Jafariah Jaafar

Improvement of separation efficiencies of anion-exchange chromatography using monolithic silica capillary columns modified with polyacrylates and polymethacrylates containing tertiary amino or quaternary ammonium groups

Anion-exchange (AEX) columns were prepared by on-column polymerization of acrylates and methacrylates containing tertiary amino or quaternary ammonium groups on monolithic silica in a fused silica capillary modified with anchor groups. The columns provided a plate height (H) of less than 10 microm at optimum linear velocity (u) with keeping their high permeability (K=9-12 x 10(-14) m2). Among seven kinds of AEX columns, a monolithic silica column modified with poly(2-hydroxy-3-(4-methylpiperazin-1-yl)propyl methacrylates) (HMPMA) showed larger retentions and better selectivities for nucleotides and inorganic anions than the others. The HMPMA column of 410 mm length produced 42,000-55,000 theoretical plates (N) at a linear velocity of 0.97 mm/s with a backpressure of 3.8 MPa. The same column could be employed for a fast separation of inorganic anions in 1.8 min at a linear velocity of 5.3 mm/s with a backpressure of 20 MPa. In terms of van Deemter plot and separation impedance, the HMPMA column showed higher performance than a conventional particle-packed AEX column. The HMPMA column showed good recovery of a protein, trypsin inhibitor, and it was applied to the separation of proteins and tryptic digest of bovine serum albumin (BSA) in a gradient elution, to provide better separation compared to a conventional particle-packed AEX column.

Effect of Land Use on Coastal Water and Perna viridis at Johor Straits, Malaysia

In this study, land use effect on river water quality and its subsequent impact on Johor Strait coastal water and green mussel, Perna viridis cultivated at the strait near the fast growing city of Johor Bahru, is investigated. Over the years, changes in land use and increased discharge of domestic, agricultural and industrial waste into the coastal water has severely impaired the water condition and threatened the profitable green mussel aquacu lture activity. Cu and Zn concentrations in water were found to be higher at sampling points closer to Johor Bahr u city while Sungai Pendas and Sungai Melayu which are less develop yielded lower pollutants concentration. The heavy metal concentrations (in mg/L) are between 0.18 to 0.38 for Zn and 3.24 to 3.44 for Cu. Coastal water recorded Zn concentratio n (in mg/L) of 0.03 to 0.05 and Cu concentration of 0.25 to 0.33 while green mussels recorded (in μg/g) 18.24 to 40.01 of Zn and 24.29 to 92.52 of Cu.

Development and validation of a selective, sensitive and stability indicating UPLC-MS/MS method for rapid, simultaneous determination of six process related impurities in darunavir drug substance

In this study a sensitive and selective gradient reverse phase UPLC-MS/MS method was developed for the simultaneous determination of six process related impurities viz., Imp-I, Imp-II, Imp-III, Imp-IV, Imp-V and Imp-VI in darunavir. The chromatographic separation was performed on Acquity UPLC BEH C18 (50 mm×2.1mm, 1.7μm) column using gradient elution of acetonitrile-methanol (80:20, v/v) and 5.0mM ammonium acetate containing 0.01% formic acid at a flow rate of 0.4mL/min. Both negative and positive electrospray ionization (ESI) modes were operated simultaneously using multiple reaction monitoring (MRM) for the quantification of all six impurities in darunavir. The developed method was fully validated following ICH guidelines with respect to specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, precision, robustness and sample solution stability. The method was able to quantitate Imp-I, Imp-IV, Imp-V at 0.3ppm and Imp-II, Imp-III, and Imp-VI at 0.2ppm with respect to 5.0mg/mL of darunavir. The calibration curves showed good linearity over the concentration range of LOQ to 250% for all six impurities. The correlation coefficient obtained was >0.9989 in all the cases. The accuracy of the method lies between 89.90% and 104.60% for all six impurities. Finally, the method has been successfully applied for three formulation batches of darunavir to determine the above mentioned impurities, however no impurity was found beyond the LOQ. This method is a good quality control tool for the trace level quantification of six process related impurities in darunavir during its synthesis.

Simultaneous determination of three organophosphorus pesticides in different food commodities by gas chromatography with mass spectrometry

A sensitive and selective gas chromatography with mass spectrometry method was developed for the simultaneous determination of three organophosphorus pesticides, namely, chlorpyrifos, malathion, and diazinon in three different food commodities (milk, apples, and drinking water) employing solid-phase extraction for sample pretreatment. Pesticide extraction from different sample matrices was carried out on Chromabond C18 cartridges using 3.0 mL of methanol and 3.0 mL of a mixture of dichloromethane/acetonitrile (1:1 v/v) as the eluting solvent. Analysis was carried out by gas chromatography coupled with mass spectrometry using selected-ion monitoring mode. Good linear relationships were obtained in the range of 0.1-50 μg/L for chlorpyrifos, and 0.05-50 μg/L for both malathion and diazinon pesticides. Good repeatability and recoveries were obtained in the range of 78.54-86.73% for three pesticides under the optimized experimental conditions. The limit of detection ranged from 0.02 to 0.03 μg/L, and the limit of quantification ranged from 0.05 to 0.1 μg/L for all three pesticides. Finally, the developed method was successfully applied for the determination of three targeted pesticides in milk, apples, and drinking water samples each in triplicate. No pesticide was found in apple and milk samples, but chlorpyrifos was found in one drinking water sample below the quantification level.

Development and validation of a rapid ultra high performance liquid chromatography with tandem mass spectrometry method for the simultaneous determination of darunavir, ritonavir, and tenofovir in human plasma: Application to human pharmacokinetics

A sensitive ultra high performance liquid chromatography with tandem mass spectrometry method was developed for the simultaneous determination of darunavir, ritonavir and tenofovir in human plasma. Sample preparation involved a simple liquid-liquid extraction using 200 μL of human plasma extracted with methyl tert-butyl ether for three analytes and internal standard. The separation was accomplished on an Acquity UPLC BEH C18 (50 mm x 2.1 mm, 1.7 μm) analytical column using gradient elution of acetonitrile/methanol (80:20, v/v) and 5.0 mM ammonium acetate containing 0.01% formic acid at a flow rate of 0.4 mL/min. The linearity of the method ranged between 20.0 and 12 000 ng/mL for darunavir, 2.0 and 2280 ng/mL for ritonavir, and 14.0 and 1600 ng/mL for tenofovir using 200 μL of plasma. The method was completely validated for its selectivity, sensitivity, linearity, precision and accuracy, recovery, matrix effect, stability, and dilution integrity. The extraction recoveries were consistent and ranged between 79.91 and 90.04% for all three analytes and internal standard. The method exhibited good intra-day and inter-day precision between 1.78 and 6.27%. Finally the method was successfully applied for human pharmacokinetic study in eight healthy male volunteers after the oral administration of 600 mg darunavir along with 100 mg ritonavir and 100 mg tenofovir as boosters.

Synthesis of visible light active doped TiO2 for the degradation of organic pollutants—methylene blue and glyphosate

BackgroundA simple hydrothermal process was applied to synthesize the doped TiO2 particles with different concentrations as well as different metal ions (Mn, Ce and La).MethodsThe synthesis of Mn-doped-TiO2 nanoparticles was done by using a hydrothermal method from hydrolysis of titanium tetrachloride in aqueous solution. The photocatalytic activities were checked by studying the degradation of two model organic pollutants.ResultsThe material was characterized by X-ray diffraction, scanning electron microscopy, and UV–Visible spectroscopy. The X-ray diffraction pattern studied for doped TiO2 particles suggests the anatase phase with a crystalline nature. Doped TiO2 particles showed a porous and complex nature with a highly rough surface. The photocatalytic activity of Mn- Ce- and La-doped TiO2 with different metal-ion concentrations of 0.15-0.60% show that the degradation rate of all of the pollutants increases with an increase in the dopant concentration from 0.15 to 0.45%, and a further increase in the dopant concentration decreased the degradation rate.ConclusionsThe results indicate that TiO2 with a concentration of 0.45% for all metal ions (Mn, Ce and La) shows the highest activity. Among studied dopent TiO2 with Mn (0.45%) showed the best degradation activity.

Catalytic Neutralization Method for Naphthenic Acid Removal in Crude Oil by Alumina Supported Ca and Ba Catalysts

The presence of naphthenic acids in crude oils has caused a major corrosion problem to the production equipment, storage and transport facilities in the petroleum industry. To overcome this problem, catalytic neutralization method will be investigated on real petroleum crude oil sample with various parameters study such as the type of basic chemical used, dosing amount, type of catalyst, catalyst calcination temperature, and catalyst ratio of basic metal and dopant. Potential catalyst was characterized by XRD, NA, and TGA-DTA for its physical properties. Cu/Ca(10:90)/Al2O3 catalyst with calcination temperature of 1000°C was an effective catalyst for all three types of crude oil. In the presence of catalyst, all three types of crude oil samples showed enhancement in the removal of naphthenic acid.

Treatment of Acidic Petroleum Crude Oil Utilizing Catalytic Neutralization Technique of Magnesium Oxide Catalyst

The presence of naphthenic acids in crude oils has caused a major corrosion problem to the production equipment, storage and transport facilities in the petroleum industry. The level of acidity of crude oil was determined by the value of Total Acid Number (TAN) in the oil samples. Two types of crude: Petronas Penapisan Melaka Heavy Crude and Petronas Penapisan Melaka Light Crude were studied. Various parameters studied were the amount of chemical dosing, type of catalyst, different catalyst calcination temperatures, and catalyst ratio of basic metal and dopant. The basic chemical used was ammonia solution in ethylene glycol (NH3-EG) with a concentration range of 100-1000 mg/L. The best experimental condition for the possible TAN for the two samples is 1000 mg/L of NH3-EG, and the catalyst reaction must be in the range of 35-40°C. Cu/Mg (10:90)/Al2O3 catalyst successfully reduced TAN in Heavy Crude for about 84.8% while for Light Crude, TAN was reduced 66.7% with the aids of Ni/Mg (10:90)/Al2O3 catalyst. Increase concentration of basic chemical, reduced the total acid number value of both crude oil.

Fourier transform infrared (FTIR) spectroscopy

The use of Fourier transform infrared (FTIR) spectroscopy has been considered to be one of the most effective techniques to study and understand the chemical and surface chemistry in various types of membrane. In this chapter, the role of FTIR techniques to monitor the change of membrane surface chemistry was discussed. Without knowing the specific functional group, which had altered the membrane surface behavior, the researcher is unable to explain different physicochemical properties that significantly changed the membrane performance. In addition, the FTIR techniques can also be used to monitor the stability and durability of the specific membrane toward their performance. In general, the use of FTIR analysis in the field of membrane application is crucial to support the justification of the changes in their properties and performance in various applications.

MIXED-MODE MONOLITHIC SILICA AS A CHROMATOGRAPHIC SEPARATION MEDIUM

Capillary electro chromatography (CEC) is a separation technique that combines the dual properties of capillary zone electrophoresis (CZE) and micro-liquid chromatography (μ-LC). A hybrid-type silica monolith capillary column was prepared from a mixture of tetramethoxysilanes (TMOS) and methyltrimethoxysilanes (MTMS). Surface modification with octadecyldimethyl-(N-N-diethylamino)silane (ODS-DEA) and N-3[-(dimethylamino)propyl]acrylamide methyl] chloride-quaternary salt, (DMAPAA-Q) was carried out to form a mixed-mode of C18 and a strong anion exchange stationary phase. The synthesized mixed-mode silica monolithic column was then characterized physically with a scanning electron microscope (SEM) and shown to have an average through-pore size and skeleton size of 2.2 µm and 2.0 µm, respectively. This new column with mixed-mode characteristic of reversed-phase (RP) and strong anion exchange (SAX) functionalities was then applied as the stationary phase in CEC for the separation of inorganic and organic ions using a 50 mM phosphate electrolyte of pH 6.9. The inorganic and organic anions were base-line separated within 10 min with column efficiency up to 114 900 plates/min.