Calibration sets selection strategy for the construction of robust PLS models for prediction of biodiesel/diesel blends physico-chemical properties using NIR spectroscopy.

Even when the feasibility of using near infrared (NIR) spectroscopy combined with partial least squares (PLS) regression for prediction of physico-chemical properties of biodiesel/diesel blends has been widely demonstrated, inclusion in the calibration sets of the whole variability of diesel samples from diverse production origins still remains as an important challenge when constructing the models. This work presents a useful strategy for the systematic selection of calibration sets of samples of biodiesel/diesel blends from diverse origins, based on a binary code, principal components analysis (PCA) and the Kennard-Stones algorithm. Results show that using this methodology the models can keep their robustness over time. PLS calculations have been done using a specialized chemometric software as well as the software of the NIR instrument installed in plant, and both produced RMSEP under reproducibility values of the reference methods. The models have been proved for on-line simultaneous determination of seven properties: density, cetane index, fatty acid methyl esters (FAME) content, cloud point, boiling point at 95% of recovery, flash point and sulphur.

Enantiomeric purity determination of ketoprofen by capillary electrophoresis: development and validation of the method.

A simple, fast capillary electrophoresis method for determining the total ketoprofen content in an oral pharmaceutical formulation is proposed. The addition of 75 mM of heptakis(tri- O-methyl)-beta-cyclodextrin to the background electrolyte allows the quantitation of the enantiomeric impurity of ( R)-(-)-ketoprofen contained in the formulation. A relative limit of detection is proposed as a measure of the lowest detectable enantiomeric impurity and the results show that the method can detect the minor enantiomer at levels as low as 0.04% in ( S)-(+)-ketoprofen. The chiral method was validated following ICH recommendations and the quality parameters obtained show the suitability of the proposed method. The analysis of samples examined during the course of a stability study under chiral and achiral conditions revealed that the total ketoprofen content did not change significantly with time and the enantiomeric impurity range was 0.1-0.4%.