Department of Chemistry, Semnan University, Semnan 35195-363, Iran.
Department of Chemistry, Semnan University, Semnan 35195-363, Iran.
Anal Chim Acta. 2017 Mar 8;957:1-9. doi: 10.1016/j.aca.2016.12.041. Epub 2017 Jan 2.
In the present work, a novel nanosorbent namely layered double hydroxides with 4-amino-5-hydroxyl-2,7-naphthalendisulfonic acid monosodium salt interlayer anion (Mg-Al-AHNDA-LDH) was synthesized and applied as a dissolvable nanosorbent in a centrifugeless ultrasound-enhanced air-agitated dispersive solid-phase extraction (USE-AA-D-SPE) method. This method was used for the separation and preconcentration of some metal ions including Cd, Cr, Pb, Co, and Ni prior to their determination using the micro-sampling flame atomic absorption spectrometry (MS-FAAS) technique. The most interesting aspect of this nanosorbent is its immediate dissolvability at pH values lower than 4. This capability drastically eliminates the elution step, leading to a great improvement in the extraction efficiency and a decrease in the extraction time. Also in this method, the use of a syringe nanofilter eliminates the need for the centrifugation step, which is time-consuming and essentially causes the analysis to be off-line. Several effective parameters governing the extraction efficiency including the sample solution pH, amount of nanosorbent, eluent condition, number of air-agitation cycles, and sonication time were investigated and optimized. Under the optimized conditions, the good linear dynamic ranges of 2-70, 6-360, 7-725, 7-370, and 8-450 ng mL for the Cd, Cr, Pb, Coand Ni ions, respectively, with the correlation of determinations (Rs) higher than 0.997 were obtained. The limits of detection (LODs) were found to be 0.6, 1.7, 2.0, 2.1, and 2.4 for the Cd, Cr, Pb, Co, and Ni ions, respectively. The intra-day and inter-day precisions (percent relative standard deviations (%RSDs) (n = 5)) were below 7.8%. The proposed method was also successfully applied for the extraction and determination of the target ions in different biological fluid and tap water samples.
在本工作中，合成了一种新型纳米吸附剂，即带有 4-氨基-5-羟基-2,7-萘二磺酸钠层间阴离子（Mg-Al-AHNDA-LDH）的层状双氢氧化物，并将其作为一种可溶解的纳米吸附剂应用于无离心超声增强空气搅拌分散固相萃取（USE-AA-D-SPE）方法中。该方法用于分离和预浓缩一些金属离子，包括 Cd、Cr、Pb、Co 和 Ni，然后使用微采样火焰原子吸收光谱（MS-FAAS）技术进行测定。这种纳米吸附剂最有趣的特点是其在 pH 值低于 4 时能够立即溶解。这种能力极大地消除了洗脱步骤，极大地提高了萃取效率，同时减少了萃取时间。此外，在这种方法中，使用注射器纳米滤器消除了需要耗时且本质上使分析成为离线的离心步骤。考察并优化了影响萃取效率的几个有效参数，包括样品溶液 pH 值、纳米吸附剂用量、洗脱条件、空气搅拌循环次数和超声时间。在优化条件下，Cd、Cr、Pb、Co 和 Ni 离子的线性动态范围分别为 2-70、6-360、7-725、7-370 和 8-450ng mL，相关系数（Rs）均高于 0.997。检出限（LODs）分别为 0.6、1.7、2.0、2.1 和 2.4ng mL。Cd、Cr、Pb、Co 和 Ni 离子的日内和日间精密度（n=5，相对标准偏差（%RSD））均低于 7.8%。该方法还成功应用于不同生物体液和自来水中目标离子的提取和测定。
