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Recovery of vitamin B from SPE cartridges stored up to days did not differ from unfrozen SPE cartridges.The copyright   holder for this preprint is the authorfunder.Yet, its role in promoting the growth of eukaryotic organisms has long been understood.Numerous forms of cobalamin have been discovered since being first identified in. The majority of the variation in cobalamin forms results from differences in the upper or axial ligand on the cobalt ion.While methylcobalamin are thought to be the main forms of cobalamin in marine microbial communities, a number of forms, including glutathionyl, nitroso and sulfitocobalamin are known from medical research. Whether or not these additional substituted forms are present in the marine environments or microbes remains unknown.More recently, forms of cobalamin produced by bacteria that contain adenine in place of, dimethylybenzimidazole in the axial position have been identified and <a href="http://www.targetmol.com/compound/D-Cycloserine">Targetmol's D-Cycloserine</a> called pseudocobalamin.As a result many eukaryotes are unable to acquire pseudocobalamin; thereby, providing yet another point of influence on algal productivity. Studies examining the role of cobalamins as a limiting nutrient that controls phytoplankton dynamics in lakes and oceans rely on accurate measurements of cobalamin variants.However, a number of issues exist that severely hamper our ability to assess the impact of cobalamin limitation on phytoplankton growth.First, the concentrations of cobalamins in water samples can approach low femtomoles per liter levels requiring large volumes of water be extracted andor transported and stored.Transportation of numerous, heavy samples are an obvious strain on logistics and budgets.While recent advances in analytical methodologies have reduced sample volumes from L to mL, those techniques utilize highperformance liquid chromatography systems that have relatively large physical sizes and power requirements that limit their use to analytical laboratories far from the field.Second, recent studies have limited the flow of the water sample through SPE cartridges due to the findings of a previously published study that demonstrated excessive loss of B at flow rates exceeding mL min.This latter study used packed columns that were prepared inhouse.At a flow rate of mL min, even a mL water sample would take over hours to extract, which would clearly reduce sample throughput.The copyright holder for this preprint is the authorfunder.With these issues in mind, a series of simple experiments was devised around the use of a commercially available solidphase extraction cartridge containing a polymerbased sorbent designed to interact with a wide array of chemical properties.The first set of experiments examined the effect of sample flowrate through the SPE cartridge on the retention of cyanocobalamin.In a second set of experiments, cyanocobalamin was extracted from a synthetic seawater matrix and the cartridges stored at C for various lengths of time to assess whether the lightweight and compact SPE cartridges could resist freezing while maintaining retention of the cyanocobalamin.The copyright holder for this preprint is the authorfunder.All other solvents, acids or bases were of ACS reagent grade or higher.Stock solutions were made in water and aliquots of l were stored at C.All solutions containing B were always made or diluted in a fivesided dark box in a dimly lighted laboratory to reduce potential photodegradation.

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