Colorimetric Determination of Zinc and Copper with 2-Carboxy-2´-hydroxy-5´-sulfoformazylbenzene

Abstract

The purpose of this investigation was to develop a new colorimetric method for zinc and copper utilizing the compound 2-carboxy-2'-hydroxy-5'-sulfoformazylbenzene (Zincon). Both elements form a blue complex with this reagent. The zinc complex is stable over the pH range 8.5 to 9.5 while the copper complex is stable in the pH range 5.0 to 9.5. This difference in effect of pH permits the determination of zinc and copper in the presence of each other. Both complexes follow Beer's law over the concentration range 0.1 to 2.4 p.p.m. of the element. The sensiti\ity is 0.003 y per sq. cm. for both zinc and copper. A n ion exchange procedure is described for the separation of zinc from interfering ions.URISG an investigation of a numbcr 01 organic coni-D pounds, selected as possible analytical reagents because of their structure, the compound 2-carboxy-2'-hydroxy-5'-sulfoformazylbenzene ( I ) was observed to give a dark blue precipitate (blue solution at high dilution) with zinc and color reactions with copper, cobalt, and nickel. These observations prompted an investigation of this compound as a possible eolorimctric reagent for zinc and copper. . 4 brief discussion of the color formation with zinc has already been presented (13). 1Various colored nietal complexes with formazyl coinpounds have been described (1,4,(9)(10)(11). The only mention of compounds of this type as colorimetric reagents is in a note by i$'izinger (9).At present, the most widely uscd colorimetric method for zinc is the one employing dithizone which has a sensitivity of 0.0016 y per sq. cm. (7). The new method has a sensitivity of 0.003 -/ per sq. em. and replaces the complexing and extraction of the dithizone method with an ion exchange separation.Zincon is proposed as a short name for the compound 2-caiboxy-2'-hydroxy-5'-sulfoformazylbenzene. According to Chenizcal Abstracts' nomenclature the name is 0-( 2-1 ~(2-hydroxy-jsulfopheny1azo)-benz ylidene] hydrazino 1 benzoic acid. APPAR4TUS AND REAGENTS9 Beckman spectrophotometer, Model DU, operated at maximum sensitivity, was used for all absorbance measurements. The ultraviolet-sensitive phototube was employed at and below 625 mp. Matched 1.00-em. Corex cells were used. A Beckman pH meter, Model G, was employed for all pH measurements.Both the straight-and goose-neck type of ion exchange columns were used. The tube containing the resin was a 7-cm. length of borosilicate glass tubing, 5 mm. inside diameter, in both cases.

Adsorption Kinetics of Cobalt (II) Ions onto Alginate Beads from Aqueous Solutions

“…Cobalt concentrations were determined by UV-Vis spectrophotometry using the Zincon method at 600 nm wavelength [6]. A blue-colored complex is produced by mixing the samples solutions with an equimolar number of moles of Zincon (analytical grade, Sigma-Aldrich) in a buffer at pH 9.…”

Anionic mechanisms of zinc uptake across the human red cell membrane.

“…Uptake of zinc into red cells is sufficiently slow that buffering was unnecessary with Zn2+ in the micromolar range, but it was necessary in anion substitution experiments. There was no electrode available to check the Zn2+ concentrations in these solutions, so an optical technique was devised, using the dye 'Zincon' (1-(2-hydroxy-5-sulphophenyl)-3-phenyl-(2-carboxyphenyl)-formazan) (Rush & Yoe, 1954).…”

Frontiers of Formazans Chemistry: A Review

“…analytical reagents for metal ions. [269][270] Such substituted formazans react almost instantaneously with metal ion in organic solution even in cold. [271][272][273][274][275][276][277][278][279][280][281][282][283][284][285][286][287][288] Formazan compounds containing heterocyclic groups such as pyridine, thiazole or oxazole ring have been found to be useful photometric reagents with high selectivity and sensitivity.…”