Anil K. Chakrabarti

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.

Solvent extraction and photometric determination of molybdenum (VI) with 2-aminobenzenethiol.

A new extractive photometric method is described for estimation of molybdenum with 2-aminobenzenethiol. The green complex in chloroform has its absorbance maximum at 700 nm and is stable for 2 hr when extracted from a solution of optimum pH range 1.4-2.8. The extraction is quantitative. The sensitivity is 0.0075 microg cm (2). Beers law is obeyed over the range 0.25-10 ppm with optimum range 0.5-4.5 ppm. The molar absorptivity is 7.08 x 10(4) 1.mole(-1). cm(-1). The overall stability constant is 2.0 x 10(8) at 25 +/- 0.1 degrees.

Selective extraction and photometric determination of trace vanadium with cinnamohydroxamic acid in MIBK and its application to steel and rock ore analysis.

A sensitive and selective photometric method for the trace determination of vanadium with cinnamohydroxamic acid extracted from 1.8 M HCl in methyl isobutyl ketone is described. The wine-red chelate formed under an optimum acidity of 1.3-2.6 M HCl absorbs with a maximum at 525 nm. Beers law is obeyed in the range 0-8 ppm of vanadium(V) and the optimum range of determination of vanadium is found to be 1-8 ppm. The molar absorptivity and Sandells sensitivity are 6.0 x 10(3) l mol(-1) cm(-1) and 0.0086 mug cm(-2) of vanadium(V) at 525 nm. The photometric determination of trace amounts of vanadium in materials such as alloys, minerals and rock ores is also reported. The solvent extraction methods are simple, rapid and highly selective with fluoride used as a masking agent for Fe and Ti. The standard deviations are minimal and the mean error is only 0.015%.

Extraction of vanadium(V) chelates with N-benzohydroxamic acid (BHA) and ammonium thiocyanate and its application in steel and rock analyses

A mixed-ligand complex of vanadium(V) with N-benzohydroxamic acid and thiocyanate formed at various acidities can be extracted into methyl isobutyl ketone, and used for photometric determination of trace amounts of vanadium in materials such as alloy steels and rocks. The absorption maximum of the violet mixed-ligand complex is at 535 nm. The values for the simple complex are 505 nm and molar absorptivity 7.4 x 10(3)l.mole(-1).cm(-1).

Spectrophotometric estimation of molybdenum with disodiom cis-1,2-dicyanoetfaylene-1,2-dithiolate

A rapid spectrophotometnc method is described for estimation of molybdenum by use of the molybdenum-dicyanoethytene dithiolate complex. The bright green complex has its absorption maximum at 665 nm and in 50% aqueous acetonitrilc is stable for several days at 3M hydrochloric add concentration, The estimation is more sélective if longer wavelengths and high acidity are used. Beers law is obeyed over the range 1-16 ppm molybdenum, optimum range 4-16 ppm. The overall formation constant Of the complex with metal to ligand ratio of 1:4 is 5 +/- 2 x 10(18). The molar absorptivity is 5.05 x 10(3) l.mole(-1).cm(-1).

2-(α-Pyridyl)-thioquinaldinamide (PTQA): a novel fluorimetric reagent in inorganic trace analysis. I: The nonextractive, nonquenching fluorescent method for the determination of chromium(VI)

A direct fluorimetric method for determining Cr(VI) in aqueous solutions is described. The nonfluorescent reagent 2-(α-pyridyl)-thioquinaldinamide (PTQA) and Cr(VI) interact to produce an intensely fluorescent species [λex(max) 360 nm; λem(max) 500 nm] showing constant and maximum fluorescence intensity in slightly acidic media (0.18N–1.08N H2SO4). The fluorescence attains its maximum value within 5 min and remains unchanged for 24 h. The system obeys Beers law from 2 ng/ml to 0.8 μg/ml of Cr(VI). Over sixty cations, anions and complexing agents are without any effect on the fluorimetric determination of 0.1 μg/ml of Cr(VI). The method has been tested with synthetic mixtures, steels, solutions containing both Cr(III) and Cr(VI), and environmental samples.

Determination of trace amounts of vanadium: A ternary extraction and photometric method using N-salicylhydroxamic acid and thiocyanate

SummaryA new extractive photometric method has been developed for a binary complex of vanadium(V) with salicylhydroxamic acid, a bluish-violet complex at pH 3.0 and a violet ternary complex system with ammonium thiocyanate at pH 0.95, both complex species being extractable into methylisobutylketone. The violet complex absorbs at 540 nm and is stable up to 48 hr at 23–25°. The sensitivity is 0.0061μg V(V) cm−2. The method has been applied for the analysis of ores and alloy steels containing vanadium.ZusammenfassungVanadin (V) bildet mit Salicylhydroxamsäure einen binären, blauvioletten Komplex bei pH 3,0 und einen ternären, violetten Komplex mit Ammoniumrhodanid bei pH 0,95. Beide Komplexverbindungen sind mit Methylisobutylketon extrahierbar. Die violette Komplexverbindung hat bei 540 nm ihr Absorptionsmaximum und ist bei 23–25° C bis zu 48 Stunden stabil. Die Empfindlichkeit der Reaktion beträgt 0,0061μg V(V)·cm−2. Die Reaktion wurde für die Analyse von Erzen und Stahllegierungen verwendet.

2-(α-Pyridyl)thioquinaldinamide: a spectrofluorimetric reagent in inorganic trace analysis. Part III. Determination of manganese in industrial and environmental samples

A highly sensitive, fairly selective, direct spectrofluorimetric method for the determination of ultratrace levels of manganese is described. The method is based on the selective oxidation of the very weakly fluorescent 2-(α-pyridyl)thioquinaldinamide by manganese(VII) to give an intensely fluorescent oxidation product (λex.= 360 nm; λem.= 500 nm). Constant and maximum fluorescence intensities were observed over a wide range of acidity, viz., 0.03–0.83 M H3PO4, for periods of between 5 min and 72 h. A linear fluorescence-concentration dependence was observed between 10–5 and 0.7 p.p.m. of manganese. More than 60 cations and anions, present in a large excess, did not interfere. The method was applied successfully to a number of standard samples (alloys, steels, sludges and sediments), environmental waters (inland and surface) and complex synthetic mixtures. The method is very simple and requires no solvent extraction or pre-concentration steps.

Spectrophotometric determination of tungsten with disodium cis-l,2-dlcyanoethylene d1thiolate

Abstract A new spectrophotometric method for determination of tungsten with disodium cis-1.2-dicyanoethylene dithiolate as reagent is described. Tungsten forms a red-violet complex in 50% water-acctonitrile solution and has an absorption maximum at 570 nm. The complex is stable in 1–3 M acid for several days. The colour reaction has a sensitivity of 0.033 μg W cm−2. The tungsten complex obeys Beers law over the range 1–20 p.p.m. with an optimal range of 6–20 p.p.m. ; the molar absorptivity is 5520. The stability constant, K of the complex was found to be 2.344·1018.