Hahm Grace, Redeker Frenio A, Jorabchi Kaveh
Department of Chemistry, Georgetown University, Washington, D.C. 20057, United States.
J Am Soc Mass Spectrom. 2024 May 1;35(5):871-882. doi: 10.1021/jasms.3c00424. Epub 2024 Apr 22.
Prevalence of F, Cl, S, P, Br, and I in pharmaceuticals and environmental contaminants has promoted standard-free quantitation using analyte-independent heteroatom responses in inductively coupled plasma (ICP)-MS. However, in-plasma ionization challenges and element-dependent isobaric interference removal methods have hampered the multielement nonmetal detection in ICP-MS. Here, we examine an alternative approach to enhance multielement detection capabilities. Analytes are introduced into an ICP leading to post-plasma formation of HF, HCl, HPO, HSO, HBr, and HI, which are then chemically ionized to BaF, BaCl, BaHPO, BaHSO, BaBr, and BaI via reactions with barium-containing ions supplied by a nanospray. Subsequent ion detection by high-resolution MS provides an element-independent approach for resolving isobaric interferences. We show that elemental response factors using these ions are linear within 2 orders of magnitude and independent of analytes' chemical structures. Using a single set of operating parameters, detection limits <1 ng/mL are obtained for Cl, Br, I, and P, while those for F and S are 1.8 and 6.2 ng/mL, respectively, offering improved multielement quantitation of nonmetals. Further, insights into ionization mechanisms indicate that the reactivities of reagent ions follow the order BaNO > BaHCO > Ba(HO) ∼ BaCHCO. Notably, the least reactive ions are generated directly by nanospray, suggesting that modification of these ions via interaction with plasma afterglow is critical for achieving good sensitivities. Moreover, our experiments indicate that the element-specific plasma products follow the order HF < HSO ∼ HCl < HPO ∼ HBr ∼ HI for their propensity to react with reagent ions. These insights provide guidelines to manage matrix effects and offer pathways to further improve the technique.
药物和环境污染物中氟、氯、硫、磷、溴和碘的存在促使人们在电感耦合等离子体质谱（ICP-MS）中利用与分析物无关的杂原子响应进行无标准定量。然而，等离子体内的电离挑战以及依赖元素的同量异位素干扰去除方法阻碍了ICP-MS中的多元素非金属检测。在此，我们研究了一种增强多元素检测能力的替代方法。将分析物引入ICP中，导致等离子体后形成HF、HCl、HPO、HSO、HBr和HI，然后通过与纳米喷雾提供的含钡离子反应将它们化学电离为BaF、BaCl、BaHPO、BaHSO、BaBr和BaI。随后通过高分辨率质谱进行离子检测，提供了一种与元素无关的解决同量异位素干扰的方法。我们表明，使用这些离子的元素响应因子在2个数量级内呈线性，且与分析物的化学结构无关。使用一组单一的操作参数，氯、溴、碘和磷的检测限<1 ng/mL，而氟和硫的检测限分别为1.8和6.2 ng/mL，实现了对非金属的改进多元素定量。此外，对电离机制的深入了解表明，试剂离子的反应活性顺序为BaNO > BaHCO > Ba(HO) ∼ BaCHCO。值得注意的是，反应活性最低的离子是由纳米喷雾直接产生的，这表明通过与等离子体余辉相互作用对这些离子进行修饰对于实现良好的灵敏度至关重要。此外，我们的实验表明，元素特异性等离子体产物与试剂离子反应的倾向顺序为HF < HSO ∼ HCl < HPO ∼ HBr ∼ HI。这些见解为管理基质效应提供了指导，并为进一步改进该技术提供了途径。
