title: Determination of 3-mercaptopropionic acid by HPLC: A sensitive method for environmental applications.
abstract: The organic sulfur compound 3-mercaptopropionic acid (3-MPA) is an important thiol intermediate in organic sulfur metabolism in natural environments. It is generated during degradation of sulfur-containing amino acids (e.g. methionine) and from demethylation of dimethylsulfoniopropionate (DMSP). This pathway is an alternative enzymatic process in the DMSP catabolism that routes sulfur away from the climatically-active dimethyl sulfide (DMS). 3-MPA detection and subsequent quantification in different matrices is difficult due to its extreme reactivity. We therefore developed a sensitive method for determination of 3-MPA based on pre-column derivatization with monobromobimane and analysis by high-performance liquid chromatography (HPLC) with fluorescence detection. This methodology was first tested with 3-MPA standards under low (0.005-0.2μmolL(-1)) and high (1-25μmolL(-1)) concentrations. For the optimization of the reaction, CHES and, alternatively, Tris-HCl buffers were evaluated in the derivatization step, with Tris-HCl showing more effective separation of thiol derivatives and a better 3-MPA peak shape. The detection limit was 4.3nmolL(-1) with a 10μL sample injection, and mean recoveries of 3-MPA ranged from 97 to 105% in estuarine waters with different salinities (0.17 and 35.9ppt). The linearity (r>0.99) and repeatability of detector response, with intra- and inter-day precision (% CV) of 2.68-7.01% and 4.86-12.5%, respectively, confirmed the reliability of the method. Previous 3-MPA analytical methods required immediate analysis due to unstable derivatives, but in this method we achieved high stability of the derivatized samples when stored at 4°C, with only a 3-5% loss after more than one year of storage. This method was successfully applied to measure 3-MPA concentrations and rates of 3-MPA production in a variety of intertidal estuarine sediment slurries. Dissolved 3-MPA concentrations in these sediment slurries varied between 2 and 237μmolL(-1) and, 3-MPA net fluxes ranged in wet sediments between -3.6±1.7 and 30±5μmolL(-1)g(-1)h(-1). Thus, the application of this optimized methodology showed an efficient performance for measuring 3-MPA in environmental samples, with a straightforward sample derivatization and a simple analysis of stable 3-MPA derivatives.
authors.affiliation: CIMAR/CIIMAR - Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, n° 289, 4050-123 Porto, Portugal. Electronic address: psalgado@ciimar.up.pt.
authors.forename: P
authors.initials: P
authors.lastname: Salgado
authors.affiliation: CIMAR/CIIMAR - Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, n° 289, 4050-123 Porto, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Visnevschi-Necrasov
authors.affiliation: Department of Marine Sciences, University of South Alabama, LSCB 25, Mobile, AL 36688, USA; Dauphin Island Sea Lab, Dauphin Island, AL 36528, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Kiene
authors.affiliation: CIMAR/CIIMAR - Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, n° 289, 4050-123 Porto, Portugal.
authors.forename: I
authors.initials: I
authors.lastname: Azevedo
authors.affiliation: CIMAR/CIIMAR - Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, n° 289, 4050-123 Porto, Portugal.
authors.forename: A C S
authors.initials: AC
authors.lastname: Rocha
authors.affiliation: CIMAR/CIIMAR - Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, n° 289, 4050-123 Porto, Portugal.
authors.forename: C M R
authors.initials: CM
authors.lastname: Almeida
authors.affiliation: CIMAR/CIIMAR - Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, n° 289, 4050-123 Porto, Portugal.
authors.forename: C
authors.initials: C
authors.lastname: Magalhães
mesh_terms: D015097:3-Mercaptopropionic Acid / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004463:Ecology; D063366:Estuaries; D016014:Linear Models; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015097:3-Mercaptopropionic Acid
keywords: 3-Mercaptopropionic acid (3-MPA); High-Performance Liquid Chromatography (HPLC); Monobromobimane; Thiols