DEVELOPMENT OF A MICRO FLOW-INJECTION MANIFOLD FOR THE DETERMINATION OF ORTHOPHOSPHATE

Fabrication of micro flow injection analysis (mu FIA) systems based on glass substrates using lithographic techniques and etching methodology has been found to produce a reliable manifold for orthophosphate analysis based on colorimetric detection. The channel dimensions used were 30 mu m deep and 325 mu m wide, and mobility of the reagents and analytes was achieved by exploiting electrokinetic mobility (at pH < 3) and electroosmotic now (at pH > 3). Detection was facilitated through the use of fibre optics coupled to a LED photodiode system. The time for analysis for the mu FIA. methods was found to be 3 min per analysis and the procedure had a limit of detection of 0.7 ppb (PO43-) with R.S.D. values in the range 1-5%. The total volume of reactants in the mu FIA device was estimated to be 0.5 mu l.