食品安全问题越来越严重,汞作为有害离子之一受到人们的广泛关注,为了寻求茶叶和火腿肠中汞含量测定的新方法.首先以罗丹明B,肼水化合物,邻羧基苯甲醛为原料反应生成一种新型的Hg2+荧光增强型探针;接着,通过荧光光谱仪测量探针与不同浓度汞离子络合后的荧光强度,研究汞离子浓度与荧光强度的关系,绘制出标准工作曲线;然后,对茶叶进行微波消解,消解后用合成的探针测定茶叶中汞的含量.结果表明:探针和络合物的最大激发波长为568.05和560.00 nm,最大发射波长为587.94和580.00 nm;检测的适宜条件为:溶剂为50%甲醇水溶液,3.0 mL pH 4.0的缓冲溶液,反应时间30 min内.该探针对Hg2+有很好的选择性,Na+,K+,Ca2+,Cu2+,Zn2+,Al3+对此探针的荧光强度几乎没有影响,Fe3+,Mg2+,Ba2+对此探针的荧光强度仅有微弱的增强,而很低浓度的Hg2+对此探针的荧光强度有显著的增强作用.Hg2+浓度在5～20 ng·L-1范围内线性相关系数为0.951 2,检出限为1.9 ng·L-1;对茶叶和火腿肠样品进行Hg2+加标回收实验,标准回收率分别为101.1%,92.6%.该方法仪器结构简单,灵敏度,准确度高,选择性好且用样量少,无需富集,有很强的实用性.

Recently,the problem of food security is more and more serious,and people pay attention to mercury because of the toxic of it.A new approach for the determination of mercury content in foodstuff is devised.In this paper,first,we design and synthesis a new kind of fluorescent probe whose matrix based on rhodamine B,hydrazine hydrate and hydroxy benzaldehyde.Through the analysis of H-NMR spectra of the synthesized product L1,we confirm that the synthetic substance is the adjacent carboxyl benzaldehyde hydrazone structure generation of rhodamine B.Then,we measure the fluorescence signal intensity of the probe with different concentrations of mercury ions fully upon complexation by fluorescence spectrometer and we can study the relationship between the mercury ion concentration and the fluorescence intensity and draw the standard working curve.Following,It’s time to discuss the microwave digestion processing of tea,after digestion we use the synthetic probe L1 for determination of mercury content in tea.The experimental results show that the maximum excitation wavelength of the probe and coordination compound are 568.05 and 560.00 nm,the maximum emission wavelength are 587.94 and 580.00 nm.Then we can find the best testing conditions to improve the degree of accuracy,that is:room temperature,50% the methanol solution,3.0 mL pH 4.0 buffer solution,in the extent of 30 min.The experimental results show that Na+,K+,Ca2+,Cu2+,Zn2+,Al3+ have little impact on the fluorescence intensity of the probe.Fe3+,Mg2+,Ba2+ has a weak enhancement to the fluorescence intensity of the probe.While a low concentrations of Hg2+ have an obviously enhanced effect on the fluorescence intensity of the probe.In contrast to other metal ions,the probe for Hg2+ has a good selectivity.Linear relationship between the magnitude of increase in fluorescence intensity and concentration of mercury ion was in the range of 5～20 ng·L-1 with detection limit(3S/N) of 1.9 ng·L-1.The proposed method was applied to determination of mercury ion in samples of tea and sausage and the obtained result and sample recovery were all satisfactory.The methods of analysis instrument has the advantages of simple structure,sensitivity,high accuracy,good selectivity and less volume of simple,without the need for enrichment,being very practical.