Ultra trace characterization of small droplets with x-ray fluorescence analysis using x-ray microbeam

x射线荧光分析使用SPring-8的BL37XU专用的x射线微探针系统进行。在Kapton衬底上蒸发1.2 nm的Cu薄膜用于评估最低检测限。采用优化的检测几何结构，达到了50 ag（或5 × 10^5的Cu原子）的检测限。所获得的检测限是世界上报道的最低检测限之一。为了产生微液滴，利用了由压电致动器驱动的液滴发生器。将液滴滴到聚丙烯薄膜上，观察液滴被氰基丙烯酸酯蒸气或液滴干燥后的残留物固定的情况。液滴发生器和自动XY工作台的结合使我们能够在设计位置产生低至30pl的小液滴。然而，基材的表面特性强烈地影响液滴的最终位置和残留。亲水性表面使残基的尺寸变宽，疏水性表面往往使残基的位置从初始位置改变

X-ray fluorescence analysis was carried out using an x-ray microprobe system dedicated in the BL37XU of the SPring-8. A thin film of Cu evaporated 1.2 nm onto the Kapton substrate was utilized for evaluating the minimum detection limits. By employing the optimized detection geometry the detection limits of 50 ag (or Cu atoms of 5 × 10^5) was achieved. The obtained detection limits is one of the lowest values reported in the worldTo generate micro droplets a droplet-generator was utilized which is driven by the piezo actuators. Liquid droplets were titrated onto the thin films of polypropylene, and the droplets fixed with the vapor of the cyanoacrylate or the residue of the dried droplets were examined. A combination of the droplet-generator and the automated XY stage has enabled us to generate a small droplet down to 30 pL onto the designed position. However surface characteristics of the substrate strongly affects the resultant position and the residue of,the droplets. A hydrophilic surface widen the size of the residue, and the hydrophobic surface often change the position of the residue from the initial position