Department of Chemistry, Iowa State University, Ames, IA, 50010, USA.
Anal Bioanal Chem. 2022 Oct;414(25):7543-7551. doi: 10.1007/s00216-022-04115-2. Epub 2022 May 18.
Single-particle inductively coupled plasma time-of-flight mass spectrometry (spICP-TOFMS) is a high-throughput method for the multiplexed analysis of nanoparticles (NPs). However, matrix interferences are a significant challenge that must be overcome for accurate NP sizing and number concentration determination. In online microdroplet calibration, multi-element droplet standards are mixed with nebulized aerosols from a NP-containing sample in a dual-sample introduction system before entering the ICP. Microdroplet standards are used to determine absolute sensitivities and calibrate the mass amount(s) of analyte element(s) in particle events. A plasma-uptake standard is added to NP-containing samples to account for variations in the nebulization and transport efficiency of aerosols into the plasma, which are used in the determination of particle number concentrations (PNCs). Since the microdroplets experience the same plasma conditions as analyte NPs, this creates a matrix-matched calibration. We studied the efficacy of online microdroplet calibration for the quantification of NPs in three organic matrices: ethanol, acetone, and acetonitrile. Organic solvents can cause a pronounced increase in sample uptake and cause plasma-related signal attenuation for nanoparticle measurements. Online microdroplet calibration corrects for both effects without the use of nanoparticle standards. Our results demonstrate accurate NP sizing and PNC determinations in organic matrices up to 98% (v/v), even when these matrices caused signals to be attenuated up to 35-times and nebulizer transport efficiencies to be up to four-times higher than that of a pure water matrix.
单颗粒电感耦合等离子体飞行时间质谱（spICP-TOFMS）是一种高通量的纳米颗粒（NPs）多指标分析方法。然而，基质干扰是一个必须克服的重大挑战，才能实现准确的 NP 尺寸和数量浓度测定。在在线微滴校准中，多元素微滴标准与含有 NP 的样品的雾化气溶胶在双样品进样系统中混合，然后进入 ICP。微滴标准用于确定绝对灵敏度并校准颗粒事件中分析物元素的质量。向含有 NP 的样品中添加等离子体吸收标准品，以说明气溶胶在进入等离子体时的雾化和传输效率的变化，这用于测定颗粒数浓度（PNC）。由于微滴经历与分析物 NPs 相同的等离子体条件，因此这创建了一个基质匹配的校准。我们研究了在线微滴校准在三种有机基质（乙醇、丙酮和乙腈）中定量 NPs 的效果。有机溶剂会导致样品吸收明显增加，并导致纳米颗粒测量时等离子体相关信号衰减。在线微滴校准无需使用纳米颗粒标准品即可纠正这两种影响。我们的结果表明，即使在这些基质导致信号衰减高达 35 倍且雾化器传输效率比纯水基质高四倍的情况下，也能在有机基质中实现准确的 NP 尺寸和 PNC 测定，最高可达 98%（v/v）。
