Electro-mediated microextraction (EMM) combined with micro-high performance liquid chromatography-ultraviolet detection was successfully developed for the determination of selected phenols, namely 4-chlorophenol (4CP), 2-nitrophenol (2NP) and 2,4-dichlorophenols (2,4 DCP) in water. A solvent-impregnated agarose gel disc was utilized as a solvent holder in this study. Under optimum extraction conditions, the method showed good linearity in the range of 0.1-250µgL-1, 0.3-250µgL-1and 0.2-500µgL-1for 4CP, 2NP and 2,4 DCP, respectively with correlation coefficients of ≥ 0.9975, ultra-trace LODs (0.03-0.1µgL-1) and satisfactory relative recovery average (85.0-114.1%) for the analysis of selected phenols. The proposed method was rapid and eco-friendly as the solvent holder was constructed using minute amounts of extraction solvent immobilized within the biodegradable agarose gel disc. A comparative microextraction technique termed solvent-impregnated agarose gel liquid phase microextraction (AG-LPME) was re-optimized and validated for the extraction of phenols in water. The method offered good linearity, ultra-trace LODs ranging 0.1-0.5µgL-1and satisfactory average of relative recovery (86.1-114.1%). The EMM was superior in terms of sensitivity and time-effectiveness compared to AG-LPME. Both techniques combine extraction and pre-concentration in mini-scaled approaches using an eco-friendly solvent holder that fulfil the green chemistry concept.
In this paper, the electrical, dielectric, Raman and small angle X-ray scattering (SAXS) structure behavior of disposed transformer oil in the presence of multi-walled carbon nanotube (MWCNT) were systematically tested to verify their versatility for preparing better alternative transformer oil in future. MWCNT nanofluids are prepared using a two-step method with concentrations ranging from 0.00 to 0.02 g/L. The test results reveal that 0.005 g/L concentration possesses the most optimum performance based on the electrical (AC breakdown and lightning impulse) and dielectric (permittivity, dissipation factor and resistivity) behavior. According to the trend of AC breakdown strength and lightning impulse pattern, there were 212.58% and 40.01% enhancement indicated for 0.005 g/L concentration compared to the disposed transformer oil. The presence of MWCNT also yielding to the decrement of dissipation factor, increased on permittivity and resistivity behavior of disposed transformer oil which reflected to the performance of electrical properties. Furthermore, it is found that these features correlated to the structural properties as systematically verify by Raman and SAXS analysis study.