Objective To establish a gas chromatography-mass spectrometry (GC-MS) method for the simultaneous determination of four carbonate compounds (CCs), including ethyl methyl carbonate (EMC), diethyl carbonate (DEC), vinylene carbonate (VC), and ethylene carbonate (EC) in workplace air. Methods Vapor-phase EMC, DEC, VC, and EC in workplace air were collected using activated carbon tubes. After desorption with dichloromethane, the samples were analyzed by GC-MS. Qualitative identification was performed based on retention times and characteristic ions, while quantitative analysis was conducted using peak areas of selected characteristic ions. Results The quantitative determination ranges for the four CCs were from 0.57×10⁻³ to 200.00 mg/L, with correlation coefficients ≥0.999 45. The detection limit ranged from 0.17 to 1.60 μg/L, and the lower limit of quantification ranged from 0.57 to 5.33 μg/L. The minimum detection concentration and minimum quantitation concentration were 0.11-1.07 and 0.38-3.55 μg/m³, respectively. Mean spiked recoveries ranged from 85.70% to 111.65%. The intra- and inter-batch relative standard deviations were 0.11%-2.04% and 1.27%-5.18%, respectively. Mean desorption efficiencies of the method ranged from 74.70% to 118.20%. EMC, DEC, and EC samples were stable for up to five days at 4 °C, while VC samples were stable for up to three days at 4 °C. Conclusion The GC-MS method is suitable for the simultaneous determination of the four CCs including EMC, DEC, VC, and EC in workplace air.

Both cholinergic dysfunction and protein citrullination are the hallmarks of rheumatoid arthritis (RA), but the relationship between the two phenomena remains unclear. We explored whether and how cholinergic dysfunction accelerates protein citrullination and consequently drives the development of RA. Cholinergic function and protein citrullination levels in patients with RA and collagen-induced arthritis (CIA) mice were collected. In both neuron-macrophage coculture system and CIA mice, the effect of cholinergic dysfunction on protein citrullination and expression of peptidylarginine deiminases (PADs) was assessed by immunofluorescence. The key transcription factors for PAD4 expression were predicted and validated. Cholinergic dysfunction in the patients with RA and CIA mice negatively correlated with the degree of protein citrullination in synovial tissues. The cholinergic or alpha7 nicotinic acetylcholine receptor (α7nAChR) deactivation and activation resulted in the promotion and reduction of protein citrullination in vitro and in vivo, respectively. Especially, the activation deficiency of α7nAChR induced the earlier onset and aggravation of CIA. Furthermore, deactivation of α7nAChR increased the expression of PAD4 and specificity protein-3 (SP3) in vitro and in vivo. Our results suggest that cholinergic dysfunction-induced deficient α7nAChR activation, which induces the expression of SP3 and its downstream molecule PAD4, accelerating protein citrullination and the development of RA.