Determination of acetonitrile and ethanol in water by guided microwave spectroscopy with multivariate calibration

The feasibility of using guided microwave spectroscopy (GMS) utilizing the frequency range 0.25-3.20 GHz, was combined with multivariate calibration f or the determination of acetonitrile or ethanol concentration in water. A w ide range of different concentrations was used (up to 30% v/v), Partial lea st squares (PLS) and weighted ridge regression (WRR) was applied to generat e a model for prediction, based upon the microwave spectra. A high level of collinearity was observed in both of the sample data sets and this was red uced by background subtraction. The prediction ability for the two types of regression models were found to be comparable with the percentage error of prediction (PEP) being approximately 2.5% for the acetonitrile samples and 1.1% for ethanol samples.