The primary measurement standard for the number concentration of liquid-borne particles adopted by the National Metrology Institute of Japan was upgraded to cover particle diameters in the range of 600 nm–10 m. The main aim was to report the extension of the lower limit of the measurement range in particle diameters from 2 m to 600nm, and the reduction of the measurement uncertainty inherent in the previous method using the total-counting-type flow cytometric technique. To extend the measurement range, we adopted a mass-measurement-type optical particle counting method, which consisted of a pair of optical particle counters with a pulse height analyzer, an electronic balance, and a syringe sampler. The relative expanded uncertainties with a coverage factor of k = 2 for the 600nm and 10 m suspension measurements were 4.3% and 3.5%, respectively. The validity of the results was confirmed in both cases via comparison with the results obtained using an independent microscopic counting method. With the change in the measurement method, a reduction of the uncertainty was accomplished: e.g., from a 4.4% to a 3.5% relative expanded uncertainty (k = 2) for a 10 m polystyrene latex particle suspension.

日本国家计量院采用的液载粒子数浓度的主要测量标准升级为涵盖600 nm-10 m范围内的粒子直径。主要目的是报告粒径测量范围的下限从 2 m 扩展到 600 nm，并降低了使用总计数型流式细胞术技术的先前方法中固有的测量不确定性。为了扩大测量范围，我们采用了质量测量型光学粒子计数方法，该方法由一对带脉冲高度分析仪的光学粒子计数器、一个电子天平和一个注射器进样器组成。覆盖因子为k的相对扩展不确定性= 2 对于 600nm 和 10m 悬浮测量分别为 4.3% 和 3.5%。通过与使用独立显微计数方法获得的结果进行比较，在这两种情况下都证实了结果的有效性。随着测量方法的改变，不确定性得以降低：例如，对于 10 m 聚苯乙烯乳胶颗粒悬浮液，相对扩展不确定性 ( k = 2)从 4.4% 降至 3.5% 。