A chemometric strategy to evaluate the comparability of PLS models obtained from quartz cuvettes and disposable glass vials in the determination of extra virgin olive oil quality parameters by NIR spectroscopy

In the present study, a chemometric strategy was deployed for comparing the analytical performances of quartz cuvettes and disposable glass vials in the analysis of olive oil by near infrared spectroscopy (NIRS). Nowadays, laboratories that perform ‘highly frequent’ analysis on extra virgin olive oil (EVOO) by NIRS usually employ quartz cuvettes. This results in time-consuming measurements, especially in the cleaning phase, and an increased cost for non-green cleaning solvents. The use of mono-use glass vials may reduce time and costs significantly, but their analytical performances in EVOO analysis, have not yet been investigated. In order to reach this goal, a set of 106 EVOO samples from different Italian olive-growing areas were collected and analysed using both quartz cuvettes and mono-use glass vials. From spectral data, multivariate calibration models were developed to estimate quality parameters of extra virgin olive oil: methyl esters of fatty acids (FAMEs) and triacylglycerols (TAGs) determined by a fast-GC approach and an UHPLC system, respectively. An optimisation procedure was performed in order to individuate the best pre-treatment and the optimal complexity for each model. The predictive ability of each PLS model was evaluated on an independent test set. The Passing-Bablok linear regression was lastly used to statistically compare the performances of the two different types of cuvettes. In light of the outcomes of the present study, analytical performances of quartz cuvettes and disposable glass vials were considered not significantly different in predicting the olive oil quality parameters taken into account.