Flow-Injection Analysis of Chloride in Milk with a Dialyzer and a Coated Tubular Inorganic Chloride-Selective Electrode

Abstract

A rapid and reliable automated procedure for the direct measurement of the chloride content in milk is described. The method is based on the principles of the flow-injection technique; a dialyzer is used to eliminate interferences and the dialyzed chloride is measured with a coated tubular chloride-selective electrode. With this system potential change caused by the interference of casein is obviated, giving a stable baseline. Results obtained for chloride in milk at a sampling rate of 120 samples per hour compared well with data obtained by the standard Volhard titration method. With 30-μl samples a working range of 250–5000 mg/1 chloride is covered with a coefficient of variation of better than 0.50%.     

Ion-Selective Electrode Determination of Sodium and Potassium in Blood and Urine

Abstract

The Beckman Electrolyte 2 Analyzer (E2A) has been studied for its response to sodium and potassium content in various laboratory prepared pH-adjusted mixtures of metal chlorides in the absence and presence of albumin and α-, β-and γ -globulins. These mixtures also included MITS, a Mock Ionic Test Serm, containing sodium chloride (15OmM), potassium chloride (4mM), calcium chloride (1mM) and magnesium chloride (1mM). Results for sodium and potassium are often low for these non-clinical standards.

Responses have also been studied for patient blood serum and urine samples. Some comparisons have been made with data obtained by flame photometry. The blood serum data obtained with the Electrolyte 2 Analyzer are statistically compared with those obtained by flame photometry.     

Three component flow injection analysis with on-line dialysis. Simultaneous determination of free calcium, total calcium and total chloride in milk by flow injection analysis and on-line dialysis

Summary A fast and reliable fully automated three-component flow injection procedure for the simultaneous determination of free calcium, total calcium and total chloride in milk is described where the three components from a single sample injection (30 l milk samples) are determined at a sampling rate of 60 samples per hour. The samples are directed to three different channels by using two dialysers in series. Interferences in the determination of free calcium are eliminated by using a dialyser (first in the series) which also separates the total and free calcium. Free calcium is determined by UV/VIS spectrophotometry at 580 nm and total calcium by atomic absorption spectrometry (AAS) at 422.7 nm. Interferences from phosphates in milk in the determination of total calcium by AAS are overcome by using a nitrous oxide-acetylene flame with the necessary suppression with potassium ions. A second dialyser in series is used to eliminate interferences, especially the interference of casein, before the dialysed chloride is measured with a coated tubular chloride-selective electrode. The results obtained for the free calcium, total calcium and total chloride in milk at a sampling rate of 60 samples per hour compared well with data obtained by standard methods. With 30 l samples the relative standard deviation for milk samples having different concentrations of free calcium (110–170 mg/l free calcium), total calcium (1000–1500 mg/l total calcium) and total chloride (1000–1800 mg/l total chloride) were better than 0.37, 1.01 and 0.25, respectively.     

Spectrophotometric determination of sodium by ion-pair extraction with crown ether complexes and monoanionic dyes

A highly selective photometric procedure for the determination of sodium in blood serum is proposed, based on the ion-pair extraction of a sodium—cryptand complex. A comparative study of cryptands with various cavity sizes, different pairing anions and extraction solvents is described. The use of cryptand 211, picrate and toluene, as ligand, pairing anion and extraction solvent, respectively, allows sodium to be determined at the μg ml^?1 level. A 350-fold amount of potassium (by weight) does not interfere, nor do other alkali metals. Possible interferences by multivalent cations are masked by EDTA.     

A fluorescent sensor with high selectivity and sensitivity for potassium in water

This communication describes a new optical sensor suitable for practical measurement of extracellular (serum or whole blood) potassium. The sensor responds rapidly and reversibly to changes in potassium concentrations typical of whole blood samples. No interferences from clinical concentrations of calcium or pH are observed, and the sodium interference is very minor. Excitation and emission occur in the visible light region. This new potassium sensor is currently used in the Roche OPTI CCA, a commercially available whole blood analyzer.     

Model experiments for determinations of zinc—amino acid complexes in biological fluids by polarography

The Ilkovi? constant was determined for zinc and zinc—amino acid complexes by using differential pulse polarography in 0.1 M sodium chloride—sodium diethylbarbiturate buffer at pH 7.4. A single well-behaved wave was obtained, except for cysteine and cystine for which useful calibration curves could not be obtained. The non-equilibrium dialysis of the amino acid complexes was studied in a hollow-fiber dialyzer. It is concluded that the dialysis step could be used in a method intended to measure available zinc but that the polarographic method needs further modification.     

Palladium Biosensor

In this paper we proposed a palladium(II) biosensor. The biosensor is based on determining of interactions between palladium(II) and metallothionein modified hanging mercury drop electrode by means of differential pulse voltammetry. We studied influence of two supporting electrolytes (potassium or sodium chloride) on the signals of the biosensor. Based on the results obtained we found potassium chloride (0.05 M) as the most suitable supporting electrolyte to determine palladium(II). The detection limit of the biosensor for palladium ions was evaluated as 100 nM with RSD about 10%. Moreover, we utilized the biosensor for measurement of the target molecule in the presence of human blood serum and human urine.     

Determination of Low Level Sulfides in Environmental Waters by Automated Gas Dialysis/Methylene Blue Colorimetry

Abstract

A sensitive and rapid automated method has been developed for the selective analysis of acid extractable sulfide in environmental samples by combining gas dialysis separation techniques with methylene blue detection procedures. Acid extractable sulfide is separated from the sample matrix by the gas dialysis membrane and subsequently trapped in a dilute sodium hydroxide receiving stream. This stream is reacted with N, N-dimethyl-p-phenylenediamine and ferric chloride to produce methylene blue which is then quantitated colorimetrically at 660 nm. For standards and nonturbid environmental samples, there is good agreement between the results obtained by this procedure and the standard methylene blue method. The effect of interferences on the accurate determination of sulfide by both methods was also examined and it was found that cupric ions significantly interfered with sulfide estimation. To obtain adequate sulfide recoveries in tap water and environmental samples ascorbic acid must be added as an antioxidant. A detection limit of 2 μg/L of sulfide has been obtained using this procedure.     

Spectrophotometric determination of trace amounts of cadmium and zinc in waste water with 4-(2-pyridylazo)-resorcinol and mixed ionic and non-ionic surfactants

A spectrophotometric method for determination of trace amounts of cadmium and zinc in waste water with PAR and mixed ionic and non-ionic surfactants is described. The interferences of foreign ions can be eliminated by masking with a mixture of triethanolamine, potassium fluoride, ethylenediamine and sodium hexametaphosphate. By virtue of the difference between the absorbances before and after addition of a little sodium diethyldithiocarbamate, cadmium and zinc can be determined directly in aqueous solution without separation. Beer's law is obeyed for 0-20 microg of Cd or 0-12 microg of Zn in 25 ml of solution. The apparent molar absorptivities at 505 nm are 8.65 x 10(4) l.mole(-1).cm(-1) for Cd and 8.21 x 10(4) l.mole(-1).cm(-1) for Zn. Results obtained by applying the proposed method to waste-water samples agree well with those obtained by atomic-absorption spectrophotometry.     

Flow injection analysis : Part VI. The determination of phosphate and chloride in blood serum by dialysis and sample dilution

The rapid determination of chloride and inorganic phosphate in blood serum based on continuous flow spectrophotometry was adapted to Flow Injection Analysis by applying dialysis as well as differential dilution of the injected samples. In addition to the manual injection procedure, an automated microsampling unit was developed and used. By continuous dialysis, chloride could be determined reproducibly at a sampling rate of 125 samples per hour at sample volumes of 60 μl or less. A similar sampling rate and high precision were obtained for the determination of inorganic phosphate by using differential dilution.     

Studies on bis(crown ether)-based ion-selective electrodes for the potentiometric determination of sodium and potassium in serum

Bis(crown ether)-based ion-selective electrodes for sodium and potassium are described, based on the bis[(12-crown-4)-2-ylmethyl]-2-dodecyl-2-methyl malonate sensor(I) for sodium and the bis[(benzo-15-crown-5)-15-ylmethyl] pimelate sensor(II) for potassium. The best results were obtained when the sensors were used in association with 2-nitrophenyl octyl ether as plasticising solvent mediator and potassium tetrakis(4-chlorophenyl)borate as anion excluder in poly(vinyl chloride) matrices. Electrode slopes were near-Nernstian, with detection limits of less than 10(-5) M. The electrode features are compared with those of a sodium glass membrane electrode, for sensor I, and with a valinomycin-based potassium electrode, for sensor II. The electrodes are also discussed in relation to others reported for sensors I and II and are shown to be superior. However, although the electrodes described offer promising alternatives to glass electrodes for sodium and valinomycin electrodes for potassium, data for sodium and potassium measurements in blood serum indicate a need for further research in order to improve the correlation with flame photometric measurements.     

Polarography of disodium pentacyanonitrosylferrate(II): Part 2. Determination at Therapeutic Levels in Serum,Plasma, and Whole Blood

Disodium pentacyanonitrosylferrat(II) (sodium nitroprusside) is determined at therapeutic (ng ml^?1) levels in plasma, serum and blood with conventional and high-performance differential pulse polarography (d.p.p. and h.p.d.p.p.) at a dropping mercury electrode or a static mercury drop electrode. Serum or plasma (3 ml) is treated with perchloric acid containing 1 mg ml^?1 potassium hexacyanoferrate(II), centrifuged for 10 min and subjected to polarography. For spiked serum, calibration graphs are linear over the range 30–1000 ng ml^?1 sodium nitroprusside, regardless of the polarographic technique; the estimated detection limit is 15 ng ml^?1 (5 × 10^?8 M). Calculated therapeutic levels range from 100 to 1000 ng ml^?1. Similar results were obtained for spiked plasma. A similar procedure is suitable for whole blood and was used to study the in-vitro degradation of sodium nitroprusside (200 ng ml^?1) on incubation at 37°C. The in-vitro loss is rapid (t_{$\text{1}\text{2}$} ≈ 6 min) but meaningful in-vivo levels can be obtained when the blood is collected in a 0.9% sodium chloride solution at 0°C. Thiocyanate, the main metabolite of nitroprusside, and thiosulphate, which is a potential antidote for cyanide, do not interfere.     

自行配制的系列标准样品应用于刚玉质耐火材料的X射线荧光光谱分析

用矾土标准物质、白云石标准样品、基准氧化铝及优级纯氯化钾和氯化钠作为基本材料,并应用Excel公式算法求得上述各物质的准确质量,配制成一组包括各被测组分的质量分数呈梯度分布的12种混合物,分别将上述各混合物置于铂-金坩埚中与无水四硼酸锂熔融,所得玻璃状熔块即为自制的一组供X射线荧光光谱分析刚玉质耐火材料用的系列标准样品。按所给的各分析通道的参数,测定了此类耐火材料中8项组分(即SiO2、Al2O3、MgO、Na2O、K2O、Fe2O3、CaO及TiO2)。另取基准氧化铝一份,按试验方法作空白试验,从而消除其中可能存在的痕量杂质的干扰。将所配制的系列标准样品应用于实样分析,所得8项组分的测定结果与用化学分析法所测得结果相符,其测定值的相对标准偏差(n=10)均小于12%。     

Tandem on-line dialysis with a double and single dialyser in flow injection dialysis — Simultaneous determination of calcium and high chloride in industrial effluents

The on-line double membrane dialyser described previously was coupled in series to a single dialyser in the manifold of a flow injection system to include the determination of samples with a high chloride content simultaneously with calcium in industrial effluents from a single sample injection. 50 μl of industrial effluent samples are injected into a carrier stream and are simultaneously dialysed in the double on-line dialyser for chloride and calcium. The dialysed chloride sample zones are further directed to a second dialyser that is incorporated in series with the first dialyser. This enables laboratories to determine samples with a very high chloride content up to 60 g/l simultaneously with calcium by using an automated tandem on-line dialysis technique. The fast and reliable fully automated two-component flow injection procedure operated at a sampling frequency of 90 samples per hour and the results obtained for chloride and calcium in industrial effluents compared well with those obtained by standard methods.     

Constantes d'acidite de l'acide pyrophosphorique et constantes de stabilite des complexes avec le potassium et le sodium: en|The acidity constants of pyrophosphoric acid and the stability constants of complexes with potassium and sodium ions

(The acidity constants of pyrophosphoric acid and the stability constants of complexes with potassium and sodium ions)The effect of potassium and sodium ions on the acidity constants of pyrophosphoric acid is studied by potentiometry at 25°C and at an ionic strength of 0.5 mol l^-1. Comparison of the results obtained in potassium chloride or sodium chloride medium with those found in tetramethylammonium chloride medium provides evidence of the formation of potassium and sodium complexes of the type MHP₂O^2-₇ and MP₂O^3-₇. Stability constants of these complexes are calculated and distribution diagrams of the species as a function of pH are given for the three different media utilized.     

Improvement of direct determination of Cu and Mn in seawater by GFAAS and total elimination of the saline matrix with the use of hydrofluoric acid

Hydrofluoric acid, added to seawater, can assist in the removal of chloride in the drying step by precipitating fluoride salts, thus suppressing the chloride interference effects induced on the atomization signals of Cu and Mn. By adding HF to seawater before the analysis, MgF₂ and CaF₂ are precipitated at the bottom of the sampling flask, without precipitating Cu and Mn, and are consequently not introduced into the graphite furnace. Because sodium salts are eliminated at the pretreatment step, the whole seawater matrix is eliminated before the atomization of Cu or Mn. Therefore, the analyzed volume of seawater can be increased by using the multi-injection procedure without degradation of the limit of detection and risks of spectral interferences. The limit of detection obtained for Cu and Mn are 0.05 and 0.01 μg L⁻¹, respectively, for a 50 μL analyzed seawater volume.     

Pollution-free method for the determination of iron in iron ore

A method for the determination of total iron in iron ores and concentrates is described which avoids the use of mercuric chloride. The sample is decomposed either by an acid attack or by fusion with sodium peroxide. The hot sample solution in about 6M hydrochloric acid is treated with hot 10% stannous chloride solution till pale yellow, followed by addition of a slight excess of 2% titanous chloride solution; the excess is then oxidized with perchloric acid (1 + 1). The solution is rapidly cooled in ice-water, and the iron (II) is titrated with potassium dichromate (sodium diphenylsulphonate as indicator). The results show the same degree of precision, accuracy, and degree of interference as those obtained by the standard stannous chloride-mercuric chloride method.     

Response surface methodology in the development of a stacking-sensitive capillary electrophoresis method for the analysis of tricyclic antidepressants in human serum

Stacking methods are very important in overcoming the poor detection limits in capillary electrophoresis (CE). In this paper, the separation and determination of several tricyclic antidepressants by a stacking method is described. The inclusion of acetonitrile (ACN) in the sample causes stacking (transient pseudoisotachophoresis) especially in presence of sodium chloride. An experimental design (central composite design) together with the response surface methodology has been used to find the optimum composition of the separation buffer and the optimal stacking conditions in few experiments. The response functions used are the product of the total resolution by the number of peaks, for the optimization of the separation buffer, and the product of the total resolution by the mean of the peak heights, for the optimization of the stacking conditions. About 28% of the capillary volume is loaded with sample. The calibration curves are linear over the working range (50-300 ng/mL). With a bubble capillary, the limits of detection (LODs) are in the order of 5 ng/mL. For the analysis of serum samples, enrichment with sodium chloride and the protein precipitation with ACN are enough to avoid interferences and to get stacking. Recoveries between 91.6 and 104% and RSD between 0.6 and 12% are obtained in the analysis of samples of lyophilized human serum and non-lyophilized human serum, spiked with the drugs.     

A study of the titrimetric potassium silicofluoride method for determination of silica in aluminosilicate materials

A critical study of the titrimetric potassium silicofluoride method for determination of silica reveals that quantitative precipitation of the sificofluoride is possible in 3.5-7.5N acid containing 1% sodium fluoride and >/ 12% potassium chloride. An aqueous wash solution (pH approximately 5.3) containing 0.1% sodium fluoride and 12% potassium chloride has been found ideal for washing the precipitate without significant hydrolysis even at 35 degrees C. The interference of large amounts of aluminium (up to 160 mg of Al(2)O(3)) is eliminated by precipitating the silicofluoride in 6-7.5N acid solution, the aluminium then forming practically no fluoro-complex, because of extensive protonation of fluoride. Interference by large amounts of boron (up to 160 mg of B(2)O(3)) is eliminated by precipitating silicofluoride with the minimum permissible potassium chloride concentration (12%) and washing with the aqueous wash solution at room temperature. Nitrazene Yellow has been used as a more sensitive indicator.