Spectrophotometric determination of trace phosphate ions by amplitude-modulated flow analysis coupled with malachite green method.

摘要: An amplitude-modulated flow analysis coupled with lock-in detection is proposed for the determination of trace phosphate. The rate F(S) sample solution varied in response to a periodic signal V(c) alternating waveform. A coloring reagent (ammonium molybdate + Malachite Green) delivered at constant F(R). Under total F(T), both solutions are merged diluent (water). Phosphate ion reacts and then Green form green pairs acidic media. Downstream, absorbance mixed measured 625 nm. output voltage V(d) from detector sent amplifier, where wave component that has same frequency as distinguished background signals. can be determined amplitude thus extracted. calibration curve linear (r(2) > 0.998) limit (3.3sigma) 0.17 micromol dm(-3). Compared conventional flow-based method no modulation, present less susceptible baseline drift due mainly adsorption ion-pair on optical window, because quantification based not itself but absorbance. Good recoveries around 100% obtained phosphate ions spiked into real water samples.