Abstract
A spectrophometric method for the determination of Cr(III) with 4-(2- thiazolylazo)-resorcinol was developed. Cr(III) slowly forms a red complex with TAR at pH 5.7. Irradiating the reacting mixture with microwave energy can accelerate the complex formation. The absorbance reached its maximum with 5 min of irradiation and remained stable, at least, for 24 h. N-cetyl-N,N,N-trimethylammonium bromide (CTAB) was used for increasing the sensitivity and solubility of the system. The method allowed the determination of chromium ranging from 0.050 to 3.0 mg mL-1 (9.62 x 10-7 to 5.77 x 10-5 mol L-1) with a molar absorptivity of 2.73x104 L-1 mol-1 cm-1 and a detection limit of 17 ng mL-1 (3.3 x 10-7 mol L-1) at 545 nm. The selectivity was improved by using EDTA and citrate as masking agents. Fe(III) interferes and must be extracted previously, if present in the sample. The proposed method has been successfully applied to the determination of chromium in steel. The precision (R.S.D. < 2%) and accuracy were satisfactory.
Highlights
The most important application of chromium in the metallurgic industry is its use as an alloying element in steels
The absorbance reached its maximum in 4 min and remained stable, at least for 24 h, when the chromium(III)-TAR complex was formed with the aid of microwave energy
The results showed that CTAB must be present in the system in a concentration of at least 2.5 x 10-3 mol L-1 to avoid precipitation
Summary
The most important application of chromium in the metallurgic industry is its use as an alloying element in steels In these materials, chromium contributes to increase the hardness, tempering and oxidation resistance.[1]. Very few methods for chromium determination are based on the complex formation with Cr(III) in aqueous solution.[2] spectrophometric determination of chromium(III) invariably involves heating the reactants with reflux. This is probably due to the slow reactions of Thiazole azo compounds have attracted much attention, as they are sensitive chromogenic reagents in addition to being important complexing agents. 1-(2-thiazolylazo)-2-napthol (TAN)[8] and 4-(2-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
