A compact portable flow analysis system for the rapid determination of total phosphorus in estuarine and marine waters.
The development and evaluation of a portable flow analysis system for the in situ determination of total phosphorus is described. The system has been designed with rapid underway monitoring in mind. The system employs an ultra-violet photo-reactor and thermal heating for peroxodisulfate digestion of total phosphorus to orthophosphate, followed by spectrophotometric detection with a multi-reflective flow cell and low-power light emitting diode using the molybdenum blue method. Reagents are stored under gas pressure and delivered using software controlled miniature solenoid valves. The fully automated system has a throughput of 115 measurements per hour, a detection limit of 1 microg PL(-1), and gives a linear response over the calibration range of 0-200 microg PL(-1) (r(2)=0.9998), with a precision of 4.6% RSD at 100 microg PL(-1) (n=10). Field validation of the instrument and method was performed in Port Philip and Western Port Bays in Victoria, SE Australia, where 2499 analyses were performed over a 25 h period, over a cruise path of 285 km. Good agreement was observed between determinations of samples taken manually and analysed in the laboratory and those measured in situ with the flow analysis system.
Gentle
Brady S
BS
Water Studies Centre, School of Chemistry, P.O. Box 23, Monash University, Clayton, Vic. 3800, Australia.
Ellis
Peter S
PS
Faber
Peter A
PA
Grace
Michael R
MR
McKelvie
Ian D
ID