Abdulrahman S. Attiyat

Potentiometric selectivity study of TMC-crown formazane lonophore for cesium

Abstract A potentiometric selectivity study was made using TMC-crown fromazane, a dibenzo 14-membered ring cyclic compound, with two oxygen and two nitrogen atoms in the ring skeleton, as an ionophore for cesium ion. Eight electrodes with different electrode matrix compositions were constructed. Two plasticizers (NPOE and NPP′E) and different amounts of potassium tetra( p -chlorophenyl)borate were incorporated in the different electrode matrices. The effects of the different compositions on the sensitivity, selectivity, and linearity of the cesium calibration curve are reported. The effect of 1% trioctylphosphine oxide (TOPO) added to the electrode matrix was also studied. Sensitive and selective cesium-ion-selective electrodes were constructed using NPOE plasticizer, 200% molar ratio of the tetraphenylborate to ionophore, with and without TOPO. Selectivity coefficients for cesium with respect to rubidium, potassium, sodium, lithium, strontium, calcium, magnesium, and hydrogen were determined.

Flow injection study of the potentiometric lithium selectivity of cyclic dioxadiamides containing oxygen and nitrogen atoms

SummaryFour 15-membered ring cyclic compounds with two oxygen and two nitrogen atoms incorporated in the ring were prepared and evaluated as neutral carriers in lithium ion-selective electrodes. These ionophores, along with potassium tetrakis (p-chlorophenyl)borate and o-nitrophenyloctyl ether (NPOE), were included in the PVC matrix that coated the tip of a silver-wire electrode. The potentiometric selectivities of the electrodes towards lithium over sodium, potassium, calcium and magnesium were determined. Selectivity coefficients, KLi, Napot., as low as 9.5×10−3 were obtained and smaller coefficients for other metals, KLi, Mpot., were found. A calibration curve for lithium in the presence of 140 mmol/l sodium, with a linear portion having a slope of 51 mV/decade, was obtained. The effect of incorporating 1% trioctylphosphine oxide (TOPO) in the electrodes was studied. Comparison with the results obtained with 15-crown-4-ethers is made.

Study of the spectrophotometric measurement of lithium using TMC-crown formazane

Abstract TMC-crown formazane was investigated as a selective spectrophotometric chelating agent for lithium. Measurement in the presence of 880-fold molar ratio of sodium was made. As little as 0.5 m M lithium was readily measured. The effect of the sodium ion concentration on the background lithium signals was studied. Sodium causes depression of the lithium signal, and the relative effect diminishes as the total sodium concentration is increased. In a background solution containing 140 m M sodium, a 10 m M increment of sodium is equivalent to 0.007 m M lithium. The effect of time on the signals was also studied. A 0.61% relative standard deviation was achieved for the measurement of 3 m M lithium in the presence of 50 m M sodium.

Sequential atomic absorption spectrometric determination of chloride and iodide in a flow system using an on-line preconcentration technique

A flow injection method is described for the sequential determination of chloride and iodide in a mixture of the two. The chloride–iodide mixture is precipitated from solution by silver nitrate and the precipitated silver chloride is dissolved by ammonia solution to determine chloride after which the precipitated silver iodide is dissolved by potassium cyanide solution to determine iodide. The method allows the analysis of about 15 samples h–1 and mixtures with different chloride : iodide ratios can be analysed at the µmol dm–3 level.

Indirect Atomic Absorption Spectrometric Determination of Ammonia, Thiosulfate and Cyanide in an Unsegmented Flow System

Abstract A flow injection analysis method (FIA), has been developed for the determination of cyanide, thiosulfate and ammonia by atomic absorption spectrometry (AAS). Aqueous solution of the analyte was injected into an on-line column containing glass beads and packed with silver chloride and deionized water was used as the carrier. The analyte dissolves the silver chloride and the dissolved silver complex is introduced to the nebulizer of the AAS. This method has proved to be sensitive, simple and precise. Detection limits of 1.0 × 10−7 M, 5.0×10−7 M and 5.0x10−6M were obtained for thiosulfate, cyanide and ammonia, respectively. The precision of the technique was 2.0%, 2.4% and 1.4% in case of thiosulfate, cyanide and ammonia, respectively. The effects of flow rate and sample volume on the FIA/AAS signals are presented.

Reverse flow injection analysis: Determination of trace amounts of metals using an on-line preconcentration technique

Determination of metal ion concentrations by reversed flow injection analysis using precipitation as a preconcentration technique is presented. The precipitate formed from the reaction of the cation and the anion, in a Tygon tube containing glass beads connected to the atomic absorption spectrophotometer, is dissolved by injection of a solution of a suitable dissolving reagent. The dissolving reagent dissolves the precipitate and the cation is transported to the atomic absorption spectrophotometer, yielding the signal. Three cations were tested to demonstrate the feasibility of the procedure: silver, calcium, and iron which were precipitated as silver chloride, calcium carbonate, and ferric hydroxide, respectively. Three dissolving reagents were investigated with silver chloride precipitate: ammonia, thiosulfate ion, and cyanide ion. Three other reagents were also used to dissolve ferric hydroxide precipitate: hydrochloric acid, phosphoric acid, and nitric acid. One reagent, hydrochloric acid, was used as a dissolving agent for calcium carbonate precipitate. Detection limits were 5 × 10−3, 4 × 10−2, and 8 × 10−4 ppm, respectively, for silver, iron, and calcium using thiosulfate, phosphoric acid, and hydrochloric acid as respective dissolving agents. The method could be applied easily to many routine analyses, such as water analysis due to its rapidity, precision, and small reagent consumption.

Discrete microsample injection into a gaseous carrier.

Discrete injection (DI) of mul- volume liquid samples into a continuous flow of air as carrier is demonstrated. Atomic-absorption (AA) detection is used. Calibration graphs for zinc, obtained by using the DI-AA-air carrier method have a slope 1.8 times that of graphs obtained by the flow-injection analysis (FIA)-AA-air carrier method. The DI-AA-air carrier signals are higher and sharper than the FIA-AA-water carrier signals, and even exceed the AA steady-state signals for the same zinc solutions, owing to improved nebulization/atomization. The air-carrier method is more rapid than the liquid-carrier method. Measurement rates of 600/hr are possible. The signals show precision comparable to that attainable with water as carrier. The method is particularly useful for flame or plasma detectors and is potentially useful with different gases or vapours as carriers, and for gas-liquid reactions in FIA.

Atomic Absorption Spectrometric Determination of Silver, Bromide and Iodide Ions in a Flow System Using an on-Line Preconcentration Technique

Abstract Silver, bromide and iodide ions are determined using a flow analysis system and precipitation as a reconcentration technique. The precipitate formed by reaction of cation and anion in a Tygon tube containing glass beads and connected to the atomic absorption spectrophotometer is dissolved by passing a solution of suitable dissolving agent. The dissolving agent dissolves the precipitate and the formed soluble complex is transported to the atomic absorption spectrophotometer, yielding a signal. The signal height is proportional to silver concentration which is in turn proportional to anion concentration. Silver was precipitated as AgCl and dissolved by S2O3=, CN− and NH3 solutions, bromide was precipitated as AgBr and dissolved by S2O3=and CN− solution and iodide was precipitated as AgI and dissolved by CN− solution. This method has proved to be sensitive, simple and precise. The lowest detection limit is 4.6×10−9M for silver when it is precipitated as AgCl and dissolved by s2O3 2− solution, 1×10−6...

FIA Potentiometric and Solvent Extraction Studies of Alkali Metal and Alkaline Earth Cation Complexation by bis(Tert-butylbenzo)-21-crown-7

Abstract A flow injection analysis study of the potentiometric selectivity of bis[4(5)-tert-butylbenzo]-21-crown-7 (D(tBB)21C7) for cesium over the other alkali metal cations and three alkaline earth cations has been conducted. A PVC matrix membrane containing D(tBB)21C7 as an ionophore was coated on the tip of a silver wire incorporated in a flow cell. No selectivity for cesium over rubidium and only low selectivity over potassium were noted. However, very high selectivities for cesium over sodium, lithium, strontium, calcium, and magnesium were observed. Selectivity of D(tBB)21C7 in the solvent extraction of alkali metal cations was determined by the picrate extraction method. The percent extraction into deuteriochloroform decreased in the order cesium, rubidium > potassium » sodium » lithium. Thus good agreement was observed between the responses of D(tBB)21C7 towards alkali metal cations in polymeric membrane electrodes and in solvent extraction.

Study of the relative effects of classes of solvents on the atomic absorption spectrophotometric determination of copper and zinc

Abstract The relative signals of copper and zinc in 15 different solvents were recorded. A more than sevenfold increase in the atomic absorption signal of copper and a more than sixfold increase in the signal of zinc, compared with the aqueous, were achieved when ketones were used. The order of the solvents having the same number of carbon atoms in enhancing the signal was as follows: ketones > secondary alcohols > primary alcohols > aldehydes. Within each group of solvents used, the atomic absorption signal decreases as the number of carbon atoms of the solvent increases for primary and secondary alcohols. A different trend is observed in ketones, when copper is analyzed, being maximum when butanone is used. Branching in the solvent skeleton appears to enhance the signal. The effect of aspiration rate on the signal was also studied for the different solvents.