Complex Formation of Sudan I with Cu(II) and Its Identification from Chilli Species

Abstract

The new chemical method for identifying and quantifying Sudan I ( 1-[(2,4-dimethylphenyl)azo]-2-naphthalenol ) from chilli species is devised to overcome the shortcoming with complex operation, longer analytical period of High performance liquid chromatography (HPLC) assay. Sudan I complexed with Cu 2+ leads to the shift of visible absorption wavelength from 478 nm to 526 nm. The major product is the Sudan I complex with general formula [Cu(Sudan I)]Cl. Bonds formed between Cu 2+ and nitrogen, oxygen lead to a larger conjugated system, which accounts for the bathochromic shift. The effect of several factors is investigated. The optimum amount of NaOH (0.1 mol·l -1 ) is 0.2 ml, and the appropriate reaction temperature is kept at 50℃. For the calibration of [Cu(Sudan I)]Cl, the limits of detection (3σ/m) is 0.446 mg·l -1 and apparent molar absorptivity is about 1.094×10 4 l·mol -1 cm -1 . The recoveries (spiked in hot chilli pepper at the levels of 5 mg·kg −1 ) range from 94% to 105%.

Oxidation and Complexation-Based Spectrophotometric Methods for Sensitive Determination of Tartrazine E102 in Some Commercial Food Samples

“…A reduction process, which corresponds to a spontaneous auto−reduction of the Cu 2+ into Cu + , was observed in cases of complexation of Cu 2+ ions with sudan(I) [31] and sudan(II) [32]. Because of these features of sudan dyes, tartrazine is considered as chromogenic chelating and redox sensitive agent reacting with copper(II) to form Cu + -Tz complex under optimum conditions.…”

A reliable method of quantification of trace copper in beverages with and without alcohol by spectrophotometry after cloud point extraction

“…36 A similar reduction process, which corresponds to a spontaneous auto-reduction of the Cu 2+ into Cu + , was also observed in the cases of complexation of Cu 2+ ions with the 6,6-dimethyl-2,2-bipyridine, 37 β-ketoimine calyx [4]arene, 38 and Sudan I. 39 In a later study, it is implied that the Cu(I)-Sudan I complex formed after prereduction of copper (II) in alkaline media at 50 o C is a positively charged metal-ligand complex with a 1:1 stoichiometric ratio by means of cyclic voltammetric, UV-visible and IR spectrophotometric studies. Because of these features of Sudan dyes, Sudan II is considered as a chromogenic chelating and redox sensitive agent in spectrophotometric detection of copper after preconcentration with CPE.…”

Voltammetric Determination of Sudan 1 in Food Samples Using Its Cu(II) Compound

“…Azo dyes can act as chelating reagents for metal ions. Sudan 1 can react with Cu(II) to form metal-Sudan complex ( 15 , 16 ), where alkaline solution was preferred for the investigation of interaction between Sudan 1 and copper. In our study, oxidation peak potentials of Sudan 1 at pH=5.0 and 10 (75% methanol) were 0.879 and 0.489 V, respectively.…”

“…Until now, several analytical methods have been developed for the analysis of Sudan 1, such as capillary liquid chromatograpy ( 9 ), Raman spectroscopy ( 10 ), UFLC-MS/MS ( 11 ), HPLC ( 12 – 14 ) and fluorescence spectroscopy ( 15 ), among which HPLC is preferred for determination of Sudan 1 ( 16 ). These techniques are sensitive but they require expensive instruments, time for pretreatment, experienced operators and large amount of organic solvents ( 17 ).…”