<abstract xmlns="http://www.w3.org/1999/xhtml">

<sec id="j_jvetres-2019-0044_s_005">
<h3>Introduction</h3>
<p>Some azo dyes, including Sudans I–IV and Para Red, are genotoxic and may be biotransformed to cancerogenic aromatic amines. They are banned as food and feed additives, but their presence has been detected in food. Aromatic amines are also considered potentially toxic. Online EC–MS is a promising tool to study the transformation mechanisms of xenobiotics such as azo dyes. The aim of the study was to investigate emulation of how azo dyes are enzymatically transformed to amines with EC–MS.</p></sec>
<sec id="j_jvetres-2019-0044_s_006">
<h3>Material and Methods</h3>
<p>The reduction reactions of five azo dyes (Sudans I–IV and Para Red) were conducted using a glassy carbon working electrode and 0.1% formic acid in acetonitrile. Reduction results were compared with the literature and <italic>in silico</italic> to select preliminary candidates for metabolites. The LC-MS/MS method was used to confirm results obtained by electrochemical reactor.</p></sec>
<sec id="j_jvetres-2019-0044_s_007">
<h3>Results</h3>
<p>A limited number of pre-selected compounds were confirmed as azo dyes metabolites – aniline for Sudan I, aniline and 4-aminoazobenzene for Sudan III, <italic>o</italic>-toluidine for Sudan IV, and 4-nitroaniline for Para Red. No metabolites were found for Sudan II.</p></sec>
<sec id="j_jvetres-2019-0044_s_008">
<h3>Conclusions</h3>
<p>Electrochemistry–mass spectrometry was successfully applied to azo dyes. This approach may be used to mimic the metabolism of azo dyes, and therefore predict products of biotransformation.</p></sec></abstract>

Introduction
Some azo dyes, including Sudans I–IV and Para Red, are genotoxic and may be biotransformed to cancerogenic aromatic amines. They are banned as food and feed additives, but their presence has been detected in food. Aromatic amines are also considered potentially toxic. Online EC–MS is a promising tool to study the transformation mechanisms of xenobiotics such as azo dyes. The aim of the study was to investigate emulation of how azo dyes are enzymatically transformed to amines with EC–MS.

Material and Methods
The reduction reactions of five azo dyes (Sudans I–IV and Para Red) were conducted using a glassy carbon working electrode and 0.1% formic acid in acetonitrile. Reduction results were compared with the literature and in silico to select preliminary candidates for metabolites. The LC-MS/MS method was used to confirm results obtained by electrochemical reactor.

Results
A limited number of pre-selected compounds were confirmed as azo dyes metabolites – aniline for Sudan I, aniline and 4-aminoazobenzene for Sudan III, o-toluidine for Sudan IV, and 4-nitroaniline for Para Red. No metabolites were found for Sudan II.

Conclusions
Electrochemistry–mass spectrometry was successfully applied to azo dyes. This approach may be used to mimic the metabolism of azo dyes, and therefore predict products of biotransformation.

Electrochemical reduction of azo dyes mimicking their biotransformation to more toxic products

Journal of Veterinary Research

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Introduction
Some azo dyes, including Sudans I–IV and Para Red, are genotoxic and may be biotransformed to cancerogenic aromatic amines. They are banned as...

Azo dye	Acquired m/z ratio
Sudan I	94	105			128			159		161		181	198
Sudan II		105		122		138	158		160			181			201
Sudan III	94		108		128		158		160		173	181	198
Sudan IV			108				158		160
Para Red			108					159	160					199

Analyte	Ionisation	Precursor	Products	Collision energy (eV)
1,2-dihydroxynaphthalene	positive	161.0	131.0/77.1	−33.0/−18.0
2,4-dimethyaniline	positive	122.6	108.1/80.1	−27.0/−21.0
1-amino-2-naphthol	positive	160.0	130.0/103.3	−13.0/−11.0
4-aminoazobenzene	positive	197.6	93.2/77.1	−25.0/−49.0
4-nitroaniline	negative	137.0	107.0/93.0	30.0/18.0
aniline	positive	94.2	77.1/51.0	−25.0/−30.0
o-toluidine	positive	108.0	91.1/65.1	−21.0/−27.0

Electrochemical reduction of azo dyes mimicking their biotransformation to more toxic products

Published Online: Sep 13, 2019

Page range: 433 - 438

Received: Jan 25, 2019

Accepted: Jul 02, 2019

DOI: https://doi.org/10.2478/jvetres-2019-0044

Keywords
azo dyes, red-ox, biomimetics, 3R, replacement

© 2019 K. Pietruk et al. published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

Signals (m/z ratio) acquired during the electrochemical step

Mass spectrometry parameters for analytes in scope of the LC–MS/MS method

Compounds selected as the candidates for metabolites of azo dyes selected from the literature and in silico data

Electrochemical reduction of azo dyes mimicking their biotransformation to more toxic products

Published Online: Sep 13, 2019

Page range: 433 - 438

Received: Jan 25, 2019

Accepted: Jul 02, 2019

DOI: https://doi.org/10.2478/jvetres-2019-0044

Keywordsazo dyes, red-ox, biomimetics, 3R, replacement

© 2019 K. Pietruk et al. published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

Signals (m/z ratio) acquired during the electrochemical step

Mass spectrometry parameters for analytes in scope of the LC–MS/MS method

Compounds selected as the candidates for metabolites of azo dyes selected from the literature and in silico data

Keywords
azo dyes, red-ox, biomimetics, 3R, replacement