C. S. P. Iyer

Flow injection on-line preconcentration and flame atomic absorption spectrometric determination of iron, cobalt, nickel, manganese and zinc in sea-water

A rapid and sensitive flow injection analysis–atomic absorption spectrometric procedure is described for the determination of iron, cobalt, nickel, manganese and zinc based upon on-line preconcentration on a microcolumn packed with C18 material. These metals were complexed with 5,7-dichlorooxine from weakly acidic or neutral solutions in the flow system and adsorbed on the column. The preconcentrated elements were eluted with acidified methanol (pH ≥ 2) and injected directly into the nebulizer for atomization in an air–acetylene flame for measurement. The retention efficiency was better than 98%, resulting in sensitivity enhancement factors of 60, 80, 80, 80 and 60 for a 1 min preconcentration time for iron, cobalt, nickel, manganese and zinc, respectively. The respective detection limits were 4.0, 1.0, 1.0, 0.5 and 0.5 ppb, respectively. The throughput of samples was 30 h–1, with a loading time of 1 min. The method was applied to sea-water samples.

Determination of arsenic in sea water by sorbent extraction with hydride generation atomic absorption spectrometry

A rapid and sensitive sorbent extraction hydride generation-flow injection analysis atomic absorption spectrometric (HG-FIAS-AAS) method is described for the determination of As(III) and As(V) based upon online preconcentration on a microcolumn packed with activated alumina. In the present procedure these arsenicals are complexed with quinolin-8-ol-5-sulphonic acid from neutral solutions in the flow injection system and adsorbed on the column. The preconcentrated species are eluted with 10% HCl, mixed with 0.5% sodium borohydride and carried to the HG-FIAS cell with a carrier gas flow rate of 75 ml min(-1). The retention efficiency is found to be better than 98% with sensitivity enhancement of 12 and 10 for As(III) and As(V), respectively, for a 20 s preconcentration period. The respective detection limits are 0.05 and 2 ng ml(-1) for As(III) and As(V). The throughput of the samples is found to be 60 h(-1), with a loading time of 20 s. The method has been applied to sea water samples.

Differential pulse anodic stripping voltammetric determination of ziram (a dithiocarbamate fungicide).

A d.c. polarographic technique has been used previously for the determination of the pesticide, ziram, in aqueous samples, this paper reports differential pulse anodic stripping voltammetric determination of ziram zinc in rice samples using a static mercury drop electrode. The procedure developed distinguishes inorganic zinc and ziram zinc in sodium acetate-sodium chloride media. The procedure developed is suitable for the determination of concentrations as low as 10 ppb of ziram with a precision of 2.1% for five successive determinations of 150 ppb of ziram.

Ion-chromatographic determination of iodide in sea water with UV detection

A highly sensitive and selective ion-chromatographic procedure with UV detection at 227 nm was developed for the determination of trace amounts of iodide. The procedure utilizes 0.1M NaOH as eluent, which enables the determination of 1–100 μg I−1 I− with a precision of ca. 6%. 1000-fold amounts of other anions such as fluoride, chloride, phosphate, sulphate, bromide, nitrite and nitrate do not interfere. The method has been applied to determine iodide in sea water samples from the Indian coast.

Flow Injection On-Line Preconcentration and Flame AAS Determination of Copper, Cadmium and Lead in Marine Sediment Samples

Abstract A rapid and sensitive AAS method is described for the determination of copper, cadmium and lead based upon on-line preconcentration on a microcolumn packed with C18 material. These heavy metals are complexed with dithizone from ammonical solutions in the flow injection system and adsorbed on the column. The preconcentrated species were eluted with acidified methanol (pH ≥ 2) and injected directly into the nebulizer for atomization in an air-acetylene flame for measurement. The retention efficiency was better than 98% resulting in sensitivity enhancement factors of 80, 90 and 60 for 10 ml sample containing copper, cadmium and lead, respectively. The respective detection limits are 1.2, 0.6 and 3.0 ppb for copper, cadmium and lead. The throughput of the samples was found to be 30/h, with a loading time of 1 min. The method has been applied to the analysis of marine sediment samples.

Ultratrace determination of europium in high-purity lanthanum, praseodymium and dysprosium oxides by luminescence spectrometry

A luminescence spectrometric method was developed for the determination of ultra trace amounts of europium (down to 1 x 10(-13) M) in high purity lanthanum, praseodymium and dysprosium oxides. This is based on the enhanced luminescence of europium-thenoyltrifluoroacetone (TTA)-dibenzo-18-crown-6 (DBC)-Triton X-100 in the presence of terbium. The fluorescence intensity is linear with europium concentration in the range 1 x 10(-11) - 1 x 10(-6) M under the recommended conditions. The optimized procedure is successfully utilized for the determination of ultratrace amounts of europium in lanthanium, praseodymium and dysprosium oxides.

Spectrophotometric determination of ziram (dithiocarbamate fungicide) by thiocyanate and rhodamine 6G method

A sensitive spectrophotometric method has been developed for the determination of ziram in water, vegetables and grains. The method is based on the dissociation of dithiocarbamate complex of zinc with thiocyanate and rhodamine 6G at pH 4 to form a pink coloured complex that is stabilized by gelatin. The method is simple and Beers law is obeyed over the concentration range of 0.05-1 ppm of ziram. The method is free from interference of similar dithiocarbamate fungicides containing Mn(2+) and Fe(3+) ions.

Simultaneous determination of copper, mercury and lead by first-order derivative spectrophotometry using dithizone as reagent

A first-order derivative spectrophotometric method has been developed for the simultaneous determination of copper, mercury and lead at μg/L levels using dithizone as reagent. The procedure involves the simultaneous extraction of these elements by dithizone in chloroform from weakly alkaline solutions. Linear calibration curves were obtained in the ranges 0.5–10 (Cu), 1–10 (Hg) and 1–10 (Pb) μg present in 40 ml of aqueous phase with detection limits of 5 μg/L (Cu) and 20 μg/L (Hg and Pb). The R.S.D.s for 100 μg/L of copper, mercury and lead were 2.5, 2.6 and 3.1% respectively, for 5 determinations. The method is applicable for the determination of copper and lead in marine sediment samples with good precision and accuracy.

Mixed-Ligand Chelate Extraction of Trivalent Lanthanides and Actinides with 3-Phenyl-4-Benzoyl-5-Isoxazolone and Neutral Oxo-donors

Mixed-ligand chelate extraction of trivalent lanthanides such as La, Eu and Lu and a trivalent actinide, Am, into xylene with mixtures of 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) and bis-2-ethylhexyl sulphoxide (B2EHSO) or tributylphosphate (TBP) from Perchlorate solutions has been investigated. The results demonstrate that these trivalent metal ions are extracted as M(PBI)3 with HPBI alone, in the presence of B2EHSO as M(PBI)3 · 2 B2EHSO or in the presence of TBP as M(PBI)3 • 2 TBP. The equilibrium constants of the above species are found to increase monotonically with decreasing ionic radii of these metal ions. Although addition of an adduct-forming reagent to the chelate system can bring a decrease in the separation factor between Eu-Lu, it is notable that the addition of neutral oxo-donor improves the separation of the Eu-Am and La-Eu pairs. The thermodynamic parameters for the extraction of Eu(III) with HPBI alone as well as with mixtures of one of the neutral oxo-donors in xylene have also been calculated at 298 °K using the temperature coefficient method.

Mixed-ligand chelate extraction of trivalent lanthanides with 4,4,4-trifluoro-1-phenyl-1,3-butanedione and neutral oxo-donors

Mixed-ligand chelate extraction of trivalent lanthanides such as Nd(III), Eu(III) and Lu(III) into benzene with mixtures of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HBFA) and bis-2-ethylhexyl sulphoxide (B2EHSO) or triphenylphosphine oxide (TPhPO) from thiocyanate solutions was investigated. The results demonstrate that these metal ions are extracted as Ln(BFA)(3) with HBFA alone and in the presence of a neutral oxo-donor, B2EHSO or TPhPO(S), as Ln(BFA)(3).S and Ln(BFA)(3).2S. The equilibrium constants of the above species increase monotonically with decreasing ionic radii of these metals ions. The addition of a neutral donor to the metal chelate system not only enhances the extraction efficiency but also improves the selectivity among these trivalent lanthanides. Hence this mixed-ligand system may be useful for the extraction and separation of individual lanthanides and also for the separation of lanthanides as a group from other metal ions.