DD-SIMCA as an alternative tool to assess the short-term stability of a marine sediment reference material candidate

Abstract

The stability test is essential in the production of a reference material (RM). They can be classified as short-term (transport conditions) and long-term (shelf time). The evaluation of the stability test is carried out using the regression method, as indicated by ISO Guide 35. However, some studies have highlighted the use of multivariate methods in the evaluation of tests performed in RM production. Therefore, this work presents the data driven soft independent modeling class analogy (DD-SIMCA) method as a viable alternative for evaluating data from the short-term stability test of a candidate reference material for metal determination with marine sediment matrix. The test was performed isochronously for one month at a temperature of 60 °C. The samples were decomposed (in triplicate) by the EPA 3051 A method and analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP OES). Samples mass fractions stored at standard temperature (−20 °C) were (mg kg⁻¹): 70.4 ± 4.5 for Ba, 12.0 ± 0.7 for Co, 17.9 ± 1.0 for Cu, 60.7 ± 3.3 for Zn, 49137 ± 4790 for Al, and 60021 ± 3090 for Fe. These values were compared with the mass fractions of samples subjected to the test condition (60 °C) for four weeks, which were (mg kg-1): 70.0 ± 4.0 for Ba, 12.1 ± 0.5 for Co, 17.4 ± 0.8 for Cu, 60.6 ± 2.9 for Zn, 48388 ± 3424 for Al, and 58049 ± 1886 for Fe. A comparison was made between the mass fractions from the standard and test conditions by the regression method. The model applied in the DD-SIMCA method was constructed using two principal components, an alpha value and confidence interval of 0.05, and the instrumental quintuplicates of the samples stored at −20 °C. The samples subjected to 60 °C fit the constructed model, indicating that there was no significant difference between the properties of these samples and those that were maintained in reference temperature. The RM candidate was considered stable at a temperature of 60 °C for a period of one month, both by the regression method and by the DD-SIMCA method. The multivariate method DD-SIMCA was considered a possible alternative and confirmatory tool in evaluating the results of testing short-term stability realized during RM production.