Determination of eight fungicides in tanned leather by liquid chromatography with mass spectrometry and with diode array spectrophotometric detection

Abstract

Tanned leather needs to be protected against microorganisms which is why various biocides are currently used. To evaluate the effectiveness of leather treatment and to control the concentrations of potentially harmful compounds, simple and reliable analytical procedures are required. In this work, two such procedures are proposed for the determination of eight fungicides in leather, consisting of acetonitrile extraction and liquid chromatography with electrospray ionization – mass spectrometry or diode array spectrophotometric detection (HPLC-ESI-ITMS and HPLC-DAD, respectively). According to the elution order, the analyzed compounds were: 2-bromo-2-nitropropane-1,3-diol (BNPD), methyl 1H-benzimidazol-2-yl-carbamate (CBZ), 2-mercaptobenzothiazole (MBT), 4-chloro-3-methylphenol (PCMC), 2-phenylphenol (OPP), 2-(thiocyanomethylthio)-benzothiazole (TCMTB), 2-n-octyl-4-isothiazolin-3-one (OIT), 1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1,2,4-triazole (PRO) and 2,5-diphenyloxazole (PPO) as an internal standard. For accuracy testing, three-point standard addition was performed with the percentage recoveries in the ranges 75.0–115% and 91.9–117% for HPLC-ESI-ITMS and HPLC-DAD, respectively. The chemical composition of acetonitrile leather extract had a minor effect on the IS-normalized signal magnitude within the calibration range of each fungicide, as demonstrated by signal suppression/enhancement factors of 84.1–112% and 93.6–102%. The detection power of HPLC-ESI-ITMS was better for all compounds compared to that of HPLC-DAD; however, in real-world samples both procedures consistently detected and quantified individual fungicides. The averaged quantification difference between the two procedures was evaluated yielding σ_N% values in the range 7.28–16.4%. It is concluded that the two procedures can be used interchangeably for the quantification of eight fungicides declared for use in the leather industry and that PPO is suitable as an internal standard in both.