Quantitative analysis of soil calcium by laser-induced breakdown spectroscopy using addition and addition-internal standardizations

Abstract

Matrix mismatching in the quantitative analysis of materials through calibration-based laser-induced breakdown spectroscopy (LIBS) is a serious problem. In this paper, to overcome the matrix mismatching, two distinct approaches named addition standardization (AS) and addition-internal combinatorial standardization (A-ICS) are demonstrated for LIBS experiments. Furthermore, in order to examine the efficiency of these methods, the concentration of calcium in ordinary garden soil without any fertilizer is individually measured by each of the two procedures. To achieve this purpose, ten standard samples with different concentrations of calcium (as the analyte) and copper (as the internal standard) are prepared in the form of cylindrical tablets, so that the soil plays the role of the matrix in all of them. The measurements indicate that the relative error of concentration compared to a certified value derived by induced coupled plasma optical emission spectroscopy is 3.97% and 2.23% for AS and A-ICS methods, respectively. Furthermore, calculations related to standard deviation indicates that A-ICS method may be more accurate than AS one.

Calcium determination in biochar-based fertilizers by laser-induced breakdown spectroscopy using sodium as internal standard

“…In particular, due to the common fluctuations observed in LIBS measurements associated to both, instrumentation and sample heterogeneity, various strategies are experimented for the calibration of LIBS methods, which include various different spectral preprocessing and multivariate (linear and non-linear) calibration models [17][18][19][20]. Among these, internal standardization, which consists in normalizing the analyte signal by the signal of an internal standard (IS), is a well known methodology used to minimize fluctuations in spectroscopic techniques including LIBS [21][22][23][24]. To perform internal standardization, the IS concentration must be known and nearly constant [25,26].…”

Calcium evaluation of human fingernail using laser plasma spectroscopy by simultaneously applying addition and modified external standardizations

“…6, 7). Finally, the calcium concentration of each matrix ( C A-matrix ) was calculated from the slope (a) of the linear calibration curve via the following equation [9],…”

“…In order to determine the concentration of a specified species in the sample under study by CB-LIBS, one should experimentally establish a suitable standardization, that is, a reliable relationship between the integral intensity ( S ) of an appropriate spectral line of the neutral or ionized atom and the concentration (C) related to the analyte. Generally, until now, four types of standardization methods have been commonly utilized: external, internal, addition and addition-internal combinatorial [7][8][9].…”

“…Since the analyte and the internal standard in any standard sample or target receive the same treatment, the ratio of their signals will be unaffected by any lack of reproducibility in the procedure. In order to simultaneously overcome matrix effects and problems related to the irreproducibility which more often affect final results of the measurement and, consequently, cause some serious determinate errors, one can apply combination of addition and internal standardization methods, named addition-internal combinatorial standardization [9].…”

Laser Induced-Breakdown Spectroscopy (Libs): Histórico, Fundamentos, Aplicações E Potencialidades

“…Além disso, a calibração por adições de padrão pode levar a uma baixa frequência analítica, pois uma curva de calibração com alguns padrões de calibração (geralmente cinco padrões) deve ser preparada para cada amostra individualmente. 121,133 A padronização interna é uma alternativa de calibração para minimizar as flutuações do sinal analítico, devido às condições instrumentais operacionais, aos erros de amostragem e, em um menor grau, aos efeitos de matriz. [134][135][136] Bons resultados têm sido obtidos com esta estratégia de calibração para análise de amostras geológicas e alimentícias complexas.…”