School of Chemistry and Chemical Engineering, South China University of Technology, Wushan RD., Tianhe District, Guangzhou 510640, PR China.
Anal Chim Acta. 2010 Feb 28;661(2):161-6. doi: 10.1016/j.aca.2009.12.018. Epub 2009 Dec 22.
In this article, we report a new method that involves headspace single-drop microextraction and ion chromatography for the preconcentration and determination of fluoride. The method lies in the in situ hydrogen fluoride generation and subsequent sequestration into an alkaline microdrop (15 microL) exposed to the headspace above the stirred aqueous sample. The NaF formed in the drop was then determined by ion chromatography. The influences of some crucial single-drop microextraction parameters such as the extraction temperature, extraction time, sample stirring speed, sulphuric acid concentration and ionic strength of the sample, on extraction efficiency were investigated. In the optimal condition, an enrichment factor of 97 was achieved in 15 min. The calibration working range was from 10 microg L(-1) to 2000 microg L(-1) (R(2)=0.998), and the limit of detection (signal to noise ratio of 3) was 3.8 microg L(-1) of fluoride. Finally, the proposed method was successfully applied to the determination of fluoride in different milk samples. The recoveries of fluoride (at spiked concentrations of 200 microg L(-1) and 600 microg L(-1) into milk) in real samples ranged from 96.9% to 107.7%. Intra-day precision (N=3) in terms of peak area, expressed as relative standard deviation, was found to be within the range of 0.24-1.02%.
本文报道了一种新的方法，涉及顶空单滴微萃取和离子色谱法用于氟化物的预浓缩和测定。该方法在于原位生成氟化氢，随后将其捕获到暴露于搅拌水样上方的顶空的碱性微滴（15 μL）中。在滴中形成的 NaF 随后通过离子色谱法进行测定。研究了一些关键的单滴微萃取参数，如萃取温度、萃取时间、样品搅拌速度、硫酸浓度和样品的离子强度，对萃取效率的影响。在最佳条件下，15 分钟内实现了 97 的富集因子。校准工作范围为 10 μg L(-1)至 2000 μg L(-1)（R(2)=0.998），检测限（信噪比为 3）为 3.8 μg L(-1)的氟化物。最后，该方法成功应用于不同牛奶样品中氟化物的测定。在实际样品中，氟化物（在牛奶中以 200 μg L(-1)和 600 μg L(-1)的浓度添加）的回收率在 96.9%至 107.7%之间。以峰面积表示的日内精密度（N=3），表示为相对标准偏差，在 0.24%至 1.02%范围内。
