Separation and preconcentration system based on microextraction with ionic liquid for determination of copper in water and food samples by stopped-flow injection spectrofluorimetry

In this work, an efficient in situ solvent formation microextraction (ISFME) was combined with stopped-flow injection spectrofluorimetry (SFIS) for the determination of copper. In the proposed approach, thiamine was oxidized with copper(II) to form hydrophobic and highly fluorescent thiochrome (TC), which was subsequently extracted into ionic liquid as an extractant phase. A small amount of an ion-pairing agent (NaPF₆) was added to the sample solution containing a water-miscible ionic liquid ([Hmim][BF₄]) to obtain a hydrophobic ionic liquid ([Hmim][PF₆]), which acted as the extraction phase. After centrifuging, phase separation was performed and the enriched analyte was determined by SFIS. ISFME is an efficient method for separation and preconcentration of metal ions from aqueous solutions with a high ionic strength. Variables affecting the analytical performance were studied and optimized. Under optimum experimental conditions, the proposed method provided a limit of detection (LOD) of 0.024 μg L⁻¹ and a relative standard deviation (RSD) of 2.1%. The accuracy of the combined methodology was evaluated by recovery experiments and by analyzing certified reference material (GBW 07605 Tea). Finally, the proposed method was successfully applied to copper determination in water and food samples.     

Spectrophotometric determination of gliclazide in pharmaceuticals and biological fluids through ternary complex formation with eosin and palladium (II)

A simple and sensitive spectrophotometric method has been developed for the determination of gliclazide (GLZ) in pharmaceutical formulations and biological fluids. The proposed method is based upon the formation of a ternary complex between palladium (II), eosin and GLZ in the presence of methyl cellulose as a surfactant and acetate buffer of pH 4.5. The ternary complex showed an absorption maximum at 550 nm. The solution of ternary complex obeyed Beer's law over the concentration range of 0.5-4 microg ml(-1) with minimum detectability (S/N = 2) of 0.05 microg ml(-1) (1.545 x 10(-7) M). The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The proposed method was successfully applied to the analysis of commercial tablets. The results obtained were in good agreement with those obtained using the official or reference spectrophotometric method. The proposed method was further applied to spiked human urine and plasma, the percentage recoveries were 97.84 +/- 0.72 and 97.43 +/- 0.83, respectively, (n = 4). A proposal of the reaction pathway was presented.     

Optimization of magnetic ionic based dispersive liquid-liquid microextraction of cadmium in water and food samples using experimental design prior to flame atomic absorption spectrophotometry

A magnetic ionic based dispersive liquid liquid microextraction (MIL-DLLME) procedure was optimized for the analysis and extraction of cadmium in water and food samples by flame atomic absorption spectrophotometry (FAAS). Contribution of experimental variables were optimized through central composite design combined with response surface analysis. Under optimized conditions, the limit of detection was found 0.6 ng mL^?1 with the relative standard deviation of 1.7%. Dynamic range was obtained in the concentration range of 2–700 ng mL^?1 with correlation coefficient of 0.9983. Relative recoveries were ranged from 94% to 99% with enrichment factor of 172. The validation of the optimized method was successfully confirmed by reference material analysis. The optimized method allows the analysis of cadmium in water and food samples with good reliability of the determination. Compared with the conventional procedures, the method enabled a fast, green and simple determination of cadmium in the real sample with minimal solvent consumption and a higher extraction capability.     

Selective speciation and determination of inorganic arsenic in water,food and biological samples

A procedure for the speciation of arsenic(III) and arsenic(V) in natural water samples has been established in the presented work. Arsenic(III) ions were quantitatively recovered on Alternaria solani coated Diaion HP-2MG resin at pH 7, while the recoveries of arsenic(V) was below 10%. Arsenic(V) in the mixing solution containing As(III) and As(V) was reduced by using KI and L(+) ascorbic acid solution, then the procedure was applied to determination of total arsenic. Arsenic(V) was calculated as the difference between the total arsenic content and As(III) content. The determination of arsenic was performed by using hydride generation atomic absorption spectrometry. The influences of some alkali, earth alkali and transition metals on the biosorption of arsenic(III) were investigated. The preconcentration factor was 35. The detection limits for As(III) (N = 20, k = 3) was found as 11 ng L⁻¹. The relative standard deviation and relative error of the determinations were found to be lower than 7% and 4%, respectively. The accuracy of the method was confirmed with certified reference materials. The method was successively applied for the determination and speciation of inorganic arsenic in water, food and biological samples.     

Ionic liquid-based dispersive liquid-liquid microextraction and enhanced spectrophotometric determination of molybdenum (VI) in water and plant leaves samples by FO-LADS

A new simple and rapid ionic liquid-based dispersive liquid-liquid microextraction (IL-DLLME) has been applied to preconcentrate trace levels of molybdenum (VI) as a prior step to its enhanced determination by fiber optic-linear array detection spectrophotometry (FO-LADS). In this method, a small amount of [Hmim][Tf₂N] (1-hexyl-3-methylimmidazolium bis (trifluormethylsulfonyl) imid) as an extraction solvent was applied to extract molybdenum - pyrogallol red complex, which was formed in an aqueous solution in the presence of N-cetyl-N-N-N-trimethyl ammonium chloride as a sensitizing agent. Under optimum conditions, enhancement factor, detection limit and relative standard deviation (n = 5, for 30 μg L⁻¹ of molybdenum (VI)) in 10 mL water sample were 72.6, 1.43 μg L⁻¹ and 2.8%, respectively.     

A preconcentration procedure for copper,nickel and chromium ions in some food and environmental samples on modified Diaion SP-850

A sensitive and simple method for the simultaneous preconcentration of trace amount of Cu²⁺, Ni²⁺ and Cr³⁺ ions in some real samples has been reported. In this method these elements are adsorbed as respective complex with Bis(2-hydroxyacetophenone)-1,2-propanediimine (BHAPPDI) on Diaion SP-850 and the retained metal ions are eluted using 8 ml of 4 M nitric acid. The influences of the analytical parameters including pH, solid phase ingredients amount and condition of eluting solution and sample volume were investigated. The effects of matrix ions on retentions of the analytes were also examined. The recoveries of analytes were generally higher than 90% with a relatively low RSD. The method has been successfully applied for these metal ions contents evaluation in some food and environmental samples.     

Miniaturized hollow fibre assisted liquid‐phase microextraction and gas chromatography for determination of trace concentration of sufentanil and alfentanil in biological samples

A simple and highly sensitive method that involves miniaturized hollow fibre assisted liquid‐phase microextraction with gas chromatography‐flame ionization detector was developed for the determination of trace concentration of sufentanil and alfentanil in biological samples. These drugs were extracted from 5 ml of aqueous solution with pH 10.0 into an organic extracting solvent (1‐octanol) impregnated in the pores and lumen of a hollow fibre. After extraction for a prescribed time, 2.0 µl of the extraction solvent was injected directly in to the GC injection port. Under the optimized conditions, (1‐octanol as extracting solvent, stirring rate of 700 rpm, 15% (w/v) salt addition, pH 10.0 and 25 min sampling time at 50 °C) large enrichment factors of 535 and 420 were achieved for sufentanil and alfentanil, respectively. Dynamic linear ranges were in the range of 0.05 to 500 ng/ml for sufentanil and 0.1 to 500 ng/ml for alfentanil. Limits of detection 0.01 and 0.02 ng/ml were obtained for sufentanil and alfentanil, respectively. The percent relative intra‐day and inter‐day standard deviations were found to be less than 8.4% (n = 5). Finally, this method was successfully applied for the separation, preconcentration and determination of trace concentration of sufentanil and alfentanil in plasma and urine samples. Copyright © 2012 John Wiley & Sons, Ltd.     

Hollow fiber-based liquid phase microextraction (HF-LPME) as a new approach for the HPLC determination of fluoroquinolones in biological and environmental matrices

In this paper, a three phase hollow fiber-based liquid phase microextraction (HF-LPME) combined with a HPLC procedure using diode array (DAD) and fluorescence detection (FLD) has been developed for the determination of eight widely used fluoroquinolones: marbofloxacin (MRB), norfloxacin (NRF), ciprofloxacin (CPR), danofloxacin (DNF), enrofloxacin (ENR), gatifloxacin (GTF), grepafloxacin (GRP) and flumequine (FLM). A Q3/2 Accurel PP polypropylene hollow fiber supporting 1-octanol was used between a 2 M Na2SO4 aqueous solution (pH 7) as donor phase and aqueous solution (pH 12) as acceptor phase. The microextraction parameters were optimised from an experimental central composite design. The procedure allows very low detection and quantitation limits of 0.3-16 ng L(-1) and 1-50 ng L(-1), respectively. The proposed method was applied to the determination of the analytes in bovine urine and in environmental water samples (surface, tap and wastewater).     

Modified ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction combined with spectrofluorimetry for trace determination of ofloxacin in pharmaceutical and biological samples

Background and the purpose of the study

Ofloxacin is a quinolone synthetic antibiotic, which acts against resistant mutants of bacteria by inhibiting DNA gyrase. This antibacterial agent is widely used in the treatment of respiratory tract, urinary tract and tissue-based infections, which are caused by Gram-positive and Gram-negative bacteria. In this work, an efficient modified ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction (M-IL-CIA-DLLME) was combined with spectrofluorimetry for trace determination of ofloxacin in real samples.

Methods

In this microextraction method, hydrophobic 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim] [PF₆]) ionic liquid (IL) as a microextraction solvent was dispersed into a heated sample solution containing sodium hexafluorophosphate (NaPF₆) (as a common ion) and the analyte of interest. Afterwards, the resultant solution was cooled in an ice-water bath and a cloudy condition was formed due to a considerable decrease of IL solubility. After centrifuging, the enriched phase was introduced to the spectrofluorimeter for the determination of ofloxacin.

Results and major conclusion

In this technique, the performance of the microextraction method was not influenced by variations in the ionic strength of the sample solution (up to 30% w/v). Furthermore, [Hmim][PF₆] IL was chosen as a green microextraction phase and an alternative to traditional toxic organic solvents. Different parameters affecting the analytical performance were studied and optimized. At optimum conditions, a relatively broad linear dynamic range of 0.15-125 µg l^-1 and a limit of detection (LOD) of 0.029 µg l^-1 were obtained. The relative standard deviation (R.S.D.) obtained for the determination of five replicates of the 10 ml solution containing 50 µg l^-1 ofloxacin was 2.7%. Finally, the combined methodology was successfully applied to ofloxacin determination in actual pharmaceutical formulations and biological samples.     

A novel preconcentration procedure using cloud point extraction for determination of lead,cobalt and copper in water and food samples using flame atomic absorption spectrometry

In this work, a new cloud point extraction (CPE) procedure was developed for the separation and preconcentration of lead(II), cobalt(II), and copper(II) in various water and food samples. Complexes of metal ions with 1-Phenylthiosemicarbazide (1-PTSC) were extracted into the surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114) from samples. After phase separation, the enriched analytes were determined by flame atomic absorption spectrometry (FAAS). Factors affecting cloud point extraction, such as pH, reagent and surfactant concentrations, temperature, and incubation time were evaluated and optimized. The interference effect of some cations and anions was also studied. After optimization of the CPE conditions, the preconcentration factor of 25 and the limits of detection (L.O.D.) obtained for lead(II), cobalt(II), and copper(II) based on three sigma (n = 20) were 3.42, 1.00, and 0.67 μg L⁻¹, respectively. The method presented precision (R.S.D.) between 1.7% and 4.8% (n = 7). The presented preconcentration procedure was applied to the determination of metal ions in reference standard materials (SRM 1515 Apple leaves and GBW 07605 Tea) and some real samples including tap water, spring water, sea water, canned fish, black tea, green tea, tomato sauce and honey.     

Three-phase,liquid-phase microextraction combined with high performance liquid chromatography-fluorescence detection for the simultaneous determination of fluoxetine and norfluoxetine in human plasma

A three-phase, liquid-phase microextraction using a hollow fibre (HF-LPME) combined with high performance liquid chromatography-fluorescence detection (HPLC-FL) was developed for the analysis of fluoxetine (FLX) and its active metabolite, norfluoxetine (NFLX), in human plasma. An HF-LPME system using a disposable 7-cm polypropylene porous hollow fibre, 5 mL of alkaline plasma solution (donor phase), n-hexyl ether (extraction solvent) and 20 mM hydrochloric acid (acceptor phase) was used in the extraction. The method was validated after optimisation of several parameters that influence LPME efficiency. A reverse-phase LiChrospher 60 RP-Select B column (125 mm × 4 mm, 5 μm particle size) was used with 0.005 M sodium acetate buffer (pH 4.5) and acetonitrile at a 50:50 (v/v) as the mobile phase at a flow rate of 0.6 mL min⁻¹. In these conditions satisfactory chromatographic resolution and efficiency for the analytes were obtained. Fluorescence detection at 230 nm excitation wavelength and 290 nm emission wavelength was performed. Linearity over a range of 5–500 ng mL⁻¹, with determination coefficients (R²) of 0.9999 and 0.9962 for FLX and NFLX, respectively, was established. Venlafaxine was used as the internal standard for both analytes. Extraction recoveries from plasma samples were 70.9% for FLX and 59.7% for NFLX. The intra-day coefficients of variation (CVs) were below 5.4%, and inter-day CVs were below 13.0%, for both analytes at concentrations of 20, 80 and 160 ng mL⁻¹. HF-LPME extraction followed by HPLC-FL detection for FLX and NFLX analyses demonstrated excellent sample clean-up and selectivity. This method was simple, cheap, and easy to perform, yielding substantial analytes enrichment. The method was applied to the analysis of samples from 12 patients under fluoxetine treatment and proved suitable for routine therapeutic drug monitoring for this antidepressant.     

Utilization of membrane filtration for preconcentration and determination of Cu(II) and Pb(II) in food,water and geological samples by atomic absorption spectrometry

A method for separation–preconcentration of Cu(II) and Pb(III) ions by membrane filtration has been presented. The analyte ions were collected on acetate membrane filter as their 1-2-pyridylazo 2-naphthol (PAN) complexes. The analytes were determined by flame atomic absorption spectrometry. The analytical parameters including pH, eluent type, sample volume, amount of PAN, etc. were examined in order to gain quantitative recoveries of analyte ions. The effects of foreign ions on the recoveries of analyte ions were also investigated. The detection limits by three sigma were found to be 1.2 and 3.5 μg L⁻¹ for Cu(II) and Pb(II), respectively. The preconcentration factor was 60 for Cu(II) and 20 for Pb(II). The validation of the presented procedure was checked by the analysis of certified reference materials. The optimized method was successfully applied to food, water and geological samples with good results.     

Influence of tetrahydrocannabinols (delta8-THC and delta9-THC) on body weight, food, and water intake in rats

Female Wistar rats, six to a group, were injected daily for a 23-day period with Δ⁸-THC (5.0 mg/kg), Δ⁹-THC (2.5 mg/kg) or vehicle. Body weight, food and water intake were recorded every second day. It was found that Δ⁸-THC caused a decrease of body weight, to a level maintained throughout the injection period, with only slight signs of recovery. Both drugs caused a marked decrease of water intake. Food intake was not significantly affected by the drugs. Factors in relation to the effects of THC on body weight, food and water intake are discussed.     

Three-phase hollow fiber liquid-phase microextraction based on two immiscible organic solvents for determination of tramadol in urine and plasma samples

Recently, the new concept of three-phase liquid microextraction was introduced based on applying two immiscible organic solvents in lumen and wall pores of hollow fiber. In the present work, this novel microextraction technique combined with gas chromatography-mass spectrometry has been developed for determination of tramadol, an analgesic agent, in plasma and urine samples. A systematic investigation of the proposed method was applied to find optimal extraction conditions and evaluate the interaction effects between the factors by designing experiments according to the methodology of Box-Behnken response surface design. Analysis of variance (ANOVA) revealed that the important factors contributing to extraction efficiency are extraction time, stirring rate and hollow fiber length. Under the optimum conditions, the developed method provided a preconcentration factor of 546, good repeatability (RSD % = 6.4), and good linearity (r² = 0.995) for spiked plasma and urine real samples. The linear dynamic range from 0.1 to 400 μg L⁻¹ and limit of detection (LOD) of 0.08 μg L⁻¹ were obtained under selected ion monitoring mode. The results demonstrated that three-phase hollow fiber microextraction based on two immiscible solvents is a simple and accurate technique with very good preconcentration factor and clean-up for extraction of tramadol from biological samples.     

Effects of heroin on lever pressing for intracranial self-stimulation,food and water in the rat

Male rats maintained with continuous access to levers for intracranial self-stimulation (ICSS), water, and food were subjected to five consecutive daily injections of heroin (5 mg/kg). Rates of lever pressing for ICSS were increased in 8 rats, 2–6 hrs after administration of heroin. Rates of lever pressing for water and food were not significantly changed during this period. Naloxone (5 mg/kg) pretreatment attenuated by 82% the facilitative effect of heroin on ICSS. A second group of 8 rats maintained at reduced ICSS rates failed to show an increase in lever pressing for ICSS with heroin. The facilitative effect of heroin described in this study is consistent with previously reported studies describing the effects of morphine on ICSS.     

A novel chemiluminescence quenching method for determination of sulfonamides in pharmaceutical and biological fluid based on luminol-Ag(III) complex reaction in alkaline solution

A novel chemiluminescence (CL) quenching method for the determination of sulfonamides is proposed. The CL reaction between Ag(III) complex [Ag(HIO₆)₂]^5? and luminol in alkaline solution was investigated. The quenching effect of sulfonamides on CL emission of [Ag(HIO₆)₂]^5?–luminol system was found. Quenching degree of CL emission was proportional to sulfonamide concentration. The effects of the reaction conditions on CL emission and quenching were examined. Under optimal conditions, the detection limits (s/n = 3) were 7.2, 17 and 8.3 ng/mL for sulfadiazine, sulfameter, and sulfadimethoxine, respectively. The recoveries of the three drugs were in the range of 91.3–110% with RSDs of 1.9–2.7% for urine samples, and 106–112% with RSDs of 1.6–2.8% for serum samples. The proposed method was used for the determination of sulfadiazine at clinically relevant concentrations in real urine and serum samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

Development of high performance liquid chromatography‐ultraviolet detection method for screening mebendazole,clorsulon, diaveridine,and tolfenamic acid in animal‐based food samples

This study focused on the detection and validation of the residues of the four veterinary drugs, mebendazole, clorsulon, diaveridine, and tolfenamic acid, using high performance liquid chromatography (HPLC) and an ultraviolet (UV) detector. Utilizing C18 column as a stationary phase and applying appropriate mobile phases to each analysis according to the properties of the analytes, target compounds in food samples were successfully detected and separated within 15–50 min. Additionally, in order to optimize detection, liquid‐liquid extraction (LLE) and purification steps were established to minimize the endogenous peaks and their interferences. The method was validated through testing of linearity, accuracy, precision, the limit of detection (LOD) and the limit of quantification (LOQ). The LOQ levels of the four drugs were lower than the maximum residual limit, and the coefficient of determination (R²) was over 0.99. The recovery results ranged from 82.3–105.2%, 79.3–83.3%, 79.4–86.0%, and 81.7–88.5% with relative standard deviations lower than 20% for mebendazole, clorsulon, diaveridine, and tolfenamic acid, respectively, corresponding to the CODEX guideline. This proposed method reduces costs and enables easier application in rural or remote areas where testing facilities or instruments often are unavailable. Copyright © 2013 John Wiley & Sons, Ltd.     

Parameters and pitfalls to consider in the conduct of food additive research,Carrageenan as a case study

This paper provides guidance on the conduct of new in vivo and in vitro studies on high molecular weight food additives, with carrageenan, the widely used food additive, as a case study. It is important to understand the physical/chemical properties and to verify the identity/purity, molecular weight and homogeneity/stability of the additive in the vehicle for oral delivery. The strong binding of CGN to protein in rodent chow or infant formula results in no gastrointestinal tract exposure to free CGN. It is recommended that doses of high Mw non-caloric, non-nutritive additives not exceed 5% by weight of total solid diet to avoid potential nutritional effects. Addition of some high Mw additives at high concentrations to liquid nutritional supplements increases viscosity and may affect palatability, caloric intake and body weight gain. In in vitro studies, the use of well-characterized, relevant cell types and the appropriate composition of the culture media are necessary for proper conduct and interpretation. CGN is bound to media protein and not freely accessible to cells in vitro. Interpretation of new studies on food additives should consider the interaction of food additives with the vehicle components and the appropriateness of the animal or cell model and dose–response.