Amin T. Haj-Hussein

Flow injection spectrophotometric determination of cyanide by the phenolphthalin method

The phenolphthalin method for the determination of cyanide has been modified and adapted to a continuous flow system based on the flow injection principle. Aqueous cyanide samples are injected into a carrier stream (0.001 M NaOH), which is then merged with the combined reagent stream of phenolphthalin and carbonate buffer (pH 10.3), and the mixture is passed through an on-line cupric sulfide packed column. The resulting phenolphthalein (the oxidized form of phenolphthalin) is measured in a flow-through spectrophotometer at 552 nm, to determine the cyanide content. The chemical factors and flow injection analysis (FIA) variables influencing the system are discussed. The calibration graph is linear from 0.6 to 4.3 ppm cyanide. At a sampling rate of about 70 samples h(-1) with 50 mul sample injections, precision was about 1% relative S.D.

Ultraviolet Determination of Chloride in Water by Flow Injection Analysis

Abstract A flow injection method (FIA) has been developed for the determination of chloride with Hg-EDTA complex as reagent. Spectrophotometric detection in the ultraviolet region at 250 nm was used for measuring the absorbance of [HgYCl]3− complex ion, where H4Y is EDTA. A manifold consisting of two lines was used. The EDTA carrier and the Hg-EDTA reagent streams were buffered at pH 4.6 (Acetate buffer). This UV-FIA method has a detection limit of 0.2 ppm chloride. At a sampling rate of 60 samples per hour, with 50 μl sample injections, high reproducibility of measurements was achieved, with about 1% relative standard deviation. The method was used for the determination of chloride in natural waters and potable water supplies. The effects of sample volume, flow rate, coil length, and possible interferences on the FIA spectrophotometric signals were reported.

Simultaneous spectrophotometric determination of copper, nickel and palladium by flow injection analysis

A flow injection method has been developed for the simultaneous spectrophotometric determination of ternary and binary mixtures of copper, nickel and palladium. The system involves the sequential measurement of the absorbances of the metal-EDTA complexes at 700, 590, 380 and 340 nm. Sample solutions were buffered at pH 3.2 using a phthalate buffer. The EDTA carrier stream and samples contained 0.5 M sodium nitrate solution and the phthalate concentration in samples was adjusted to 0.08 M to minimise refractive index effects. Solutions could be analysed at rates of up to 100 h–1, and the relative standard deviation was less than 1%. The effects of the length of the dispersion coil and the sample volume on the FIA-spectrophotometric signals are presented.

Multicomponent flow injection analysis using spectrophotometric detection with reagent spectral overlap: Application to determination of calcium and magnesium in blood serum using Eriochrome Black T

Abstract The flow injection principle was used in the photometric determination of calcium and magnesium with Eriochrome Black T as reagent. The reagent spectrum overlapped the absorption spectra of the complexes (520 nm), and a novel correction for both the dilution and the consumption of the reagent by the sample analytes is described for a single channel manifold. Correction is made either graphically or computationally using an iterative procedure. Sequential determinations were accomplished by measurements at pH 10.1 and 10.5, which results in differences in the relative absorbances of the clacium and magnesium complexes. At a sampling rate of 100–120 samples per hour with 20-μl sample injections, precision was ±2% relative standard deviation. The technique was demonstrated by the determination of calcium and magnesium in deproteinized serum samples.

Indirect ultraviolet determination of silver with nickelocyanide ion by flow injection analysis.

A flow-injection method for the ultraviolet spectrophotometric determination of silver, based on its reaction with nickelocyanide ion, Ni(CN)(2-)(4), in ammoniacal buffer medium (pH 10) and subsequent measurement of the decrease in the absorption of the Ni(CN)(2-)(4) complex at 275 nm is described. The calibration graph is linear in the range 10-400 mum silver. At a sampling rate of about 60 samples h(-1) with 35 mul sample injections, precision was about 1% relative standard deviation. The proposed method was successfully applied to the determination of silver in some common silver minerals.

High-performance liquid chromatography of copper, mercury, nickel, and cadmium bisdibenzyldithiocarbamate complexes

High-performance liquid chromatographic separations of Cu(II), Hg(II), Ni(II), and Cd(II) bisdibenzyldithiocarbamates at nanogram levels by adsorption chromatography on silica gel were reported. Lichrosorb Si 60 (10 ..mu..m) was used as the stationary phase and benzene-cyclohexane mixtures as the mobile phase.

Indirect ultraviolet determination of cyanide by flow injection analysis using absorption of the Hg-EDTA complex at 250 nm

Abstract The flow injection principle was used in the determination of cyanide ion by the decrease in the ultraviolet absorption of the Hg-EDTA complex at 250 nm. The decrease in the absorbance is linear with cyanide concentration in the range of 0.5–52 ppm. A manifold consisting of two lines was used. The EDTA carrier and the Hg-EDTA reagent streams were buffered at pH 10 (ammoniacal buffer). The method has a detection limit of 0.5 ppm cyanide. At a sampling rate of ca.60 samples per hour with 100-μl sample injections, precision was about 1% relative standard deviation. The effects of the concentration of the Hg-EDTA reagent, pH, sample volume, flow rate, coil length, and anion interference on the FIA-ultraviolet signals are reported.

Ultraviolet spectrophotometric determination of copper in copper ores by flow-injection analysis

A flow-injection analysis (FIA) method for the ultraviolet spectrophotometric determination of copper in copper ores is described. The ore samples are dissolved in concentrated perchloric acid, the excess acid is neutralized with ammonia solution, and the resulting solution is used for the determination of copper. The UV-FIA system is based on the reaction of copper (II) ions with pyrophosphate and subsequent measurement of the absorbance of the dipyrophosphatocuprate (II) complex at 240 nm. The main factors which control the formation of this complex and the FIA variables influencing the system are discussed. The calibration graph is linear from 2-50 ppm copper. At a sampling rate of about 70 samples h(-1) with 50 mul sample injections, precision was about 1% relative standard deviation. Results obtained compare well with those obtained by atomic absorption spectrometry.

Spectrophotometric determination of cyanide by flow injection analysis

The flow injection technique is shown to provide fast, reliable, and sensitive determination of cyanide. Spectrophotometric detection in the ultraviolet region at 267 nm was used for measuring the absorbance of tetracyanonickelate (II) complex ion. The nickel carrier stream and the sample solutions were buffered at pH 10 (ammoniacal buffer). The method has a detection limit of 0.2 ppm cyanide. At a sampling rate of 90 samples per hour, with 60 ..mu..l sample injections, high reproducibility of measurements was achieved, with about 1% relative standard deviation. The effect of sample volume, flow rate, coil length, and anions interference on the FIA-spectrophotometric signals are reported.

Novel Flow Injection/Potentiometric Measurement of Slightly Soluble Salts in Small Volumes: Determination of Solubility Product Constants of Some Silver Salts

Abstract The flow injection technique is shown to provide fast, reliable and sensitive determination of solubility product constants of silver acetate, silver sulfate, silver oxide, silver bromate and silver chloride in microliter volume samples. Potentiometric detection using electrodes of the first kind and second kind was used for measuring silver ions and chloride ions, respectively. The solubilities were determined from measurement of the silver ion concentration in the saturated solutions. In the case of silver chloride, the solubility product constant was calculated from the concentrations corresponding to the intersection of the silver ion calibration curve and the chloride ion calibration curve, i.e., where the potentials of the two electrodes are equal. Tenth-molar sodium nitrate was used for all solutions to maintain constant ionic strength. At a concentration range of 1.00 × 10−2 − 1.00 × 10−5 M silver, and 1.00 × 10−2 − 1.00 × 10−4 M chloride, a Nernstian response of 60 m V per decade was obt...