研究2-（5-溴-2吡啶偶氮）-5-二乙氨基苯酚（5-Br-PADAP）分光光度法测定手掌面镀锌工具遗留印迹的锌含量。 考察了缓冲液用量、 pH、 显色剂用量等反应条件对测定的影响； 在优化好的条件下, 建立了标准曲线并测定了不同接触时间、 时间间隔条件下手掌面镀锌工具遗留印迹的锌含量。 研究结果表明, pH 8.0的硼砂-硼酸缓冲液4 mL, 1 g·L-1的5-Br-PADAP溶液0.2 mL以及10%曲拉通-X-100溶液1 mL为最佳测定条件, 在此条件下, Zn2+在0~14 μg范围内呈良好的线性关系, 回归方程为y=1.851 34x+0.002 29； 在接触时间10 s~5 min内, 手掌面镀锌工具遗留印迹锌含量呈上升趋势, 在5~10 min内趋于平缓, 在接触时间5 min时已基本达到饱和状态, 锌含量在0.425~2.377 μg·cm-2； 手掌面镀锌工具遗留印迹锌含量在间隔时间0~2 h急剧下降, 在2~7 h内下降的幅度逐渐变小, 当间隔时间达到7 h时, 锌含量仅为0.188 μg·cm-2, 与间隔0 h锌含量相比减少了约90%。 因此, 微量金属显现实验一定要尽早进行。 此外, 不同间隔时间条件下手掌面锌含量的变化规律与喷洒显现实验中遗留印迹强度变化并非完全对应, 这说明手掌面上的锌含量并非唯一可以影响不同间隔时间条件下遗留印迹强度的因素。 首次在实验中证实了Zn2+与蛋白质结合后可以被络合能力更强的5-Br-PADAP分子夺取出来而显色的假设。 运用此种宏观微观相结合的方法进行研究, 有利于对微量金属显现实验中各影响因素机理的探讨, 为进一步的研究奠定了基础。

Spectrophotometric determination of the amount of zinc on the imprint left on hands by zinc coatings with 2-(5-Bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) as a chromogenic reagent has been studied in this paper. The effect of reaction conditions including volume and pH of buffer solution as well as the volume of chromogenic reagent on the determination has also been studied. On the optimized condition, the standard curve of zinc has been established and the amount of zinc on the imprint left on hands by zinc coatings with different contact time and time elapse has been determined separately. As the results shown, the optimized reaction condition is 4 mL of boric acid and borax buffer solution(pH 8.0), 0.2 mL of 5-Br-PADAP with the concentration of 1 g·L-1 and 1 mL of Triton-X-100 with volume fraction of 10%. Under this circumstance, high linearity of zinc is followed between 0 and 14 μg and the regression equation of zinc is y=1.851 34x+0.002 29. The amount of zinc on the imprint left on hands by zinc coatings, ranging from 0.425 to 2.377 μg·cm-2, increases with contact time from 10 second to 5 min and varies insignificantly from 5 to 10 min. The amount of zinc left on hands declines sharply with time elapse from 0 h to 2 h, and then slowly from 2 to 7 h. The amount of zinc within 7 h is only 0.188 μg·cm-2, which is 90% lower than that of 0 h. Therefore, it is suggested that the trace metal detection should be conducted as soon as possible. Besides, the amount of zinc on the imprint left on hands by zinc coatings with different time elapse is not entirely comply with the intensity of imprint left by zinc coatings. This demonstrates that the amount of zinc on hands is not the only factor influencing the intensity of imprint on hands with different time elapse. Additionally, it also proves the hypothesis that zinc in the complex of zinc and protein can be captured and bonded by 5-Br-PADAP resorting to a stronger chelating capacity in the experiment for the first time. The application of the combined methods in a macro and micro view is useful for study in mechanism of influencing factors in trace metal detection, which lays foundations l for further researches.