| Based on the development of phenylfluorone reagents and considersation on the relationship of molecular structure and analytical characteristics of derivatives of phenylfluorone, a new reagent, dimethylphenylazosalicylfluorone (DMPASF), was designed and synthesized in this laboratory. After purified, the molecular structure of the reagent was confirmed by ultraviolet spectrum (UV), infrared spectrum (IR), EIS- /EIS+ and element analysis. DMPASF was a weak acid, its dissociation constants in water were determined and calculated by spectrophotometry and Klygin's formula. According to electronic charge distribution and the dissociation constants of the reagent, a suit dissociation procedure was supposed. Based on literature and the experiences of our laboratory, several 1-alkyl-3-methylimidazolium hexafluorophosphate were also synthesized.Firstly, we investigated color reaction of DMPASF with aluminum (III). In the presence of ammonium acetate solution and CTMAB, DMPASF reacted with aluminum (III) rapidly to form 3:1 red complex with a maximum absorption peak at 564nm. The apparent molar absorptivity was found to be 1.40×105 L·mol - 1·cm- 1. Beer's law is obeyed in the range of 0～6μg/25ml for aluminum. Moreover, color system has excellent selectivity. Most of metal and nonmetal ions can be tolerated in considerable amounts without any masking reagent. The proposed method has been applied to determination of aluminum in water samples and magnesium alloy and the results are satisfying. Base on above study, we also investigated color reaction of DMPASF with uranium (VI). In the presence of ammonium acetate solution and CTMAB, DMPASF reacted with uranium (VI) rapidly to form 3:1 red complex. The complex has a maximum absorption peak at 556nm, with apparent molar absorptivity of 1.28×105 L·mol-1·cm-1. Beer's law is obeyed in the range of 0～20μg/25ml for uranium. Its sensitivity and selectivity were superior to other uranium regents in literature. The proposed method has been applied to determination of uranium in seawater samples and the results are satisfying.Although color reaction of DMPASF with aluminum (III) or uranium (VI) has high sensitivity, it is not good enough to determine ultra trace Al and U in complicated samples. In order to advance the sensitivity further more, room temperature ionic liquid was used to replace traditional volatilizable organic reagents in liquid-liquid extraction of aluminum and uranium. 1-Octyl-3-methylimidazolium hexafluorophosphate ([C8mim] PF6) was choosed as medium. After the complex of aluminum and DMPASF was formed in optimal conditions in 1000ml calibrated bottle, 5ml [C8mim] PF6 was added into the solution and the complex was extracted after 10 minutes'surge. Then, aluminum was stripped from ionic liquid by 10ml 1mol·L-1HNO3 and determined by graphite furnace Atomic absorption spectrometry. Extraction efficiency and stripping efficiency were more than 95% respectively. The determination of trace aluminum in dialysis brine was carried out with the recommended method. After the complex of uranium and DMPASF was formed in optimal conditions in 1000ml calibrated bottle, 5ml [C8mim] PF6 was added into the solution and the complex was extracted after 10 minutes'surge. Then, uranium was stripped from ionic liquid by 10ml 3mol·L-1HCl and determined by spectrophotometry with chlorophosphonazo III (CPAIII), with apparent molar absorptivity of 3.17×106 L·mol-1·cm-1. Extraction efficiency and stripping efficiency were more than 95% respectively. The preconcentration coupled with spectrophotometry with CPAIII was developed for determination of ultra trace uranium in seawater and the results are satisfying.
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