Our previous study demonstrated massive emissions of liquid crystal monomers (LCMs) from liquid crystal display (LCD)-associated ewaste dismantling; however, the compositions, priority list, and inventory of LCMs in waste LCD panels remain unknown. Herein, we conducted the first comprehensive identification covering a broader range of LCMs, including 21 biphenyls and analogues (BAs), 28 cyanobiphenyls and analogues (CBAs), and 44 fluorinated biphenyls and analogues (FBAs), in waste television/ computer LCD panels. A total of 64 of the 93 target LCMs, including 19 BAs, 6 CBAs, and 39 FBAs, were widely detected in collected waste LCD panels. Approximately 10−18 of the 64 detectable LCMs were identified as the main compositions in various waste LCD panels, which contributed to >90% of the total LCMs. Total concentrations of FBAs in the television/computer LCD panel samples were comparable to those of BAs but much higher than those of CBAs, indicating FBAs and BAs being the commonly used LCM categories. The composition distribution of LCMs varied between television/computer LCDs and among different brands of television/computer LCDs. A preliminary estimate of the globally direct release of LCMs from waste television/computer LCD panels into various environmental compartments was about 1.07−107 kg/year, which will increase considerably in the near future.
The prevalently used LC–MS/MS
methods for the simultaneous
determination of synthetic phenol antioxidants (SPAs) and relevant
metabolites suffer from a serious drawback of low sensitivity for
2,6-di-tert-butyl-4-hydroxytoluene (BHT) and a common
issue of background contamination, which hampers the simple and accurate
detection of these substances at trace levels in environmental samples.
In this study, we developed an improved LC–MS/MS method for
the simultaneous determination of eight SPAs and four relevant metabolites,
including BHT. By use of atmospheric pressure chemical ionization
(APCI), the sensitivity of BHT in the LC–MS/MS was enhanced
approximately 260 times versus results obtained by using electrospray
ionization (ESI), which allowed the analysis of BHT up to 1.1 ng/g
in indoor dust and 0.06 ng/g in human plasma. Similarly, the sensitivity
of 2,4,6-tri-tert-butylphenol and 2,6-di-tert-butyl-4-sec-butylphenol was also enhanced
with APCI, which avoided their separate analysis by GC–MS.
By installation of a C18 column after the eluent mixer
and before the injector as a trap column, the target analytes leached
out from the LC system were eluted at a much later retention time
than those in the samples, which resulted in complete elimination
of the instrumental background contamination. These improvements enable
the method to be well applied to the real samples.
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