[Study of direct fluorophotometric and flow-injection fluorophotometric methods based on the inhibitory effect for the determination of trace formaldehyde].

Sulfite reacts with o-phthalaldehyde in the presence of ammonium forming the highly fluorescing isoindole-1-sulfonate in neutral or weakly acid solution, and formaldehyde has inhibitory effect on it. Based on this principle, the authors developed the direct fluorophotometric and flow-injection fluorophotometric methods for the determination of trace formaldehyde. The maximum excitation wavelength and the maximum emission wavelength are 320 and 390 nm respectively. With the direct fluorophotometric method, formaldehyde in the concentration range of 0.10-1.60 microg x mL(-1) can be determined with a detection limit of 0.046 microg x mL(-1). With the flow-injection fluorophotometric method, formaldehyde in the concentration range of 0.10-2.00 microg x mL(-1) can be determined with a detection limit of 0.085 microg x mL(-1). The methods were applied respectively to the analysis of river water with satisfactory results.