An Enhancement of Europium-/Gadolinium- Diphacinone -DL-Histidine- Cetylpyridine Bromide System for the Determination of Diphacinone in Serum

Abstract

As one of the first generation anticoagulant rodenticide, diphacinone (DPN) was extensively used in China, and often occurred accidental and intentional intoxications. To meet the needs of clinical emergency rescue, a simple, rapid and sensitive method was necessary for the determination of DPN in serum. In this paper, a fluorimetric method using a ternary europium-gadolinium-DPN-DL-histidine-cetylpyridine bromide system was developed. The fluorescence intensity was measured with a 1 cm quartz cell at 335 nm excitation wavelength and 612 nm emission wavelength. The fluorescence intensity of the europium-DPN- DL- histidine complex system was further enhanced by using gadolinium ion (Gd(3+)) in a cetylpyridine bromide (CPB) colloid-type suspension. By adding Gd(3+) at pH 8.5 to 9.5 in the presence of an ammonia-ammonium chloride buffer solution, about a 100-fold enhancement of the fluorescence intensity was achieved. The enhanced fluorescence intensity showed a good linear relationship with the DPN concentration from 0.01 mg/L to 5.0 mg/L. The limit of detection was 0.001 mg/L in serum. The established method was used to determine DPN in real human serum in clinical specimens. The luminescence mechanism was discussed in detail. In the fluorescence system of the europium-gadolinium-DPN-DL-histidine-CPB, the CPB not only acted as the surfactant but also acted as the energy donor.