ASTM D7578 Standard Guide for Calibration Requirements for Elemental Analysis of Petroleum Products and Lubricants
4. Summary of Guide
4.1 This guide covers procedures used for calibrating instruments or methods for the analysis of petroleum products or lubricant samples for elemental analysis measurements. The means of calibration may vary from none to elaborate dependent on the test method and the measurement technique used. Test method requirements will take precedence over this guide where applicable.
4.2 This guide may also be applicable to non-petroleum based biofuels. Work is underway to validate this.
5. Significance and Use
5.1 Crude oil, petroleum, petroleum products, additives, biofuels, and lubricants are routinely analyzed for their elemental content such as chlorine, nitrogen, hydrogen, phosphorus, sulfur, and various metals using a variety of analytical techniques. Some of these methods require little to no method calibration; some others require only simple one step calibration; while others require elaborate calibration routine before the product is analyzed for its elemental content.
5.2 Fairly often it can be shown that the round robin results by a co-operator are all biased with respect to those from other laboratories. Presumably, the failure to follow good laboratory practices and instructions in the test methods can be a causal factor of such errors. A further consequence is an unnecessarily large reproducibility estimate or the data being dropped from the study as an outlier.
5.2.1 Another cause of such discrepancies could be different or inadequate calibration practice used in the laboratory. Most test methods spell out the calibration requirements but often do not quote the frequency required letting the laboratories use good laboratory practices for this task. Thus, uniform practice for instrument calibration would be beneficial in standardizing the test procedures and obtaining consistent results across the laboratories.
5.3 Committee D02 has already issued standard practices for uniform sample preparation (D7455), standard operating procedures for ICP-AES (D7260) and XRF (D7343) as well as standard quality assurance protocol (D6792). This guide should be considered as a continuing effort on behalf of this subcommittee to achieve standardized practices in all parts of an analytical sequence.
