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Determining plasticizers and other additives migrated from plastic materials becomes a hard task when these substances are already present in the laboratory environment. This work dealt with this drawback in the multiresidue determination of four plasticizers (2,6-di-tert-butyl-4-methyl-phenol (BHT), diisobutyl phthalate (DiBP), bis(2-ethylhexyl) adipate (DEHA) and diisononyl phthalate (DiNP)) and a UV stabilizer (benzophenone (BP)) by gas chromatography/mass spectrometry (GC/MS) using DiBP-d4 as internal standard. The ubiquity of DiBP by a non-constant leaching process in the laboratory was detected, which could not guarantee the achievement of a trustworthy quantification. To handle this, the assessment of the level of DiBP in solvent blanks having fixed the probabilities of false non-compliance (α) and false compliance (β) at 0.01 was performed. On the other hand, another special case was that of DiNP, in whose chromatogram finger peaks appear because of an array of possible C9 isomers. PARAFAC, used for the identification and quantification of all the substances, is a useful chemometric tool that enabled a more reliable determination of this analyte since no peak areas were considered but chromatographic and spectral loadings. Since phthalates may migrate from rubber latex items, an evaluation of the existence of matrix effects on the determination of the five analytes was conducted prior to an extraction with hexane from a dummy for infants. As matrix effects were present, the quantification of the compounds under study was performed following the standard addition method using PARAFAC sample loadings as response variable. As a result, the presence of BHT was confirmed, being its concentration equal to 37.87μgL(-1). Calibrations based on PARAFAC yielded the following values for the decision limit (CCα): 1.16μgL(-1) for BHT, 1.34μgL(-1) for BP, 1.84μgL(-1) for DEHA and 51.42μgL(-1) for DiNP(for α=0.05 and two replicates).

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In this work, the robustness of the sample preparation procedure for the determination of six tranquillizers (xylazine, azaperone, propionylpromazine, chlorpromazine, haloperidol and azaperol) and a beta-blocker (carazolol) in animal muscle by LC/MS-MS was assessed through the experimental design methodology. The results of the experimentation were evaluated from different statistical strategies, such as hypothesis testing using an external variance previously estimated, Lenth"s method and Bayesian analysis. Both Lenth"s and Bayes" approaches enabled to determine the effect of every variable even though no degrees of freedom were left to estimate the residual error. The same conclusion about the robustness of the extraction step was reached from the three methodologies, namely, none of the seven factors examined influenced on the method performance significantly, so the sample preparation procedure was considered to be robust.