Synthesis, characterisation and application of mercapto- and polyaminophenol-bifunctionalised MCM-41 for dispersive micro solid phase extraction of Ni(II) prio to inductively coupled plasma-optical emission spectrometry (DMSPE-ICP-OES)

Abstract

Highly ordered adsorbent mesoporous silica (MCM-41) was synthesised using a rapid method and its subsequent chemical modification with 3-mercaptopropyltrimethoxysilane (MPTMS) in toluene medium at 60°C was performed. The electro-reduction product of 4-nitrophenol (EP4NP), as a new kind of polyaminophenol-type chelating agent with a high affinity to Ni(II), was then incorporated into MPTMS-MCM-41. The resulting materials (MCM-41, MPTMS-MCM-41 and EP4NP-MPTMS-MCM-41) were characterised by scanning electron microscopy, powder X-ray diffraction, nitrogen gas sorption and Fourier transform-infrared spectrometry. The new modified adsorbent EP4NP-MPTMS-MCM-41 was then employed for preconcentration of ultra-trace amounts of Ni(II) by dispersive micro solid phase extraction prior to inductively coupled plasma-optical emission spectrometry. The effects of variables such as pH, mass of the chelating agent, the amount of EP4NP-MPTMS-MCM-41, stirring time of extraction step, HCl concentration and stirring time during elution were optimised and the calibration curve was plotted. The limits of detection and quantitation were 0.006 and 0.019 μg L⁻¹, respectively. The mean, standard error and relative standard deviation for five replicates of 0.5 μg L⁻¹ Ni(II) were calculated to be 0.48 μg L⁻¹, 4.0% and 3.2%, respectively. The proposed method was successfully applied for determination of Ni(II) in wastewater samples.

Keywords:

• 4-nitrophenol
• electropolymerisation
• nickel(II)
• mesoporous MCM-41
• dispersive micro solid phase extraction