Optimization of sol-gel hybrid mediated hollow fiber-solid phase microextraction for the analysis of selected aldehydes

Hexanal and heptanal are two promising aldehydes that have been found in biological samples of lung cancer patients. In general, aldehydes can be detected in trace level as low as part per billion or part per trillion levels. Since reliable technique is needed to detect the analyte of interest especially in complex matrices, a new hybrid silica-based material as the adsorbent of hollow fiber-solid phase microextraction (HF-SPME) was synthesized. In the present work, the solgel hybrid material was held in the pores of HF by in situ gelation and was used to extract the two test aldehydes using direct immersion sampling mode. Several solgel parameters affecting the extraction performance of the in-house sol-gel hybrid material were optimized. The extraction efficiencies of the new silica-based hybrid material for the target aldehydes were based on peak area response obtained from gas chromatography-flame ionization detector. The best extraction efficiencies of hexanal and heptanal were obtained using a mol ratio of 1:4 for the two precursors used, 6 mmol water, 6 mmol methanol and 2.5 mmol trifluoroacetic acid for in situ gelation HF-SPME. The new in situ sol-gel silicabased adsorbent material exhibits high potential for HF-SPME of hexanal and heptanal

Copper(ii)ion determination in water samples using magnetite-calcium alginate sorbent and flame atomic absorption spectrometry analysis

Conventional technique such as liquid-liquid extraction (LLE) is widely used in the analysis of Cu(II) ions from water samples. However, LLE is time consuming, tedious, and consume lots of high purity organic solvents. Solid phase extraction (SPE) is an interesting alternative to LLE but it is prone to channelling and is rather expensive. A greener technique such as magnetic solid phase extraction (MSPE) avoids the use of column cartridge and overcome channelling problem. MSPE using magnetite-calcium alginate (Fe3O4-CaAlg) as sorbent is proposed for the extraction of Cu(II) ion from tap and lake water samples and analysis performed using flame atomic absorption spectrometry (FAAS). Characterization of the synthesised sorbent was performed using Fourier transform infrared spectroscopy and scanning electron microscope. The optimum conditions for Fe3O4-CaAlg MSPE of Cu(II) were achieved at a sample solution of pH 6 with 100 mL sample volume and the existence of interfering ions (Na+, K+, Mg2+, and Cl-) was found not to affect the extraction efficiency of the sorbent for Cu( II) ion significantly at the concentrations tested. Other MSPE parameters used were 10 min extraction time, 50 mg sorbent, 10 mL of 0.1 M HNO3 as desorption solvent and 5 min desorption time (sonication assisted). The calibration graph was linear from 20 - 600 ppb with good coefficient of determination (R2 = 0.9998). The LOD (3SD/slope) and LOQ (10SD/slope) of Cu(II) using Fe3O4-CaAlg MSPE with FAAS were in 6.75 and 22.5 ppb, respectively. The LOD achieved with the Fe3O4-CaAlg MSPE with FAAS is applicable to the determination of Cu(II) in real water samples (tap water and UTM lake water). Good relative recoveries and precision were achieved with this proposed method. The Fe3O4-CaAlg has great potential as an alternative sorbent for Cu(II) determination from water samples using the greener MSPE method

Cyclodextrin-modified micellar electrokinetic chromatography for the enantioseparation of imidazole and vinpocetine drugs

In the present work, cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method was developed and applied for enantioseparation of three imidazole drugs and vinpocetine. The three imidazole drugs namely tioconazole, isoconazole and fenticonazole were simultaneously separated for the first time by MEKC technique using dual cyclodextrin (CD) approach. A combination of two neutral CDs; 2-hydroxypropyl-�-CD (HP-�-CD) and heptakis (2,6-di-O-methyl)-�-CD (DM-�-CD) (35 mM: 10 mM) in background electrolyte (BGE) containing 35 mM phosphate buffer (pH 7.0), 50 mM sodium dodecyl sulfate (SDS) and 15% (v/v) acetonitrile at 27 kV and 30oC gave the best separation of six stereoisomers of imidazole drugs with resolutions, Rs 1.90-27.22 and peak efficiencies, N > 180 000 in less than 15 min. The samples were injected electrokinetically at 3 kV for 3 s and detection was carried out at 200 nm. The method was linear over the concentration range of 25-200 mg/L (r2 > 0.998) and the detection limits (S/N = 3) of the three imidazole drugs were found to be 2.7-7.7 mg/L. The CD-MEKC method was successfully applied to the determination of the three imidazole drugs in spiked human urine to give mean recoveries ranging from 72.3 to 107.5% (RSD < 6%, n = 3). The method was also applied to the analysis of commercial cream formulation of tioconazole and isoconazole. Good mean recoveries were obtained, ranging from 93.6-100% (RSD < 7%, n = 3). The best chiral separation of vinpocetine that gave four resolved peaks was achieved using 40 mM HP-�-CD in 50 mM phosphate buffer (pH 7.0) consisting of 40 mM SDS and 10% v/v acetonitrile at a separation temperature of 25oC and separation voltage 25 kV. Samples were injected electrokinetically at 5 kV for 7 s. Vinpocetine detection was accomplished using diode array detector at 200 nm. The complete vinpocetine separation was achieved in less than 15 min with peak resolution, Rs 1.40-5.80

New methyltrimethoxysilane-(3-mercaptopropyl)- trimethoxysilane coated hollow fiber-solid phase microextraction for hexanal and heptanal analysis

Determination of volatile organic compounds (VOCs) in various matrices is often accomplished using solid phase microextraction (SPME) as a superior mode of extraction. Alternatively, another configuration of solid phase microextraction (SPME) namely hollow fiber-solid phase microextraction (HF-SPME) is a great approach to redress some limitations of the ordinary SPME fibers including fiber breakage, coating stripping and sample carry over. The HF-SPME technique highlights the use of hollow polypropylene (PP) membrane to hold and protect the adsorbent inside its lumen. Unlike the conventional SPME, the inexpensive HF device can be disposed after single use. Introducing extracting phase via sol-gel technology has gained great interest owing to its simple preparation method and promising way to obtain materials with good characteristics. In the present work, a new hybrid silica material based on methyltrimethoxysilane-(3-mercaptopropyl)trimethoxysilane (MTMOS-MPTMOS) was introduced as a new extractant of HF-SPME and the effectiveness of the proposed method was tested for analysis of hexanal and heptanal as the target VOC analytes. Preparation of the HF-SPME MTMOS-MPTMOS was simple in which the hybrid material was synthesized via sol-gel method and was self-polymerized in small segments of HF. Parameters affecting the efficiency of the HF-SPME MTMOS-MPTMOS in extracting both aldehydes were thoroughly investigated and analyzed by gas chromatography-flame ionization detection (GC-FID). It was found that the highest efficiency was achieved as the extraction was conducted in 30 min at a stirring rate of 1000 rpm in a 10 mL of sample solution whereby the back-extraction was performed via vortex for 3 min using 100 µL methanol as desorption solvent. Under the optimal conditions, linearity was observed over a range of 0.020-10.00 µg mL-1 with detection limits of 0.015 µg mL-1 and 0.010 µg mL-1 for hexanal and heptanal, respectively. The applicability of the HF-SPME MTMOS-MPTMOS for analysis of hexanal and heptanal in human urine sample was proven from the quantitative recoveries (&gt, 90) achieved. The HF-SPME MTMOS-MPTMOS offers an attractive alternative for rapid and convenient extraction tool and showed good potential for analysis of hexanal and heptanal from aqueous samples

Magnetic sporopollenin-cyanopropyltriethoxysilane-dispersive micro-solid phase extraction coupled with high performance liquid chromatography for the determination of selected non-steroidal anti-inflammatory drugs in water samples

A facile dispersive-micro-solid phase extraction (D-μ-SPE) method coupled with HPLC for the analysis of selected non-steroidal anti-inflammatory drugs (NSAIDs) in water samples was developed using a newly prepared magnetic sporopollenin-cyanopropyltriethoxysilane (MS-CNPrTEOS) sorbent. Sporopollenin homogenous microparticles of Lycopodium clavatum spores possessed accessible functional groups that facilitated surface modification. Simple modification was performed by functionalization with 3-cyanopropyltriethoxysilane (CNPrTEOS) and magnetite was introduced onto the biopolymer to simplify the extraction process. MS-CNPrTEOS was identified by infrared spectrometrywhile the morphology and the magnetic property were confirmed by scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM), respectively. To maximize the extraction performance of ketoprofen, ibuprofen, diclofenac and mefenamic acid using the proposed MS-CNPrTEOS, important D-μ-SPE parameters were comprehensively optimized. The optimum extraction conditions were sorbent amount, 40 mg; extraction time, 5 min; desorption time; 5 min; sample volume, 15 mL; sample pH 2.0; and salt addition, 2.5% (w/v). The feasibility of the developed method was evaluated using spiked tap water, lake water, river water and waste water samples. Results showed that ketoprofen and ibuprofen were linear in the range of 1.0–1000 μg L−1 whilst diclofenac and mefenamic acid were linear in the range 0.8–500 μg L−1. The results also showed good detection limits for the studied NSAIDs in the range of 0.21–0.51 μg L−1 and good recoveries for spiked water samples in the range of 85.1–106.4%. The MS-CNPrTEOS proved a promising dispersive sorbent and applicable to facile and rapid assay of NSAIDs in water samples