Instituto de Investigacións Mariñas de Vigo (IIM-CSIC), 36208, Vigo, Spain.
Instituto de Investigacións Mariñas de Vigo (IIM-CSIC), 36208, Vigo, Spain.
Talanta. 2021 Sep 1;232:122289. doi: 10.1016/j.talanta.2021.122289. Epub 2021 Mar 17.
The determination of palladium (Pd) in environmental samples by ICP-MS is challenging as all its isotopes are extensively interfered due to isobaric (e.g. Cd on Pd, Cd on Pd), polyatomic (e.g. MoO on Pd, YO on Pd) and doubly-charged (e.g. Pb on Pd) species formed in the plasma from elements usually present at concentrations several orders of magnitude higher. As a result, the determination of Pd in natural waters is extremely scarce despite is has been proven that this metal is subject to a significant anthropogenic impact mainly linked to its use in catalytic converters in motor vehicles. In order to overcome this situation, we have developed an ultra-trace interference-free methodology for the determination of Pd in natural waters by ICP-MS after on-line matrix separation and preconcentration. The method is based on the strong affinity of Pd towards a commercially-available carboxymethylated polyethylenimine resin, which also has the ability to retain most of the transition metals. However, Pd is not eluted from the resin at typical elution conditions (e.g. 2 M HNO3, which removes all the interference-forming metals), but this can be attained by passing a diluted thiourea solution (10 M). Therefore, the interference-free on-line determination of Pd in natural waters was successfully achieved using a two-step elution procedure. Procedural blank values were 0.012 ± 0.003 ng kg (n = 6), which results in a detection limit of 0.010 ng kg, allowing the determination of dissolved Pd in natural samples at low, ambient concentrations. The optimized methodology was applied to determine the concentrations of Pd in the Gironde estuary, which represents the first dissolved Pd profile along an estuarine salinity gradient and one of the first dataset of Pd concentrations in natural waters at ambient levels in almost 4 decades. The simplicity of the preconcentration setup and the possibility for its automation offers new analytical opportunities, which will be useful for future studies aiming to improve our understanding of the behavior of Pd in natural waters.
采用电感耦合等离子体质谱法（ICP-MS）测定环境样品中的钯（Pd）具有挑战性，因为所有同位素都因等离子体中形成的同量异位素（例如 Cd 对 Pd、Cd 对 Pd）、多原子（例如 MoO 对 Pd、YO 对 Pd）和双电荷（例如 Pb 对 Pd）物种而受到广泛干扰，而这些元素的浓度通常要高几个数量级。因此，尽管已经证明这种金属受到人为影响很大，主要与它在汽车催化转化器中的使用有关，但在天然水中测定钯的情况却极为罕见。为了克服这种情况，我们开发了一种超痕量无干扰的方法，用于通过在线基体分离和预浓缩后采用 ICP-MS 测定天然水中的 Pd。该方法基于 Pd 对市售羧甲基化聚乙烯亚胺树脂的强亲和力，该树脂还具有保留大多数过渡金属的能力。然而，Pd 不会在典型洗脱条件（例如去除所有形成干扰的金属的 2 M HNO3）下从树脂中洗脱，但可以通过通入稀释的硫脲溶液（10 M）来实现。因此，采用两步洗脱程序成功实现了天然水中 Pd 的无干扰在线测定。程序空白值为 0.012 ± 0.003 ng kg（n = 6），检出限为 0.010 ng kg，允许在低环境浓度下测定天然样品中的溶解 Pd。优化后的方法应用于测定吉伦特河口的 Pd 浓度，这是在河口盐度梯度上测定的第一个溶解 Pd 剖面，也是近 40 年来在环境水平下测定天然水中 Pd 浓度的第一批数据集之一。预浓缩装置的简单性及其自动化的可能性为分析提供了新的机会，这将有助于未来的研究，以提高我们对 Pd 在天然水中行为的理解。
