RESUMO
With the increasing number of food safety problems caused by the abusing and misusing of plant hormones, it will be increasingly important to strengthen the trace detection of plant hormones in foods. In this study, benzyl methacrylate_methyl methacrylate_based amphiphilic polymer micelles were prepared, and a method for trace determination of five plant hormones was established by using these micelles. This method was rapid, sensitive and reproducible. Through optimization, the best experimental conditions were obtained as follows: 2 g/L polymer micelles, 50 mmol/L NaOH_H3BO3 buffer (pH 9. 2), 15 kV running voltage. Based on this novel method, naphthalene acetic acid in the solution of rooting powder was determined.
RESUMO
Luminescent particles of lead carboxymethyl cellulose (Pb(CMC)2) containing salicyl fluorones (THBF), Pb(CMC)2-THBF were synthesized by the sol-gel method, using sodium carboxymethyl cellulose (NaCMC) as precursor and Pb2+ as precipitant. Pb(CMC)2-THBF can emit the intense and stable solid substrate room temperature phosphorescence (SS-RTP) on filter paper. And EDTA can chelate Pb2+ in Pb(CMC)2-THBF, causing it to decompose into aqueous soluble components PbY2-, CMC- and THBF, which can react with Ag+ to form Ag(CMC)2-THBF, causing the decrease of phosphorescence intensity. Based on the facts above, a new method for the determination of trace silver by SS-RTP quenching method was established. The linear range of this method is 8.0-40.0 fg spot(-1) (20.0-100.0 pg ml(-1)), with a detection limit (LD) of 2.2 fg spot(-1) (corresponding to a concentration range of 5.5 x 10(-13) g ml(-1)), and the regression equation of working curve is DeltaI(p) = 12.56 + 0.5527C(Ag+) (fg spot(-1), 0.4 microl spot(-1)), n = 8, r = 0.9992. This method has been applied to the determination of trace silver in human hair and tea sample with satisfactory results. The mechanism of SS-RTP emission is also discussed.
