Li Lu, Huang Yuming, Wang Yan, Wang Weidong
College of Chemistry and Chemical Engineering, Southwest University, The Key Laboratory of Eco-environments in Three Gorges Reservoir Region, The Key Laboratory of Luminescence and Realtime Analysis, Ministry of Education; Beibei, Chongqing 400715, China.
Anal Chim Acta. 2009 Jan 12;631(2):182-8. doi: 10.1016/j.aca.2008.10.043. Epub 2008 Nov 1.
The end functionalization of CNTs can introduce oxygen-containing negatively functional groups such as -COOH, -OH, or -CO on their surface site. If cationic surfactant such as cetyltrimethylammonium chloride (CTAC) was added to the functionalized CNTs, then interactions such as hydrophobic and ionic may lead to formation of hemimicelle/admicelle aggregates on the CNTs, a new kind of adsorbents, namely, the hemimicelle capped CMMWCNTs, is obtained. The application of the hemimicelle capped carbon nanotubes-based nanosized solid-phase extraction (SPE) adsorbents in environmental analysis is reported for the first time using arsenic as model target. The effect of adsorption and desorption conditions for arsenic including the amount of surfactant, initial pH of sample solution, the ultrasonic time of sample solution, the amount of electrolyte, flow rate, eluent and its amount were investigated and optimized prior to its determination by atomic fluorescence spectrophotometry (AFS). Arsenic can be quantitatively retained on the hemimicelle capped CMMWCNTs at pH 5-6 from sample volume up to 500 mL and then eluted completely with 2 molL(-1) HNO(3) in the presence of 10 mgL(-1) CTAC. The method detection limit for arsenic determination with AFS detection was 2ngL(-1), and the relative standard deviation (RSD, n=11) was 5.3% at the 0.5 microgL(-1) level. The recoveries of arsenic in the spiked environmental water samples ranged from 94% to 104.29% with 500 mL of water sample. The proposed method has been applied successfully to the analysis of arsenic in aqueous environmental samples, which demonstrates the hemimicelle capped CMMWCNTs can be an excellent SPE adsorbents for arsenic pretreatment and enrichment from real water samples.
碳纳米管的末端功能化可在其表面位点引入含氧化负官能团，如-COOH、-OH或-CO。如果将阳离子表面活性剂如十六烷基三甲基氯化铵（CTAC）添加到功能化的碳纳米管中，那么诸如疏水和离子等相互作用可能导致在碳纳米管上形成半胶束/反胶束聚集体，从而获得一种新型吸附剂，即半胶束包覆的羧基化多壁碳纳米管（CMMWCNTs）。首次报道了以砷为模型目标，将半胶束包覆的碳纳米管基纳米级固相萃取（SPE）吸附剂应用于环境分析。在通过原子荧光分光光度法（AFS）测定之前，研究并优化了砷的吸附和解吸条件，包括表面活性剂的用量、样品溶液的初始pH值、样品溶液的超声时间、电解质的用量、流速、洗脱剂及其用量。在pH 5-6时，砷可从高达500 mL的样品体积中定量保留在半胶束包覆的CMMWCNTs上，然后在10 mgL(-1) CTAC存在下用2 molL(-1) HNO(3)完全洗脱。采用AFS检测法测定砷的方法检出限为2 ngL(-1)，在0.5 microgL(-1)水平下相对标准偏差（RSD，n = 11）为5.3%。在500 mL水样中，加标环境水样中砷的回收率在94%至104.29%之间。所提出的方法已成功应用于水性环境样品中砷的分析，这表明半胶束包覆的CMMWCNTs可成为从实际水样中预处理和富集砷的优良SPE吸附剂。
