Determination of copper(II) ion in water samples using sol-gel hybrid cyanopropyltriethoxysilane-methyltrimethoxysilane as sorbent in micro-solid phase extraction

Abstract

Column solid phase extraction sorbents have been used for metal ions analysis from various water samples. However, column SPE has its limitation such as channeling and it is rather expensive. The use of micro dispersive solid phase extraction (µ-D-SPE) offers a solution to channeling and it also cut cost as it only uses small amount of sorbent and no column as compared to SPE. In this study, a hybrid material, cyanopropyltriethoxysilane-methyltrimethoxysilane (CNPrTEOS-MTMOS) was successfully synthesized using sol-gel method. The sol-gel method is simple and can be carried out in room temperature. The synthesized sorbent was characterized using attenuated total reflectance (ATR) and scanning electron microscope (SEM). The as-synthesized material was applied as a new sorbent in dispersive-micro solid phase extraction (D-µ-SPE) of Cu(II) ion in different water sample namely sewage effluent, tap, bottled, zam-zam and UTM lake water. The results obtained were compared with Drinking Water Quality Standard, Ministry of Health Malaysia, (2010). Extracted Cu(II) ion was analyzed using flame atomic absorption spectroscopy (FAAS). The optimum µ-DSPE condition obtained were 20 mg CNPrTEOS-MTMOS as sorbent mass, 40 mL water sample volume, sample pH 10, and 8 min extraction time. Cu(II) was desorbed from the sorbent using 0.3 M HNO₃ as desorption solvent with vortex assisted. The calibration graph was linear in the range 100-1000 ppb with coefficient of determination (R²) of 0.9994.  Limit of detection (LOD = 3SD/slope) and limit of quantification (LOQ = 10SD/slope) obtained were 29 and 98 ppb respectively.  The as-synthesized sol-gel hybrid CNPrTEOS-MTMOS showed a great potential as sorbent for µ-D-SPE for Cu(II) ion in various water samples (sewage effluent, tap, bottled, zam-zam and UTM lake water) with good recoveries (89-109%) and precision (2.33% RSD).