Pacific Northwest National Laboratory, P.O. Box 999, MSIN K8-88, Richland, Washington 99352, USA.
J Phys Chem A. 2009 Feb 26;113(8):1531-8. doi: 10.1021/jp8079149. Epub 2009 Jan 26.
The hygroscopic behavior of CH(3)SO(3)Na, CH(3)SO(3)NH(4), (CH(3)SO(3))(2)Mg, and (CH(3)SO(3))(2)Ca particles as a function of relative humidity (RH) has been studied using microscopic Fourier transform infrared (micro-FTIR) spectroscopy. The approach used exposure of substrate-deposited, approximately 1 microm dry-size particles to humidified nitrogen followed by micro-FTIR spectroscopy over a selected sample area. The results show that CH(3)SO(3)Na particles undergo characteristic phase transitions at deliquescence relative humidity (DRH) of 71% and efflorescence relative humidity (ERH) of approximately 40%. In contrast, CH(3)SO(3)NH(4), (CH(3)SO(3))(2)Mg, and (CH(3)SO(3))(2)Ca particles do not undergo phase transitions and exhibit continuous, reversible uptake and evaporation of water under the influence of changing RH. The extent of water uptake is quantified and presented as water-to-solute ratios (WSR) in particles as a function of RH. The WSR values are determined from the integrated absorbance of the water and the solute-specific bands in IR spectra recorded at different RH.
采用微观傅里叶变换红外（micro-FTIR）光谱法研究了 CH(3)SO(3)Na、CH(3)SO(3)NH(4)、(CH(3)SO(3))(2)Mg 和 (CH(3)SO(3))(2)Ca 颗粒在相对湿度（RH）下的吸湿行为。该方法采用将沉积在基底上的、约 1 微米干粒径的颗粒暴露于加湿氮气中，然后在选定的样品区域进行 micro-FTIR 光谱分析。结果表明，CH(3)SO(3)Na 颗粒在 71%的潮解相对湿度（DRH）和大约 40%的风化相对湿度（ERH）下经历特征相变。相比之下，CH(3)SO(3)NH(4)、(CH(3)SO(3))(2)Mg 和 (CH(3)SO(3))(2)Ca 颗粒不会发生相变，并且在 RH 变化的影响下表现出连续的、可逆的水分吸收和蒸发。水分吸收的程度被量化，并表示为 RH 下颗粒中水与溶质的比值（WSR）。WSR 值是根据在不同 RH 下记录的 IR 光谱中水分和溶质特定带的积分吸光度确定的。
