动力学分光光度法测定微量草酸的研究

本文详细讨论了草酸对锡－苯基荧光酮－溴化十六烷基三甲基铵三元络合物显色反应的催化动力学条件，建立了动力学光度法测定微量草酸的新方法，本法Ｓａｎｄｅｌｌ灵敏度为７．４ｎｇ／ｃｍ＾２，草酸浓度在０－１．０μｇ／ｍＬ范围有良好线性关系，方法可直接用于菠菜中草酸含量的测定。     

痕量草酸的催化荧光分析

在０．０４ｍｏｌ／Ｌ Ｈ２ＳＯ４介质中及８０℃条件下,草酸对Ｋ２Ｃｒ２Ｏ７氧化罗丹明Ｂ这一荧光猝灭反应具有较强的催化作用。以自来水冷却中止反应,采用荧光法研究了催化测定草酸的各种影响因素,建立了一个测定范围和检出限分别为０．０３－３μｇ／ｍＬ和０．０１μｇ／ｍＬ草酸的催化荧光分析法,用于尿样分析,结果满意。     

荧光动力学光度法同时测定硝酸根及亚硝酸根的研究

基于亚硝根对溴酸钾氧化罗丹明６Ｇ的催化及锌粉使硝酸根还原为亚硝酸根的原理，建立了同时测定亚硝酸根和硝酸根的荧光动力学法，用于饮用水、质控水样、饮料中硝酸根及亚硝酸根的测定，测定下限分别为０．０７４ｎｇＮＯ２＾－／ｍｌ和０．２５ｎｇＮＯ３＾－／ｍｌ。     

荧光动力学法测定痕量硫氰根离子的研究

本文利用痕量硫氰根离子对溴酸钾氧化罗丹明６Ｇ反应的抑制作用，建立了痕量硫氰根离子的荧光动力学检测方法。方法检测限０．４ｎｇ／ｍＬ。线性范围０．４－３２．０ｎｇ／ｍＬ。应用于吸烟人和非吸烟人唾液、湖水、血清中痕量硫氰根离子的测定，结果令人满意。     

离子色谱法测定尿液中的C2O42-、Ca2+、Mg2+

利用离子色谱法测定尿液中的草酸根、钙、镁离子：测定草酸根时，先在尿液中加入氯化钙使之转化成草酸钙沉淀，分离后用盐酸溶解草酸钙沉淀，然后进行测定测定钙、镁离子时，在酸性尿液中加入氧化剂过硫酸钾，在微沸状态下氧化尿液中的有机物，从而避免对色谱柱的污染：草酸根、钙、镁离子的回收率分别为108．3％～109．7％、94．9％～100．7％、97．2％～97.4％，相对标准偏差分别为2．4％、2.5％、3．1％。     

以酚藏花红为指示剂催化荧光法测定痕量亚硝酸根的研究

基于稀磷酸介质中，亚硝酸根对溴酸钾氧化酚藏花红反应的催化作用，建立了催化荧光法测定痕量亚硝酸根的新方法。反应在５５℃水浴中进行８ｍｉｎ，线性范围为０．２７～７．３μｇ／Ｌ，其回归方程为ΔＦ＝０．４０＋１０．９３ｃ，ｒ＝０．９９９４。用于水样中痕量亚硝酸根的测定，结果良好。     

荧光猝灭法测定痕量亚硝酸根

研究了用荧光猝灭法测定了亚硝酸根。本方法是基于亚硝酸根与碘化钾反应生成了单质碘,碘可以使２’,７’０二氯荧光素（ＤＣＦ）发生荧光猝灭,从而间接测定亚硝酯根。亚硝酸根浓度在１０￣１２０μｇ／Ｌ范围内,荧光强度差值与亚硝酸根浓度呈线性关系。检测限为５．６μｇ／Ｌ。本法简便、灵敏度较高,已用于合成样和分析纯试剂中亚硝酸根的测定。     

溴酸钾氧化吡罗红G催化动力学光度法测定痕量NO2^—

研究了在磷酸介质中亚硝酸根催化溴酸钾氧化吡罗红Ｇ而使褪色，建立了催化动力学光度法测定痕量亚硝酸根的新方法，测定范围为０．２－２０μｇ／ｍＬ，检出限为０．２ｎｇ／ｍｌ，用于食品和水样中的亚硝酸根测定获得满意结果。     

亚硝酸根的催化光度法测定

本法基于甲酸介质中，亚硝酸根对溴酸钾氧化甲基橙褪色的催化效应，用正交法确定最佳测定条件。本法测定亚硝酸根的线性范围为０～０．２０μｇ／ｍＬ灵敏度为２．８３×１０－１０ｇ／ｍＬ。用于测定水样中的亚硝酸根，结果良好。     

光化学荧光分析法测定头孢氨苄的研究

在ｐＨ４．０的缓冲溶液中，头孢氨苄在紫外光照射下能发生光化学反应，形成具有荧光的产物，λｅｘ为３４５ｎｍ，λｅｍ为４３２ｎｍ。在头孢氨苄浓度为０．１－４．０μｇ／ｍｌ范围内，荧光强度与浓度呈良好的线性关系，由此建立了头孢氨苄的光化学荧光测定法。方法的检出限为０．０１μｇ／ｍｌ，相对标准偏差为０．９３％。本法简便，快速且灵敏度高，可用于尿液中头孢氨苄含量的测定。     

Determination of trace amount of oxalic acid with zirconium(IV)-(DBS-arsenazo) by spectrophotometry

A novel method is proposed for the determination of trace amount of oxalic acid in the present article. In 1.0M hydrochloric acid medium, oxalic acid can react with the zirconium(IV) in Zr(IV)-(DBS-arsenazo) complex and replaces the DBS-arsenazo to produce a hyperchromic effect at 520 nm. The hyperchromic degree is proportional to the concentration of the oxalic acid added over a defined range. Based on this property, a new method for the spectrophotometric determination of trace oxalic acid was developed. Beer's law is held over the concentration range of 9.0 x 10(-6) to 5.0 x 10(-4)M for oxalic acid with a correlation coefficient of 0.9995. The apparent molar absorptivity of the method is epsilon520 nm = 1.16 x 10(3)L mol(-1)cm(-1) and the detection limit for oxalic acid is 0.815 microg/mL. The developed method was directly applied to the determination of oxalic acid in tomato samples with satisfactory results.     

Catalytic kinetic spectrophotometry for the determination of trace amount of oxalic acid in biological samples with oxalic acid-rhodamine B-potassium dichromate system

A new catalytic kinetic spectrophotometric method was proposed for determining trace oxalic acid based on the catalytic effect of oxalate on the oxidation of potassium dichromate with rhodamin B in 0.10 M of sulfuric acid. Good linearity is obtained over the concentration range 0.40-6.0 microg/mL of oxalic acid. After the reactions of the catalytic and non-catalytic systems were terminated by using 2.00 mL of 4 M sodium hydroxide solution, they can be stable for 3 h at room temperature. The apparent activation energy of the catalytic reaction is 12.44 kJ/mol. The effect of 50 coexisting substances was observed. The method was used to determine trace oxalic acid in tea, spinach and urine samples with satisfactory results.     

Polarographic determination of traces of zirconium in ores by use of complex-forming compounds adsorbable at the dropping mercury electrode

A polarographic method is proposed for the determination of trace zirconium down to the 5 x 10(-9)M level, based on the adsorption of the complex of zirconium with oxalic acid + cupferron + diphenylguanidine at the dropping mercury electrode in sodium acetate-acetic acid solution (pH 5.7). Under optimum conditions the wave-height is proportional to the concentration of zirconium in the range from 0 to 0.4 mug ml . The serious interference from titanium(IV) can be effectively eliminated by solvent extraction with 3% tri-n-octylamine from lN sulphuric acid and stripping with 0.1 M perchloric acid-lM hydrochloric acid-2M nitric acid mixture. The mechanism giving rise to the wave for the zirconium complex has been investigated. The method has been applied to the determination of trace zirconium in ores and ceramics.     

示波极谱法烟丝中尼古丁含量测定及电极反应机理

研究了用示波极谱法直接测定烟丝中的尼古丁含量的新方法.在0.2mol/L草酸底液中(pH=4.0),于-1.22V处得到尼古丁的灵敏还原峰,峰电流与尼古丁浓度在1.5～31.5mg/L范围内呈良好的线性关系,检测下限达0.37mg/L.该方法用于烟丝中尼古丁含量的测定,简单快速,测定回收率在91%左右.     

Polarographic determination of trace amounts of thorium

A sensitive linear-sweep polarographic method for the determination of thorium is described. It is based on the thorium complex with Xylidyl Blue I (XBI) in a medium containing ethylenediamine, 1,10-phenanthroline, oxalic acid and ninhydrin, at pH 10.5-11.5. The complex has been proved to be Th(XBI)(2), with log beta' = 9.6. The method can be used to determine trace amounts of thorium over the range 3.5 x 10(-8)-3 x 10(-6)M. The detection limit is 1 x 10(-8)M. A solvent extraction procedure is necessary to eliminate interference from several cations. The method has been applied to determination of traces of thorium in minerals, with good results.     

Kinetic spectrophotometric method for the determination of oxalic acid by its catalytic effect on the oxidation of safranine by dichromate

A new catalytic kinetic spectrophotometric method for the determination of oxalic acid has been described based on its catalytic effect on the redox reaction between safranine and dichromate in dilute sulfuric acid media. The reaction is monitored photometrically by measuring the decrease in absorbance of safranine at the maximum wavelength of 530 nm. Under the optimum conditions, a calibration graph from 0.10 to 10.00 microg ml(-1) of oxalic acid with a detection limit of 0.08 microg ml(-1) was obtained. The relative standard deviation (R.S.D.) for ten replicate measurements of 1.0 and 5.0 microg ml(-1) oxalic acid was 2.7 and 2.5%, respectively. The purposed method is simple, sensitive, selective and inexpensive. The applicability of the proposed method was determined by the determination of oxalic acid in spinach and wastewater samples with satisfactory results.     

Volumetric estimation of potassium permanganate and potassium dichromate in mixtures with oxalic acid

1. A simple method has now been developed for the volumetric estimation of potassium permanganate and potassium dichromate in mixtures The method consists in taking an aliquot volume of the mixture in an Erlenmeyer flask, adding sufficient quantities of sulphuric acid and manganous sulphate (catalyst) and titrating with a standard solution of sodium oxalate or oxalic acid run in from the burette, until the colour changes from orange-red to yellow. The oxalic acid run ingives a measure of the permanganate present in the mixture Then the mixture in the flask is titrated with a standard solution of Mohr's salt using diphenylbenzidine as indicator. The volume of Fe⁺² solution run in the second stage gives a measure of the dichromate present in the original mixture. 2. The reverse titration does not give accurate results, because it is affected by the induced reaction between oxalic acid and dichromate which is induced by the reaction between oxalic acid and permanganate during the first stage of the reaction. This induced reaction has been studied in some detail.     

Analytical applications of the photochemical action of light: Determination of oxalic acid by photo-oxidation in the presence of ferric salts

A new method has been developed for the determination of oxalic acid. This depends upon the photochemical oxidation of oxalic acid in. the presence of ferric sulphate. The method involves exposing a measured volume of oxalic acid solution, with an excess of ferric alum and some sulphuric acid,tosunlight in quartz or pyrex beaker for 15 to 30 minutes. The progress of the reaction is indicated by the disappearance of the yellow colour of the ferricoxalate complex from the solution. After completion of the reaction, the ferrous salt formed is determined using standard sodium vanadate and either diphenylbenXXXdine or diphenylamme-sulphonate as internal indicator in the presence of sufficient phosphoric acid. Formic acid does not interfere in the photochemical method of deteminination.     

LC Determination of Trace Short-Chain Organic Acids in Wheat Root Exudates Under Aluminum Stress

A novel and reliable high-performance liquid chromatographic method for trace short-chain organic acids measurement in wheat root exudates under aluminum stress has been optimized and validated. The chromatographic separation of the short-chain organic acids (citric, oxalic, malonic, succinic, tartaric, malic, and acetic acids) was achieved with Bio-rad Aminex HPX-87H cation exchange resin column. These seven organic acids were identified and quantified in 25 min. Well-shaped peaks were obtained for trace organic acids using dilute sulfuric acid as mobile phase. Under optimum conditions, Bio-rad Aminex HPX-87H column showed distinct advantages of the ability to well separate different short-chain organic acids (especially for tartaric and malic acids, as well as malonic and acetic acids) in wheat root exudates under aluminum stress, and offered accurate and precise results for the analysis of these organic acids. This HPLC method can efficiently eliminate the aluminum’s interference and is quite suitable to the trace detection of trace organic acids in wheat root exudates under aluminum stress.

     

LC Determination of Trace Short-Chain Organic Acids in Wheat Root Exudates Under Aluminum Stress

A novel and reliable high-performance liquid chromatographic method for trace short-chain organic acids measurement in wheat root exudates under aluminum stress has been optimized and validated. The chromatographic separation of the short-chain organic acids (citric, oxalic, malonic, succinic, tartaric, malic, and acetic acids) was achieved with Bio-rad Aminex HPX-87H cation exchange resin column. These seven organic acids were identified and quantified in 25 min. Well-shaped peaks were obtained for trace organic acids using dilute sulfuric acid as mobile phase. Under optimum conditions, Bio-rad Aminex HPX-87H column showed distinct advantages of the ability to well separate different short-chain organic acids (especially for tartaric and malic acids, as well as malonic and acetic acids) in wheat root exudates under aluminum stress, and offered accurate and precise results for the analysis of these organic acids. This HPLC method can efficiently eliminate the aluminum’s interference and is quite suitable to the trace detection of trace organic acids in wheat root exudates under aluminum stress.