Sudan III (Sudan Red III)

An ultrasensitive and selective fluorescence assay for Sudan I and III against the influence of Sudan II and IV

We report on an ultrasensitive and selective fluorescence assay for Sudan I and III against the influence of Sudan II and IV based on ligand exchange mechanism. Calcein as a fluorescence indicator and Sudan I-IV as model analytes were employed to investigate the analytical feature of this assay platform. Results show that the fluorescence of calcein can be efficiently quenched by Cu(II). When the ligand exchange reaction proceeds, calcein is deprived of Cu(II) by Sudan I and III, resulting in the fluorescence recovery of calcein. However, the ligand exchange reaction does not happen in the presence of Sudan II or IV due to the 2-methyl steric effects, which is favorable for selective determination of Sudan I and III against the influence of Sudan II and IV. It was found that the fluorescence enhancement efficiency (FEE) against the concentration of Sudan (c(Sudan), nmol L??) shows a linear relationship. The calibration equations are FEE(Sudan I)=0.0032 c(Sudan I)-0.02613, and FEE(Sudan III)=0.0033 c(Sudan III)-0.02467 over the corresponding linear range of 11.25-2078.29 and 9.44-1035.78 nmol L?? with the correlation coefficients (R(2)) of 0.9984 and 0.9955, respectively. And the detection limits (3σ/slope) are calculated to be 211.3 and 208.5 pmol L?? for Sudan I and III, respectively, showing ultralow detection limit. The Sudan dye in a commercial chilli powder sample was assayed with satisfactory results.

UPLC-ESI-MS/MS analysis of Sudan dyes and Para Red in food

An analytical method for the simultaneous determination of Sudan dyes (Sudan Red G, Sudan I, Sudan II, Sudan III, Sudan Red 7B and Sudan IV) and Para Red in food by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-ESI-MS/MS) was developed. Samples were extracted with acetonitrile, and water added into the extract. The supernatant was analysed by UPLC-MS/MS after refrigeration and centrifugation. The sample was separated on an Acquity BEH C(18) column, and detected by MS/MS with the multiple reaction monitoring mode. Matrix calibration was used for quantitative testing of the method. The linear matrix calibrations of Sudan dyes and Para Red were 2-50 and 10-250 ng g(-1), respectively, and the regression coefficients were >0.9945. The recoveries were 83.4-112.3% with good coefficients of variation of 2.0-10.8%. The limits of detection were between 0.3 and 1.4 ng g(-1) for the six Sudan dyes, and between 3.7 and 6.0 ng g(-1) for Para Red. The limits of quantification were between 0.9 and 4.8 ng g(-1) for the six Sudan dyes, and between 12.2 and 19.8 ng g(-1) for Para Red.

Assay of the set of all Sudan azodye (I, II, III, IV, and Para-Red) contaminating agents by liquid chromatography-tandem mass spectrometry and isotope dilution methodology

A high-throughput mass spectrometric method is presented for the simultaneous detection of Sudan I, II, III, IV, and Para-Red azodyes in foodstuff. The method is based on the use of deuterium-labeled internal standards and atmospheric pressure chemical ionization (APCI) in a triple-quadrupole instrument. The gas-phase breakdown pattern of each labeled and unlabeled analogue displays the naphthoic moiety as a common fragment. The search for the parents of this common species (parent ion scans) allows, by flow injection and in a single run, the evaluation of the presence of each polluting species spiked in typical foodstuffs. A detailed assay of each azodye was performed by LC-APCI and isotope dilution method, through the multiple reaction monitoring approach, using deuterium-labeled internal standards. Sudan dyes can be quantified above the threshold of 10 ppb except for Sudan Para-Red, for which the limit of quantification was 20 ppb, likely due to the different ionization efficiency.

Determination of sudan dyes in red wine and fruit juice using ionic liquid-based liquid-liquid microextraction and high-performance liquid chromatography

The liquid-liquid microextraction (LLME) was developed for extracting sudan dyes from red wine and fruit juice. Room temperature ionic liquid was used as the extraction solvent. The target analytes were determined by high-performance liquid chromatography. The extraction parameters were optimized. The optimal conditions are as follows: volume of [C(6)MIM][PF(6)] 50 μL; the extraction time 10 min; pH value of the sample solution 7.0; NaCl concentration in sample solution 5%. The extraction recoveries for the analytes in red wine and fruit samples are 86.79-108.28 and 68.54-85.66%, whereas RSDs are 1.42-5.12 and 1.43-6.19%, respectively. The limits of detection and quantification were 0.428 and 1.426 ng/mL for sudan I, 0.938 and 3.127 ng/mL for sudan II, 1.334 and 4.445 ng/mL for sudan III, 1.454 and 4.846 ng/mL for sudan IV, respectively. Compared with conventional liquid-liquid extraction (CLLE) and ultrasonic extraction (UE), when LLME was applied, the sample amount was less (LLME: 4 mL; CLLE: 10 mL; UE: 10 mL), the extraction time was shorter (LLME: 15 min; CLLE: 110 min; UE: 50 min) and the extraction solvent amount was less (LLME: 0.05 mL IL; CLLE: 15 mL hexane; UE: 20 mL hexane). The proposed method offers a simple, rapid and efficient sample preparation for determining sudan dyes in red wine and fruit juice samples.

Low-level detections of Sudan I, II, III and IV in spices and Chili-containing foodstuffs using UPLC-ESI-MS/MS

Sudan dyes are red, synthetic azo dyes that are not allowed in foodstuffs in the European Union (Council Directive 94/36/EC). However, subppm levels of Sudan dye in spices are regularly reported, and it is assumed that these appearances are due to cross-contamination. In this paper, we present a newly developed fast and sensitive method for the quantification of Sudan I, II, III, and IV, using liquid-liquid extraction and UPLC-MS/MS analysis, and giving quantification limits ranging from 2.5 to 200 μg/kg. The method was applied to 21 samples, and 17 of them contained Sudan dye at low concentrations (3.3-8 709 μg/kg). Interestingly, it was observed that the distribution of Sudan dye in the sample is not homogeneous, which may lead to false negatives or to overestimations of the concentration, and that the pretreatment (blending or not) of the sample seriously influences the final result of the analysis.