K. Janardhan Reddy

Development of an extractive spectrophotometric method for the determination of copper(II) in leafy vegetable and pharmaceutical samples using pyridoxal-4-phenyl-3-thiosemicarbazone (PPT).

A highly sensitive extractive spectrophotometric method has been developed for the determination of copper(II) using pyridoxal-4-phenyl-3-thiosemicarbazone(PPT) as an analytical reagent. The PPT forms reddish brown species of copper(II) at a pH range of 3.0-5.5, and the complex was extracted into n-butanol. The Cu(II)-PPT complex shows maximum absorbance at 440 nm, with molar absorptivity and Sandells sensitivity being 2.16 x 10(4) L mol(-1) cm(-1) and 2.94 x 10(-3) microg cm(-2), respectively. The system obeys Beers law in the range of 0.2-5.0 mg/L. The regression coefficient of the Beers law straight line is 0.338, and the correlation coefficient is 0.96. The detection limit of the method is 0.0065 microg mL(-1). Most of the common metal ions generally found associated with copper do not interfere. The repeatability of the method was checked by finding the relative standard deviation. The developed method has been successfully employed for the determination of copper(II) in leafy vegetable and pharmaceutical samples. The method is evaluated by analyzing samples from the Bureau of Analyzed Samples (BCS 233, 266, 216/1, 207, and 179) and by intercomparison of experimental values using AAS.

Liquid‐Liquid Extraction of Tetravalent Hafnium from Acidic Chloride Solutions using Bis(2,4,4‐trimethylpentyl) Dithiophosphinic Acid (Cyanex 301)

Abstract Liquid‐liquid extraction studies of tetravalent hafnium from acidic chloride solutions have been carried out with bis(2,4,4‐trimethylpentyl) dithiophosphinic acid (Cyanex 301) as an extractant diluted in kerosene. Increase of acid concentration decreases the percentage extraction of metal. Plot of log D vs. log [HCl] gave a straight line with a negative slope of 2±0.1 indicating the exchange of two moles of hydrogen ions for every mole of Hf(IV) extractacted into the organic phase. Extraction of Hf(IV) increases with increase of extractant concentration. The plot of log D vs. log [HA] is linear with slope 2±0.1, indicating the association of two moles of extractant with the extracted metal species. The addition of sodium salts enhanced the percentage extraction of metal, and followed the order NaSCN>Na2SO4> NaNO3>NaCl. Stripping of metal from the loaded organic (LO) with HCl and H2SO4 indicated sulphuric acid as the best stripping agent. Increase of temperature increases the percentage extraction of metal indicating the process is endothermic. Regeneration and recycling capacity of Cyanex 301, extraction behavior of associated elements such as Zr(IV), Ti(IV), Al(III), Fe(III), and IR spectra of the Hf(IV)‐Cyanex 301 complex was studied.

Synergistic Extraction of Zirconium(IV) and Hafnium(IV) with 4‐Acylbis(1‐phenyl‐3‐methyl‐5‐pyrazolones) in the Presence of Neutral Organophosphorus Extractants

Abstract Various 4‐acylbis(1‐phenyl‐3‐methyl‐5‐pyrazolones), namely, 4‐adipoylbis(1‐phenyl‐3‐methyl‐5‐pyrazolone) (H2AdBP), 4‐sebacoylbis(1‐phenyl‐3‐methyl‐5‐pyrazolone) (H2SbBP) and 4‐dodecandioylbis(1‐phenyl‐3‐methyl‐5‐pyrazolone) (H2DdBP) were synthesized and examined with regard to the solvent extraction behavior of zirconium(IV) and hafnium(IV) from hydrochloric acid solutions. The results demonstrate that Zr(IV) and Hf(IV) extracted into chloroform with 4‐acylbis(1‐phenyl‐3‐methyl‐5‐pyrazolones) (H2X), as ZrO(HX)2 and HfO(HX)2, respectively. The equilibrium constants (K ex) of the extracted complexes follow an order H2SbBP>H2AdBP>H2DdBP. The synergistic extraction of Zr(IV) and Hf(IV) was also investigated with mixtures of H2SbBP and tri‐n‐butylphosphate (TBP), tri‐n‐octylphosphine oxide (TOPO), and trialkylphosphine oxide (TRPO), where the complexation strength follows the order TOPO>TRPO>TBP. The equilibrium constants of the synergistically extracted complexes have been correlated with the donor ability of the phosphoryl oxygen of the neutral organophosphorus extractants in terms of their 31P NMR chemical shifts and their basicity values (KH =nitric acid uptake constant).

Enhanced extraction and separation of zirconium(IV) and hafnium(IV) with 3-phenyl-4-benzoyl-5-isoxazolone in presence of various neutral organophosphorus extractants

Various 3-phenyl-4-aroyl-5-isoxazolones, namely, 3-phenyl-4-benzoyl-5-isoxazolone (HPBI), 3-phenyl-4-(4-fluorobenzoyl)-5-isoxazolone (HFBPI) and 3-phenyl-4-(4-toluoyl)-5-isoxazolone (HTPI) were synthesized and examined with regard to the solvent extraction behavior of Zr(IV) and Hf(IV) from hydrochloric acid solutions. The results demonstrated that Zr(IV) and Hf(IV) extracted into chloroform with 3-phenyl-4-aroyl-5-isoxazolones (HA), as ZrOA2 and HfOA2, respectively. The equilibrium constants of the extracted complexes follow an order HFBPI > HPBI > HTPI, which is in accordance with their pKa values. The synergistic extraction of Zr(IV) and Hf(IV) was also investigated with mixtures of HPBI and tri-n-octylphosphine oxide (TOPO), trialkylphosphine oxide (TRPO), and tri-n-butylphosphate (TBP), where the complexation strength follows the order TOPO > TRPO > TBP. The equilibrium constants of the synergistically extracted complexes have been correlated with the donor ability of phosphoryl oxygen of the neutral organophosphorus extractants in terms of their 31P NMR chemical shifts and their basicity values. The addition of neutral organophosphorus extractant to the metal chelate system not only enhances the extraction efficiency but also improves the selectivity between these metal ions.

Studies of zinc(II) in pharmaceutical and biological samples by extractive spectrophotometry: using pyridoxal-4-phenyl-3-thiosemicarbazone as chelating reagent

Piridoxal-4-fenil-3-tiossemicarbazona (PPT) e proposto como um novo reagente sensivel para a determinacao espectrofotometrica de zinco(II). PPT reage com zinco(II) no intervalo de pH entre 5,0 e 6,0, para formar um complexo colorido amarelo, o qual foi adequadamente extraido em n-butanol. A absorbância do complexo Zn(II)-PPT foi medida em diferentes intervalos de tempo, a 430 nm, para averiguar a estabilidade do complexo. Foi observado que o desenvolvimento da cor foi instantâneo e estavel por mais de 48 h. O sistema obedece a lei de Beer ate 6,0 µg mL-1 de zinco(II), com uma excelente linearidade em termos do valor do coeficiente de correlacao, de 0,999. A absortividade molar e sensitividade de Sandell da especie extraida e 1,6 X 104 L mol-1 cm-1 e 4,085 X 10-3 µg cm-2, respectivamente, a 430 nm. O limite de deteccao do metodo e 0,04 µg mL-1. Para avaliar a precisao do metodo, determinacoes foram efetuadas em diferentes concentracoes; o desvio padrao relativo nao excedeu 3,1%. A composicao do complexo de zinco(II) com PPT foi estudada pelos metodos de variacao continua de Job, da razao molar, metodo de Asmus e da razao da inclinacao. PPT tem sido empregado satisfatoriamente para a determinacao de zinco(II) isoladamente, ou na presenca de outros ions, normalmente associados ao zinco(II) em amostras farmaceuticas e biologicas. Varios materiais de referencia (NIST 1573, NBS 1572 e NIST SRM 8435) tem sido testados para a determinacao de zinco, com o proposito de avaliar a exatidao do presente metodo. Os resultados do metodo proposto sao concordantes com os obtidos por espectrometria de absorcao atomica com chama.