José L. Gómez Ariza

N-oxalylamine(salicylaldehyde hydrazone) as an analytical fluorimetric reagent for the determination of nanogram amounts of aluminium

The synthesis, characteristics and analytical applications of N-oxalylamine(salicylaldehyde hydrazone), OSH, are described. The Al(III)-OSH system was studied and a spectrofluorimetric method is proposed for the determination of Al in a medium of water-dimethylformamide (1 + 1) at pH 3.7. Under these conditions the complex has excitation and emission maxima at 387 and 474 nm, respectively. The detection limit is 5 p.p.b. and Al can be determined up to 160 p.p.b. Interferences were evaluated; Ga(III), In(III), Sb(III) and Zr(IV) gave the greatest perturbations. The method has been applied to the determination of aluminium in mineral waters.

Asymmetric derivatives of carbohydrazide and thiocarbohydrazide as analytical reagents.

The synthesis and analytical properties of two asymmetric derivatives of carbohydrazide and thiocarbohydrazide with pyridine and phenol have been studied. The compounds tested are 1-(2-pyridylmethylideneamino)-3-(salicylideneamino)urea and 1-(2-pyridylmethylideneamino)-3-(salicylideneamino) thiourea. The analytical utility of these reagents is outlined. A spectrophotometric method for determining the formation constants of the complexes is described.

Spectrophotometric determination of palladium in catalysts and carbenicillin with 1-(2-pyridylmethylidene)-5-(salicylidene)-thiocarbohydrazone

A selective and sensitive method is described for the spectrophotometric determination of palladium using 1-(2-pyridylmethylidene)-5-(salicylidene)thiocarbohydrazone reagent. The orange complex is formed in pH 8.3 EDTA-bicine-borate buffer in a medium containing 32%V/V dimethylformamide, and the absorbance is measured at 505 nm. The molar absorptivity is 16 500 l mol–1 cm–1, and in the determination of 0.75 µg ml–1 of palladium the relative standard deviation is about 2%. The effect of interferences was studied and the selectivity of the reaction was enhanced by using appropriate masking agents. The method was applied to the determination of palladium in synthetic mixtures, hydrogenation catalysts and carbenicillin (semi-synthetic penicillin).

N,N′-oxalylbis(salicylaldehyde hydrazone) as an analytical spectrophotometric and fluorimetric reagent. Part I. Study of the metal reactivity and application to the determination of aluminium

The synthesis, characteristics and analytical applications of N,N,′-oxalylbis(salicylaldehyde hydrazone)(OBSH) are described. The reaction between aluminium and OBSH was studied both spectrophotometrically and spectrofluorimetrically, and methods for the determination of the ion are proposed on the basis of the yellow chelate formed. The spectrophotometric procedure is sensitive (Iµ390= 14.5 × 103 l mol–1 cm–1) and the colour is developed at pH 4.7 in a solution containing 60%V/V of dimethylformamide. The fluorimetric method permits the determination of 0–200 p.p.b. of aluminium in chloroacetic-chloroacetate medium (λex.= 390 nm, λem.= 475 nm). Interferences were evaluated for both procedures and indicated that perturbation from transition metal ions such as Pd(II), Ga(III), In(III), Zr(IV), V(V) and Fe(III) may occur although some of them can be eliminated with masking agents or an ion-exchange resin. The methods have been applied to the determination of aluminium in different real samples.

Spectrophotometric determination of indium in nickel alloys and zinc ores with 1-(2-pyridylmethylideneamine)-3-(salicylideneamine)thiourea.

A sensitive method for the spectrophotometric determination of indium with 1-(2-pyridylmethylideneamine)-3-(salicylideneamine)thiourea is proposed. A yellow complex is formed at pH 4.5 (succinate buffer) in a medium containing 40% dimethylformamide, and the absorbance is measured at 415 nm. The molar absorptivity is 6.2 x 10(4)l.mole(-1).cm(-1). The relative standard deviation of the procedure is 1.5%. The method has been applied to determination of indium in a nickel alloy and three zinc ores, with prior isolation of indium by co-precipitation with ammonia and extraction into n-butyl acetate from 5M hydrobromic acid.

Determination of nanogram amounts of aluminium and indium with 4,4′-oxalylbis(hydrazonomethyl)diresorcinol

Fluorimetric determinations of aluminium and indium, based on the formation of fluorescence complexes between AlIII or InIII and 4,4′-oxalylbis(hydrazonomethyl)diresorcinol are proposed. With excitation at 415 nm, aluminium and indium chelates have emission maxima at 470 and 475 nm, respectively; the respective detection limits are 0.8 and 2.6 ng ml–1. Determinations of aluminium in tap waters and indium in nickel alloy and Zn-Sn-Cu-Pb ore were carried out.

Fluorimetric determination of gallium in a nickel alloy and aluminium with N-oxalylamine(salicylaldehyde hydrazone).

A fluorimetric determination of gallium, based on the formation of the fluorescent chelate with N-oxalylamine(salicylaldehyde hydrazone) (OSH)-Ga(III), is proposed. The complex has excitation and emission maxima at 395 and 475 nm, respectively. The detection limit is 3 ng/ml and Ga can be determined up to 277 ng/ml. The method has been applied to the determination of gallium in a nickel alloy and aluminium. Extraction with n-butyl acetate from 6M hydrochloric acid medium has been used to separate Ga from the interfering elements in the alloys.

Spectrophotometric determination of zinc with 1-[Di(2-pyridyl)methylene)-5-salicylidenethiocarbonohydrazide

The synthesis, physico-chemical properties and analytical applications of 1-[di(2-pyridyl) methylene]-5-salicylidenethiocarbonohydrazide (DPST) are described. The reaction between zinc and DPST has been studied spectrophotometrically and a method for the determination of this ion is proposed based on the yellow chelate formed. The spectrophotometric procedure is sensitive, with a molar absorptivity at 417 nm of 60 500 | mol–1 cm–1(pH 5.6), in a solution containing 30%V/V of dimethylformamide. The conditions for optimum colour development and the nature of the reaction and interferences were studied. The method was applied to the determination of zinc in potable waters and pharmaceutical preparations.

Evaluation of biacetyl(2-pyridyl)hydrazone thiosemicarbazone as spectrophotometric analytical reagent

SummaryThe synthesis and analytical properties of biacetyl(2-pyridyl)hydrazone thiosemicarbazone (BPHT) have been studied. A spectrophotometric method has been used to determine the protonation constants of the reagent and a Spectrophotometric survey of the reactions of various cations with BPHT has been made. BPHT gives coloured complexes with various cations such as Ni(II), Co(II), Fe(II), Cu(II), Pd(II), Zn(II), Cd(II), In(III). The sensitivity has been compared with that of other analogous reagents of the biacetyl type.

Spectrophotometric determination of cobalt with cyclohexane-1, 2-dione bis(2-pyridylhydrazone)

A method for the spectrophotometric determination of cobalt with cyclohexane-1,2-dione bis(2-pyridylhydrazone) is described. The pink complex is formed at an initial pH of 4–5 in a medium containing 12%V/V dimethylformamide, and the absorbance is measured at 525 nm at a final perchloric acid concentration of ca. 0.5 M. The molar absorbtivity is 13700 l mol–1 cm–1. The method has been applied to the determination of cobalt in alloys and minerals.