A solid phase extraction (SPE) method has been developed using a newly synthesized titanium (IV) butoxide-cyanopropyltriethoxysilane (Ti-CNPrTEOS) sorbent for polar selective extraction of aromatic amines in river water sample. The effect of different parameters on the extraction recovery was studied using the SPE method. The applicability of the sorbents for the extraction of polar aromatic amines by the SPE was extensively studied and evaluated as a function of pH, conditioning solvent, sample loading volume, elution solvent and elution solvent volume. The optimum experimental conditions were sample at pH 7, dichloromethane as conditioning solvent, 10 mL sample loading volume and 5 mL of acetonitrile as the eluting solvent. Under the optimum conditions, the limit of detection (LOD) and limit of quantification (LOQ) for solid phase extraction using Ti-CNPrTEOS SPE sorbent (0.01-0.2; 0.03-0.61 µg L(-1)) were lower compared with those achieved using Si-CN SPE sorbent (0.25-1.50; 1.96-3.59 µg L(-1)) and C18 SPE sorbent (0.37-0.98; 1.87-2.87 µg L(-1)) with higher selectivity towards the extraction of polar aromatic amines. The optimized procedure was successfully applied for the solid phase extraction method of selected aromatic amines in river water, waste water and tap water samples prior to the gas chromatography-flame ionization detector separation.
A three-phase hollow fiber liquid-phase microextraction method coupled with CE was developed and used for the determination of partition coefficients and analysis of selected nitrophenols in water samples. The selected nitrophenols were extracted from 14 mL of aqueous solution (donor solution) with the pH adjusted to pH 3 into an organic phase (1-octanol) immobilized in the pores of the hollow fiber and finally backextracted into 40.0 microL of the acceptor phase (NaOH) at pH 12.0 located inside the lumen of the hollow fiber. The extractions were carried out under the following optimum conditions: donor solution, 0.05 M H(3)PO(4), pH 3.0; organic solvent, 1-octanol; acceptor solution, 40 microL of 0.1 M NaOH, pH 12.0; agitation rate, 1050 rpm; extraction time, 15 min. Under optimized conditions, the calibration curves for the analytes were linear in the range of 0.05-0.30 mg/L with r(2)>0.9900 and LODs were in the range of 0.01-0.04 mg/L with RSDs of 1.25-2.32%. Excellent enrichment factors of up to 398-folds were obtained. It was found that the partition coefficient (K(a/d)) values were high for 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,6-dinitrophenol and that the individual partition coefficients (K(org/d) and K(a/org)) promoted efficient simultaneous extraction from the donor through the organic phase and further into the acceptor phase. The developed method was successfully applied for the analysis of water samples.
In this study, salting-out assisted liquid-liquid extraction (SALLE) as a simple and efficient extraction technique followed by high-performance liquid chromatography (HPLC) was employed for the determination of vitamin D3 in milk samples. The sample treatment is based on the use of water-miscible acetonitrile as the extractant and acetonitrile phase separation under high-salt conditions. Under the optimum conditions, acetonitrile and ammonium sulfate were used as the extraction solvent and salting-out agent, respectively. The vitamin D3 extract was separated using Hypersil ODS (250x i.d 4.6 mm, 5 µm) HPLC column that was coupled with diode array detector. Vitamin D2 was used as internal standard (IS) to offset any variations in chromatographic conditions. The vitamin D3 and the IS were eluted in 18 min. Good linearity (r2 > 0.99) was obtained within the range of 25-600 ng g-1 with the limit of detection of 15 ng g-1 and limit of quantification of 25 ng g-1. The validated method was applied for the determination of vitamin D3 in milk samples. The recoveries for spiked samples were from 94.4 to 113.5%.
Torrefaction process of biomass material is essential in converting them into biofuel with improved calorific value and physical strength. However, the production of torrefied biomass is loose, powdery, and nonuniform. One method of upgrading this material to improve their handling and combustion properties is by densification into briquettes of higher density than the original bulk density of the material. The effects of critical parameters of briquetting process that includes the type of biomass material used for torrefaction and briquetting, densification temperature, and composition of binder for torrefied biomass are studied and characterized. Starch is used as a binder in the study. The results showed that the briquette of torrefied rubber seed kernel (RSK) is better than torrefied palm oil shell (POS) in both calorific value and compressive strength. The best quality of briquettes is yielded from torrefied RSK at the ambient temperature of briquetting process with the composition of 60% water and 5% binder. The maximum compressive load for the briquettes of torrefied RSK is 141 N and the calorific value is 16 MJ/kg. Based on the economic evaluation analysis, the return of investment (ROI) for the mass production of both RSK and POS briquettes is estimated in 2-year period and the annual profit after payback was approximately 107,428.6 USD.
In this work, we reported the synthesis, characterization and adsorption study of two β-cyclodextrin (βCD) cross-linked polymers using aromatic linker 2,4-toluene diisocyanate (2,4-TDI) and aliphatic linker 1,6-hexamethylene diisocyanate (1,6-HDI) to form insoluble βCD-TDI and βCD-HDI. The adsorption of 2,4-dinitrophenol (DNP) on both polymers as an adsorbent was studied in batch adsorption experiments. Both polymers were well characterized using various tools that include Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer-Emmett-Teller analysis and scanning electron microscopy, and the results obtained were compared with the native βCD. The adsorption isotherm of 2,4-DNP onto polymers was studied. It showed that the Freundlich isotherm is a better fit for βCD-TDI, while the Langmuir isotherm is a better fit for βCD-HMDI. The pseudo-second-order kinetic model represented the adsorption process for both of the polymers. The thermodynamic study showed that βCD-TDI polymer was more favourable towards 2,4-DNP when compared with βCD-HDI polymer. Under optimized conditions, both βCD polymers were successfully applied on various environmental water samples for the removal of 2,4-DNP. βCD-TDI polymer showed enhanced sorption capacity and higher removal efficiency (greater than 80%) than βCD-HDI (greater than 70%) towards 2,4-DNP. The mechanism involved was discussed, and the effects of cross-linkers on βCD open up new perspectives for the removal of toxic contaminants from a body of water.
An emulsification liquid-liquid microextraction (ELLME) method was successfully developed using phenolic-based deep eutectic solvent (DES) as an extraction solvent for the determination of phenoxy acid herbicides, 3,6-dichloro-2-methoxybenzoic acid (dicamba) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) in environmental water samples. Five different phenolics-based DESs were successfully synthesized by using phenol (DES 1), 2-chlorophenol (DES 2), 3-chlorophenol (DES 3), 4-chlorophenol (DES 4) and 3,4-dichlorophenol (DES 6) as the hydrogen-bond donor (HBD) and choline chloride as the hydrogen-bond acceptor (HBA). The DESs were mixed at 1 : 2 ratio. A homogeneous solution (clear solution) was observed upon the completion of successful synthesis. The synthesized DESs were characterized by using Fourier transform infrared and nuclear magnetic resonance (NMR). Under optimum ELLME conditions (50 µl of DES 2 as extraction solvent; 100 µl of THF as emulsifier solvent; pH 2; extraction time 5 min), enrichment factor obtained for dicamba and MCPA were 43.1 and 59.7, respectively. The limit of detection and limit of quantification obtained for dicamba were 1.66 and 5.03 µg l-1, respectively, meanwhile for MCPA were 1.69 and 5.12 µg l-1, respectively. The developed ELLME-DES method was applied on paddy field water samples, with extraction recoveries in the range of 79-91% for dicamba and 82-96% for MCPA.
Molecularly imprinted silica gel (MISG) was incorporated through dispersion in agarose polymer matrix to form a mixed matrix membrane (MMM) and was applied for the determination of three sulfonamide antibiotic compounds (i.e. sulfamethoxazole (SMX), sulfamonomethoxine (SMM), and sulfadiazine (SDZ)) from environmental water samples. Several important microextraction conditions, such as type of desorption solvent, extraction time, amount of sorbent, sample volume, pH, and effect of desorption time, were comprehensively optimized. A preconcentration factors of ≥ 20 was achieved by the extraction of 12.5 mL of water samples using the developed method. This microextraction-HPLC method demonstrated good linearity (1-500 μg L-1) with a coefficient of determination (R2) of 0.9959-0.9999, low limits of detection (0.06-0.17 μg L-1) and limits of quantification (0.20-0.56 μg L-1), good analyte recoveries (80-96%), and acceptable relative standard deviations (< 10%) under the optimized conditions. The method is systematically compared to those reported in the literature.
In this work, a simple, fast, sensitive, and environmentally friendly method was developed for preconcentration and quantitative measurement of bisphenol A in water samples using gas chromatography with mass spectrometry. The preconcentration approach, namely biosorption-based dispersive liquid-liquid microextraction with extractant removal by magnetic nanoparticles was performed based on the formation of microdroplet of rhamnolipid biosurfactant throughout the aqueous samples, which accelerates the mass transfer process between the extraction solvent and sample solution. The process is then followed by the application of magnetic nanoparticles for easy retrieval of the analyte-containing extraction solvent. Several important variables were optimized comprehensively including type of disperser solvent and desorption solvent, rhamnolipid concentration, volume of disperser solvent, amount of magnetic nanoparticles, extraction time, desorption time, ionic strength, and sample pH. Under the optimized microextraction and gas chromatography with mass spectrometry conditions, the method demonstrated good linearity over the range of 0.5-500 µg/L with a coefficient of determination of R2 = 0.9904, low limit of detection (0.15 µg/L) and limit of quantification (0.50 µg/L) of bisphenol A, good analyte recoveries (84-120%) and acceptable relative standard deviation (1.8-14.9%, n = 6). The proposed method was successfully applied to three environmental water samples, and bisphenol A was detected in all samples.
Realising the need to devise a simple, sensitive, and reliable detection method, this study investigated the development of a dual-stacking transient isotachophoresis (t-ITP) and sweeping in micellar electrokinetic chromatography with diode array detector (t-ITP/sweeping-MEKC-DAD) for the determination of selected non-steroidal anti-inflammatory drugs (NSAIDs); ketoprofen, diclofenac and naproxen from aqueous matrices. Prior to the system setup, various parameters were optimised to assess the potential use of the t-ITP paired with the sweeping stacking technique in micellar background electrolyte for dual preconcentration and separation of trace amounts of NSAIDs. Once the optimum conditions have been established, the method performance was validated and applied to 17 environmental water samples. Based on the results, the combined t-ITP and sweeping approach significantly improved the stacking and separation sensitivity. A large volume of samples could also be introduced and subsequently separated by MEKC with greater focusing effects due to the sweeping. Under optimised conditions, the developed method exhibited excellent linearity at a high range (0.1-500 ng/mL, r2 ≥ 0.998), low limits of detection (LODs) of 0.01-0.07 ng/mL, and a remarkable relative recovery (RR) of 99.6-101.9% with a relative standard deviation (RSD) of 1.4-8.6% (n = 9). Ultimately, the sensitivity enhancement factors improved up to 666-fold using the optimised method. Therefore, the proposed method presents a simplified yet effective and suitable for the determination of NSAIDs from aqueous matrices.
Depression is a common mental disorder that may lead to major mental health problems, and antidepressant drugs have been used as a treatment of choice to mitigate symptoms of major depressive disorders by ameliorating the chemical imbalances of neurotransmitters in brain. Since abusing antidepressant drugs such as selective serotonin reuptake inhibitors and tricyclic antidepressant drugs can cause severe adverse effects, continuous toxicological monitoring of the parent compounds as well as their metabolites using numerous analytical methods appears pertinent. Among them, capillary electrophoresis has been popularly utilized since the method has a lot of advantages viz. using small amounts of sample and solvents, ease of operation, and rapid analysis. This review paper brings a survey of more than 30 papers on capillary electrophoresis of antidepressant drugs published approximately from 1999 until 2018. It focuses on the reported capillary electrophoresis techniques and their applications and challenges for determining antidepressant drugs and their metabolites. It is organized according to the commonly used capillary zone electrophoresis method, followed by non-aqueous capillary electrophoresis and micellar electrokinetic chromatography, with details on breakthrough findings. Where available, information is given about the background electrolyte used, detector utilized, and sensitivity obtained.
This work describes the development of a new methodology based on magnetic nanoparticles assisted dispersive liquid-liquid microextraction (DLLME-MNPs) for preconcentration and extraction of chloramphenicol (CAP) antibiotic residues in water. The approach is based on the use of decanoic acid as the extraction solvent followed by the application of MNPs to magnetically retrieve the extraction solvent containing the extracted CAP. The coated MNPs were then desorbed with methanol, and the clean extract was analysed using ultraviolet-visible spectrophotometry. Several important parameters, such as the amount of decanoic acid, extraction time, stirring rate, amount of MNPs, type of desorption solvent, salt addition and sample pH, were evaluated and optimized. Optimum parameters were as follows: amount of decanoic acid: 200 mg; extraction time: 10 min; stirring rate: 800 rpm; amount of MNPs: 60 mg; desorption solvent: methanol; salt: 10%; and sample pH, 8. Under the optimum conditions, the method demonstrated acceptable linearity (R2 = 0.9933) over a concentration range of 50-1000 µg l-1. Limit of detection and limit of quantification were 16.5 and 50.0 µg l-1, respectively. Good analyte recovery (91-92.7%) and acceptable precision with good relative standard deviations (0.45-6.29%, n = 3) were obtained. The method was successfully applied to tap water and lake water samples. The proposed method is rapid, simple, reliable and environmentally friendly for the detection of CAP.
A dynamic pH junction was used in capillary electrophoresis (CE-DAD) to on-line preconcentrate, separate, and determine trace amounts of sulfonamide antibiotics (SAs) in milk and yoghurt samples in this study. A sample matrix with 0.15% acetic acid and 10% methanol (MeOH) at a pH of 4.0, and a background electrolyte (BGE) that contained 35 mM sodium citrate with 10% MeOH at a pH of 8.5, and an acidic barrage of 0.4% acetic acid with 10% MeOH at a pH of 2.5 were utilised to achieve a stacking effect for SAs through a dynamic pH junction. Under optimised conditions, the proposed preconcentration method showed good linearity (30-500 ng/mL, r2 ≥ 0.9940), low limits of detection (LODs) of 4.1-6.3 ng/mL, and acceptable analytes recovery (81.2-106.9%) with relative standard deviations (RSDs) within 5.3-13.7 (n = 9). The limits of quantification (LOQs) were below the maximum residue limit approved by the European Union (EU) in this type of matrices. Sensitivity enhancement factors of up to 129 were reached with the optimised dynamic pH junction using CE with a diode array detector (DAD). The method was used to determine SAs in fresh milk, low-fat milk, full-cream milk, and yoghurt samples.