An alternative method is proposed for the quantitative analysis of biodiesel in diesel-biodiesel blends. It is based on ultraviolet visible (UV-Vis) spectroscopy and applies univariate calibration, in which the wavelength at 356 nm is considered. Statistical comparisons between the results obtained from the method proposed here and from the infrared (IR) spectrometry method (EN 14078) show that the UV Vis method offers equivalent results compared with the standard one. Furthermore, the alliance between the UV Vis technique and partial least squares (PLS) provides the quantification of biodiesel in blends adulterated with vegetable oil. It means that the UV Vis PLS model can recognize the difference between biodiesel and vegetable oil, whereas the univariate methods, either UV Vis or IR, cannot. Therefore, the methods developed to quantify biodiesel in blends are proposed as more practical and simpler alternatives to the official method. (C) 2016 Elsevier Ltd. All rights reserved.