Fluorescence Properties Of 2-Pyridinecarbaldehyde-p-phenylenedi Hydrazone And Its Application To Iron And EDTA Determination

The fluorescence analysis method has been widely used in foodstuff, enviroment and biological analysis due to its simple instrument, good anti-interference ability and high sensitivity. It was the key point of establishing new fluorescence method that the fluorescent probe with high sensitivity and selectivity should be designed and synthesized. It was reported that shiff bases had high specificity for metal ion recognition. So, 2-pyridinecarbaldehyde and p-phenylenediamine were chosed as reactants to synthesize shiff base and it was found that this new shiff base could be used as the fluorescent probe for ferric ion selective detection. Further, it can be used to determinate EDTA. The major work are as follows:1. A new schiff base: 2-pyridinecarbaldehyde-p-phenylenedihydrazone (short for 2PC-PPH) was synthesized and its spectral properties were studied. It was found that ferric ion (Fe³⁺) could selectively quench the fluorescence emission of 2PC-PPH at 344 nm, whereas many other metal ions, such as Mn²⁺, Zn²⁺, Cu²⁺, K+, Al³⁺, Ca²⁺, Ni²⁺, Co²⁺, Cr³⁺ and Fe²⁺, could not quench its fluorescence. Based on this, a novel method for ferric ion selective detection was established. Under the optimum conditions, the decreasing fluorescence intensity of 2PC-PPH is proportional to the concentration of Fe³⁺ within the range of 6.0×10^-7 1.0×10^-5 mol?L^-1. The detection limit (3S/N) for Fe³⁺ determination is 3.6×10^-7 mol L^-1 and the relative standard deviation for the determination of 1.0×10^-5 mol L^-1 iron is 4.9% (n = 11). The proposed method was successfully applied to determine iron in tea and milk powder.2. EDTA is a widely used chelator. It can form ternary complexes with rare earth complexes and stable complexe with Fe³⁺. Considering to this, the fluorescence change of Fe³⁺-2PC-PPH system in the presence of EDTA was examined. It was found that EDTA could further coordinate with Fe³⁺-2PC-PPH complex and enhance its fluorescence. Based on this, we established a new method for EDTA deremination. A series of reaction conditions were studied to examine their effects on the fluorescence of 2PC-PPH- Fe³⁺-EDTA-HAC-NaAC system. Also, the selectivity of the system was investigated. Under the optimum conditions, the linear range and detection limit (3S/N) for EDTA determination are 2.0×10-6 1.4×10^-5 mol L^-1 and 1.5×10^-7 mol L^-1, respectively. The relative standard deviation for the determination of 7.0×10^-6 mol L^-1 EDTA is 3.7% (n = 11). The method was successfully applied to determine EDTA in tap water, lake water and contact lens solution.