This acid extraction method is specifically intended for the determination of combined nitrogen in petroleum distillates and heavy oils in concentrations ranging from 0.1 to 100 ppm. Non-extractable samples, and samples containing nitrogen concentrations ranging from 20 ppm to several percent, can be handled by a direct Kjeldahl analysis. The method applies to oil samples as well as a large variety of other materials; e.g., corrosion products, deposits, catalysts, etc.

The types of nitrogen compounds which can be determined are those which usually are determined by a macro-Kjeldahl procedure and include amines, amides, pyridines, pyrroles and quinolines. The method does not apply to organic nitro-compounds or to those containing a -N = N- linkage.