This standard covers the determination of the chemical composition of natural gas streams where precise physical property data of the hexanes and heavier fraction is required. This procedure is applicable for gaseous hydrocarbon mixes which may contain nitrogen and carbon dioxide and/or hydrocarbon complexes C1 through C14 that fall within the ranges listed. This standard had previously seen only minor revisions since its adoption as a technical standard in 1986. In this revision, portions that had become obsolete and that did not reflect current industry practices were revised. In addition, the example calculations that utilize GPA 2145 to reflect the 2009 revision of GPA 2145 and all calculations related to those presented in GPA 2172 were removed and referenced to GPA 2172. Also, the QA/QC related material previously included in this standard have been removed and referenced to GPA 2198. The most significant changes to the standard involve updates to the method to maintain consistency with modern technologies.