Alternative method to quantify biodiesel and vegetable oil in diesel-biodiesel blends through H NMR spectroscopy.

An alternative method is proposed for the quantitative analysis of biodiesel in diesel-biodiesel blends. It is based on hydrogen nuclear magnetic resonance (H NMR) spectroscopy and applies univariate calibration, in which the integrals of the spectra are considered. Statistical comparisons between the results obtained from the method proposed here and from the infrared (IR) spectrometry method, which is recommended by the European Standard EN 14078, show that the H NMR method offers equivalent results compared with standard ones.

Quantitative spot-test analysis of metformin in pharmaceutical preparations using ultraviolet-visible diffuse reflectance spectroscopy.

A quantitative spot-test for the determination of metformin in pharmaceutical preparations using diffuse UV-visible reflectance is reported. The procedure is quite simple, involving in the formation of a metformin-nickel(II) complex on a glass filter membrane with a later measurement of the reflectance in the spectrophotometer using an integration sphere. The analytical results obtained with commercial products were statistically compared with those resulting from a method recommended by JP and by USP, where complete agreement was observed.