Eco-friendly solvent bar microextraction based on a natural deep eutectic solvent and multivariate optimization for simultaneous determination of spironolactone and canrenone in urine and plasma samples.

Simultaneous measurement of spironolactone and canrenone in urine and plasma provides valuable insight into renal function, and therapeutic efficacy and can be utilized to identify potential health risks and ensure patient safety throughout treatment. By adopting greener methods to analyze these compounds, significant reductions in the environmental impact of such studies can be achieved. For this purpose, a sensitive and eco-friendly solvent bar microextraction method using natural deep eutectic solvent (NDE) followed by high-performance liquid chromatography-diode array detection (HPLC-DAD) was developed to determine spironolactone and canrenone in urine and plasma samples. The extraction solvents were synthesized using NDE-based terpenoids containing menthol and camphor in various ratios. The extraction efficiency percentage (EE%) of both drugs was measured using response surface methodology (RSM) based on central composite design (CCD), and 29 extraction tests were conducted to determine the optimum conditions. Although all parameters were found to be significant, the extraction and elution times were critical for isolating the target analytes. Under optimized conditions, the linear dynamic ranges for spironolactone (SPI)/canrenone (CAN) were 11.7-104/13.1-104 µg L-1 and 21.7-104/24.6-104 µg L-1 in urine and plasma samples, respectively with R2 ≥ 0.993. The ranges of intra-/interprecision (relative standard deviation (RSD) %, n = 5) were 1.31-9.17%/ 2.4-11% with extraction recovery ≥ 88.6% for both drugs. The comparison findings with previously published methods confirmed that the developed NDE-solvent bar microextraction (SBME)-HPLC-DAD method for spironolactone and canrenone analysis displayed confident sensitivity, feasible operation, and simple analysis. Furthermore, the method's applicability and effectiveness were proven by successfully analyzing spironolactone and its metabolite canrenone in patients' urine and plasma samples.

Application of physical vapor deposition technology for practical utilization of nano-size copper oxide for lead uptake from solution: kinetics, equilibrium, and recycling studies.

For the first time, copper oxide-coated glass beads (CuO-GBs) were fabricated using physical vapor deposition (PVD) technology for sequestrating Pb2+ ions from solution is addressed. Compared to other coating procedures, PVD offered high-stability uniform CuO nano-layers attached with 3.0-mm glass beads. Heating of copper oxide-coated glass beads after deposition was rather necessary to achieve the best stability of the nano-adsorbent. Detection of nano-size copper oxide on the beads was made by FTIR (intense peak at 655 cm-1 for CuO bond stretching) and XRF (Cu peak at 8.0 keV). Scanning electron micrographs taken at high magnification power indicated the presence of CuO in nano-range deposited over glass beads. The maximum deposited amount of CuO on the beads was 1.1% and accomplished at the following operational conditions: internal pressure 10-5 mmHg, Ar flow rate 8.0 mL/min, voltage 84 V, pre-sputtering time 20 s, total sputtering time 10.0 min, and post-heating temperature 150 °C for 3 h. A univariate analysis indicated that the optimum Pb2+ uptake by CuO-GBs from solution was achieved at pH 7.0-8.0, 7 beads/50 mL, 120-min contact time, and 15-mg/L initial concentration. Kinetic data for Pb2+ uptake was best presented by a pseudo-second-order model with a relative prediction error of 3.2 and 5.1% for GBs and CuO-GBs, respectively. On the other hand, Pb2+ equilibrium isotherms at 25 °C were fairly presented by the Langmuir model, and the predicted saturation values were 5.48 and 15.69 mg/g for GBs and CuO-GBs, respectively. CuO and CuO-GBs had similar Pb2+ saturation values (~ 16 mg/g), although the latter demonstrated 4 times faster kinetic, thanks to fixation CuO on glass beads. Moreover, the chemical stability of copper oxide-coated glass beads was tested under different conditions. Recycling of copper oxide-coated glass beads was also investigated, and 90% of the surface was recovered using 0.01-M HNO3.

Simultaneous determination of furosemide and carbamazepine in biological matrices by solvent bar microextraction combined with high-performance liquid chromatography-diode array detector and central composite design.

A sensitive and simple sample pretreatment method based on a two-phase solvent bar microextraction (SBME) technique coupled with HPLC-diode array detector (DAD) was developed for simultaneous extraction and determination of trace amounts of furosemide and carbamazepine in human urine and plasma samples. The significance of operational factors on carbamazepine and furosemide extraction efficiency % (EE%) was screened using full factorial design (FFD) while central composite design (CCD) was used to model the entire process. A quadratic model was found convenient to correlate the extraction EE% of selected drugs with dominant experimental factors. A Pareto chart was also used to examine the importance of factors on drugs' EE%. The analytical performance of the method in urine and plasma samples demonstrated good linearity (R2 ˃ 0.992) with detection limits ranging from 4.2 to 10.9 µg L-1 , and extraction recovery over 89.45% for both drugs in urine and plasma samples. A comparison against published methods was also performed and the results revealed that the developed method exhibits a confident sensitivity, feasible operation, and simple analysis for both drugs. Finally, the practicability of the validated SBME-HPLC-DAD method was demonstrated by successfully applying it to the analysis of furosemide and carbamazepine in real patient urine samples.

Solvent Bar Microextraction Combined with HPLC-DAD for Simultaneous Determination of Diuretics in Human Urine and Plasma Samples.

BACKGROUND: A simple and powerful microextraction procedure, the solvent bar microextraction (SBME), was used for the simultaneous determination of two diuretics, furosemide and spironolactone in human urine and plasma samples, using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD). METHODS: The appropriate amount (2 µL) of 1-octanol as an organic solvent confined within 2.5 cm of a porous hollow fiber micro-tube, sealed at both ends was used for this procedure. The conditions for the SBME were optimized in water and the analytical performance was examined in spiked human urine and plasma samples. RESULTS: The optimized method exhibited good linearity (R2> 0.997) over the studied range of higher than 33 to 104µg L-1 for furosemide and spironolactone in urine and plasma samples, illustrating a satisfactory precision level with RSD values between 2.1% and 9.1%. DISCUSSION: The values of the limits of detection were found to be in the range of 6.39 to 9.67µg L-1, and extraction recovery ˃ 58.8% for both diuretics in urine and plasma samples. The applicability and effectiveness of the proposed method for the determination of furosemide and spironolactone in patient urine samples were tested. CONCLUSION: In comparison with reference methods, the attained results demonstrated that SBME combined with HPLC-DAD was proved to be simple, inexpensive, and promising analytical technology for the simultaneous determination of furosemide and spironolactone in urine and plasma samples.

Development of Dioctyl Phthalate@Fe3O4 Nanocomposite Reinforced Hollow Fiber Solid/ Liquid Phase Microextraction Followed by HPLC-DAD for the Determination of Atorvastatin and Gemfibrozil in Human Urine.

BACKGROUND: The desirable levels of lipids, especially in patients with coronary artery disease, might not be achievable with a single lipid-lowering drug; thus, combination therapy using atorvastatin and gemfibrozil seems to be a promising approach. However, the potential for drugdrug interaction needs to be taken into consideration, and the combination (atorvastatin and gemfibrozil) is recommended only when other options for reducing lipids have been exhausted. OBJECTIVES: Many studies are conducted for the determination of atorvastatin or gemfibrozil in biological fluids and tablets; however, the simultaneous determination of the two drugs in complex biological matrices is limited. Consequently, the development of a sensitive method for simultaneous determination of atorvastatin and gemfibrozil in urine samples is urgently needed to make sure that the doses of both medications are given to patients correctly to prevent the risk of side effects outcomes associated with the adverse drug-drug interaction. METHODS: A synthesized nanocomposite sorbent, dioctyl phthalate coated on the surface of magnetite (DOP@Fe3O4), was reinforced and immobilized into the pores of 2.5 cm segment hollow fiber microtube via ultrasonication, and the lumen of the microtube was filled with 1-octanol as an organic solvent with two ends heat-sealed. The prepared (DOP@Fe3O4-HF-SLPME) device was directly immersed into 10 mL of a sample solution containing atorvastatin and gemfibrozil with agitation. Subsequently, the microextraction device was transferred to HPLC-micro-vial containing an appropriate solvent, and the selected analytes were desorbed under ultrasonication prior to HPLCDAD analysis. The main factors influencing the adsorption and desorption process of the selected drugs have been optimized. RESULTS: The DOP@Fe3O4-HF-SLPME combined with the HPLC-DAD method was analytically evaluated for the simultaneous determination of atorvastatin and gemfibrozil in human urine samples using the optimized conditions. In spiked urine samples, the method showed a good linearity R2˃ 0.998, RSD from 1.41- 5.33%, and the limits of detection/ quantification (LOD/ LOQ) were 0.11/ 0.36 and 0.73/ 2.42 µg L-1 for atorvastatin and gemfibrozil, respectively. The enrichment factors of atorvastatin and gemfibrozil were 83.4 and 101.2, with extraction recoveries of 80.9% and 99.0%, respectively. The developed method demonstrated comparable results against referenced methods and a satisfactory result for determining the selected drugs in the patient's urine samples. CONCLUSION: The DOP@Fe3O4-HF-SLPME followed by HPLC-DAD was proved to be an efficient, sensitive, and cost-effective biopharmaceutical analysis method for trace levels of atorvastatin and gemfibrozil in the biological fluid matrix.

Cu(II) biosorption by living biofilms: Isothermal, chemical, physical and biological evaluation.

Dissolved copper in stormwater runoff is a significant environmental problem. Biosorption of dissolved metals using microorganisms is known as a green, low-cost and efficient method. However, the role of live biological agents in the remediation of dissolved copper in Sustainable Drainage (SuDS) has not been reported. In this study, the effect of pH, initial concentration and temperature, on bacteria in different stages of biofilm development on a geotextile, along with Cu(II) removal efficiencies, were evaluated. Maximum Cu(II) removal efficiency (92%) was observed at pH 6. By decreasing the pH from 6 to 2, a log 5 reduction in bacteria was observed and Carboxyl groups transformed from -COO- to -COOH. The maximum biosorption capacity (119 mg g-1) was detected on day 1 of biofilm development, however, maximum removal efficiency (97%) was measured on day 21 of biofilm incubation. Exteracellular Polymeric Substance (EPS) showed a better protection of CFUs in more mature biofilms (day 21) with less than 0.1 log decrease when exposed to 200 mL-1 Cu(II), whereas, biofilm on day 1 of incubation showed a 2 log reduction in CFUs number. Thermodynamic studies showed that the maximum Cu(II) biosorption capacity of biofilms, incubated for 7 days (117 mg g-1) occurred at 35 °C. Thermodynamic and kinetic modelling of data revealed that a physical, feasible, spontaneous and exothermic process controlled the biosorption, with a diffusion process observed in external layers of the biofilm, fitting a pseudo-second order model. Equilibrium data modelling and high R2 values of Langmuir model indicated that the biosorption took place by a monolayer on the living biofilm surface in all stages of biofilm development.

The biosorption of mercury by permeable pavement biofilms in stormwater attenuation.

This study reports on the evaluation of the equilibrium, thermodynamics and kinetics of mercury (II) biosorption using a living biofilm, developed on a nonwoven polypropylene and polyethylene geotextile, typically used within the structure of Sustainable Drainage System (SuDS) devices. Batch biosorption assays were carried out with variables such as pH, initial concentrations, contact time, temperature and biofilm incubation time. Langmuir, Freundlich and Dubinin Radushkevich (D-R) models were applied to the equilibrium data which revealed the maximum biosorption capacities and efficiencies at pH 5.5 with a contact time of 120 min at 25 °C. With 20 mg L-1 added Hg (II), living biofilm samples with incubation times of 1, 7, 14, 21 and 28 days, biosorption values were 101.31 (55.72%), 24.41 (67.12%), 16.81 (61.37%), 9.70 (62.57%) and 13.34 (65.38%) mg g-1, respectively. Free mean biosorption energy from the D-R model was between 2.24 and 2.36 kJ mol-1 for all biofilm development incubation times, that revealed the physical biosorption mechanism for Hg(II). The thermodynamic studies showed that the Hg(II) biosorption of living biofilm was thermodynamically feasible and had a spontaneous and exothermic nature. Kinetic parameters revealed that Hg(II) biosorption onto living biofilm had a good correlation with a pseudo second-order kinetic model. FTIR spectra after biosorption suggested that amine, hydroxyl and carboxyl groups were the main functional groups available and responsible for Hg(II) biosorption onto living biofilm. Experimental data suggested that a living biofilm developed on a nonwoven polypropylene and polyethylene geotextile can be efficient in the removal of mercury ions from contaminated urban and industrial runoff.

Multi-walled Carbon Nanotubes Reinforced into Hollow Fiber by Chitosan Sol-gel for Solid/Liquid Phase Microextraction of NSAIDs from Urine Prior to HPLC-DAD Analysis.

BACKGROUND: The efficient analytical method for the analysis of nonsteroidal antiinflammatory drugs (NSAIDs) in a biological fluid is important for determining the toxicological aspects of such long-term used therapies. METHODS: In the present work, multi-walled carbon nanotubes reinforced into a hollow fiber by chitosan sol-gel assisted-solid/ liquid phase microextraction (MWCNTs-HF-CA-SPME) method followed by the high-performance liquid chromatography-diode array detection (HPLC-DAD) was developed for the determination of three NSAIDs, ketoprofen, diclofenac, and ibuprofen in human urine samples. MWCNTs with various dimensions were characterized by various analytical techniques. The extraction device was prepared by immobilizing the MWCNTs in the pores of 2.5 cm microtube via chitosan sol-gel assisted technology while the lumen of the microtube was filled with few microliters of 1-octanol with two ends sealed. The extraction device was operated by direct immersion in the sample solution. RESULTS: The main factors influencing the extraction efficiency of the selected NSAIDs have been examined. The method showed good linearity R2 ≥ 0.997 with RSDs from 1.1 to 12.3%. The limits of detection (LODs) were 2.633, 2.035 and 2.386 µg L-1, for ketoprofen, diclofenac, and ibuprofen, respectively. The developed method demonstrated a satisfactory result for the determination of selected drugs in patient urine samples and comparable results against reference methods. CONCLUSION: The method is simple, sensitive and can be considered as an alternative for clinical laboratory analysis of selected drugs.

Separation and flame atomic absorption spectrometric determination of total chromium and chromium (III) in phosphate rock used for production of fertilizer.

Due to the commercial value of phosphate rock (PR) as a fertilizer precursor, it is necessary to investigate its heavy metals content. Chromium (Cr) may present as Cr(III) or Cr(VI) in PR; but quantitative differentiation between them is not an easy task. This is due to possible interconversion of Cr species during the digestion/leaching process. In this work, ultrasound digestion (USD) of PR was optimized (300 mg PR, 4.0 mL of 4.0 mol L(-1) nitric acid, 15 min sonication) for the sake of leaching Cr species prior to their determination by flame atomic absorption spectroscopy. Using multi-walled carbon nanotube (MWCNT) as adsorbent, solid phase extraction (SPE) was used to separate Cr(III) from the digestate at pH 9, while total Cr was estimated after reducing Cr(VI) into Cr(III). The optimum USD/SPE method gave LOQ and LOD of Cr(III) of 0.96 mg kg(-1) and 0.288 mg kg(-1), respectively. The method sensitivity was 1.44×10(-3) AU kg mg(-1) within the studied Cr concentration range (5-400 mg kg(-1)). The USD/SPE method was validated by analyzing lake sediments LKSD-4 certified reference material, and by comparison with classical digestion method (CD). Application of USD/SPE on Jordanian PR samples gave total Cr rang 29.1-122.0 mg kg(-1) (±1.4-6.3), while Cr(III) ranged between 23.8 and 101.7 mg kg(-1) (±1.3-5.5). AFPC Rock Check Program samples gave total Cr range 238.9-394.7 mg kg(-1) (±11.5-24.1), while Cr(III) ranged between 202.4 and 335.8 mg kg(-1) (±11.4-18.3). These results were very close to the results obtained by the CD method.

Improving the adsorption efficiency of phenolic compounds into olive wood biosorbents by pre-washing with organic solvents: Equilibrium, kinetic and thermodynamic aspects.

The adsorption properties of olive wood (OW) toward phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2-nitrophenol, 4-nitrophenol and 2,4-dinitrophenol, were improved by washing OW with some organic solvents (ethanol, tetrahydrofuran, ether, dichloromethane or hexane). Adsorption isotherms were classified according to Giles and Smith classification, in which L2-shape was obtained after OW washing. The adsorption data were modeled using Langmuir and Freundlich isotherm equations and it was found that adsorption capacity and affinity have increased after OW washing. Thermodynamic (ΔG°, ΔH° and ΔS°), kinetic and intra-particle diffusion parameters were estimated before and after OW washing. It was found that the adsorption of phenols on OW was of physical nature, spontaneous, exothermic and followed second order rate equation. After OW washing, adsorption spontaneity has increased. Both pore diffusion and kinetic resistances have most likely affected the adsorption process. The results presented in this work suggested that washing OW with any one of the tested solvents would enhance uptake of the tested phenols into OW sorbent. Discussing some economical and environmental aspects suggested that the use of ethanol might be preferred.

A simple and accurate analytical method for determination of three commercial dyes in different water systems using partial least squares regression.

A simple analytical procedure is proposed for simultaneous determination of three common dyes (Basic Blue 9, Brilliant Blue E-4BA, and Reactive Blue 2) in natural waters without prior separation of the solutes. A popular chemometric method, partial least squares regression PLS-1, was effectively applied for spectral resolution of a highly overlapping system. At the best modeling conditions, mean recoveries and relative standard deviations (RSD) for dyes quantification by PLS-1 were found to be 102.1 (4.4), 95.7 (8.4), and 98.9 (6.2) for Basic Blue, Brilliant Blue, and Reactive Blue, respectively. The estimated limits of detection (LOD) were estimated using net-analyte signal concept and were 0.11, 0.52, 0.49 mg L(-1) for Basic Blue, Brilliant Blue, and Reactive Blue, respectively. The quantitative determination of dyes spiked in real water samples was carried out successfully by PLS-1 with satisfactory recoveries for dyes (90-106%).

Preparation of an efficient sorbent by washing then pyrolysis of olive wood for simultaneous solid phase extraction of chloro-phenols and nitro-phenols from water.

Simultaneous preconcentration of phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol was improved by using olive wood (OW) washed with ethanol then pyrolyzed at 200°C as preconcentrating sorbent. Various OW sorbents were prepared by either washing OW (with ethanol, ether, dichloromethane, tetrahydrofuran or n-hexane); or by pyrolysis (at 100, 150, 200, 250 or 300°C); or by combined pyrolysis/washing. The adsorbents were characterized by elemental analysis, total acidity/basicity, methylene blue relative surface area, point of zero charge, distribution coefficients of the phenols, and sample loading flow rate. It seems that washing and pyrolysis have removed compounds covering the OW pores, which improved the OW porosity and exposed more acidic groups on the OW surface. The pores and the surface acidic groups seem to play major role in phenols sorption. Ethanol-washed OW then pyrolyzed at 200°C gave the best preconcentration performance towards phenols (300 mg sorbent, 150 mL of the sample (pH 7), and elution with 3 mL of acetonitrile). The method was linear up to 100 µg L(-1); limit of quantification: 0.20-0.48 µg L(-1). The method could detect phenol and 2,4-dinitrophenol in industrial wastewater with spiked recovery range from 80.2% to 91.4% (± 1.1 to 5.5%RSD) for all the phenols.

Bio-separation, speciation and determination of chromium in water using partially pyrolyzed olive pomace sorbent.

Speciation of Cr(III)/Cr(VI) from water using olive pomace (OP) was improved by partial pyrolysis of OP. The sorbents were characterized by physicochemical techniques. Sorption of Cr(III) on raw and partially pyrolyzed OP sorbents followed Freundlich isotherm and second-order rate kinetics. OP pyrolyzed at 150°C (sorbent OP-150) exhibited maximum sorption capacity, favorability and the lowest sorption energy. Sorption was exothermic and spontaneous for the raw-OP and OP pyrolyzed at 100 or 150°C; but endothermic and non-spontaneous for OP pyrolyzed at 200, 250, 300 or 400°C. A speciation method of chromium was proposed, in which Cr(III) was selectively retained at pH 3 on sorbent OP-150; while total Cr was determined after reduction of Cr(VI). The method was selective with a detection limit for Cr(III) of 1.58 µg L(-1). The method was applied on natural and industrial waters (recoveries >97.7%, RSD's <9%) and on tobacco leaves certified reference material (INCT-PVTL-6).

Derivatization of 2-chlorophenol with 4-amino-anti-pyrine: a novel method for improving the selectivity of molecularly imprinted solid phase extraction of 2-chlorophenol from water.

Molecularly imprinted polymer (MIP) may not selectively recognize small template of limited number of functional groups, such as 2-chlorophenol (2-CP). In this work, a novel method was proposed to improve the recognition ability of the molecularly imprinted solid phase extraction (MISPE) of 2-CP from environmental waters. This was achieved by derivatization of 2-CP with 4-amino-anti-pyrine (4-AAP) to enlarge its molecular size and add more binding sites. For that purpose, two MISPE methods of 2-CP were developed. In method 1, a polymer imprinted with 2-CP was used as the extracting sorbent but it suffered from low selectivity and high detection limit of 2-CP (7.10 ng L(-1)). In method 2, a polymer imprinted with 4-AAP derivatized 2-CP (2-CP-4-AAP) was used as the extracting sorbent. Prior to loading the water sample it was subjected to a simple derivatization procedure with 4-AAP. Method 2 showed high recognition ability/selectivity towards 2-CP-4-AAP with lower detection limit of 0.05 ng L(-1) for 2-CP-4-AAP. Method 2 was able to detect the presence of 2-CP-4-AAP in unspiked real water samples and almost full spike recovery was achieved.

Partially pyrolyzed olive pomace sorbent of high permeability for preconcentration of metals from environmental waters.

The aim of this work is to develop a preconcentration procedure of Cd(2+), Zn(2+) and Cu(2+) in environmental waters using olive pomace (OP) prior to their determination by flame atomic absorption spectrometry (FAAS). Raw OP as preconcentrating sorbent was found to have low permeability towards the passed water samples and thus long time was needed. Even reducing the vacuum pressure caused cartridge blockage. Novel preconcentrating sorbents of high permeability were then prepared by heat pretreatment under inert atmosphere (partial pyrolysis) of OP at various temperatures (100, 150, 200, 250 and 300 degrees C). The permeability of OP pyrolyzed at 200 degrees C (sorbent OP-200) was enhanced 11 times relative to the raw OP, which significantly reduced the time required in the preconcentration process. A preconcentration procedure was optimized using OP-200 as preconcentrating sorbent, in which the detection limits were 42 ng L(-1) for Cu(2+), 76 ng L(-1) for Zn(2+) and 172 ng mL(-1) for Cd(2+). The method was linear within the studied concentration range (2-100 ng mL(-1)). The proposed method gave recoveries from 83+/-6 to 103+/-5% for determination of metals in tap water; and recoveries from 81+/-6 to 100+/-6% in well water. The method was validated by comparison with independent method and by analysis of lake sediments LKSD-4 certified reference material.

Simultaneous determination of pesticides at trace levels in water using multiwalled carbon nanotubes as solid-phase extractant and multivariate calibration.

The application of solid-phase extraction with multivariate calibration for simultaneous determination of three toxic pesticides in tap and reservoir waters was presented. The proposed analytical method was used for the determination of atrazine, methidathion, and propoxur in complex water samples without the need for chromatographic separation. Among the applied multivariate calibration methods, partial least squares (PLS-1) method was found the most effective for pesticides quantification. Multiwalled carbon nanotubes (MWCNTs) adsorbent showed a perfect extraction/preconcentration of pesticides present at trace levels. The experimental factors that affect pesticides extraction by MWCNTs adsorbent such as sample volume, eluent volume, solution pH, and extraction flow rate were studied and optimized. The figures of merit of the proposed method were: limits of detection 3, 2, and 3 microg l(-1) and linear ranges 5-30, 3-60, and 5-40 microg l(-1) for atrazine, methidathion, and propoxur, respectively. A good precision was reported for the method, R.S.D. values were always less than 5.0%. Satisfactory results were reported for simultaneous determination of trace levels of pesticides in complex matrices. In tap water, the percent recoveries for pesticides were extended from 95 to 104% and R.S.D. from 1 to 3%, while lower recoveries were observed in reservoir water: 84-93% (R.S.D.: 1-3). Although the pesticides can be accurately quantified by SPE and liquid chromatography, SPE-PLS-1 method was found simpler and operated at lower running costs.

Solid-phase extraction and simultaneous determination of trace amounts of sulphonated and azo sulphonated dyes using microemulsion-modified-zeolite and multivariate calibration.

A simple and rapid analytical method for the determination of trace levels of five sulphonated and azo sulphonated reactive dyes: Cibacron Reactive Blue 2 (C-Blue, trisulphonated dye), Cibacron Reactive Red 4 (C-Red, tetrasulphonated azo dye), Cibacron Reactive Yellow 2 (C-Yellow, trisulphonated azo dye), Levafix Brilliant Red E-4BA (L-Red, trisulphonated dye), and Levafix Brilliant Blue E-4BA (L-Blue, disulphonated dye) in water is presented. Initially, the dyes were preconcentrated from 250 ml of water samples with solid-phase extraction using natural zeolite sample previously modified with a microemulsion. The modified zeolite exhibited an excellent extraction for the dyes from solution. The parameters that influence quantitative recovery of reactive dyes like amount of extractant, volume of dye solution, pH, ionic strength, and extraction-elution flow rate were varied and optimized. After elution of the adsorbed dyes, the concentration of dyes was determined spectrophotometrically with the aid of principle component regression (PCR) method without separation of dyes. The results obtained from PCR method were comparable to those obtained from HPLC method confirming the effectiveness of the proposed method. With the aid of SPE by M-zeolite, the concentration of dyes could be reproducibly detected over the range 25-200 ppb for C-Yellow and L-Blue and from 50 to 250 ppb for C-Blue, C-Red, and L-Red. The multivariate detection limits of dyes were found to be 15 ppb for C-Yellow and L-Blue and 25 ppb for C-Blue, C-Red, and L-Red dyes. The proposed chemometric method gave recoveries from 85.4 to 115.3% and R.S.D. from 1.0 to 14.5% for determination of the five dyes without any prior separation for solutes.

Critical evaluation and comparison of enrichment efficiency of multi-walled carbon nanotubes, C18 silica and activated carbon towards some pesticides from environmental waters.

In this work, optimization of multi-residue solid phase extraction (SPE) procedures coupled with high-performance liquid chromatography for the determination of Propoxur, Atrazine and Methidathion from environmental waters is reported. Three different sorbents were used in this work: multi-walled carbon nanotubes (MWCNTs), C18 silica and activated carbon (AC). The three optimized SPE procedures were compared in terms of analytical performance, application to environmental waters, cartridge re-use, adsorption capacity and cost of adsorbent. Although the adsorption capacity of MWCNT was larger than AC and C18, however, the analytical performance of AC could be made close to the other sorbents by appropriate optimization of the SPE procedures. A sample of AC was then oxidized with various oxidizing agents to show that ACs of various surface properties has different enrichment efficiencies. Thus researchers are advised to try AC of various surface properties in SPE of pollutants prior to using expensive sorbents (such as MWCNT and C18 silica).

Effect of oxidation of activated carbon on its enrichment efficiency of metal ions: comparison with oxidized and non-oxidized multi-walled carbon nanotubes.

The effect of oxidation of activated carbon (AC) with various oxidizing agents (nitric acid, hydrogen peroxide, ammonium persulfate) on preconcentration of metal ions (Cr3+, Mn2+, Pb2+, Cu2+, Cd2+ and Zn2+) from environmental waters prior to their flame atomic absorption spectroscopic analysis was investigated. The highest recoveries and adsorption capacities towards metal ions were achieved when using nitric acid-oxidized AC (sorbent AC-NA) as preconcentrating sorbent at pH 9. A preconcentration procedure was optimized using AC-NA as sorbent, which was then compared with non-oxidized AC in terms of analytical performance of the preconcentration method. Higher sensitivity, lower detection limits and wider linear ranges were achieved when AC-NA was used. The analytical performance of the method using AC-NA as preconcentrating sorbent was also compared with nitric acid-oxidized multi-walled carbon nanotubes (sorbent MWCNT-NA) and non-oxidized multi-walled carbon nanotubes (sorbent MWCNT). The analytical performance of the preconcentration method using AC-NA was close to MWCNT-NA, but AC-NA was better than non-oxidized MWCNT. Application of the optimized preconcentration method (using AC-NA sorbent) to environmental waters (tap water, reservoir water, stream water) gave spike recoveries of the metals in the range 63-104%.

Effect of dimensions of multi-walled carbon nanotubes on its enrichment efficiency of metal ions from environmental waters.

The effect of dimensions (length and external diameter) of multi-walled carbon nanotubes (MWCNTs) on its preconcentration efficiency towards some metal ions (Pb2+, Cd2+, Cu2+, Zn2+ and MnO4(-)) from environmental waters prior to their analysis by flame atomic absorption spectroscopy (FAAS) was investigated. MWCNTs (as-received from the manufacturer) of various external diameters and lengths were involved. Other variables optimized included effects of pH of water sample, composition and volume of eluent, mass of the MWCNTs, breakthrough volume and coexisting ions. Maximum recovery of metal ions was obtained at pH 9 where it was thought that precipitation of metals as their hydroxides played the major factor in metals uptake by MWCNT. It was suggested that the use of appropriate dimensions of MWCNTs may support the trapping process of the precipitated metal hydroxides by MWCNTs. It was found that long MWCNT of length 5-15 microm and external diameter 10-30 nm gave the highest enrichment efficiency towards almost all the targeted metal ions. It could be used for preconcentration of MnO4(-), Cu2+, Zn2+ and Pb2+ with almost full recovery; but not for Cd2+ due to its low recovery. The optimized solid phase extraction (SPE) procedure was capable of determining metal ions in the linear range 20-100 ng mL(-1) (except for Zn2+ from 20 to 150 ng mL(-1)). Detection limits were 0.709 ng mL(-1) for MnO4(-), 0.278 ng mL(-1) for Pb2+, 0.465 ng mL(-1) for Cu2+, 0.867 ng mL(-1) for Zn2+. Application of the optimized SPE procedure to environmental waters (tap water, reservoir water and stream water) gave spike recoveries of the metals in the range of 81-100%.