Direct Analysis of Saline Matrices by HR ICP-OES Application Note · PlasmaQuant 9100 Elite

Introduction

Brines play an important role in many industrial processes, e.g., in the production of magnesium and chlorine by electrolysis, as agent for water-injection in oil-wells, or as starting material for the fabrication of high-purity salts and preservatives. In some regions, naturally occurring brines and sea water are also considered to be an attractive candidate for drinking water production. Yet the direct elemental analysis of saline matrices using ICP techniques in routine laboratories is challenging in respect to (a) achieving good signal stability with low signal to noise levels, (b) ionization interferences of alkali and alkaline earth metals that often lead to intensity deviations in the range from ± 5 to 10%, and (c) maintenance issues, memory effects, and short lifetime of glassware and clogging.

Since saline matrices are used for various purposes, a large number of elements with limits of detection as low as possible are of interest. Due to its high sensitivity, ICP-MS is typically the method of choice to achieve limits of detection in the ppt range. However, ICP-MS typically tolerates matrix concentrations not higher than 0.3%, which requires high dilution of the samples. Thus, matrixspecific limits of detection are compromised depending on the applied dilution factor. In general, ICP-OES instrumentation is more matrix tolerant compared to ICP-MS. The comparatively low sensitivity of conventional ICP-OES, however, hampers achieving sufficiently low limits of detection.

The HR ICP-OES PlasmaQuant 9100 Elite exhibits excellent matrix and plasma robustness, being able to tolerate salt concentrations of up to 300 g/L. Additionally, the high-resolution optical system achieves high sensitivity and ensures free line selection. The PlasmaQuant 9100 Elite allows for running undiluted saline samples of almost any salt concentration with the highest sensitivity amongst ICP-OES instrumentation. Matrix specific limits of detection (ppt to ppb range) can be achieved.

Within this study, the performance of the PlasmaQuant 9100 Elite was studied on an exemplary saline matrix of 35 g/L NaCl for concentrations, limits of detection, and long-term stability of B, Ba, Be Br, Ca, Co, Cr, Fe, I, K, Li, Mg, Mn, Mo, Na, P, S, Si, Sr, V, and Zn.