实验技术与管理

气相色谱（GC）与原子荧光光谱（AFS）联用技术因其高稳定性和高准确性在汞检测领域得到了广泛认可，然而该联用系统体积庞大、管路较长，且仪器利用率较低，这些因素限制了其在检测行业中的应用和推广。为解决上述问题，该研究基于通用仪器专用化的策略，对实验室原子荧光光谱仪进行小型化设计，研制了一种小型化冷原子荧光检测器（AFD），其体积约为传统原子荧光光谱仪的1/30，并实现了在实验室气相色谱仪上的直接搭载。该系统在保留传统气相色谱检测器功能的基础上，实现了气相色谱与原子荧光光谱联用分析，填补了实验室气相色谱仪在烷基汞检测领域的空白。实验结果表明，该系统对甲基汞和乙基汞的检出限分别达到0.073 7 pg和0.094 4 pg。

[Objective] Gas chromatography(GC) coupled with atomic fluorescence spectrometry(AFS) has been widely recognized for its high stability and accuracy in mercury detection. However, the large size, long tubing, and low utilization efficiency of conventional GC-AFS systems have limited their application in the analytical industry. Therefore, this study introduces a novel approach of shrinking a laboratory atomic fluorescence spectrometer to develop a miniaturized cold atomic fluorescence detector(AFD). [Methods] Instrument design and development: Through an integrated design, the AFD size was condensed to 1/30 that of a traditional atomic fluorescence spectrometer so that it can be directly mounted on a laboratory gas chromatograph as a platform. The AFD mainly consists of three modules: a high-temperature pyrolysis module, a fluorescence cell optical path module, and a tail gas collection module. With its temperature resistance limit above 1 000 ℃, the high-temperature pyrolysis module ensures the stable pyrolysis of alkylmercury samples at 900 ℃ while maintaining its own surface temperature below 60 ℃. Critical advancements through innovative designs of a composite housing with a gradient thermal insulation system and a hydrogen-oxygen combustion heating system were achieved in this module to meet the aforementioned technical requirements. The fluorescence cell optical path module features a compact fluorescence excitation optical path structure fabricated via 3D printing to ensure the accuracy of the specialized light-blocking system. Crucial technical innovations were implemented in its miniaturized optical, closed-loop light source control, and fluorescence cell excitation systems. The tail gas collection module primarily collects and manages the exhaust gas generated during detection, forming a closed-loop gas circulation system that effectively prevents gas diffusion(leakage rate <0.1 μL/min) from the sample after detection. Simultaneously, this module integrates a gold wire trap specifically designed for mercury vapor(collection efficiency ≥99.8%) and facilitates the convergence of the sample gas flow during analysis, ensuring the stability of mercury vapor excitation. [Results] Performance testing and validation: The GC system equipped with the AFD achieved instrument detection limits of 0.073 7 and 0.094 4 pg(3σ, n=7) for methylmercury and ethylmercury, respectively. The system exhibited good linear response within the concentration range of 5～100 pg. The correlation coefficients(R²) of the calibration curves for methylmercury and ethylmercury were 0.9993 and 0.9999, respectively. The system also demonstrated good repeatability through six consecutive measurements of a 10-pg spiked sample. The relative standard deviations(RSDs) of the retention times for methylmercury and ethylmercury were 0.08% and 0.04%, respectively. Quantitative repeatability tests showed peak area RSDs of 1.63% and 1.86% for methylmercury and ethylmercury, respectively. Spike recovery experiments using the standard addition method revealed the recoveries for methylmercury and ethylmercury ranging from 78.2% to 102.2% and from 71.9% to 106.4%, respectively, across three spiking levels(5, 20, and 100 pg). [Conclusions] A miniaturized cold AFD was successfully developed. By optimizing optical, gas path, and circuit integration, the AFD size was condensed to 1/30 that of a traditional cold atomic fluorescence spectrometer so that it can be directly mounted on a laboratory GC. This detector employs a synergistic design comprising a high-temperature pyrolysis module, fluorescence cell optical path module, and tail gas collection module, all of which ensure its high sensitivity and stability despite its small size. The developed system fills the gap in the laboratory GC market for alkyl mercury detection. Experimental results demonstrate its instrument detection limits of 0.073 7 and 0.094 4 pg for methylmercury and ethylmercury, respectively.