采用化学还原法合成牛血清白蛋白(BSA)修饰的金纳米簇(AuNCs),基于Co²⁺对AuNCs的荧光猝灭作用,提出了一种快速、简便、灵敏测定Co²⁺含量的方法。以柠檬酸为还原剂、BSA为保护剂、氯金酸为原料合成AuNCs。分取0.20 mL AuNCs溶液,加入0.6 mL pH 9.0碳酸钠-碳酸氢钠缓冲溶液,用水稀释至1.00 mL,在发射波长630 nm处测量上述体系(空白体系)的荧光强度F₀。取10片维生素B₁₂药片,研磨后,分取0.127 0 g,用水溶解并稀释至100 mL,分取10 μL于空白体系中,混匀后静置反应5 min,测量荧光强度F,利用荧光强度的差值ΔF(ΔF=F₀-F)进行定量。结果显示:合成的AuNCs分布均匀,Co²⁺对AuNCs体系有荧光猝灭作用,属于动态猝灭过程。添加10倍Co²⁺浓度的干扰离子,Fe²⁺、Pb²⁺、Al³⁺、Zn²⁺、Mg²⁺、Cr³⁺、Cu²⁺、Sr²⁺、Mn²⁺、Ca²⁺不产生干扰,Fe³⁺、Ni²⁺的干扰可通过添加三乙醇胺和邻二氮菲掩蔽,Hg²⁺的干扰严重。Co²⁺浓度分别在2.0×10^-11~1.5×10^-10mol·L^-1和1.5×10^-10~9.9×10^-10mol·L^-1内与对应的ΔF呈线性关系,检出限(3s/k)为1.7×10^-12mol·L^-1。按照标准加入法对两个厂家的实际样品进行回收试验,所得测定值和标签值较为接近,Co²⁺回收率均接近100%,测定值的相对标准偏差(n=5)均小于5.0%。

AuNCs modified by BSA were synthesized using chemical reduction method. Based on the fluorescence quenching effect of Co²⁺ on AuNCs, a fast, simple, and sensitive method for determining Co²⁺ was proposed. AuNCs were synthesized using citric acid as the reducing agent, BSA as the protective agent, and chloroauric acid as the raw material. An aliquot (0.20 mL) of the AuNCs solution was taken, and 0.6 mL of pH 9.0 sodium carbonate-sodium bicarbonate buffer solution was added. The mixture was diluted to 1.00 mL by water, and the fluorescence intensity F₀ of the above system (blank system) was measured at emmison wavelength of 630 nm. Ten vitamin B₁₂ tablets were taken and ground, and an aliquot (0.127 0 g) was taken, dissolved and diluted to 100 mL by water. The above solution of 10 μL was taken, and added into the blank system. The mixed solution was settled for 5 min, and the fluorescence intensity F was measured. The fluorescence intensity difference ΔF(ΔF=F₀-F) was used for quantification. As shown by the results, the synthesized AuNCs were evenly distributed, and Co²⁺had a fluorescence quenching effect on the AuNCs system, belonging to dynamic quenching process. Adding interference ions with a concentration of 10 times Co²⁺, ions of Fe²⁺, Pb²⁺, Al³⁺, Zn²⁺, Mg²⁺, Cr³⁺, Cu²⁺, Sr²⁺, Mn²⁺, Ca²⁺ did not cause interference. The interference of Fe³⁺ and Ni²⁺ could be masked by addition of triethanolamine and ortho phenanthrene, while the interference of Hg²⁺ was severe. Linear relationships between values of the concentration and ΔF of Co²⁺ were kept in the ranges of 2.0×10^-11-1.5×10^-10mol·L^-1 and 1.5×10^-10-9.9×10^-10mol·L^-1, with detection limit (3s/k) of 1.7×10^-12mol·L^-1. Test for recovery was made according to standard addition method on actual samples from two manufacturers, and determined values and label values were relatively close, giving recovery of Co²⁺ close to 100%, and RSDs (n=5) of the determined values less than 5.0%.