cFI Method for o-Phosphate
Room temperature, 80 s/hour, detection limit 1 ppM P
The colorimetric assay of phosphate is based on a two-step reaction. First phospho molybdate is formed rapidly, followed by slower reduction of the yellow complex by ascorbic acid to form molybdenum blue colloid.
The traditional, constant flow method , is one of the most frequently performed FI based assays. It was, for the first time performed in FI mode almost 50 years ago (Ruzicka 1975), and recorded as shown here, by injecting sample volume 40 mL, at a flow rate of 0.8mL/min, in each channel.
Mixing coils #1 and #2 were 50 cm long, channel I.D. was 0.8mm.Colorimetric detection was carried out in 1 cm light path cell at 660 nm. The present day routine assays of orthophosphate are very similar to this old design, yet the method can be redesigned to be more sensitive, faster and more efficient.
1.2.29.
J. Ruzicka, W.B.Stewart, Anal. Chim. Acta 79, (1975) 79
J. Ruzicka, E.H. Hansen, Flow Injection Analysis 2nd Ed. Wiley NY. 1988
