Degradation studies of CI Reactive Blue 19 on biodegraded cellulosic fabrics via liquid chromatography‐photodiode array detection coupled to high resolution mass spectrometry

Abstract

When textile substrates biodegrade in landfills, the fate of textile colorants is unknown, and potentially poses an ecotoxic threat. In this study, we developed a systematic analytical method to evaluate the biodegradation of reactive dyes, the most common class of dye applied to cotton fabrics. The cotton fabrics were dyed with CI Reactive Blue 19 and biodegraded in soil in a laboratory‐controlled environment over intervals of 45 and 90 days. A dye isolation method using a low concentration of alkali (0.15% sodium hydroxide) was developed and applied (80°C for 1 hour) to isolate intact and degraded dye from the fabric samples. To quantify the intact dye isolated from the fabric samples, a quantification method was then developed using liquid chromatography‐photodiode array detection. The quantification method provided excellent linearity (R2 = 0.9997 ± 0.0002), accuracy (% error = −2% ± 4), precision (% coefficient of variation = 2% ± 4) and sensitivity (lower limit of quantification = 0.4 ± 0.2 µg/mL) for concentrations ranging from 1 to 50 µg/mL. After validation, the method was applied and showed a reduction of dye in biodegraded samples (after 45 and 90 days) compared with undegraded control samples (0 days). To characterise the isolated dye degradation product, quadrupole time‐of‐flight tandem mass spectrometry was utilised. Analysis showed that the degradation product was formed by losing a -SO3- group from the intact hydrolysed form of the dye, creating a more hydrophobic degradation product compared with the intact hydrolysed form of dye.

Characterization of synthetic dyes for environmental and forensic assessments: A chromatography and mass spectrometry approach

“…Therefore, to analyze reactive dyes and their hydrolysis and degradation products, it is necessary to break the glucose–dye bond. In earlier studies, it has been shown that in alkaline conditions, reactive dyes can be isolated from cotton fibers and become hydrolyzed by the cleavage of the glucose–dye linkage [19,20]. In addition to chemical treatment, enzymatic treatment relies on the action of cellulase enzymes, which can digest dye–cellulose linkages and release the dye from the fabric.…”

“…Dye degradation is an indispensable part when using dyes for applications, and this phenomenon has attracted the attention of most dye researchers. Chromatography has been the most effective technique for separation dye mixtures, and it has been widely applied for characterizing dye degradation products [20,36–39]. According to Sinha et al., HPLC chromatography can help to observe the decolorization process, since the shift of major peak and the appearance of a new peak can be seen from the HPLC chromatogram, indicating the discoloration of dye into different intermediates [38].…”

“…Furthermore, in Sultana et al. 's work, a quantification analysis of soil‐biodegraded reactive blue 19 using LC‐DAD‐Q‐TOF has been conducted, and the results showed a reduction in the number of dyes isolated from the biodegraded fabrics [20].…”

“…These ion‐pairing agents are salts, which are not compatible with ESI MS since their high basicity and stability generate ionization suppression and poor results for MS analysis [41]. For this reason, researchers use HPLC or MS separately to characterize the reactive dyes [20,23]. A solution for this could be replacing the C18 column with other columns, such as the HILIC column.…”

“…In the case of reactive dyes, due to the nature of their interaction with fibers, treatment procedures (chemical and enzymatic) are required for analyses on fabrics (see chromatography section for more details). Since sample preparation is required, LC‐MS, coupled with an ESI source in negative mode, is normally the best option [18,20,37].…”