Improved quantification of mass fraction of colorants in textile by high-performance liquid chromatography coupled with tandem mass spectrometric detector

The DIN 54231:2005 and ISO 16373-2:2014 standard methods recommend the application of HPLC separations and detection by either diode array (HPLC-DAD) or mass spectrometric detectors (LC-MS or LC-MS/MS) for the evaluation of mass concentration of colorants (y >= 1.0 mu g/mL) in textile sample extracts. The present investigation reports for the first time that the LC-MS/MS method has low accuracy for most of textile colorants if the recommended calibration range of the standard methods (1.0 mu g/mL to 20 mu g/mL or 5.0 mu g/mL to 50 mu g/mL) is used. The present paper reports that the quantification of mass concentration of colorants in textile extract by the LC-MS/MS method does not match with the quantification by the HPLC-DAD method, which has fit-for-purpose linearity and accuracy in the ranges mentioned above. A systematic study of the MS/MS method was performed to prepare real and spiked samples for quantifying mass concentration of colorants (y <= 1.0 mu g/mL) in textile extracts for compounds having LOQ <= 1.0 mg/kg. The results obtained could match with the quantification by the HPLC-DAD method. A lower calibration range was needed to quantify the dyes in the diluted sample extracts in which the background matrix constituents had lower influence on the quantification. Significantly, the LC-MS/MS method utilizing sample dilution and lower calibration range was validated and then used to proficiency test (PT) samples with success. Furthermore, the evaluation of mass fraction of disperse yellow 3 in PT sample by exact-matching double isotope dilution mass spectrometry was also performed. The strategy presented herein to quantify a wide range of colorants using the LC-MS/MS method could improve the reproducibility of analyzing colorants using protocols of standard recommendations.