在常温常压下, 由于甲烷(CH4)在水中的溶解度很低, 使用常规拉曼光谱技术很难获得水中溶解的低浓度甲烷的拉曼信号。 为解决上述问题, 提出了一种四氯化碳(CCl4)萃取辅助的探测新方法。 利用萃取作用, 把溶解在水中的微量甲烷富集到四氯化碳溶液中, 通过对其中溶解的CH4拉曼信号的探测以检验水中微量CH4的存在, 以此提高实验室条件下水中溶解甲烷的探测灵敏度。 在实验室条件(25 ℃, 1 atm)下, 分别对CH4的饱和水溶液(浓度约为1.14 mmol·L-1)、 CCl4萃取液以及CH4的饱和CCl4溶液进行了光谱探测分析。 结果表明, 对CH4的饱和水溶液直接探测, 未能获得CH4的拉曼信号; 通过萃取辅助, 成功地在CCl4萃取液中检测到CH4的拉曼信号, 其强度与CH4的饱和CCl4溶液的信号强度相近, 实现了在实验室条件下对水中溶存甲烷气体的探测。

While under laboratory conditions, the concentration of methane dissolved in water is too low to be detected because of the low solubility of methane using Raman spectroscopy. In the present paper, a novel approach based on CCl4 extraction was introduced, and used in the measurement of methane dissolved in water using Raman spectroscopy under laboratory conditions. Saturated aqueous solution of CH4, CCl4 solution after extraction of CH4 from the saturated aqueous solution and the saturated CCl4 solution of CH4 were prepared, and the Raman spectra of three samples were obtained. The obtained results show that the CH4 dissolved in saturated aqueous solution(the concentration of CH4 is about 1.14 mmol·L-1) can’t been detected using Raman spectroscopy under laboratory conditions, but the CH4 Raman peak can be clearly seen in the spectra obtained for CCl4 solution after extraction. All the results demonstrate that the proposed approach can improve the Raman spectroscopy sensitivity of methane detection dissolved in water, and this approach has significant potential to be developed as an effective method for detection of methane dissolved in water.