Total-reflection X-ray fluorescence analysis (TXRF) nowadays is a well established technique for the elemental analysis of samples and matrices from water solutions to ores. The spreading of the technique is mainly due to the advantages of using very low amount of sample to achieve a multielemental characterization, avoiding time-consuming and expensive sample preparation strategies. For the analysis, samples are usually directly deposited on the reflectors or prepared as slurries and, then, few microliters are pipetted onto it. In the case of slurry preparation, several approaches (considering different amount of sample mass, dispersant agent volume, internal standard concentration, etc.) have been developed for any kind of sample and matrix. After the analysis of a reference material, the recovery is the most parameter used to check the quality of the analysis. However, in this way, we find one way to prepare the sample and not the best way for sample preparation. The classical univariate approach cannot provide a full understanding of the effect of the parameters variation on the analysis. In fact, it has been demonstrated that the factors combination can influence the quality of the analysis more than the single parameters. For this reason, a multivariate experimental design should be applied for the identification of the effect of each factor and their combinations on the analytical performances. In this work, a full factorial experimental design was applied to develop the most suitable protocol for the preparation of soil organic matters and amendments as slurries for TXRF analysis. Two factors were considered for the slurry preparation: sample mass (10 mg – 100 mg) and dispersant volume (1 mL – 5 mL of 1% Triton X-100 solution). The analyses were performed with two different Bruker S2 Picofox TXRF spectrometers equipped with a Mo and a W sources, respectively. In the first step, the study was done on a the reference material NIST 1635a and using recovery as monitoring parameter. The best results were obtained with the combination 10 mg in 3 mL and 10 mg in 5 mL. Secondly, the validation of the two methods was performed using a second reference material (NIST 1573a) and recovery, relative standard deviation, limits of detection and quantification. On the base of these parameters, the best sample method (10 mg in 3 mL) were applied to soil organic matter and amendments samples. The set of samples is composed of three humic acids, three humates, three peats, two biochars, one digestate and one compost. The obtained results are statistically similar to the ones obtained with ICP-OES which is the recognized method for the analysis of this class of samples demonstrating the good analytical performances of the new developed method.
Customization of the sample preparation for TXRF analysis using a multivariate experimental design: the case of soil organic matter and amendments
C. Porfido;G. Squeo;R. Terzano;
2023-01-01
Abstract
Total-reflection X-ray fluorescence analysis (TXRF) nowadays is a well established technique for the elemental analysis of samples and matrices from water solutions to ores. The spreading of the technique is mainly due to the advantages of using very low amount of sample to achieve a multielemental characterization, avoiding time-consuming and expensive sample preparation strategies. For the analysis, samples are usually directly deposited on the reflectors or prepared as slurries and, then, few microliters are pipetted onto it. In the case of slurry preparation, several approaches (considering different amount of sample mass, dispersant agent volume, internal standard concentration, etc.) have been developed for any kind of sample and matrix. After the analysis of a reference material, the recovery is the most parameter used to check the quality of the analysis. However, in this way, we find one way to prepare the sample and not the best way for sample preparation. The classical univariate approach cannot provide a full understanding of the effect of the parameters variation on the analysis. In fact, it has been demonstrated that the factors combination can influence the quality of the analysis more than the single parameters. For this reason, a multivariate experimental design should be applied for the identification of the effect of each factor and their combinations on the analytical performances. In this work, a full factorial experimental design was applied to develop the most suitable protocol for the preparation of soil organic matters and amendments as slurries for TXRF analysis. Two factors were considered for the slurry preparation: sample mass (10 mg – 100 mg) and dispersant volume (1 mL – 5 mL of 1% Triton X-100 solution). The analyses were performed with two different Bruker S2 Picofox TXRF spectrometers equipped with a Mo and a W sources, respectively. In the first step, the study was done on a the reference material NIST 1635a and using recovery as monitoring parameter. The best results were obtained with the combination 10 mg in 3 mL and 10 mg in 5 mL. Secondly, the validation of the two methods was performed using a second reference material (NIST 1573a) and recovery, relative standard deviation, limits of detection and quantification. On the base of these parameters, the best sample method (10 mg in 3 mL) were applied to soil organic matter and amendments samples. The set of samples is composed of three humic acids, three humates, three peats, two biochars, one digestate and one compost. The obtained results are statistically similar to the ones obtained with ICP-OES which is the recognized method for the analysis of this class of samples demonstrating the good analytical performances of the new developed method.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
