溶剂浮选-间接光度法测定抗坏血酸

于pH 7.0的磷酸盐缓冲介质中,CTMAB＋及I3-离子间借静电引力形成离子缔合物,可将其浮选入5.0 mL苯中,此缔合物在溶剂中,于365 nm处有吸收峰,较简单的I3^-离子在相同条件下的吸收峰（350 nm）红移了15 nm。在此溶液体系中存在抗坏血酸时使离子缔合物产生褪色反应,且在抗坏血酸浓度在25μg/50 mL以内时与吸光度的降低值（ΔA）间呈线性关系。在抗坏血酸浓度为6.0μg/50 mL时连续测定6次,所得结果的RSD为1.2%,回收率在96%-101%之间。     

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.     

Potential of Gelatin‐Zinc Oxide Nanocomposite as Ascorbic Acid Sensor

We report on the studies relating to fabrication of gelatin B (GB) and zinc oxide (ZnO) based nanocomposite (GB‐ZnO) film deposited on indium‐tin‐oxide (ITO) glass plate, and used for the immobilization of ascorbate oxidase (AsOx) which was further used for ascorbic acid (AA) detection. The structural and morphological studies of GB‐ZnO, and AsOx/GB‐ZnO/ITO bioelectrodes were carried out using XRD, SEM and FTIR techniques. This bioelectrode showed a broad range of linearity (5–500 mg/dL), low detection limit (1 mg/dL), higher sensitivity (0.106 µA mg/dLcm^?2) and low value of the apparent Michaelis? Menten constant (K_m^app=0.35 mg/dL) for AA. Efforts are being made to utilize this electrode for sensing AA in real samples in a bid to develop a strip based sensor.     

Nafion-甲基紫精修饰电极抗坏血酸氧化酶生物传感器的研究

本文用Nafion-甲基紫精修饰电极为基底,以牛血清白蛋白和戊二醛为交联剂,将抗坏血酸氧化酶固定在电极上,制成修饰电极抗坏血酸氧化酶生物传感器。用这种生物传感器测定人体血清中抗坏血酸,线性范围在7.5×10~(-4)～7.5×10~(-7)mol/L之间,响应时间为5s,检测下限为2.5×10~(-7)mol/L。该传感器具有选择性好、灵敏度高和响应时间短等特点。     

饮料、甜橙、药片和尿液中维生素C的流动注射分析——2,6-二氯吲哚酚光度法

流动注射2,6-二氯吲哚酚光度法测定维生素C具有灵敏,快速的特点,检出限为0.5μg/ml,分析速度120样/h,取Vc 40μg/ml时测量的相对标准偏差为±0.5％。测定各类样品中Vc含量获得较好的结果。     

双酶电极测定血清中抗坏血酸的研究

本文将抗坏血酸氧化酶和过氧化酶固定在玻碳电极上,制成双酶生物传感器。该生物传感器具有选择性好,灵敏度高、响应快等优点。     

固蓝盐B分光光度法测定药物中抗坏血酸

探讨了一种简便的选择性高的药物中抗坏血酸的测定方法。该方法是基于在酸性介质中抗坏血酸和固蓝盐B的反应,产物的最大吸收为420nm.摩尔吸光系数为1.31×10~4L·mol~(-1)·cm~(-1).方法已应用于某些药物中抗坏血酸的测定,结果与碘量法一致,回收率为98.4％～105％,相对标准偏差低于3.7％。     

聚邻苯二胺修饰电极抗坏血酸氧化酶生物传感器的研究

本文报道了聚邻苯二胺／抗坏血酸氧化酶生物传感器，用这种传感器测定人体血清中的抗坏血酸，线性范围在１．０×１０＾－４～２．５×１０＾－７ｍｏｌ／Ｌ之间，响应时间为７ｓ，检测限为１．０×１０＾－８ｍｏｌ／Ｌ。该传感器具有选择性好、灵敏度高和响应时间短等特点。     

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.     

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。     

果蔬,饮料中抗坏血酸的新亚铜灵光度分析法

新亚铜灵光度法测定抗坏血酸具有灵敏、快速的特点。抗坏血酸的浓度在2～20 mg/L范围内与吸光度呈良好的线性关系。用于猕猴桃、西红柿、刺梨汁等样品的分析,其相对标准偏差在0.6～1.2%,测定各种样品抗坏血酸的含量与靛酚滴定法比较,获得一致的结果。     

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。     

以2-磷酸抗坏血酸酯为底物检测碱性磷酸酯酶的微分脉冲伏安法

提出以2_磷酸抗坏血酸酯为碱性磷酸酯酶(ALP)底物微分脉冲伏安法测定ALP的方法 ;2_磷酸抗坏血酸酯在ALP的催化作用下发生水解反应生成抗坏血酸 ,抗坏血酸在玻碳电极上 +0.40V(vsAg/AgCl)被氧化而产生一个灵敏的氧化峰 ,氧化峰电流随着酶浓度的增大而增大 ,借助此氧化峰电流可以测定ALP ,进而可用于以ALP为标记酶的酶免疫分析 ;用微分脉冲伏安法对酶催化反应条件和酶催化反应产物的测定条件进行了详细的研究 ,建立了以2_磷酸抗坏血酸酯为底物的伏安酶联免疫分析新体系 ,测定游离ALP的线性范围是0.4～2.0×103 U/L,检测限为0.3U/L,对游离的IgG_ALP的测定最大稀释比为1∶200000。     

Simultaneous Determination of Uric Acid and Ascorbic Acid Using Edge Plane Pyrolytic Graphite Electrodes

Edge plane pyrolytic graphite electrodes have been applied for the determination of uric acid and ascorbic acid. The separate determination of uric acid was found to produce three linear ranges from 100 nM to 3400 μM with a detection limit of 30 nM found to be possible. Uric acid detection was also explored in the presence of 200 μM ascorbic acid where a detection limit of 52 nM was found to be possible. The detection of ascorbic acid in the presence of uric acid was also explored over three linear ranges of ascorbic acid with a limit of detection of 80 nM. Last the simultaneous determination of both uric acid and ascorbic acid is investigated over the range 100 nM to 1000 μM where detection limits of 50 nM and 120 nM were obtained respectively. Analysis of uric acid in a growth tissue medium was found to be successful, confirming the applicability of the methodology to real matrices. This protocol is shown to provide low detection limits, easy handling (no electrode modification), good voltammetric peak separation of uric acid and ascorbic acid and a wide linear dynamic range.     

掺铁氰根聚吡咯修饰电极测定抗坏血酸的研究

本文对掺铁氰根聚吡咯电极的聚合、伏安行为、电催化效应及其在抗坏血酸测定中的应用进行了研究。该膜电极性能稳定，对抗坏血酸催化效果好，抗坏血酸浓度在５×１０－６～６×１０－３ｍｏｌ／Ｌ范围内有很好的线性关系，用于测定果汁饮料中抗坏血酸获得满意结果。     

流动注射化学发光传感器测定抗坏血酸

基于抗坏血酸抑制ＫＭｎＯ４－鲁米诺体系化光反应这一效应，设计出一种简便，快速，灵敏度高的消耗型化学发光抗坏血酸传感器。该传感器线性响应范围为１．０＊１０＾－５－４．０＊１０＾－３ｇ／Ｌ；相对标准偏差为２．３％（１．０＊１０＾－４ｇ／Ｌ，ｎ＝１１）；     

Flow Injection Analysis Determination of Ascorbic Acid with Spectrofluorimetric Detection

Abstract

A flow injection system for the fluorescence determination of low level of ascorbic acid is proposed. The method is based on the rapid oxidation of ascorbic acid by thallium(I). The fluorescence signal at 419 nm is proportional to the amount of ascorbic acid in the range of (1.4–28.0) × 10^?7 mole. The relative standard deviations for ten replicate measurements of 1.4 × 10^?6 mole of ascorbic acid was 1.3%. The sample rate of 45 ± 5 sample per hour was achieved. The usefulness of the method was tested in the determination of ascorbic acid in fruit juices and vitamin C tablets.     

Selective Determination of Uric Acid in Presence of Ascorbic Acid and Dopamine at Neutral pH Using Exfoliated Graphite Electrodes

Exfoliated graphite electrodes have been used to detect uric acid at neutral pHs, by following its oxidation. A linear range of 5–53 μM and a detection limit of 5 μM are observed at a pH of 7.0. Uric acid was found to be selectively adsorbed on exfoliated graphite surface in the presence of excess ascorbic acid. This leads to its selective determination in the presence of ascorbic acid. Simultaneous detection of uric acid, dopamine and ascorbic acid has also been demonstrated on exfoliated graphite electrodes in a pH 7 buffer.