自动电位滴定法快速测定钾盐中的钾含量

钾含量的测量常用火焰光度法和四苯硼钾重量法。火焰光度法适用于微量分析 ,对较高含量钾的测定误差较大 ,四苯硼钾重量法的测定准确度高 ,但操作繁琐 ,测定周期长 ,易出错。本文采用四苯硼钠溶液电位滴定法 ,测定高、中含量组分钾 ,测定周期短 ,所用试剂少 ,且不受样品中水不溶物的干扰 ,选择性好 ,测定的准确度和精密度均在 0 .2 %以下 ,适用于钾盐、卤水、复合肥和钾肥中钾的测定。1　实验部分1 .1　仪器和药品ZD 2型自动电位滴定仪 (上海雷磁仪器厂 ) ,PK 1型钾离子选择电极 ,2 1 7型饱和甘汞电极 (双盐桥 )。四苯硼钠标准液 :0 .1mol…     

Precise potentiometric titration of manganese

Summary A method for the precise automatic potentiometric titration of manganese is described. Manganese ions are titrated with permanganate as a titrant in fluoride medium. The ideal quantity to titrate is about 30 mg of manganese. The endpoint of the reaction is recorded automatically. By adding more than 98% of the titrant by weight and the remaining part by means of an automatic burette the precision of the method could be improved to 0.03%. Systematic deviations are eliminated by calibrating the reagent with well-known reference solutions.

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Genaue potentiometrische Manganbestimmung

Zusammenfassung Mangan wird mit Permanganat in Fluoridmedium titriert. Die optimale Menge für die Titration beträgt etwa 30 mg Mn. Der Endpunkt der Reaktion wird automatisch registriert. Durch Zusatz von mehr als 98% des Titrationsmittels als Einwaage und Vervollständigung der Reaktion mit Hilfe einer automatischen Bürette kann eine Genauigkeit von 0,03% erzielt werden. Systematische Fehler werden durch Eichung mit bekannten Referenzlösungen vermieden.

     

Critical comparison of evaluation methods of potentiometric titration data using a microcomputer-controlled automatic potentiometric titration system

A microcomputer-controlled automatic potentiometric titrator withP controlled intelligent auto-sampler has been built for serial analysis. Controlling and evaluating programs have also been written. In order to use the most powerful evaluating method, a comparison was made between the methods. The data of the titration curves were obtained by the implicit relation characterizing the curve. The different evaluating methods were tested by using these data. The effects of random errors stemming from measurements were also investigated. The methods used were: two point differentiating formula, differentiation of interpolating and smoothing spline functions, the Gran method, and implicit regression with the Gauss-Newton-Marquardt method. Regression is outstanding among the methods, but it needs much more computing time compared with others. The second-best method is the differentiation with smoothing spline function with end point determination based on finding the sign reversal of the second derivative. This method is much faster than regression.     

An environmental friendly method for the automatic determination of hypochlorite in commercial products using multisyringe flow injection analysis

A multisyringe flow injection analysis system was used for the determination of hypochlorite in cleaning agents, by measurement of the native absorbance of hypochlorite at 292 nm. The methodology was based on the selective decomposition of hypochlorite by a cobalt oxide catalyst giving chloride and oxygen. The difference of the absorbance of the sample before and after its pass through a cobalt oxide column was selected as analytical signal. As no further reagent was required this work can be considered as a contribution to environmental friendly analytical chemistry. The entire analytical procedure, including in-line sample dilution in three steps was automated by first, dilution in a stirred miniature vessel, second by dispersion and third by in-line addition of water using multisyringe flow injection technique. The dynamic concentration range was 0.04-0.78 g L⁻¹ (relative standard deviation lower than 3%), where the extension of the hypochlorite decomposition was of 90 ± 4%. The proposed method was successfully applied to the analysis of commercial cleaning products. The accuracy of the method was established by iodometric titration.     

A simple automatic system using the HP-85 microcomputer for programmed potentiometric titration

A simple way of constructing an automatic titration system is proposed, based on combination of a digital pH-meter and an automatic burette with an HP-85 microcomputer. An inexpensive interface unit based on a MOTOROLA 6800 has been developed, which permits communication of the computer with the pH-meter and the burette. The system constructed is very flexible and can find wide application in potentiometric titration and direct potentiometry with different kinds of ion-selective electrodes.     

火试金富集--自动电位滴定法测定粗碲中的银含量

粗碲是由铜、铅、锌冶炼带来的副产品,其中含有大量的金、银等贵金属。快速准确检测粗碲中银含量,具有十分重要的意义。样品预先采用硫酸溶解,还原沉淀金、银,过滤分离大部分的铋、硒、碲等元素,经配料、高温熔融,熔融态的金属铅捕集试料中的贵金属形成铅扣,试料的其他物质与熔剂生成易熔性熔渣。将铅扣灰吹,得金银合粒,清除合粒表面粘附的杂质,经硝酸分金,用硫氰酸钾滴定法测定银量。银的加标回收率在99.5%～101%,相对标准偏差(RSD)小于5%。方法速度快,稳定性好,适用于粗碲中银含量的测定。     

Determination of vanadium(V) by direct automatic potentiometric titration with EDTA using a chemically modified electrode as a potentiometric sensor

A chemically modified electrode (CME) was prepared and studied as a potentiometric sensor for the end-point detection in the automatic titration of vanadium(V) with EDTA. The CME was constructed with a paste prepared by mixing spectral-grade graphite powder, Nujol oil and N-2-naphthoyl-N-p-tolylhydroxamic acid (NTHA). Buffer systems, pH effects and the concentration range were studied. Interference ions were separated by applying a liquid-liquid extraction procedure.The CME did not require any special conditioning before using. The electrode was constructed with very inexpensive materials and was easily made. It could be continuously used, at least two months without removing the paste.Automatic potentiometric titration curves were obtained for V(V) within 5 × 10⁻⁵ to 2 × 10⁻³ M with acceptable accuracy and precision. The developed method was applied to V(V) determination in alloys for hip prothesis.     

自动电位滴定法测定粗锡合金和废铅炉砖回收物料中银

在采用自动电位滴定法对粗锡合金和废铅炉砖回收物料中Ag进行测定时,Cu的存在会产生干扰。实验探讨了用自动电位滴定测定时Cu对Ag的干扰,结果表明,用KI滴定不大于5mg Ag时,Cu最大允许量为100mg。据此,利用AgI沉淀溶度积最小的特性,建立了用KI自动电位滴定法测定粗锡合金和废铅炉砖回收物料中Ag的方法。用HCl-HNO3(1+3)溶样,以H2SO4冒烟除尽Cl-,在HNO3(1.6mol/L)-酒石酸(20g/L)-聚乙烯醇(0.2g/L)介质中,以0.6g抗坏血酸还原Fe3+为Fe2+,用复合Ag环电极和KI标准溶液(0.01mol/L)进行电位滴定。对滴定剂、指示电极、试样分解、酸介质、试剂用量和共存物质的影响等分析条件进行了实验优化。Ag量在1.0~50.0mg内与耗用KI标准溶液体积呈线性关系,相关系数为0.999 99,检出限(3s/k)为0.61μg。方法用于各试样中0.15%~31.69%Ag的测定,相对标准偏差(RSD,n=5~9)为0.79%~8.7%,加标回收率为85%~108%,测定值与火试金重量法结果相一致。     

Micro and semimicro determination of sulfur in organic compounds by potentiometric titration with lead perchlorate

Summary A method for the micro- and semimicro-determination of sulfur in organic compounds is described. After combustion in an oxygen-flask, the sulfur-containing species are oxidized to sulfate with sodium nitrite. The sulfate is titrated potentiometrically with 0.01M lead perchlorate in a 60% 1,4-dioxane solution at p_H 4 to 6.5. A lead ion-specific electrode is used in conjunction with an expanded-scale p_H meter to monitor the emf. Results are within the ±0.3% absolute limits considered acceptable for microanalysis. Halogens do not interfere. The interference of fluoride is eliminated by complexation with boric acid. If, in addition to sulfur, both fluorineand chlorine are present, the former is removed by acidification with perchloric acid. Phosphorus interferes and must be separated prior to sulfur analysis.

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Zusammenfassung Ein Verfahren zur Mikro- und Halbmikrobestimmung von Schwefel in organischen Verbindungen wurde beschrieben. Nach Verbrennung im Schöniger-Kolben wird mit Natriumnitrit zu Sulfat oxydiert. Dieses wird mit 0,01-m Bleiperchlorat potentiometrisch in 60%iger Dioxanlösung bei p_H 4 bis 6,5 titriert. Eine für Blei spezifische Elektrode wird in Verbindung mit einem p_H-Meter mit gedehnter Skala zur Messung der E. M. K. verwendet. Die Resultate sind mit einer absoluten Fehlerbreite von ±0,3% für mikroanalytische Zwecke akzeptabel. Halogene stören nicht. Fluor wird mit Borsäure maskiert. Wenn außer Schwefel auch Fluorund Chlor anwesend sind, entfernt man Fluor mit Perchlorsäure. Phosphor stört und muß daher vor der Schwefelbestimmung entfernt werden.

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Work performed under the auspices of the U. S. Atomic Energy Commission.     

Accurate and precise determination of 2–25 mg amounts of uranium by means of a special automatic potentiometric titration

Analytical and Bioanalytical Chemistry - A precise and accurate potentiometric titration of 2–25 mg of uranium is described. The uranium is reduced to U(IV) according to the method of Eberle...     

Differential electrolytic potentiometric titration method for the determination of ciprofloxacin in drug formulations

A simple and rapid differential electrolytic potentiometric titration method for the determination of ciprofloxacin was developed. The work is based on the fast complexation reaction between iron(III) and ciprofloxacin in a ratio of 1:3, respectively, in sulfuric acid media of 0.09 mol dm⁻³. Among the electrodes tested silver amalgam electrodes were found to be a suitable indicating system. By applying a current density of 0.5 μA cm⁻² to these electrodes and using iron(III) solution of 0.097 mol dm⁻³ as a titrant, normal titration curves were obtained. The method was successfully applied for the determination of ciprofloxacin in drug formulations as low as 4.0 ppm.     

The potentiometric titration of surfactants and soaps using ion-selective electrodes

Summary Several quaternary ammonium halides have been evaluated for the precipitation titration of anionic surfactants and soaps. The titrants were hexadecyltrimethylammonium chloride and bromide, hexadecylpyridinium chloride, and diisobutylphenoxyethoxyethyl(dimethyl)benzylammonium chloride. Hexadecylpyridinium chloride yielded the highest precision and largest potentiometric break. Titrations were monitored with a commercically available fluoroborate ion-selective indicator electrode and a double-junction reference electrode. Commercially available perchlorate, nitrate, and calcium electrodes may also be used for emf monitoring. This obviates the need of preparing special liquid membrane or other electrodes mostly used heretofore in the potentiometric titration of surfactants and soaps. Electrophoresis purity reagent sodium dodecylsulfate is recommended for the standardization of the quaternary ammonium halides. The reverse titration, of cationic surfactants vs. standard sodium dodecylsulfate, is similarly feasible.Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore Laboratory under contract number W-7405-ENG-48.     

Development of a novel potentiometric titration method for determination of polypropylene degradation

In this study, a novel potentiometric titration of hydroperoxide in degraded polypropylene (PP) is proposed. This titration is quite sensitive compared with the conventional ones such as UV and manual titrations, and its detection limit was about 2 meq/kg. The sensitivity was equal to that of molecular weight measurement by GPC for the degraded PP and, in addition, the volatilization behavior of the hydroperoxide could be detected. This titration was found to be very effective for the determination of PP degradation.     

用氟钽酸根指示电位滴定钽的新方法

A new potentiometric titration method for the determination of tantalum in sulfuric acid and hydrofluoric acid media is described. EMF's were monitored with a double-junction reference electrode and a flurortantalate ion selective indicator electrode made in this laboratory previously. Five titrants have been evaluated for the precipitation titration. CPC, BDTAC and TPA yield the highest precision and largest potentiometric breaks, then rank CETAB and Hyamine 1622 in turn. CPC is considered to be the most satisfactory owing to the most sharp end-point break yielded when 10^-^4M of Ta is titrated with it. The concentration of H2SO4 suitable for the titration is 0.18 to 1.8M and that of HF is 0.23 to 1.7M. The method is suitable for Ta content in the range of 0.5 to 150 mg with a coefficient of variation of 0.15% (9 results) for 20 mg of Ta. HCl, H3PO4, tartaric acid and (NH4)2C2O4 as wellas a large amount of Fe^3^+, Ni^2^+, Cr^3^+, WO2^-^4, Zr^4^+, La^3^+, Al^3^+, MoO2^-^4 and Nb^5^+ do not interfere, while ClO^-^4, H2O2 and BF^-^4 must be avoided. The method has been found to be very useful for the determination of Ta in steels and crystalline lithium tantalate. The results obtained are in good agreement with those of comparable methods. This method is very simple and provides a fast determination process.     

Non-aqueous quantitative determination of the carbonyl functional group by constant-current potentiometric titration

A non-aqueous direct titration procedure has been developed for the determination of aldehydes and ketones. It uses two platinum-wire indicating electrodes with a constant current of 0.5 muA. The solvent medium is 0.15M sodium perchlorate in tetrahydrofuran. The titrant is sodium fluorenyl in a mixture of 1,2-dimethoxyethane and tetrahydrofuran. All types of carbonyl compounds react with the sodium fluorenyl, but steric hindrance prevents complete reaction with certain ketones containing bulky groups. The lowest concentration of carbonyl that can be determined with acceptable accuracy and precision is 7.5 x 10(-3)M, the error being < 3% and the precision better than +/-2.5%. Most reducible compounds interfere, e.g., peroxides, acid halides, nitro-compounds, acids, and water, and cannot be differentiated potentiometrically. The method can be extended to other reducible functional groups, e.g., nitro groups and acid chlorides.     

The determination of molybdenum in high-nickel alloys by potentiometric titration with cerium(IV) solutions

A combination of ion-exchange separation and potentiometric titration is used in the determination of the molybdenum content of various high-nickel alloys that contain more than 4% molybdenum. The molybdenum(VI) fraction of a sample separated by ion exchange is reduced with tin(II) chloride and titrated with cerium(IV) sulfate. The method facilitates accurate, routine determinations without the extreme care that is required by the standard photometric method or the length and complexity of the gravimetric method. By suitable adjustment of the sample size or the strength of the titration solution, effective titrations can be conducted on samples containing up to 100% molybdenum.     

Compleximetric titration of thorium with potentiometric end-point indication

In this redox-based direct potentiometric method, thorium is titrated with ethylenediaminetetraacetic acid (EDTA) in the presence of the Cu(II)—EDTA complex and ammonium thiocyanate. The indicator electrode is platinum. Solutions of irradiated thorium fuel, with less than 25 μmol in a sample aliquot, can be titrated. Solutions used to dissolve thorium samples contain aluminum, which can be masked kinetically, by pH adjustment, or with oxalate. Metal ions forming EDTA complexes with stability constants similar to or greater than that of copper(II) interfere.     

A simple differential titrator for automatic potentiometric titration at zero current, with two identical indicator electrodes

A simple differential titrator for automatic potentiometric titration at zero current, with two identical indicator electrodes, is described. The autoburette is a normal microburette connected to one tube of a peristaltic pump, and the differentiating system is a closed-flow circuit in a second tube of the pump, this tube containing two electrodes 5 cm apart. The apparatus has been applied to the determination of halides and sulphide-disulphide mixtures, with electrodes coated with an appropriate silver salt.