Determination of Geochemically Important Sterols and Triterpenols in Sediments Using Ultrahigh-Performance Liquid Chromatography Tandem Mass Spectrometry (UHPLC–MS/MS)

Abstract

A fast, sensitive, and selective ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method that is able to quantify geochemical biomarkers in sediment is described. A pool of 10 sterols, which can be used as biomarkers of autochthonous (cholesterol, cholestanol, brassicasterol, ergosterol), allochthonous (stigmasterol, β-sitosterol, campesterol, and stigmastanol) and anthropogenic (coprostanol and epicoprostanol) organic matter (OM), and three triterpenols (lupeol, α-amyrin, and β-amyrin) were chosen as the analytes. The method showed excellent analytical parameters, and, compared with the traditional GC-MS methods that are commonly applied for the analysis of sterols, this method requires no sample cleanup or derivatization and presents improved values for the LOD and LOQ. UHPLC can separate the diastereoisomers (epicoprostanol, coprostanol, and cholestanol) and the isomers (lupeol, α-amyrin, and β-amyrin). The method was successfully applied for the quantification of the biomarkers, and thus, it was applied to assess the OM sources and the impacts of anthropogenic activities in sediments from different environments, such as Antarctica and other Brazilian systems (Continental Shelf, São Sebastião Channel, and Santos Estuary). Unique profiles of the biomarkers were observed for the contrasting environments, and β-amyrin and cholesterol were more predominant in the Santos Estuary and Antarctica samples, respectively. The sterol ratios indicated a higher level of sewage contamination in the Santos Estuary.

Quantification of Sterol and Triterpenol Biomarkers in Sediments of the Cananéia-Iguape Estuarine-Lagoonal System (Brazil) by UHPLC-MS/MS

“…The two most abundant signals in the MS/MS spectra were chosen as the product ions. The UHPLC-MS/MS method for determination of sterols and triterpenols was previously validated in relation to linearity, intraday and interday assays of accuracy and precision, and recovery [ 15 ]. A representative UHPLC-MS/MS chromatogram for the analytes in a standard solution mixture is shown in Figure 2 .…”

“…Peak 3 corresponds to the elution of lupeol, but its transitions also correspond to α - and β -amyrin, which present different retention times and were quantified using the calibration curve for lupeol. More details about the validation of the UHPLC-MS/MS method are described by Bataglion et al [ 15 ].…”

“…However, the highest concentration of coprostanol found herein is similar to that found for Santos estuary that is near to a city with ca. 420,000 inhabitants (48 ng/g) [ 15 ].…”

“…Higher plants, especially angiosperms, display triterpenols as typical and exclusive biomarkers. Triterpenols, such as lupeol and α - and β -amyrin, are the most common triterpenols found in sediments of riverine and estuarine environments [ 15 ].…”

“…The fraction containing sterols is usually derivatized to increase their volatility and decrease the limits of detection (LOD) [ 19 ]. In this sense, liquid chromatography (LC) as a separation technique and tandem mass spectrometry (MS/MS) as a detection method are combined to overcome the inherent challenges of OM complexity [ 15 ]. Some methods employing analytical platforms based on liquid chromatograph tandem mass spectrometry (LC-MS/MS) for the analysis of selected sterols have been described over the last years for a range of matrices [ 20 , 21 ] and more recently for sediments [ 15 ].…”