Conductometric determination of quaternary ammonium salts by sodium perchlorate and vice versa

A conductometric method is proposed for the determination of quaternary ammonium salts (chloride or bromide), based on the poor solubility of the relative perchlorates. A comparison between expected and found values shows that the method is suitable, rapid, and easy for quantities in the range from 0.2 to 5 g. The error depends on the solubility of the relative perchlorate. The apparent and tentative solubility product of the studied compounds were calculated. The obtained values allowed to propose benzyltributyl ammonium chloride (BTBA Cl) as precipitant for the conductometric titration of perchlorate. This easy, rapid and accurate determination can be used to analyze the perchlorate ion even in concentrated solutions and to determine stability constants for complex formation in aqueous solutions. Received: 11 June 1997 / Revised: 8 October 1997 / Accepted: 11 October 1997     

Chloride analysis in magnesium metal using ion chromatography with conductometric detection

A simple, rapid and accurate method for the determination of chloride in magnesium metal has been developed. The quantitative determination of chloride was accomplished by anion exchange chromatography with conductometric determination. A Metrosep Anion Dual 2 analytical column connected in series with a Metrosep RP guard column was used for chloride separation. A solution containing a mixture of 1.3 mM Na2CO3 and 2 mM NaHCO3 was used as eluent. The method requires a sample dissolution using nitric acid. The limit of detection for the determination of chloride is 50 mg kg(-1) and the relative standard deviation was 5% for the overall method. The recovery of chloride added was 99-102%. No interference was observed from either the closely eluting "system peak" or the nitrate peak in the determination of chloride.     

Flow-through bulk optode for the fluorimetric determination of perchlorate

A flow-through fluorescence bulk optode for the flow-injection determination of perchlorate is described. As the active constituents the optode incorporates the lipophilized pH indicator fluorescein octadecyl ester and methyl tridodecyl ammonium chloride, dissolved in a plasticized poly (vinyl) chloride membrane entrapped in a cellulose support. The optode is applied in conjunction with the flow injection technique for perchlorate determination at pH 4.5 (acetic-acetate). The sensor is readily regenerated with the pH 10.4 (TRIS) carrier solution. The analytical characteristics of this optode with respect to perchlorate response time, dynamic measurement range, reproducibility and selectivity are discussed. The proposed FI method is applied to the determination of perchlorate in waters from different sources.     

A new liquid-membrane electrode for selective determination of perchlorate

A new liquid-membrane electrode which responds to perchlorate ion is described. It incorporates a 10(-2)M solution of the nitron-perchlorate ion-pair complex, in nitrobenzene, as a liquid membrane. The electrode exhibits near-Nernstian response for 10(-2)-2 x 10(-5)M perchlorate with an anionic slope of 56 mV pClO (4)). The response time is 20-90 sec, the working pH 2.5-8.5, the lower limit of detection 8 x 10(-6)M perchlorate and the selectivity for perchlorate relative to 27 inorganic and organic anions of different nature is reasonably high. Periodate, permanganate and thiocyanate, however, interfere. Determination of 2-1000 microg ml perchlorate in aqueous solutions shows an average recovery of 98.8% and a mean relative standard deviation of 1.9%. The electrode has been successfully used for direct potentiometric determination of the purity of perchlorate propellants and the solubility products of some sparingly soluble perchlorates.     

气相色谱测定食品中丙酸及其盐类

建立了气相色谱测定食品中丙酸及丙酸盐的分析方法。针对含油脂和不含油脂的食品，分别建立了脱脂提取法和直接提取法。考察不同pH值对丙酸溶解性和加标回收率的影响，通过对净化条件、pH值、提取剂的种类和提取次数等条件的优化，确定最佳处理条件为：样品加盐酸溶液调节pH ≤ 2，用5 mL正己烷脱脂，用5 mL乙酸乙酯提取2次，合并提取液，使用HP-INNOWAX毛细管色谱柱对丙酸进行分离，用氢火焰离子化检测器检测，外标法定量。结果表明，使用脱脂提取法得到丙酸的回收率为87.5%~97.6%，相对标准偏差为3.09%~6.86%（n=6）；使用直接提取法得到丙酸的平均回收率为90.1%~102.1%，相对标准偏差为3.32%~6.33%（n=6）。两种方法的线性范围为2~1000 mg/L（相关系数为0.9998），检出限为0.003 g/kg，定量限为0.01 g/kg。方法适用于多种食品中丙酸的检测，具有准确、快速、简便、灵敏度高等优点，为食品中丙酸含量的测定提供了新途径。     

Transport properties of some cationic polysaccharides 2. Charge density effect

The charge density effect on the behavior of some cationic polysaccharides in aqueous and nonaqueous (methanol) solutions was studied by viscometric and conductometric measurements. The polyelectrolytes investigated contain quaternary ammonium salt groups, N-alkyl-N,N-dimethyl-2-hydroxypropylene ammonium chloride, attached to a dextran backbone. This new class of polyelectrolytes has various linear charge density parameters, xi, located below and above the critical threshold value of counterions condensation, xi(c)=1(xi=0.25-3.18). The viscometric data revealed that all copolymers exhibit a polyelectrolyte behavior and were plotted in the terms of Rao equation. The conductometric measurements of solutions of these copolymers were presented as a function of polymer concentration and charge density. The results were analyzed within the Manning's theory and lower experimental values of the equivalent conductivity than the theoretical ones were found. Possible reasons of this discrepancy have been discussed. The interaction parameters were evaluated and these were found to depend on both the polymer concentration and the charge density. The conductometric behavior of these cationic polysaccharides has shown that counterion condensation is not a threshold phenomenon, their association to the charged groups of the polyions taking place for xi>1 as well as xi<1.     

Determination of oxybutinin chloride in pharmaceuticals by reversed-phase ion-pair liquid chromatography with two counter-ions in the eluent

A reliable stability-indicating method using reversed-phase ion-pair high-performance liquid chromatography for the determination of the anticholinergic drug oxybutinin chloride in pharmaceuticals is reported. Sample extraction is easy and fairly rapid and recovery and precision of the method are excellent. Due to the simultaneous use of an organic amine and of an alkanesulphonate in the mobile phase, good selectivity towards related (quaternary ammonium) anticholinergic drugs was obtained.     

A conductometric method for colloid titrations

A negative or positive colloid sample solution can be directly titrated, respectively, with a polycationic (poly-N, N-diallyldimethylammonium chloride) or polyanionic (potassium polyvinylsulfate) titrant to a conductometric end-point. With the conventional toluidine blue indicator method a positive colloid solution is titrated directly with a polyanionic titrant, but a negative colloid solution must be treated with an excess of a polycationic titrant, which is back-titrated with the polyanionic titrant. For positive colloid solutions, both indicator and conductometric methods are suitable; for negative colloids the conductometric method is preferable because of its constant titration vlues over a range of pH values.     

Natural radioactivity in building materials utilized in the State of Kuwait

A simple radiochemical procedure is described for the determination of⁹⁰Sr in brines, which are very highly concentrated in sodium, calcium, potassium, magnesium, chloride and sulfate ions. The method is based on the different solubility of yttrium as compared to that of strontium, calcium and magnesium in ammonium chloride solutions, and utilizes Eichroms resin TRU·Spec for the purification of the yttrium fraction. The overall time required for the⁹⁰Sr analysis (excluding the counting time) is less than one day. Because the procedure involves only rather simple steps, it is well suited for routine analyses of large sample numbers.     

Analysis of wastewater for anionic and cationic nutrients by ion chromatography in a single run with sequential flow injection analysis

To prevent nutrient enrichment and, hence the undesirable ecological impacts, the nutrients monitored in wastewater samples include two anionic species, i.e., nitrate and orthophosphate, and a cationic species, ammonium. Ion chromatography (IC) is one of the popularly used techniques for determinations of nitrate and phosphate in these samples, whereas determination of ammonium in wastewater samples is typically done using manual or automated wet chemistry, e.g., flow injection analysis (FIA). We have developed a sequential IC–FIA method, using Lachat’s QC8000 IC system, which allows determinations of nitrate, phosphate and ammonia in a single injection. In this system, a QuikChem Small Suppressor cartridge is regenerated in between the samples. A sample is injected while leaving the suppressor off-line. Ammonium, a cation, elutes in the void volume of an anion-exchange column. The unsuppressed column effluent, exiting the conductivity flow cell, up to this point is used for FIA determination of ammonia. When ammonia exits the conductivity flow cell, a fully regenerated suppressor is brought in-line for conductometric detection of the anions. Analog data are simultaneously acquired from colorimetric and conductometric detectors, for the cationic and anionic nutrients, respectively. The method is accurate with spike recoveries in wastewater samples ranging from 91% for nitrate to 114% for chloride. It is precise with RSD values, for replicate analyses (n=7) of a mid-range standard, ranging from 0.4% for phosphate to 1% for nitrate.     

Some observations on catalytic conductometric titrations

Conductometric and high-frequency conductometric methods for the determination of the endpoint of catalytic titrations were developed. Titrations of sodium acetate were made in a mixture of acetic anhydride and acetic acid (7:3–11:3) which was 0.05–0.1 mol dm⁻³ in sodium perchlorate. Integral and derivative titration curves were recorded in both coulometric and volumetric titrations. Different acylation reactions, as well as dehydration of formic acid, were used as the indicator reactions. The optimal conditions of determination—choice of volume ratio of acetic anhydride to acetic acid, rate of the titrating reagent addition, concentration of sodium perchlorate, and concentration of several alcohols, water, and formic acid as components of the indicator reactions—were determined. Using the catalytic conductometric method, amounts of 0.04–11 mg of sodium acetate were determined with a relative standard deviation of less than 0.8 and 1.6% in volumetric and coulometric addition, respectively. Using the catalytic high-frequency conductometric method, amounts of 1–11 mg of sodium acetate were determined with relative standard deviation less than 0.5% (volumetrically) or less than 1.4% (coulometrically). The obtained results were compared with those of potentiometric and catalytic thermometric titrations.     

Zur relativkonduktometrischer bestimmung des schwefels in erdölprodukten

The relative conductometric method for the determination of sulphur, which has already been used for microelemental analysis, is applied to various petroleum products. The results obtained show that the method is not only very suitable for the rapid determination of the total sulphur content but also gives information on the nature of the combustion processes for sulphur-containing compounds.     

The solubility of sulfur dioxide in aqueous solutions of sodium chloride and ammonium chloride in the temperature range from 313 K to 393 K at pressures up to 3.7 MPa: experimental results and comparison with correlations

The solubility of sulfur dioxide in aqueous solutions of single solutes sodium chloride and ammonium chloride was measured using a static method at temperatures from 313 K to 393 K and total pressures up to 3.7 MPa corresponding to gas molalities of up to 10 mol/kg. Similarily to the system sulfur dioxide–water, also in systems with sodium and ammonium chloride a second (sulfur dioxide-rich) liquid phase is observed at high sulfur dioxide concentrations. A model to describe the phase equilibria is presented. Experimental results are reported and compared to correlations.     

Microscale extraction of perchlorate in drinking water with low level detection by electrospray-mass spectrometry

Improper treatment and disposal of perchlorate can be an environmental hazard in regions where solid rocket motors are used, tested, or stored. The solubility and mobility of perchlorate lends itself to ground water contamination, and some of these sources are used for drinking water. Perchlorate in drinking water has been determined at sub-mug l(-1) levels by extraction of the ion-pair formed between the perchlorate ion and a cationic surfactant with electrospray-mass spectrometry detection. Confidence in the selective quantification of the perchlorate ion is increased through both the use of the mass based detection as well as the selectivity of the ion pair. This study investigates several extraction solvents and experimental work-up procedures in order to achieve high sample throughput. The method detection limit for perchlorate based on 3.14sigma(n-1) of seven replicate injections was 300 ng l(-1) (parts-per-trillion) for methylene chloride extraction and 270 ng l(-1) for methyl isobutyl ketone extraction. Extraction with methylene chloride produces linear calibration curves, enabling standard addition to be used to quantify perchlorate in drinking water. Perchlorate determination of a contaminated water compared favorably with results determined by ion chromatography.     

Conductometric titration of nitrate by formation of the silver-1,10-phenanthroline-nitrate ternary complex

Nitrate forms an insoluble ternary complex, Ag(phen)(2)NO(3), with silver in the presence of 1,10-phenanthroline (phen). A simple and direct conductometric titration of nitrate, based on the formation of this ternary complex, has been investigated. The sample solution is adjusted to pH 4.3 with acetate buffer and titrated with 0.1M Ag(phen)(+)(2) complex solution in 40% ethanol-water mixture. The relative error is less than 0.5% and relative standard deviation less than 0.4%. The effect of ammonium ion and urea has also been studied. The method has been successfully applied to determination of nitrate-nitrogen in fertilizer.     

Kinetics of the Zn(II)/Zn(Hg) electrode reactions in DMSO solutions of halide ions

The electrode reaction Zn(II)/Zn(Hg) in complex chloride, bromide, and iodide solutions with DMSO as solvent and ammonium perchlorate as supporting electrolyte has been studied at the equilibrium potential by the faradaic impedance method and a square-wave method. Furthermore, double-layer data have been determined by electrocapillary measurements. The results indicate that the zinc chloride and bromide complexes do not contribute noticeably to the exchange current density, while in the iodide system both the solvated zinc ion and the first complex take part in the charge transfer. From the dissimilar results valid for water and DMSO solutions the conclusion is made that probably ligand bridging at the amalgam by the halide ions is operative in water solutions, whereas in DMSO the larger solvent molecules adsorbed can form a steric hindrance to ligand bridging by chloride or bromide ions.     

离子色谱法测定葡萄酒中的高氯酸盐

建立了离子色谱测定红酒中高氯酸盐的分析方法。以4种葡萄酒为典型样品,测定了其中的高氯酸盐含量。使用Metrosep A Supp5阴离子分析柱（150 mm×4.0 mm）进行分离,柱温为40℃,流动相为1.0 mmol/L碳酸钠水溶液-丙酮（85：15,v/v）,流速为0.8 mL/min。结果表明,高氯酸盐在0.1~10 mg/L内具有良好的线性关系,相关系数为0.9998,方法回收率大于86.0%,相对标准偏差小于2.6%。该方法前处理方便快捷、检测灵敏度高,可满足红酒中高氯酸盐含量的测定。     

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).     

Rapid estimation of chlorate in presence of perchlorate

Summary A rapid and simple method is described for the determination of chlorate in the presence of a large amount of perchlorate. The solution containing the mixture is acidified with either sulphuric acid or hydrochloric acid and titrated in the presence of sodium bromide directly against titanous chloride using quinoline yellow as indicator near the end point. The limit of uncertainty of the method is 0.361 mg for a sample analysing 52.48 mg of sodium chlorate.     

Extraction Spectrophotometric Determination of Trace Amounts of Perchlorate Based on Ion-Pair Formation with Thionine

A simple, rapid, and sensitive extraction-spectrophotometric method has been developed for the determination of trace amounts of perchlorate. This method is based on the extraction of perchlorate as an ion pair with thionine into isobuthyl methyl ketone and measuring the absorbance of the organic phase at 603 nm. The effect of different variables such as pH, reagent concentrations, and standing time was investigated and optimum conditions were established. The effects of other cations and anions on the extraction were also studied. The calibration curve was linear in the range of 40–1000 ng mL^?1 with correlation coefficient of 0.9998. The detection limit based on 3S_b criterion was 23 ng mL^?1 and the relative standard deviation for 400 ng mL^?1 of perchlorate was 1.9%. The proposed method was applied to determination of perchlorate in water samples.