The determination of carboxyl groups in polyethylene terephthalate

Three methods for the determination of carboxyl groups in polyethylene terephthalate are investigated, viz. (a) dissolution in hot benzyl alcohol, addition of chloroform, and titration with benzyl alcoholic potassium hydroxide solution to the phenol red end-point, (b) dissolution in a mixture of o-cresol and chloroform, and potentiometric titration with ethanolic potassium hydroxide solution, and (c) dissolution in a mixture of o-cresol, chloroform and acetone, and titration with ethanolic potassium hydroxide solution with HF-indication of the end-pointThe three methods yield the same results when applied to several samples of different carboxyl content. For several reasons the potentiometric method is preferred to the other two methods.     

Simultaneous Spectrophotometric Determination of Silicate and Phosphate by Flow Injection Analysis

Abstract

A method is reported for the simultaneous determination of phosphate and silicate by flow injection analysis based on the different rate of formation of the heteromolybdic acids of the two anions. Measurements are based on the colour of the ion-pairs formed between the said molybdic acids and Rhodamine B. The method allows the determination of the two anions at a rate of 20 samples/h over the ranges 0.05–2.5 ppm (phosphate) and 0.8–15 ppm (silicate), which allows application to a variety of waters.     

淋洗液自动发生-离子色谱法测定重整催化剂中氯的含量

建立了重整催化剂中氯含量的淋洗液自动发生-离子色谱测定方法.以4 mL 7.5 mol/L NaOH溶液提取重整催化剂中Cl-,以淋洗液自动发生装置产生的KOH溶液为流动相,进行离子色谱法测定.结果表明,溶液中Cl-线性关系良好,相关系数为0.9999,测定结果的RSD小于0.76%,加标回收率为98.7%～102.8...     

Determination of potassium in sea-water by capillary isotachophoresis

Summary A new analytical procedure for the determination of potassium in sea-water was developed using capillary isotachophoresis and ion-exchange. After the sea-water sample was passed through the column packed with an ammonium form cation-exchange resin, sodium ion was removed with 2×10^–2 mol/l ammonium chloride solution and then potassium ion was eluted with 3×10^–1 mol/l ammonium chloride solution. Simultaneous determination of potassium and sodium ions was performed with a newly developed electrolyte system; the leading electrolyte was 5 mmol/l cesium hydroxide containing 2 mmol/l 18-crown-6, 0.01% hydroxypropyl methylcellulose (HPMC) and 70% methanol; the terminating electrolyte was 5 mmol/l tetrabutylammonium bromide containing 0.01% HPMC and 70% methanol. A large amount of ammonium in the eluate did not interfere with the isotachophoretic measurement of potassium and sodium ions. A linear working curve was obtained for artificial sea-water samples containing up to 700 mg/l potassium ion. The proposed method was applied to the determination of potassium in surface and bottom sea-water samples.

---

Kaliumbestimmung in Meereswasser durch Capillar-Isotachophorese

     

Determination of Sulphur in Solid and Liquid Samples by Potentiometric Titration with Ion Selective Electrode.

Abstract

This paper describes a potentiometric method for the determination of sulphur in solid and liquid samples, using a sulphide ion selective electrode after the reduction distillation step. The determination of sulphide in solid and liquid samples without prior treatment was carried out by direct and titration potentiometric methods.

The reproducibility of the method and the recovery of sulphate in solid samples was investigated using analytical reagent grade 99% sodium sulphate. Portions of aproximately 100 mg of reagent were subjected to the reduction distillation process. After the ion selective electrode showed a stable value of the potential, indicating that all the sulphate had been reduced to sulphide, the potentiometric titration with lead nitrate solution was performed. A mean recovery of 98% of sulphate was found. The potentiometric titration method described in this work, can be applied to determine S⁼ in solid samples with the advantage that it does not require sample solubilization or extraction prior to the determination. The method yields an almost total reduction of sulphur and also a good precision.     

Indirect Microdetermination of Hydroxide Ions by Atomic Absorption Spectrophotometry

Abstract

A simple indirect atomic absorption spectrophotometric method is described for the determination of hydroxide ions. The method is based on the reduction of silver ions which takes place when hydroxide sample is treated with silver (I) solution in presence of manganese(II) ions. The unconsumed silver is determined by atomic absorption spectrophotometry. The effects of a number of factors have been studied and the method was employed for the determination of free alkali in paper samples.     

Indirect Electrosorptive Detection via Kinetic Facilitation in Ion Chromatography

Abstract

A new technique based on electrosorption is presented for the determination of selected anions in ion chromatography. Unlike conventional methods, which are based on the measurement of nonfaradaic currents, the present method utilizes a kinetic facilitation imparted to the electroreduction of a cationic “adsorbate probe” by specifically adsorbed anions, and hence involves the measurement of faradaic currents. Amminated, transition-metal salts of Co(III) have been found most useful as adsorbate probes for this application. The current enhancement-analyte concentration response curves obtained were determined to be linear over a limited range at mercury, but show curvature at virtually all concentrations at silver. Detection limits for this technique are slightly higher than those realized using more conventional double-layer capacitance methods. A brief discussion of the future prospects for this new approach is given.     

Simultaneous Ion Chromatographic Determination of Weakly and Strongly Retained Inorganic Anions using Aminoacids as Eluents

Abstract

At present eluents that are most widely used in ion chromatography of inorganic anions are salts with carbonate and hydroxyl eluting ions. But these eluents appear to be of no efficiency when samples containing both weakly and strongly retained inorganic anions are to be analyzed. In this case, one should use either expensive and complicated gradient elution technique or double injection with different eluents separately for weakly and strongly retained anions.

In this work, the simultaneous ion chromatographic determination of weakly and strongly retained inorganic anions without gradient elution is considered. The most common eluent for ion chromatography of anions, carbonate and aminoacids are compared. Dependence of the chromatographic behaviour of the strongly retained inorganic anions upon the concentration of the organic components in the eluent is shown.     

Sequential Separation and Indirect Voltammetric Determination of Silicate and Phosphate

Abstract

An indirect voltammetric method for the determination of silicate at the ppm level was developed. The method is based or. the D.C. polarographic current measurement of molybdate ion formed by the decomposition of 12-molybdophosphoric and 12-molybdosilicic acids. After separation of the heteropoly acids by the liquid-liquid extraction technique, the heteropoly acids are decomposed with a basic buffer. After adjusting the solution to the proper conditions, the current measurement is made at the dropping mercury electrode.     

Determination of Arsenic as the Oxidate by Ion Chromatography

Abstract

An ion chromatographic procedure is described for the analysis of arsenic as the oxo anion. The procedure involves oxidations of the arsenic to arsenate in an aqueous solution and injection onto an anion separator column, Comparison is made with a standard wet chemical procedure, and data is presented on reproducibility. In addition, there is a brief discussion of the applicability of this method to the determination of other oxo anions.     

The ION Chromatograhic Determination of Cr(III)-Cr(VI) Using an EDTA ELUANT

Abstract

Recent work in our laboratory has involved the use of ethylene diaminete traacetic acid as an eluant for the ion chromatographic determination of transition metals. We have continued this investigation into the use of EDTA by developing a potential method for the determination of Cr(III) and Cr(VT) in the same solution at the ppm level. The method involves the separation of the species as anions—the monovalent Cr(III)-EDTA anion and the divalent dichromate ion—followed by the detection of the species using a variable wavelength UV detector. The detection limits are approximately 2 ppm and the precision and stability of the system are within 6% RSD over the course of a working day. The linear operating range is in excess of two orders of magnitude.     

毛细管区带电泳技术快速分离检测爆炸残留物中的无机离子

利用间接紫外毛细管区带电泳方法完成了对爆炸残留物中7种无机离子(K+,NH+4,NO-2,NO-3,SO2-4,ClO-3,ClO-4)的分离检测。阳离子测定采用的缓冲体系为10 mmol/L吡啶（pH 4.5）-3 mmol/L冠醚,K+和NH+4在2.6 min内达到基线分离,检出限分别为0.25 mg/L和0.10 mg/L(S/N=3)。阴离子测定采用的缓冲体系为40 mmol/L硼酸-1.8 mmol/L重铬酸钾-2 mmol/L硼酸钠（pH 8.6）,氢氧化四甲铵为电渗流改性剂,5种阴离子在4.6 min内达到基线分离,检出限为0.10～1.85 mg/L。该方法已成功地应用于实际爆炸物样品种类的判定分析,取得了很好的结果。     

The Determination of Sodium in Alumina Using a Sodium Selective Ion Electrode

Abstract

A method has been developed for the determination of sodium in alumina using a selective ion electrode. The alumina sample is dissolved in ammonium hydrogen fluoride in platinum crucibles or sintered with boric acid using either platinum, nickel, or zirconium crucibles. Either dissolution technique completely extracts all available sodium. After dissolution, and in the presence of citrate to prevent aluminum hydroxide precipitation, the pH is adjusted to 8.7 with ammonium hydroxide, and the sodium concentration is determined by a sodium selective ion electrode.     

Ion chromatographic determination of some anions and alkaline cations in liquid crystal materials after ultraviolet irradiation

A method was developed for the quantitative determination of inorganic cations and anions present in liquid crystal materials pretreated with ultraviolet irradiation by ion chromatography. The samples were irradiated at less than 20±2 °C and then pretreated with OnGuard RP and P cartridges to remove the interferential organic compounds prior to ion chromatographic analysis for both cations and anions. With a high capacity and very hydrophilic anion exchange column, four anions (fluoride, chloride, bromide, iodide) were determined in 20 min with gradient of sodium hydroxide. By employing a cation exchange column, five cations (sodium, ammonium, potassium, magnesium, calcium) could be determined in 12 min. The spiked recoveries for the cations and anions were 84.0–108.1% and 86.1–108.2%, respectively.     

Analysis of Borosilicate Catalysts by Inductively Coupled Plasma Atomic Emission Spectroscopy

Abstract

A method was developed for the analysis of borosilicate catalysts. Samples were prepared by fusion technique with potassium hydroxide and analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The method was applied to a borosilicate NIST SRM 93 which was analyzed for major and minor elements (aluminum, sodium, silicon and boron). Despite the presence of relatively high concentration of the potassium, no matrix interferences were observed. This method provides precision and accuracy better than ±4% and ±6%, respectively.     

A Multicolumn Ion Chromatographic Determination of Nitrate and Sulfate in Waters Containing Humic Substances

Abstract

A three-column ion chromatographic system for the removal of humic substances from natural waters, and subsequent on-line concentration and determination of nitrate and sulfate using non-suppressed ion chromatography is presented. Humic substances are removed using disposable adsorption columns packed with chemically bonded amine silica material. The sample is directly transfered to an ion exchange column where the anions are concentrated ca 10 times. After reversing the flow, the ions are transferred to a third column where they are separated and quantified. The detection limit is less than 1 mg L^?1 of nitrate or sulfate in water containing 45mgL^?1 of humic acid.     

New Colorimetric Method for Determination of Tetracycline and Oxytetracycline Via Charge Transfer Complex Formation

Abstract

A colorimetric method for the determination of tetracycline and oxytetracycline is developed. It depends on nitration and reaction of the nitroderivatives with acetone in the presence of potassium hydroxide. A highly colored complex is produced. Variables such as temperature) time of heating, volume of nitrating mixture, acetone and potassium hydroxide have been evaluated to permit the selection of the most advantageous technique. Beer's Law is obeyed over the concentration range from 0.004 – 0.04 mg ml for tetracycline and oxytetracycline.     

Spectrophotometric Determination of Enniatin a and Valinomycin in Fungal Extracts By Ion Complexation

Abstract

When an ethylene dichloride solution of enniatin A is shaken with potassium picrate in potassium hydroxide solution, picrate anion is extracted into the organic phase in amount proportional to the enniatin concentration. Enniatin A can thus be determined spectrophotometrically in the range 5-60 μg/ml. Neutral lipids do not interfere. Valinomycin can be determined similarly, but cyclodepsipeptides that lack cationophoric properties are not estimated in this method.     

Assay of Bicarbonate Content in Certain Effervescent Formulations

Abstract

A quantitative method was developed for the assay of the bicarbonate content in a number of potassium-replacement effervescent tablets with citric acid. The method involved treatment of an aliquot of the crushed tablet with water, then with 0.5 N sulfuric acid, followed by quantitative absorption of the liberated carbon dioxide into 0.2 N sodium hydroxide in a closed system with a calcium chloride-protected vent. The sodium carbonate-sodium hydroxide solution was subjected to a two-step titration with standard acid using phenolphthalein and bromophenol blue indicators for the first and second step, respectively. Overall percent recovery (± SD) of potassium bicarbonate from simulated tablets were: 99.6 ± 0.9% (n = 4); in presence of potassium citrate, 100.0 ± 1.3% (n = 4); and in presence of potassium chloride and L-lysine hydrochloride, 101.5 ± 1.9% (n = 3). Application of the method to commercial products near the expiration date showed potassium bicarbonate contents of 80–90% of label claim. The method may be applied to the assay of any bicarbonate salt in other effervescent formulations.     

Vergleichende Untersuchungen zur Silicationenkonstitution in [(Ethyl)n(2-hydroxyethyl)4−nammonium]-Silicatlösungen mit n von 3 bis 1 und zum Einfluß von Alkalihydroxid

Comparing Investigations on the Silicate Constitution in [(Ethyl)_n(2-hydroxyethyl)_4?n-ammonium] Silicate Solutions with n from 3 to 1 and on the Influence of Alkali Hydroxide In [(ethyl)_n(2-hydroxyethyl)_4?nammonium]-silicate solutions with n from 3 to 1, free of alkali hydroxides, double three-ring and double four-ring silicate anions are to be found. With a growing number of 2-hydroxyethyl groups contained in the ammonium ion, the part of double four-ring ions increases. Other influating factors are the molar ratio of organoammonium hydroxide to silicon dioxide and the SiO₂-concentration. Admixtures of alkali hydroxides modify the ratio of double three-ring to double four-ring ions and cause also a degradation of both kinds of silicate ions, the effect of sodium hydroxide surpassing that of potassium hydroxide.