Microwave preservation method for DMSP, DMSO, and acrylate in unfiltered seawater and phytoplankton culture samples

A microwave-preservation method was developed to quantify total dimethylsulfoniopropionate (DMSPT), dimethylsulfoxide (DMSOT), and acrylate (acrylate(T)) concentrations in unfiltered samples to alleviate problems associated with the acidification method when applied to samples containing Phaeocystis. Microwaveand acid-preservation methods were compared using batch cultures of Phaeocystis antarctica and 11 other marine phytoplankton species for DMSPT, batch P. antarctica cultures for DMSOT and acrylate(T), and unfiltered Delaware Estuary water samples for DMSPT to demonstrate the general applicability of this method. Acidification of P. antarctica culture samples resulted in the underestimation of DMSPT (42-69%) and overe-stimation of dimethylsulfide (DMS) (2156-3819%), DMSOT (9-101%), and acrylate(T) (71-249%). By comparison, DMSPT concentrations in microwaved samples agreed with non-microwaved, non-acidified controls. In contrast to P. antarctica results, the microwave- and acid-preservation methods yielded DMSPT concentrations that were statistically indistinguishable for 11 other marine phytoplankton species and Delaware Estuary samples. Unfiltered samples stored frozen following microwave treatment or stored at room temperature if acidified after the microwaving step, resulted in no change in DMSPT or acrylateT; DMSOT concentrations increased slightly (similar to 15%) when they were not sparged to remove DMS prior to acidification and room temperature storage. Based on these findings, we propose microwaving small sample volumes (<= 7 mL) of unfiltered seawater or culture samples as a general approach to preserve samples for subsequent DMSPT, DMSOT, and acrylateT analyses, especially when the phytoplankton composition of the samples is unknown.