The best method today is 'simulated distillation' by gas chromatography. Both standard and 'high temperature' methods are widely used and accepted. These produce highly repeatable distillation curves quite quickly(45 min). However, they do not produce the various fractions needed for determination of the cut properties.
For moderate size 'cuts' , the 'spinning band' method and apparatus gives fast, repeatable, and accurate fractionation into cuts from light ends to heavy vacuum gas oils in about 6 hours using 250ml of sample.
Large scale (more than 500ml) of cuts forces one into D1160 type apparatus and the attendant imprecision and poor fractionation. Alternatively, TBP (true boiling point) apparatus can be used wit hhigh reflux ratios and theoretical stage count to achieve high separation efficiencies and sharp cuts, but the procedure is time consuming and therefore costly.
In any of these methods, expertise in reviewing and analysis of the data is essential.Lots of 'deep cut' vacuum distillation designs failed to work as expected because process engineers failed to understand and appreciate (respect) the limitations of th etest methods.
