The present invention relates to a method of detecting synthetic mud filtrate in a downhole fluid including placing a downhole tool into a wellbore, introducing a downhole fluid sample into the downhole tool, analyzing the downhole fluid sample in the downhole tool, producing at least two filtrate markers from the analyzing of the downhole fluid sample and converting the at least two filtrate markers by vector rotation to a sufficiently orthogonal signal. The first pumped fluid sample giving initial plateau readings can be a proxy for 100% drilling fluid having an initial orthogonal signal and subsequent samples can be converted to orthogonal signals that are referenced to the first pumped fluid signal to give a calculation of percent contamination of the formation fluid.