric methods were developed for the determination of thioctic acid in bulk and in its pharmaceutical preparations using iron(III) as an oxidizing agent. Method A is based on kinetic investigation of oxidation reaction of the drug with iron(III) and a subsequent chelation of the produced iron(II) with ferricyanide to form prussian blue colored product at room temperature for a fixed time of 15 minutes at 750 nm. Methods B and C are based on oxidation of the studied drug with iron(III). The equivalent iron(II) produced is allowed to react with either o‐phenanthroline or bipyridyl to give colored species measurable at 510, 522 nm, respectively. Regression analysis of Beer‐Lambert plots showed a good correlation in the concentration ranges of 0.4–4 μg/mL with a detection limit of 0.095 μg/mL for method A and 0.5–5 μg/mL with detection limits 0.137 and 0.127 for method B and C, respectively. The three methods were successfully applied for the determination of the drug in its dosage forms. The percentage recoveries were 99.88 ± 1.40, 99.98 ± 1.26 and 100.64 ± 1.07, respectively.     

阻抑动力学光度法测定痕量间二硝基苯的研究

研究发现 ,在硫酸介质中 ,痕量间二硝基苯能灵敏地阻抑 Fe3+催化高碘酸钾氧化甲基兰褪色。研究了该阻抑褪色反应的最佳条件及动力学参数 ,建立了一种测定痕量间二硝基苯的新方法。该法测定线性范围为 0 .0～ 8.0μg/L,检出限为 1 .6× 1 0 - 6 g/L。用于环境水样中间二硝基苯的测定 ,结果满意     

阻抑动力学光度法测定痕量氨三乙酸

在乙酸介质中,痕量氨三乙酸对高碘酸钾氧化玫瑰桃红R的反应有明显抑制作用,据此建立了阻抑动力学光度法测定痕量氨三乙酸的新方法。方法的线性范围是0.01～0.12μg/mL,检出限为2.3×10-3μg/mL。方法简便、快速,灵敏度高,用于合成样品和实验室废水中痕量氨三乙酸的测定,结果满意。     

动力学分光光度法测定痕量硫氰酸根的研究

利用SCN~-对溴酸钾氧化罗丹明B反应的抑制作用。建立了动力学光度法测定痕量SCN~-的新方法。检出限为0.30ng SCN~-/ml,测定范围为0.30～8.3ngSCN~-/ml.应用于吸烟者与不吸烟者尿中SCN~-的测定。结果较为满意。     

Determination of Ascorbic Acid,Total Ascorbic Acid,and Dehydroascorbic Acid in Bee Pollen Using Hydrophilic Interaction Liquid Chromatography-Ultraviolet Detection

Ascorbic acid (AA) is one of the essential nutrients in bee pollen, however, it is unstable and likely to be oxidized. Generally, the oxidation form (dehydroascorbic acid (DHA)) is considered to have equivalent biological activity as the reduction form. Thus, determination of the total content of AA and DHA would be more accurate for the nutritional analysis of bee pollen. Here we present a simple, sensitive, and reliable method for the determination of AA, total ascorbic acids (TAA), and DHA in rape (Brassica campestris), lotus (Nelumbo nucifera), and camellia (Camellia japonica) bee pollen, which is based on ultrasonic extraction in metaphosphoric acid solution, and analysis using hydrophilic interaction liquid chromatography (HILIC)-ultraviolet detection. Analytical performance of the method was evaluated and validated, then the proposed method was successfully applied in twenty-one bee pollen samples. Results indicated that contents of AA were in the range of 17.54 to 94.01 µg/g, 66.01 to 111.66 µg/g, and 90.04 to 313.02 µg/g for rape, lotus, and camellia bee pollen, respectively. In addition, percentages of DHA in TAA showed good intra-species consistency, with values of 13.7%, 16.5%, and 7.6% in rape, lotus, and camellia bee pollen, respectively. This is the first report on the discriminative determination between AA and DHA in bee pollen matrices. The proposed method would be valuable for the nutritional analysis of bee pollen.     

A Spectrophotometric Determination of Ascorbic Acid

A new, simple and sensitive method for the spectrophotometric indirect determination of ascorbic acid in fruits, beverages, and pharmaceuticals is described. In this method, the ascorbic acid reduces Cu²⁺ to Cu⁺ and reacts with 2,9‐dimethyl‐1,10‐phenanothroline (neucoproine) to form Cu (neucoproine)⁺ complex, and it was extracted with N‐phenylbenzimidoylthiourea (PBITU) in chloroform. The apparent value of molar absorptivity of the complex in terms of ascorbic acid is (3.52) × 10⁴ L mole^?1 cm^?1 at λ_max, 460. The detection limit of ascorbic acid is 40 μg L^?1 and the method obeys Beer's law over the concentration range of 0.1–4.0 μg mL^?1. The proposed method was successfully applied for the determination of ascorbic acid in various samples. The validity of the present method was checked by the flow injection analysis (FIA) method.     

2nd and 3rd Order Derivative Spectrophotometric Determination of Ascorbic Acid in Soft Drinks

Abstract

A method is developed for the 2nd and 3rd order derivative spectrophotometric determination of 0.5–6 and 0.5–7 μ.ml^?1 of ascorbic acid, respectively. For its determination in soft drinks a blank solution is prepared from the soft drink to be analyzed in order to avoid the interference from the other additives and colouring matter present.     

抗坏血酸的催化动力学光度法测定

建立了一种测定抗坏血酸的方便、快速、高灵敏度的催化动力学光度法。对氨基苯磺酸与亚硝酸根进行重氮化反应生成重氮盐,抗坏血酸对重氮盐的分解有催化作用。利用加入8－羟基喹啉与该重氮盐反应生成偶氮染料来终止反应。在波长495nm处,用1cm比色皿以水作参比测定其吸光度,最佳测定酸度为pH9.0。吸光度与空白体系的差值△A与抗坏血酸的质量浓度呈线性关系。该法测定抗坏血酸的线性范围为0．16－6．3mg/L,检出限为0.005mg/L。利用该法测定了维生素C片剂及荔枝晶中的抗坏血酸含量,并与碘量法进行对照,结果基本吻合。     

新催化动力学光度法测定微量铁的研究--棓花青-O2指示反应体系

在 p H 7.0的磷酸盐缓冲体系中 ,微量铁 ( )能显著催化溶解氧氧化木立口 花青褪色。研究了该指示反应的催化动力学行为 ,建立了测定微量铁的新催化动力学分析法 ,方法线性测定范围 0 .0 5～ 0 .6μg· m L- 1 ,检出限为 0 .0 1 μg· m L- 1 。本法选择性和重现性好 ,反应体系简单易于控制。用其测定了自来水、人发及面粉等样品中的铁 ,结果满意。     

Indirect Flow-Injection Analysis of Ascorbic Acid by Photochemical Reduction of Methylene Blue

Abstract

Ascorbic acid was determined indirectly by spectrophotometry at 666 nm based on the photochemical reduction of methylene blue using flow-injection analysis. The carrier stream was 12.7 μgml^?1 methylene blue in phthalate-HCl buffer solution at pH 3.2. The reactor was irradiated with a 500-Watt halogen lamp to facilitate the development of the photochemical reaction. The system allows determination of ascorbic acid in the range 0.18–6.12 μgml^?1 with relative standard deviations of 2.09 and 0.31% for 1.97 and 4.92 μgml^?1 samples, respectively, and a sampling frequency of 50–55 h^?1. The proposed method was applied successfully to the determination of ascorbic acid in vitamin C tablets.     

表面活性剂增敏阻抑动力学光度法测定痕量草酸

在稀盐酸介质中，微量草酸对H2O2氧化靛红的褪色反应有显著的阻抑作用，非离子表面活性剂Triton X-100对此体系有强烈的增敏作用，据此建立了表面活性剂增敏阻抑动力学光度分析测定微量草酸的新方法。方法的线性范围是0．005-0．50mg/L，检出限为0．005mg/L。方法简便，快速，灵敏度高，用于菠菜和尿样中草酸含量的测定，结果满意。