Evaluation of signal-to-background and Mg II/Mg I ratios as response for the optimization of rare earth elements determination by inductively coupled plasma optical emission spectrometry

Abstract

Elementos terras raras (ETR) fazem parte de um grupo peculiar de elementos químicos e sua determinação em amostras geológicas é importante e complexa, devido às baixas concentrações e problemas com interferências espectrais e não espectrais. Neste trabalho, planejamentos experimentais foram utilizados para otimizar as condições operacionais de um espectrômetro de emissão óptica com plasma indutivamente acoplado (ICP OES) para a determinação de ETR. A razão entre o sinal analítico dos ETR e o sinal de fundo (SBR) e a razão Mg II/Mg I foram avaliadas como respostas na otimização. De acordo com os resultados obtidos, três diferentes condições de operação foram selecionadas e classificadas como robusta, semi-robusta e melhor SBR. Limites de detecção (LOD), SBR e desvio padrão relativo de medidas de uma solução do branco (DPR branco ) foram determinados. Na condição semi-robusta (potência de 1250 W e vazão do gás nebulizador de 0,90 L min −1 ) foram obtidos LOD e DPR branco mais baixos que nas outras condições estabelecidas.Rare earth elements (REEs) is a peculiar group of chemical elements. Their determination in geological samples is important and complex due to their low concentrations and problems with spectral and non-spectral interferences. Herein, the operating conditions of an inductively coupled plasma optical emission spectrometer were optimized for the determination of REEs using experimental designs. The signal-to-background ratio (SBR) of the REEs emission signals and the Mg II/Mg I line intensity ratio were evaluated as response functions. According to the results obtained, three different sets of operating conditions were selected and classified as robust, semi-robust and best SBR conditions. Limits of detection (LOD), SBR and relative standard deviation of the blank solution (RSD blank ) were determined. The semi-robust condition (RF power of 1250 W and nebulizer gas flow rate of 0.90 L min −1 ) exhibited lower LOD and RSD blank than others tested operating conditions. Keywords: rare earth elements, ICP OES, optimization, SBR, Mg II/Mg I IntroductionInductively coupled plasma optical emission spectrometry (ICP OES) has been widely used for multielement analysis and is recognized as one of the most effective techniques for determination of major, minor and trace elements including the rare earth elements (REEs) in geological samples with complex matrices. [1][2][3][4] Recently, inductively coupled plasma mass spectrometry (ICP-MS) has shown to be a powerful tool for the direct determination of REEs, but it is still too expensive and unavailable for many laboratories. On the other hand, ICP OES is more affordable and shows good analytical qualities, such as precision and accuracy, relatively low limits of detection, high sample throughput, simultaneous determination of most elements and wide dynamic range. [5][6][7] From a geological point of view, the determination of REEs is vital to understand the geochemical processes in Evaluation of Signal-to-Background and Mg II/Mg I Ratios J. Braz. Chem. Soc. 7...

Elemental Analysis of Human Blood Serum by Microwave Plasma—Investigation of the Matrix Effects Caused by Sodium Using Model Solutions

“…In the present study, multivariate statistical methods were used for the optimization of the measuring parameters [39][40][41][42][43]. The robustness of the inductively coupled plasma was evaluated according to the Doehlert protocol, as described by Guimarães-Silva et al for ICP-OES [25]. In our case, the operating conditions were considered as factors, although the software of the MP-AES instrument allows to adjust only two parameters for the user: the read time and the nebulizing pressure.…”

“…To investigate the robustness of the microwave, plasma Mg was chosen as the test element on the same ionic and atomic lines that were described in earlier reports (MgII 280.271 nm/ MgI 285.213 nm) [24,25,37]. Although the MP-AES software offers less ionic lines compared to the ICPs, these two are both available.…”

“…The term robustness refers to the capacity of the plasma source to offset the changes originating from environmental factors, operating conditions, or matrix effects without causing a significant error in the measurement result. The robustness is reached for ICP-OES when the ratio of the signals gained at the ionic and atomic lines of Mg are higher than 6 [25].…”

“…Its effect is more complex in the case of ICP compared to AAS (atomic absorption spectrometry) as it cannot be simply explained by the low ionization potential neither linked to a single origin [24]. Its low first ionization potential is responsible for the shift which can be observed in the spatial distribution of the analyte-ionization equilibrium [25][26][27]. The relatively low concentrations of the measured trace elements in such a complex matrix make the human blood serum analysis even more difficult to carry out with reasonable precision.…”

Method Development and Total Uncertainty Estimation for Boron, Sulfur and Phosphorus Determination in Mineral Fertilizer Using ICP OES

“…The pressure of the nebulizer gas is inversely proportional to the sensitivity and Mg II /Mg I ratio that is in accordance with the literature. 34,[36][37][38] The speed of the peristaltic pump appears to be directly proportional to the sensitivity in Figure 2a but inversely proportional in Figure 2b. Figure 3 allows better visualization of the effects.…”