Search for: All records

Elemental analysis of fluorochemicals has received renewed attention in recent years stemming from the increased use of fluorinated compounds. However, fundamental drawbacks of in-plasma ionization have hindered ICPMS applications in this area. Recently, we have introduced post-ICP chemical ionization for BaF + formation using Ba-containing reagent ions supplied by nanospray, leading to major improvements in F detection sensitivity. Here, we present further insights into this post-plasma chemical ionization. First, we examine the effect of oxygen introduced into the plasma (a necessity for organic solvent introduction) on BaF + ion formation. The results indicate that excess plasma oxygen leads to abundant HNO 3 in the post-plasma flow, shifting ionization reactions toward BaNO 3 + formation and suppressing BaF + sensitivity. To amend this, we utilize reagent ions with other metal centers to impart selectivity toward F detection. Our investigations show that robustness of F detection in the presence of abundant HNO 3 improves in the order Al 3+ ≈ Sc 3+ > La 3+ > Mg 2+ > Ba 2+ as the metal center in the reagent ions, consistent with the stronger metal–F bond in the series. Sc-based ionization resulting in ScNO 3 F + shows the best balance between sensitivity and robustness in the presence of nitric acid. Similarly, this ion shows an improved tolerance relative to BaF + for a Cl-containing matrix where HCl interferes with ionization. Finally, we demonstrate a unique feature of post-plasma chemical ionization for real-time flagging of matrix effects via monitoring reagent ions. These findings provide significant improvements of post-plasma chemical ionization for elemental F analysis, particularly for online chromatographic detection where solvent gradients are utilized.