A method for the determination of 60 liquid crystal monomers in biotic and abiotic samples

Abstract

Liquid crystal monomers (LCMs) are synthetic organic chemicals widely used in the manufacture of liquid crystal displays (LCDs) of digital electronic devices. As human interactions with digital electronics such as computers and smartphones intensify, exposure to LCMs is a public health concern. Nevertheless, there is limited research on the occurrence of LCMs in biological and non-biological matrices. We developed a method to determine 60 LCMs in electronic-waste panels (i.e., computer monitors), indoor dust, feces, and urine using gas chromatography–mass spectrometry (GC–MS). Solid matrices (i.e., dust and feces) were extracted using a solid-liquid extraction (SLE) procedure whereas liquid matrices (i.e., urine) were extracted using solid phase extraction (SPE). Indoor dust and feces extracts were purified by passage through silica gel packed gravity columns. The method limits of detection (LODs) and quantification (LOQs) were in the ranges of 0.05–13.0 and 0.18–39.1 ng/mL, respectively. Recoveries of all target analytes fortified at concentrations of 10 and 100 ng/mL on LCD panels, dust, feces, and urine were in the range of 71–130%, with standard deviations of 0.01–33%. Repeated analyses of similarly fortified samples yielded intra-day and inter-day variations (CV) of 0.32–12.6% and 0.76–14.3%, respectively. Matrix effects, calculated from fortified matrices, ranged from −28.5% to 28.5%. The method was applied in the analysis of LCD panels, indoor dust, dog feces and urine, which were found to contain 22, 42, 46, and 18 of the 60 targeted LCMs, respectively. LCMs were found in LCD panels (∑LCM = 1780 ± 165 ng/cm2 for desktop computer monitors; and 166,900 ± 80,100 ng/cm2 for smartphone screens), indoor dust (∑LCM = 2030 ± 1260 ng/g), dog feces (∑LCM = 1990 ± 2000 ng/g dw), and urine (∑LCM = 24.0 ± 14.6 ng/mL). The developed method can be applied in the analysis of LCMs in a wide range of environmental and biological samples.