Multiclass profiling of lipids of archaeological interest by ultra-high pressure liquid chromatography-atmospheric pressure chemical ionization-high resolution mass spectrometry

Abstract

In the present work, an analytical methodology for the comprehensive evaluation of multiclass lipids (including mono-, di- and triacylglycerols (MAGs, DAGs and TAGs) along with sterols) in archaeological ceramic vessels has been developed. It is based on the use of ultra-high pressure liquid chromatography-atmospheric pressure chemical ionization-high resolution mass spectrometry (UHPLC-APCI-HRMS) with a time-of-flight mass analyser operated in the positive ionization mode. The vaporizer temperature of the APCI source was found to exert a critical influence on the fragmentation exhibited by the different studied TAGs. This fragmentation information combined with accurate mass measurements enabled the unambiguous identification of the targeted species. From the chromatographic side, two different methods were developed using: (i) a 2.1×50mm C18 high-throughput column (1.8μm particle size), with MeOH/H2O 50:50 (v/v) and isopropanol (i-PrOH) as mobile phases and; (ii) a 4.6×150mm C18 high-throughput column (with 1.8μm particle size), with MeOH and i-PrOH as mobile phases. The first method involved a fast 12-min gradient, which enabled a fast and sensitive screening of the lipid content in the studied samples. The second 25-min confirmatory method provided a thorough TAGs separation. Both methods were successfully applied for the comprehensive analysis of lipid traces from archaeological ceramics with LOQs below 5ngg−1 in most cases. The proposed methodology was applied on different ceramic samples, which belong to the Culture of the Iberians (6th–1st ct. BCE).