RESUMO
In the presence of pH 4.0 HAC-NaAC buffer solution, using H3BO3-KI (BKI) as absorption solution, O3 oxidized KI to produce I2, and it reacted with excess I- to form I3- that combined with the cationic surfactant (CS) such as cetylpyridinium chloride (CPCl), tetradecyl pyridinium bromide (TPB), cetyl trimethyl ammonium bromide (CTMAB), and tetradecyl dimethylbenzyl ammonium chloride (TDMAC) to produce stable (CS-I3)n association particles, which exhibited a strong resonance Rayleigh scattering (RRS) peak at 470 nm. Under the chosen conditions, as the concentration of O3 (C) increased, the concentration of I3- increased, and the RRS intensity at 470 nm (1470 nm) increased due to more association particles forming. The increased RRS intensity I470 nm was linear with O3 concentration. For the four CS systems, the linear range was 15-50, 50-100, 5-25 and 1-50 micromol x L(-1) O3 respectively. The regression equation is delta I = 8.81c-4.01, delta I = 5.44c-3.11, delta I = 15.39c-1.55, and delta I = 16.88c + 0.51. The detection limit is 4.9, 12, 2.85 and 0.56 micromol L(-1) O3 respectively. The influence of some foreign substances was examined on the determination of 2.5 x 10(6) mol x L(-1) O3, within +/- 10% relative error. Results showed that a 4.0 x 10(-5) mol x L(-1) Hg2+, 8.7 X 10(-5) mol x L(-1) Fe3+, 5.0 x 10(-5) mol x L(-1) Ca2+, 2.5 x 10(-5) mol L(-1) Zn2+ and Cu2+, 2.8 x 10(-6) mol x L(-1) Pb2+ and Cr3+, 4.2 x 10(-5) mol x L(-1) Mg2+, Mn2+ and Ba2+ do not interfere with the RRS determination. This showed that this RRS method is of good selectivity. The TDMAC system is most sensitive, and was chosen to detect O3 in air samples. The analytical results were in agreement with that of spectrophotometry results. Further more, laser scattering technique was utilized to examine the particle size distribution of (TDMAC-I3)n system. Results indicated that the particle size located in the range of 190-531 nm, in the absence of O3. Upon addition of O3, the excess KI reacted with O3 to produce I3-, and I3- interacted with the TDMAC to form (TDMAC-I3)n associated particles with a size range of 1,106-3,091 nm. This test identified that there are associated particles in the TDMAC system.
