OUTLOOK
3.6.
Bead Injection offers many opportunities for future research and applications, in my opinion more, than any other flow analysis technique.
Because BI relies on flow programming it benefits from recent development of advanced pump design (miliGAT) because broader range of flow rates empowers manipulation and metering of beads by microfluidic manipulations. Redesigned lab-on-valve is more flexible, because the externally mounted flow cell offers versatility of switching between renewable column and bead spectrophotometry mode. And, of equal importance, is broadening range of suitable sorbents, that expands the previous portfolio of Sephadex and Sepharose with OASIS and STRATA polymeric beads.
The renewable column based Sorbent Extraction (3.2.1.) now enables spectrophotometric assays to be applied down to nanomolar concentrations. Determination of iron(II) by ferrozine is an example of assay based on selective formation of metal chelate, captured on hydrophobic surface and eluted by changing polarity for subsequent monitoring at selected wavelength. This approach is useful for determination of traces of analytes in oceanography where high ionic strength of sea water matrix makes use of ion exchange impractical. Therefore literature on Solvent Extraction of Metal Chelates (Stary 1964) and Spectrophotometric Determination of Elements (Marczenko 1976) are valuable source of information on selective determination of elements that can be now performed in Sorbent Extraction format.
Recently published comprehensive reviews deal with both renewable column separations and Bead Injection Spectrophotometry and their scope also involves other detection techniques; atomic absorption, fluorescence and chemiluminiscence (Miro 2008, Vidigal 2012 and 2013).
These works summarize experience from several laboratories, and offer useful information on methodology and chemistry of many reagent based assays performed in bead injection format.
Interestingly, majority of BI based assays has been applied to chemical assays while applications to biochemistry and cellular assays are very few. The potential of BI method still has to be discovered in these areas, where this versatile technique has much to offer.
Stary 1964\
Marczenko 1976
M. Miro , S. K. Hartwell, J. Jakmunee, K. Grudpan, E. H. Hansen “Recent developments in automatic solid-phase extraction with renewable surfaces exploiting flow-based approaches’ TrAC 27 (2008) 749
S.M.P. Vidigal , I. V. Tóth, A. O.S.S. Rangel, Talanta 96 (2012) 102–106
S. M. P. Vidigal, Ildiko V. To´thb Antonio O. S. S. Rangel “Sequential injection lab-on-valve platform as a miniaturization tool for solid phase extraction” Anal. Methods, 2013, 5, 585
Literature references are most useful if
relatively recent or very old.
T. Hirschfeld.