Microchim Acta 153, 73–78 (2006) DOI 10.1007/s00604-005-0429-1 Original Paper HPLC and GC Methods for Determination of Lubricants and Their Evaluation in Analysis of Real Samples of Polyethylene Mir Ali Farajzadeh 1; , Mortaza Ebrahimi 2 , Ali Ranji 3 , Elham Feyz 4 , Vali Bejani 1 , and Amir Abbas Matin 5 1 Department of Chemistry, Faculty of Science, Urmia University, Urmia, Iran 2 Polymer Engineering Department, Amir Kabir University of Technology, P. O. Box 15875-4413, Tehran, Iran 3 National Petrochemical Company (NPC), Research and Technology Company, Mollasadra, 14358, Tehran, Iran 4 Department of Chemistry, Faculty of Science, Tehran University, Tehran, Iran 5 Chemical and Food Analysis Laboratory, Jahade Daneshgahi, Urmia University, Urmia, Iran Received May 2, 2005; accepted September 8, 2005; published online November 21, 2005 # Springer-Verlag 2005 Abstract. High performance liquid chromatography (HPLC) and gas chromatography (GC) are introduced for analysis of polymer lubricants (stearamide, ole- amide and erucamide). In the HPLC method, a reverse phase octadecylsilane (ODS) column along with acetonitrile=methanol (60:40) as a mobile phase were used. Detection of analytes was performed by a UV detector at 202 nm. The analysis time was less than 8 min. In the GC method, polar capillary column and flame ionization detector (FID) were used for sepa- rations and detection, respectively. The analysis time by GC was longer than HPLC and was about 30 min. Limits of detection, linear range and repeatability of both methods are similar, but determination of ole- amide in real samples by HPLC method is difficult due to complexity of the initial part of HPLC chroma- togram in polyethylene samples. That problem is not observed in the GC method. Detection limits in both methods for all analytes are lower than 0.003% which are much lower than the amount of lubricants in com- mercial polymers (0.05–0.2%). Key words: GC; HPLC; lubricants; stearamide; oleamide; eru- camide; polyethylene. Lubricants are substances that when compounded in a small quantity into a polymer, will provide a signifi- cant increase in the movement of polymer chains or segments without notable influence in other observ- able properties [1]. Essentially, lubricants are added to polymers to increase the overall rate of processing or to improve surface release properties during extrusion, injection molding, compression molding, etc. [2]. The factors which will be considered during the selection of lubricants are: compatibility with the host polymer, no adverse effect on other physical properties, easy introduction, no retarding effect on the gelation process, no reduction in melt strength and extensibility, good transparency, improved plate-out performance and cost [3]. According to the lubricant action, they may be divided into two basic groups based on function, external and internal lubricants [4]. A main function of lubricants is to prevent polymers that have a tendency toward tackiness from sticking to metallic parts of pro- cessing machinery. This is termed external lubrication. Another important function is to provide lubrication to the polymer under processing to improve the free flow  Author for correspondence. E-mail: farajzade@yahoo.com