Traditional methods for determining dissolved hydrolyzable amino acids (DHAA) in environmental samples involve adding concentrated hydrochloric acid (HCl) to a filtered water sample, drying the hydrolysate under N2 to remove HCl, and reconstituting in a smaller volume of water to concentrate the amino acids prior to analysis. These environmental samples are most often analyzed via liquid chromatography-fluorescence detection. While this method is able to achieve picomolar detection limits, the runtimes are often long (&gt; 30 minutes) followed by extended post-run column equilibration times and high solvent use. Additionally, N2 drying adds significant and variable time to hydrolysis when one considers the sample is in 6N HCl during the process. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods allow for more sample runs in a shorter amount of time while reducing consumables. However, DHAA analysis in samples with salts results in significant matrix suppression when using LC-MS/MS. This issue becomes especially problematic for estuarine, coastal, and open ocean samples.<br/><br/>Solid phase extraction (SPE) is used to concentrate analytes while removing potential matrix interferences (organic and inorganic). This preconcentration step also allows for the elimination of N2 drying, and instead dilutes the hydrolysate to 0.1N HCl immediately following hydrolysis and prior to analysis. Here, we investigate different SPE sorbent materials on their ability to remove salts and preconcentrate dissolved organic matter (DOM) for DHAA analysis. Bovine serum albumin (BSA) was added to artificial seawater to create a source of DHAA in a relatively “pure” sample, allowing for better detection of salt matrix effects on LC-MS/MS analyses. SPE cartridges were tested in samples with salinities ranging from fresh water (0 ppt) to seawater (35 ppt). Preliminary findings indicate that PPL and C18 cartridges remove enough salt to significantly reduce matrix effects with LC-MS/MS.

Sample preconcentration and matrix removal via SPE for the determination of dissolved hydrolyzable amino acids in estuarine samples via liquid chromatography tandem mass spectrometry

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.