Flow injection programmed to function in batch mode is used to determine molar absorptivity and to investigate the
Jaromir Jarda Ruzicka1, Graham D Marshall2, Christopher I Measures1
1Department of Oceanography University of Hawaii, Honolulu, HI, 96822, USA.
Abstract:
The ultimate goal of flow-based analytical techniques is to automate serial assays of a target analyte. However, when developing any reagent-based assay, the underlying chemistry has to be investigated and understood a step, which is almost always the most challenging component of the optimization effort. The difficulty lies in that almost all reagent-based assays were initially developed and optimized in a batch mode, with the aim to perform assays manually, within a time frame of up to 15 min, while flow injection techniques are designed to monitor concentration gradients at times prior to reaching chemical equilibria and while performing up to two assays per minute. This work resolves this discrepancy by using programming Flow Injection (pFI) that operates in a batch mode within a time frame of 1 min or less, with the aim of optimizing an assay under the same conditions and using the same instrument in which the assay will be performed. This novel concept is verified by determining a molar absorptivity of Fe(II) ferrozine complex and by comparing it with literature data. Next, the pFI-batch technique was used to investigate and optimize the phosphate assay, based on formation of phosphomolybdenum blue, with the aim of maximizing sensitivity and improving the limit of detection of this widely used method.
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