Fluorometric detection of total dissolved zinc in the southern Indian Ocean

Flow injection analysis as a tool for enhancing oceanographic nutrient measurements—A review

“…Dissolved Zn concentrations profiles resemble those of the major nutrients, with large deep to surface concentration ratios [217,218]. Concentrations of dissolved Zn are <0.1 nM in surface waters of the world's oceans [217][218][219], with approximately 98% of this pool chelated by strong organic ligands [220,221]. This reduces the bioavailable fraction of Zn, the free metal ion, to concentrations as low as 1 pM, values which have been shown to limit phytoplankton growth in culture experiments [222][223][224][225].…”

“…Zinc is a notoriously pervasive contaminant, as it is frequently used on marine vessels and equipment. Therefore accurate measurements can only be made using strict safeguards during sample collection and analysis [219,221].…”

“…The ligand, p-tosyl-8-aminoquinoline (pTAQ), selectively complexed zinc to give a fluorescent product with a detection limit of 0.1 nM for a 4.4 mL sample and a precision of ±6% (n = 5) for a 4.3 nM Zn standard. A depth profile of 12 samples plus standards and blanks was analysed in triplicate in 5.5 h. This method was recently adapted for shipboard use for low level Zn concentrations in the Indian Ocean [219]. The key modifications were: (1) using 40 M of pTAQ and (2) use of 0.16 M ammonium acetate buffer (pH 5.7) as the rinse step.…”

Determination of trace zinc in seawater by coupling solid phase extraction and fluorescence detection in the Lab-On-Valve format

“…Although this FIA technique has been used successfully on several shipboard transects and process studies in the open ocean [8][9][10], this method relies on a poorly selective fluorescent reagent which suffers from significant interferences from Ca, Mg and Cd [7]. In addition, FIA manifolds have high reagent consumption rates, necessitate regular calibrations, frequent maintenance and thus require highly trained analysts for routine operation onboard research vessels.…”

“…In addition, filtered (0.45 µm), acidified seawater samples (pH=1.7) collected in 2009 in the upper 1,300m of the south Indian subtropical gyre (32.2°S, 111.45°E) during the US-CLIVAR CO 2 Repeat Hydrography I05 transect [8,22] were analyzed for Zn using the proposed method. Prior to analysis, 20 mL aliquots of the stored acidified seawater samples (pH=1.7) were pipetted into 30 mL PTFE bottles and then buffered offline to pH 6.0 by adding 1 mL of ammonium acetate sample buffer (pH 9.1).…”