Ion-selective electrodes in organic functional group analysis: microdetermination of nitrates and nitramines with use of the iodide electrode

A simple, selective and accurate method has been described for the rapid micro and submicro determination of organic nitrates and nitramines. It is based on reaction with mercury-sulphuric acid mixture for 5 min at room temperature followed by potentiometric titration of the mercurous ions released, a solid-state iodide-sensitive electrode being used. Three equivalents of potassium iodide as titrant are consumed per mole of nitrate or nitramine group. The results obtained, with sample sizes ranging from 1.0 to 50 mumole, are precise to +/- 0.2% and the average recovery is 99%. None of the other nitrogenous functional groups responds to this reaction.     

Kinetic determination of EDTA and citrate by the displacement of fluoride from Al(3+)F(-) complexes and use of a fluoride ion-selective electrode

The displacement of fluoride from its aluminium complexes by the action of EDTA, citrate and other ligands is a relatively slow process which can be monitored potentiometrically with a fluoride ion-selective electrode. Some characteristics of these reactions are presented. There is evidence that [AlF](2+) reacts with the competitive ligand faster than the simple free (hydrated) Al(3+) species does. The relative rates of release of fluoride by the action of various aminopolycarboxylic acids have been determined. Potentiometric reaction-rate methods have been developed for the determination of 0.2-1.5 mumole of EDTA and 0.1-1.0 mumole of citric acid, with average relative errors of approximately 3%.     

Computer-controlled measurement of thermal conductivities of aqueous salt solutions

A computer-controlled method to measure liquid thermal conductivities is described, and data are presented for aqueous electrolyte solutions. The relative thermal conductivities of sodium chloride and sodium iodide solutions agree well with previously published results. The effect of temperature on the thermal conductivity was investigated, and it was found that in the range 23–67°C the relative thermal conductivity was invariant with temperature within the experimental error (less than 1%). For a given concentration of 1-1 electrolyte, the relative thermal conductivity was found to vary linearly with the molecular weight of the solute.     

Titrimetric determination of chloramine-T and some aldoses by amplification reactions

A titrimetric method with amplification has been worked out for the determination of chloramine-T and certain aldoses. It is based on Leipert determination of iodide produced in the case of chloramine-T by reduction of the determinand with excess of iodide, and extraction and subsequent reduction of the iodine liberated. In the other case, the aldoses are oxidized with iodine, the surplus oxidant is extracted, and the residual iodide is determined. The method is applicable to chloramine-T in the range 0.01-3 mg, with a relative error between -3.0 and -0.4% and a relative standard deviation of 0.6-0.8%, depending on the amount present, and to 0.05-1 mg of glucose, galactose or arabinose, or 0.1-2 mg of lactose or maltose, with a relative standard deviation of 1.4% for > 0.5 mg of aldose.     

Catalytic determination of iodide by continuous addition of catalyst to a reference solution with photometric probe monitoring

Probe photometry is proposed as a simple monitoring technique for catalytic determinations by continuous addition of catalyst to a reference solution. The approach has been tested on the catalytic determination of iodide which in the concentration range of 10-100 ng/ml, can be determined with a relative error usually lower than 4-5% and relative standard deviations of 4.6 and 4.0% for 9.98 and 79.92 ng/ml, respectively. Two alternative techniques of measuring the analytical signal (the intersection time) are suggested to improve the reproducibility: the "initial signal preadjustment" and the "two-intersection point" techniques. The method has been applied to determination of iodide in table salt samples.     

A coulometric method for the assay of some easily oxidized organic substances with iodine as an oxidizing agent

A coulometric method for the assay of easily oxidized organic substances, using iodine as an oxidizing agent, has been developed. The principle of the method is to oxidize the substance with an excess of iodine in a water-acetic acid medium and then titrate the iodide formed, with anodically generated silver ion. The titration is followed by dead-stop indication using two platinum electrodes. The method has been applied to the assay of dihydric phenols with hydroxyl groups in the ortho or para positions and to the determination of ascorbic acid in various pharmaceutical preparations. The absolute relative error varied between 0.2 and 2.8% for the 8 phenols investigated and the relative standard deviation between 0.2 and 1%. For standard solutions of ascorbic acid the absolute relative error was 0.9% and for the 6 pharmaceutical preparations investigated the relative standard deviation lay in the range 0.3-0.9%. The method is easy to apply and has a number of advantages over current iodimetric methods.     

Indirect potentiometric determination of hydrazine, isoniazid, sulphide and thiosulphate with a chloramine-T ion-selective electrode

Indirect potentiometric procedures with chloramine-T (CAT) as the oxidant and a chloramine-T ion-selective electrode are described for the determination of hydrazine and isonicotinic acid hydrazide (isoniazid) in the 1-100 mumole range and of sulphide and thiosulphate in the 0.5-50 mumole range. The reductants react stoichiometrically with a known and excessive volume of added CAT and the unconsumed excess of CAT is measured with the CAT-selective electrode. Aqueous solutions of the reductants were analysed with an error and precision of about 1-2%. Analytical recovery of isoniazid added to tablet diluents was 97-101% (average 98.9%). Results were comparable with those obtained with a titrimetric method for the determination of isoniazid in injection solutions and tablets.     

Enthalpimetry of non-aromatic alkenes

A method of increased sensitivity for hydrogen enthalpimetry of olefins in mumole quantities is reported. The method depends on a linear relationship between the amount of alkene present and the heat given off on hydrogenation at slightly more than 2 atm pressure over palladium catalyst on charcoal. Least-squares analysis of the results shows that the measured heat effect is a linear function of amount of alkene taken, with a relative standard deviation of 1-3% for samples ranging in size from 1.4 to 37.5 mumole. Extension of the method to samples in submicromolar quantities was only partially successful; in a series of measurements extending to a minimum amount of 0.64 mumole, the relative standard deviation rose to 9.6%.     

改进的红外辐射-量热法测量O2(1△)绝对浓度

The absolute O2 （1Δ）concentration measurement performed for a singlet oxygen generator（SOG）by using the infrared radiation-calorimetry method is reported with a detailed discussion of its principle and related technique. The influence of O2 （1Δ）gas temperature variation is considered and the corresponding correction has been made,which is neglected by the previous researchers and may cause a significant error in the case of measurement for the large O2 （1Δ）flowrate. Furthermore,an automatically balanced Wheatstone bridge circuit,which is necessary for O2 （1Δ）detection on the SOG of short operation period,is designed and tested by measuring the heat capacity of oxygen. The final error analyses give out a total relative error of ±16% for the O2 （1Δ）concentration,which mainly arises from the measurements of infrared radiation,pressure and temperature at the optical cell.     

Determination of some dithiocarbamates by catalytic thermometric titration

The determination of dithiocarbamates by catalytic thermometric titration is described. The dithiocarbamates can be determined in the range 0.5-20 mumole with relative errors of about 5%.     

Alternating current polarographic determination of microgram amounts of iodide ion by means of the catalytic oxidation of 1-amino-2-naphthol-4-sulfonic acid

The catalytic oxidation of 1-amino-2-naphthol-4-sulfonic, acid proceeds quickly with microgram amounts of iodide in the presence of sodium chlorate at pH between 1.3 and 2.0. The oxidation product shows a sensitive tensammetric wave at potentials of about +0.03 V vs. SCE (pH 1.75), so that the catalytic reaction was applied for the determination of microgram amounts of iodide ion. The most suitable conditions of the pH range, the concentration of ANS and sodium chlorate, reaction temperature and standing are 1.3–2.0, 3 × 10^?4M, 0.05 M, 50° C and 1 h respectively. Using the recommended procedure, iodide ion can be determined precisely in the concentration range 0.4–6.5 ng ml^?1 with a relative error of about 3%. Interference of foreign species and the application to the determination of total iodine in river and sea water are described.     

Indirect determination of some aliphatic secondary amines by catalytic thermometric titration

The determination of some secondary aliphatic amines by catalytic titration is described. The amines can be determined in the range 0.1-5 mumole with relative errors of about 3%.     

Catalytic titration of iodide, bromide and thiocyanate by use of the silver catalysed phloxin-persulphate reaction

A method for the catalytic titrimetric determination of iodide, bromide and thiocyanate is described, based on the inhibitory effect of these anions on the silver-catalysed oxidation of phloxin by persulphate in the presence of 2,2'-bipyridyl. The end-point is determined photometrically by measuring the absorbance at 537 nm. Amounts of iodide, bromide and thiocyanate in the 0.01-7.94, 0.11-4.73 and 0.12-3.59mg ranges, respectively, are titrated with a relative error of about 1%.     

Arsenic colorimetry with silver diethyldithiocarbamate

The effect of 22 interferences had been studied. Sulfur(II) must be oxidized by nitric acid; germanium, nitric acid, and perchloric acid must be removed by repeated evaporation with hydrochloric acid. Antimony, phosphate, selenium, tellurium, iron, tin, copper, nickel, and many other elements are eliminated by extraction of arsenic(III) chloride in concentrated hydrochloric acid with p-xylene or benzene. Metal ions forming complex or insoluble iodide can be blocked with an excess of potassium iodide. The method enables the determination of 2–30 μg of arsenic with a relative error <10%. It was tested with the materials of copper production.     

Bestimmung von jodid auf grund seiner katalytischen wirkung mittels der jodat-arsenit-reaktion

The catalytic action of iodide on the iodate-arsenite reaction can lie used to detect 0.5 μg of iodide at a dilution limit of 1:10⁷. The reaction time is inversely proportional to the iodide concentration so that a chronometric estimation of iodide is possible; the “simultaneous comparison” method is advantageous, being independent of temperature variations. The relative errors are ± 10% in the range 1–10 μg 1-, and ± 5% in the range 10–50 μg 1-. Silver and mercury ions interfere.     

Prediction of the chromatographic signal in gradient elution ion chromatography

This study describes the development of a signal prediction model in gradient elution ion chromatography. The proposed model is based on a retention model and generalized logistic peak shape function which guarantees simplicity of the model and its easy implementation in method development process. Extensive analysis of the model predictive ability has been performed for ion chromatographic determination of bromate, nitrite, bromide, iodide, and perchlorate, using KOH solutions as eluent. The developed model shows good predictive ability (average relative error of gradient predictions 1.94%). The developed model offers short calculation times as well as low experimental effort (only nine isocratic runs are used for modeling).     

Chemically modified carbon paste electrode for iodide determination on the basis of cetyltrimethylammonium iodide ion-pair.

A new carbon paste electrode (CPE) for the determination of iodide ion based on a cetyltrimethylammonium iodide (CTMAI) ion pair as an electroactive material is described. The electrode shows a linear response for iodide ion over the concentration range of 4 x 10(-5) M to 1 x 10(-1) M with a lower detection limit of 4 x 10(-5) M at 25 degrees C. The electrode has a Nemstian slope of -55.0 +/- 0.4 mV/decade and a fast potential response of 45 s, which is almost constant over a pH range of 5.0 - 9.0. Selectivity coefficient data of the CTMAI-CPE for some common ions show negligible interference, and the electrode has high selectivity towards the iodide ion. An average recovery of 101.83% with a relative standard deviation of 1.53% has been achieved for the determination of iodide in Flaxedil (gallamine triethiodide) ampoules, a muscle relaxant drug. The electrode has been examined for the determination of iodide in saline water; the results were found to compare favorably with those obtained using Metrohm iodide ISE. The electrode has been utilized as an end-point indicator electrode for the determination of Hg(II) and phenylmercury(I) in their aqueous solutions using potentiometric titration with a potassium iodide standard solution.     

在线超滤–离子色谱法测定地下水中碘化物

建立在线超滤–离子色谱法测定地下水中碘化物的方法。选择Metrosep A Supp 5–150型色谱柱,以3.2 mmol/L Na2CO3–1.0 mmol/L NaHCO3–8% 丙酮混合溶液为淋洗液,流量为0.7 mL/min,进样体积为200 μL,检测温度为50 ℃。碘化物的质量浓度在0.000~1.00 mg/L范围内与色谱峰面积线性关系良好,线性相关系数r=0.999 8,检出限为0.002 mg/L。实际样品测定结果的相对标准偏差为1.5%~2.2%(n=6),加标回收率为89.0%~103.3%。该方法无需进行样品前处理,可直接进样,操作简便,灵敏度高,适用于地下水中碘化物的测定。     

Photometrische Bestimmung von Antimon in Eisen und Stahl

For the determination of 2.5–100 ppm Sb in iron, plain carbon steels, low-alloy and free-cutting steels antimony is at first separated in two steps. It is coprecipitated with manganese(IV)oxide hydrate as collector, the precipitate dissolved and antimony extracted as iodide with benzene. After back extraction antimony is determined photometrically in the aqueous phase with methylfluorone. The relative error is ± 5%. One determination requires 1.5 h.     

二维离子色谱法同时测定环境水样中的碘离子、硫氰酸根和高氯酸根

建立了二维离子色谱法同时测定环境水样中的碘离子、硫氰酸根离子和高氯酸根离子的方法。先采用常规阴离子色谱柱(IonPac AS16, 250 mm×4 mm)将水样中的碘离子、硫氰酸根离子和高氯酸根离子与干扰离子进行分离。样品溶液通过抑制器后,将含有碘离子、硫氰酸根离子和高氯酸根离子的淋洗液导入富集柱(MAC-200, 80 mm×0.75 mm),再通过毛细管阴离子色谱柱(IonPac AS20 Capillary, 250 mm×0.4 mm)进行分离和定量分析。方法的线性范围为0.05～100 μg/L,相关系数达到0.9999,检出限为0.02～0.05 μg/L。样品中碘离子、硫氰酸根离子和高氯酸根离子的加标回收率在85.1%～100.1%之间,回收率的相对标准偏差(RSD)(n=6)在1.7%～4.9%之间。该法试剂用量小,灵敏度比常规离子色谱提高30～40倍,同时去除了样液中的高浓度基体杂质,适用于水样中低含量碘离子、硫氰酸根离子和高氯酸根离子的检测。