Samples for quantification of dissolved and particulate B vitamins were collected at a number of depths within the euphotic zone (see field study sites). Seawater was collected from each CTD depth using Niskin bottles and immediately filtered. Particulate samples were collected using 0.2µm in-line filters and a peristaltic pump (flow rate < 50 ml per minute), transferred into sterile cryovials. and were immediately stored at -80 degrees C until analysis. One liter of filtrate was collected and stored in 1-L bottles at -20 degrees C until analysis. Dissolved B-vitamin pre-concentration was performed as described in Suffridge et. al (2017) and Sañudo et al 2012.
All vitamin samples were analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS). The LCMS system consists of a ThermoTSQ Quantum Access electro-spray ionization triple quadrupole mass spectrometer, coupled to a Thermo Accela High Speed Liquid Chromatography system.
Particulate B-vitamins were extracted in acidic methanol (pH 3.5, 5% MeOH, 95% LC/MS Grade water) using bead-beating for cell lysis and a 30C incubation for B-vitamin extraction. A liquid phase extraction using chloroform (1:1 v/v) was used to clean up the samples prior to analysis. The extraction was performed as described in Suffridge et. al (submitted to L&O Methods, June 2016).
Cited References:
Suffridge, Christopher; Cutter, Lynda; Sanudo-Wilhelmy, Sergio (2017) A New Analytical Method for Direct Measurement of Particulate and Dissolved B-vitamins and Their Congeners in Seawater. Front. Mar. Sci. vol.4 doi.org/10.3389/fmars.2017.00011
Sanudo 2012 - Proc Natl Acad Sci U S A. 2012 Aug 28;109(35):14041-5. doi: 10.1073/pnas.1208755109. Epub 2012 Jul 23