Bijoli Kanti Pal

Liquid%liquid extraction of a rhenium%thiocyanate complex with hexamethylphosphoramide and direct spectrophotometric determination in the organic phase

A sensitive and selective method for estimation of trace molybdenum with fairly common reagents has been developed. The Mo-thiocyanate complex is extracted with hexamethyl phosphortriamide and chloroform from 0.75-1.5M hydrochloric acid. The molar absorptivity is 1.76 x 10(4) 1.mole(-1).cm(-1). The system obeys Beers law at 460nm over the molybdenum concentration range 0.75-5ppm. The method is simple, rapid, and requires no additional reducing agent. It is generally free from interference by most of the metals commonly associated with molybdenum, including rhenium. Molybdenum in alloy steel has been successfully determined.

A nonextractive quenchofluorimetric method for the determination of palladium(II) at μg/L levels using bathophenanthroline

Abstract. A very simple ultra-sensitive and selective quenchofluorimetric method for the determination of Pd(II) is described. The method is based on the quenching action by Pd(II) upon the native fluorescence of bathophenanthroline (4,7-diphenyl-1,10-phenanthroline) solution (λex (max)=291 nm; λem (max)= 451 nm) in the optimum acidity range 0.025 M–0.20 M H2SO4 at room temperature (25±5 °C). The fluorescence quenching is collinear in the range of 1–400 μg L−1 palladium(II). The developed method is very precise and accurate [S.D.=±1.2 μg L−1 Pd(II) and R.S.D.=2.5% for 11 replicate determinations of 50 μg L−1 Pd(II)]. Over fifty inorganic ions, including platinum group metals and common complexing agents do not interfere. It is a one-step process that requires no extra clean up. The developed method has been successfully tested for synthetic mixtures of various base metals and platinum group metals, synthetic mixtures corresponding to osmiridium ore, Certified Reference Materials in spiked conditions and rock samples.

2-(α-pyridyl)thioquinaldinamide: a novel fluorimetric reagent in inorganic trace analysis. : Part 2. A simple selective determination of selenium(IV) at Ultratrace Levels

Abstract The very sensitive fluorimetric determination of selenium(IV) is based on its oxidation of the non-fluorescent 2-(α-pyridyl)thioquinaldinamide in slightly acidic solution (0.05–0.15 M sulphuric acid). The excitation and emission wavelengths are 350 nm and 500 nm, respectively. Linear calibration graphs are obtained for different ranges of selenium concentration between 0.01 ng ml−1 and 0.5 μg ml−1. Over sixty ions either do not interfere or can be masked in the determination of 1 ng ml−1 Se(IV). The method is applied successfully to various synthetic mixtures and to a native sulphur sample. The reaction is fast and the fluorescent system is stable for 24 hours.

Spectrofluorimetric determination of molybdenum in some real and environmental samples

A very simple, highly-sensitive and selective quenchofluorimetric method for the rapid determination of molybdenum(VI) in aqueous media is described. The method is based on the instantaneous quenching action by the metal-ion upon the native fluorescence of bathophenanthrolinedisulphonate (4,7-diphenyl-1,10-phenanthrolinedisulphonate) solution [lambda(ex) (max) 288 nm; lambda(em) (max) 444.8 nm] in the optimum pH-range of 3.0-3.7 at room temperature (25 +/- 5 degrees ). The fluorescence quenching is co-linear in the range of 0.01-1.0 ppm molybdenum. Large excesses of over 50 cations, anions and some common complexing agents were found to have no interference. Cu, Ni, Co, Fe and V can be tolerated only up to the corresponding amount of molybdenum. Interference from greater amounts can however be removed by a one-step ion-exchange separation process. The developed method was successfully tested over several standard alloys, synthetic mixtures of various compositions, factory effluents and in spiked environmental waters.

Sensitive spectrofluorimetric determination of ruthenium at nanotrace levels using 2-(α-pyridyl) thioquinaldinamide [PTQA]

A new spectrofluorimetric method for the determination of ruthenium with nonfluorescent 2-(alpha-pyridyl) thioquinaldinamide (PTQA) is described. The oxidative reaction of Ru(III) upon PTQA gives oxidised fluorescent product (lambda(ex(max))=347 nm; lambda(em(max))=486 nm). The sensitivity of the fluorescence reaction between ruthenium and PTQA is greatly increased in the presence of Fe (III). The reaction is carried out in the acidity range 0.01-0.075 M H(2)SO(4). The influence of reaction variables is discussed. The range of linearity is 1-400 microg l(-1) Ru(III). The standard deviation and relative standard deviation of the developed method are +/-1.210 microg l(-1) Ru (III) and 2.4%, respectively (for 11 replicate determinations of 50 microg l(-1) Ru (III)). The effect of interferences from other metal ions, anions and complexing agents was studied; the masking action is discussed. The developed method has been successfully tested over synthetic mixtures of various base metals and platinum group metals, synthetic mixtures corresponding to osmiridium, certified reference materials in spiked conditions and rock samples.

Chromotropic acid as fluorogenic reagent. I. Fluorimetric determination of beryllium

A highly sensitive and almost specific fluorimetric method has been developed for rapid determination of beryllium at ng/ml and sub-ng/ml levels with chromotropic acid as reagent at pH 4.8–6.0. The fluorescence intensity λex = 362 nm, λem = 387 nm) is stable for 24 h. The calibration graph is linear over the range 0.1–60 ng/ml beryllium; a 1 ∶ 1 complex is formed. Over sixty anions and cations, and some complexing agents such as EDTA, oxalate, tartrate, ascorbic acid, thiourea, phthalate, citrate, S2O32−, SCN− and salicylate do not interfere even when present in large excess. The method has been applied successfully for the determination of beryllium in ores, alloys, steels, environmental waters and in biological samples. The method is virtually specific and requires no preconcentration or clean-up steps.

Separation of niobium and tantalum with benzo- and phenylacetylhydroxamic acids

Abstract Benzohydroxamic acid (I) or phenylacetylhydroxamic acid (II) is suggested for the quantitative separation of tantalum from niobium in an oxalate solution. The tantalum precipitate must be ignited for weighing; niobium is determined in the filtrate with another reagent. The pH range for complete separation is 4.0–6.4 for I and 4.5–6.2 for II. Single precipitation is satistactory for Nb: Ta ratios of 18 : 1 to 1 : 20 for I, and 8 : 1 to 1 : 23 for II. Titanium, zirconium, tartrate, citrate and a large excess of oxalate interfere.

Nonextractive spectrofluorimetric determination of aluminium in real, environmental and biological samples using chromotropic acid

An ultra-sensitive and highly selective nonextractive fluorimetric method is presented for the rapid determination of aluminium at nano-trace levels using chromotropic acid as a fluorimetric reagent [lambda(ex) = 360 nm and lambda(em) = 390 nm] in the pH range of 4.1-4.7. The fluorescence intensity of the metal chelate (2:3 complex) reaches a constant value within 1/2 hr and remains unchanged for over 48 hr. The fluorescence intensity aluminium concentration calibration curve is collinear between 1 and 300 ng/ml of Al. A constant fluorescence intensity is obtained over a wide range (1:50-1:1500) of Al:reagent molar concentrations. Large excesses of over 60 cations, anions and complexing agents (like tartrate, oxalate, phosphate, thio-urea, SCN(-), etc.) do not interfere in the Al determination. The developed method was successfully used in assaying aluminium in several standard reference materials (Al-bronze, brass, stainless steel) as well as in some environmental and biological samples. The method is very precise and accurate (S.D = +/-0.001 on 10 ng/ml; 11 determinations).

Gravimetric separation of titanium and zirconium from Niobium with Phenylacetylhydroxamic acid

Phenylacetylhydroxamic acid is used to separate titanium and zirconium from niobium in an oxalate medium at pH 6.5--7.5 in presence of ammonium chloride at room temperature. The method is accurate when the ratio of (TiO/sub 2/ + ZrO/ sub 2/): Nb/sub 2/O/sub 5/ is 10: 1 to 1: 1; when the niobium concentration is higher, reprecipitation is necessary. Tantalum, citrate, tartrate, lactic acid, EDTA, and a large excess of oxalate interfere. (auth)

Separation of niobium and tantalum by N-benzoyl-N-phenylhydroxylamine

The pH range 3.5 to 6.5 for the complete precipitation of niobium and a pH below 1.5 for the precipitation of tantalum in separation and gravimetric analysis using N-benzoyl-N-phenylhydroxylamine are examined. Theyare verified to be correct. There is no possibility of the precipitation of hydrous oxide, even when the niobium or the tantalum solution is made ammonical in these pH ranges. (N.W.R.)