Acidity is one of the most fundamental properties of atmospheric aerosol particles, influencing both chemical processes and environmental impacts. A couple of methods for measuring the pH of aerosol particles have been developed, yet no approach is currently available for quantifying the pH of suspending submicron particles. We developed an aerosol fluorescence cell (AFC) for quantifying the pH of aerosol particles in a continuous flow. Particles containing fluorescent pH probes (fluorescein and Oregon green 488) were injected into the AFC. Ratiometric analysis of pH for these particles was conducted by alternatively exciting them with two wavelengths of diode lasers (450 and 488 nm). The employment of the two types of fluorescent probes allowed the measurement of pH in the range of 2–7. The pH measurement by the AFC for submicron particles was compared with that measured by using pH indicator papers, providing a reasonably good agreement. Measurement of size-selected particles suggested that the AFC approach is applicable to particles of 80 nm in diameter. In combination with recent developments for analyzing renebulized water-soluble matter samples, we suggest that the AFC method can be applied not only for laboratory standards but also for atmospherically relevant samples in the future.

中文翻译：

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使用荧光探针检测亚微米气溶胶颗粒的 pH 值

酸度是大气气溶胶颗粒最基本的特性之一，影响化学过程和环境影响。已经开发了几种测量气溶胶颗粒 pH 值的方法，但目前还没有可用于量化悬浮亚微米颗粒 pH 值的方法。我们开发了一种气溶胶荧光池 (AFC)，用于量化连续流中气溶胶颗粒的 pH 值。将含有荧光 pH 探针（荧光素和俄勒冈绿 488）的颗粒注入 AFC。通过用两种波长的二极管激光器（450 和 488 nm）交替激发这些颗粒，对这些颗粒进行 pH 值比率分析。使用两种类型的荧光探针可以测量 2-7 范围内的 pH 值。将 AFC 对亚微米颗粒的 pH 测量结果与使用 pH 试纸测量的结果进行比较，结果相当一致。对选定尺寸颗粒的测量表明 AFC 方法适用于直径 80 nm 的颗粒。结合重雾化水溶性物质样品分析的最新进展，我们建议AFC方法不仅可以应用于实验室标准品，而且可以应用于未来的大气相关样品。