Determination of N/Protein in Engine Oil by Kjeldahl Method (CAT#: STEM-EA-0049-ZJF)

Introduction

Oil additives are used to improve the base oil into a high performing lubricant. By utilizing the same base stock many different oils can be manufactured, each with its own unique properties, by adding different additive packages. Combined nitrogen additives in petrochemical fuels give origin by combustion to nitrogen oxides whose emission in the atmosphere is subjected to limitations. Combustions occurring at relatively low temperatures (1400-1700 °F, 750-950 °C) produce nitrogen oxides mostly from fuel-bound nitrogen and not from atmospheric nitrogen. The use of lubricating oil triggers the production of insoluble oxidation products. To prevent deposits and reduce the risk of damage, the nitrogen content in lubricating oils must be kept low. For this reason Nitrogen is one of the quality control parameters of crude oil, lubricants and fuel oils.
Thanks to the high level of precision and reproducibility and to its simple application, Kjeldahl is nowadays the most used method for determining nitrogen and protein contents in the food and feed industry. It also has several other applications in environmental control (phenols and nitrogen in water, sludge, soil and lubricants) and in the chemical and pharmaceutical industry according to official AOAC, EPA, DIN e ISO procedures. The modern Kjeldahl method consists in a procedure of catalytically supported mineralization of organic material in a boiling mixture of sulfuric acid and sulfate salt at digestion temperature higher than 400 °C. During the process the organically bonded nitrogen is converted into ammonium sulfate. Alkalizing the digested solution liberates ammonia which is quantitatively steam distilled and determined by titration.