Oxine Concentration Research Articles

A new dispersive liquid–liquid microextraction using ionic liquid based microemulsion coupled with cloud point extraction for determination of copper in serum and water samples

A simple and rapid dispersive liquid–liquid microextraction procedure based on ionic liquid assisted microemulsion (IL-µE-DLLME) combined with cloud point extraction has been developed for preconcentration copper (Cu2+) in drinking water and serum samples of adolescent female hepatitits C (HCV) patients. In this method a ternary system was developed to form microemulsion (µE) by phase inversion method (PIM), using ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) and nonionic surfactant, TX-100 (as a stabilizer in aqueous media). The Ionic liquid microemulsion (IL-µE) was evaluated through visual assessment, optical light microscope and spectrophotometrically. The Cu2+ in real water and aqueous acid digested serum samples were complexed with 8-hydroxyquinoline (oxine) and extracted into IL-µE medium. The phase separation of stable IL-µE was carried out by the micellar cloud point extraction approach. The influence of of different parameters such as pH, oxine concentration, centrifugation time and rate were investigated. At optimized experimental conditions, the limit of detection and enhancement factor were found to be 0.132µg/L and 70 respectively, with relative standard deviation <5%. In order to validate the developed method, certified reference materials (SLRS-4 Riverine water) and human serum (Sero-M10181) were analyzed. The resulting data indicated a non-significant difference in obtained and certified values of Cu2+. The developed procedure was successfully applied for the preconcentration and determination of trace levels of Cu2+ in environmental and biological samples.

Speciation and determination of iron using dispersive liquid–liquid microextraction based on solidification of organic drop followed by flame atomic absorption spectrometry

A simple and efficient method for iron speciation (Fe2+, Fe3+) using dispersive liquid–liquid microextraction based on solidification of organic drop (DLLME-SFO) technique followed by flame atomic absorption spectrometry was developed. In this method, 1 mL of ethanol (as the disperser solvent) containing 50 µL of 1-undecanol (as the extracting solvent) was injected rapidly into the sample solution containing iron (II), iron (III) species and 1.1 × 10−3 mol L−1 oxine (as the complexing agent). The procedure is based on the complexation of Fe3+ with 8-hydroxyquinoline (oxine) at pH 3, and extraction of the resulting complex using DLLME-SFO. The total Fe was determined after the oxidation of Fe2+ to Fe3+ with concentrated nitric acid. The concentration of Fe2+ was determined from the difference between the concentration of total Fe and the Fe3+. Some parameters such as pH, oxine concentration, ratio of disperser and extractant solvent were investigated. Under the optimum conditions, the calibration graph was linear in the range of 25–250 µg L−1 for Fe3+ with a limit of detection (LOD) of 4.8 µg L−1. The relative standard deviation (RSD, %) for 10 replicate determinations of Fe3+ at 50 µg L−1 levels was 3.2%. To validate the developed method, a certified reference material (BRGM R52) was analysed and the determined value was in very good agreement with the certified value. The proposed method was successfully employed for determination of iron species in tap, well and spring water samples.

On the lability of dissolved Cu, Pb and Zn in freshwater: Optimization and application to the Deûle (France)

A procedure to determine lead and zinc by anodic stripping voltammetry and copper by cathodic stripping voltammetry in natural river samples was developed and validated. Cu determination involves the adsorption of Cu complexes with 8-hydroxyquinoline (oxine) onto a hanging mercury drop electrode. All samples were studied at natural pH and following optimal conditions were found: an accumulation step at −1.3V (all potential values in the paper are given versus the Ag/AgCl, [KCl]=3M reference electrode) during 30s for determination of Zn contents and at −0.7V during 60s for determination of Pb contents. Concerning Cu analysis, the optimal oxine concentration was found to be 10−5M with a deposition potential of −1.1V during 30s followed by an adsorption step at −0.25V during 15s. This procedure was afterwards validated by using certified reference freshwater and performing an intercalibration exercise. Finally the method was successfully applied in the Deûle River, highly contaminated by dissolved Zn and to a lesser extent by Pb and Cu, due to past and present activities of metallurgical plants. Under these optimal conditions, metal concentrations measured by our voltammetric procedures in the Deûle River were found in the range 12.4–23.2nM for Zn, 1.7–3.2nM for Pb and 4.9–7.6nM for Cu.

Optimization of experimental parameters in the determination of zinc in sea water by adsorptive stripping voltammetry

A procedure for the determination of zinc in sea water by square wave adsorptive stripping voltammetry (SWAdSV) using 8-hydroxyquinoline (oxine) as an adsorbing and complexing agent has been optimized. First, a univariate study of the Zn-Ox complex peak current as a function of pH was carried out choosing values at which adequate currents were obtained. Then, selection of the experimental conditions was made using a multivariate experimental design. Variables like pH, oxine concentration (Cox), adsorption time (tads) and adsorption potential (Eads) were optimized. The first optimization step was a 24 factorial design with 16 measurements made choosing high and low levels, and three measurements at the central point (Zn(II) 10.0 μg L-1). Analysis of variance showed that pH and Cox were the most significant factors, while tads and Eads were not significant and were kept constant in later measurements. Next, to find the optimum values for pH and Cox a 22 + star factorial design was used. The best experimental parameters were pH = 6.0; Cox = 25 μmol L-1; tads = 10 s and Eads = -0.70 V. Under these conditions the peak current was proportional to the concentration of zinc over the 0.1-48.0 μg L-1 range, with a detection limit of 0.05 μg L-1. Reproducibility for 5.0 μg mL-1 Zn(II) solution was 1.9 % (n = 16). The method was validated using spiked synthetic sea water (ASTM D665), sea water reference material (CRM-SW. Zn 5 μg kg-1) and fortified water reference material (GBW08607. Zn 5 mg kg-1) with satisfactory results. Finally, the method was successfully applied to the determination of Zn(II) in sea water samples without prior treatment.

A novel microextraction technique based on 1-hexylpyridinium hexafluorophosphate ionic liquid for the preconcentration of zinc in water and milk samples

A simple dispersive liquid–liquid microextraction methodology based on the application of 1-hexylpyridinium hexafluorophosphate [HPy][PF 6] ionic liquid (IL) as an extractant solvent was proposed for the preconcentration of trace levels of zinc as a prior step to determination by flame atomic absorption spectrometry (FAAS). Zinc was complexed with 8-hydroxyquinoline (oxine) and extracted into ionic liquid. Some effective factors that influence the microextraction efficiency such as pH, oxine concentration, amount of IL, ionic strength, temperature and centrifugation time were investigated and optimized. In the optimum experimental conditions, the limit of detection (3 s) and the enhancement factor were 0.22 μg L −1 and 71, respectively. The relative standard deviation (RSD) for six replicate determinations of 13 μg L −1 Zn was 1.92%. In order to validate the developed method, a certified reference material (NIST SRM 1549) was analyzed and the determined values were in good agreement with the certified values. The proposed method was successfully applied to the trace determination of zinc in water and milk samples.

Concentrations of cadmium and lead heavy metals in Dardanelles seawater

Cadmium and lead were determined simultaneously in seawater by differential pulse stripping voltammetry (DPSV) preceded by adsoptive collection of complexes with 8-hydroxyquinoline (oxine) on to a hanging mercury drop electrode (HMDE). In preliminary experiments the optimal analytical condition for oxine concentration was found to be 2.10(-5) M, at pH 7.7, the accumulation potential was -1.1 V, and the initial scannig potential was -0.8 V. The peak potentials were found -0.652 V for Cd and -0.463 V for Pb At the 60 s accumalation time. The limit of detection (LOD) and limit of quantitatification (LOQ) were found to be by voltammetry as 0.588 and 1.959 microg l(-1) (RSD, 5.50%) for Cd and 0.931 and 3.104 microg l(-1) (RSD, 4.10%) for Pb at 60 s stirred accumulation time respectively. In these conditions the most of the seawater samples are amenable for direct voltammetric determination of cadmium and lead using a HMDE. An adsorptive stripping mechanism of the electrode reaction was proposed. For the comparison, seawater samples were also analysed by ICP-atomic emission spectrometry method (ICP-AES). The applied voltammetric technique was validated and good recoveries were obtained.

Adsorptive square wave voltammetry of metal complexes. Effect of ligand concentration: Part II. Experimental applications

Theoretical models developed in Part I of this work for the square wave voltammetric response of inert metal complexes are applied to Cd(II)– and Cu(II)–8-OH-quinoline species adsorbed on mercury at pH 6.7. A wide range of experimental conditions were considered, taking into account the effect of ligand concentration. Cyclic voltammetry experiments were also performed for the purpose of comparison. Fitting between experimental and theoretical curves was excellent, assuming that the predominant species in bulk solution were CdOx + and Cu(Ox) 2 and that the electrochemical reaction mechanism involved ligand desorption after the reduction of both complexes. From the simulation procedure the following parameters were estimated: electrochemical rate constants k s,CdOx + = (7±1) s −1 and k s,Cu(Ox) 2 = (1.5±0.1) s −1; charge transfer coefficients α CdOx + =0.51±0.01 and α Cu(Ox) 2 =0.48±0.01; adsorption constants for the electroactive species K ad,CdOx =(4.5±0 .5) × 10 −3 cm and K ad,CuOx =(8±2)×10 −3 cm. Surface concentrations Γ M were also evaluated, observing that, for the ligand to complex ratios analysed, Γ CdOx increased steadily with oxine concentration whereas Γ CuOx remained constant. Local ligand concentrations close to the electrode were also evaluated.

Preconcentration of trace uranium from seawater with solid phase extraction followed by differential pulse polarographic determination in chloroform eluate

In the present study, an effective method is presented for the separation and preconcentration of uranium (VI) by solid phase extraction (SPE). For this purpose, U(VI) oxinate is formed by the reaction of U(VI) with 8-hydroxyquinoline and adsorbed onto the octylsilane (C-8) SPE cartridge. The analyte is completely eluted with chloroform and determined by differential pulse polarography. The SPE conditions were optimized by evaluating the effective factors such as pH, oxine concentration, type and concentration of buffer and masking agent. By the proposed method a preconcentration factor more than 100 was achieved. The average recovery of uranium (VI) oxinate (0.1 mg l −1) was 99.8%. The relative standard deviation was 1.6% for seven replicate determinations of uranyl ion in the solution with a concentration 20 μg l −1. Some concomitant ions such as Ca +2, Mg +2 and Fe +3 which interfere in extraction or determination process of uranium were masked with EDTA in aqueous phase during the extraction process. The proposed method was successfully used for the determination of uranium in Caspian Sea and Persian Gulf water samples.

Determination of copper, cadmium and lead in seawater by cathodic stripping voltammetry of complexes with 8-hydroxyquinoline

Procedures are presented to determine simultaneously copper, lead and cadmium in seawater by differential pulse cathodic stripping voltammetry (DPCSV) preceded by adsorptive collection of complexes with 8-hydroxyquinoline (oxine) onto a hanging mercury drop electrode (HMDE). In preliminary experiments the optimal analytical conditions were found to be an oxine concentration of between 0.8 and 2 × 10 −5 M, a pH between 7.5 and 8, the adsorption potential at −1.1 V, and the initial scanning potential at −0.3 V. The peak heights for low levels (sub-nanomolar) of cadmium and lead increase linearly with the adsorption time between 1 and 12 min. The limits of detection for a 1 min stirred adsorption time are 0.12 n M Cd, 0.3 n M Pb and 0.24 n M Cu; these limits are reduced 10x by increasing the adsorption time to 10 min. In these conditions most seawater samples are amenable for direct voltammetric determination of copper, cadmium and lead using an HMDE.

Apparent and Partial Specific Sorption of Oxine by Montmorillonite and Silica Gel in Binary Mixtures

AbstractOxine sorption by binary mixtures of montmorillonite and silica gel was studied at pH 5 as a function of oxine concentration and mixture composition. The investigation was made to resolve the problem of the determination of the oxine sorbed by each substance, inasmuch as the total amount sorbed by the mixture is the only value accessible experimentally. By the application of the thermodynamic method of partial quantities, the apparent and partial specific sorption by the clay and by the gel were calculated. These sorption values were found to increase with oxine concentration and to decrease as the proportion of the clay increased in the mixtures.

Investigation of the electrolytic behaviour of 8-quinolinol at the lead dioxide electrode in aqueous solutions

The electrolytic behaviour of 8-quinolinol (oxine) at the lead dioxide (PbO2) electrode was investigated in unbuffered solutions covering a pH range of about 2–12. In this pH range, the electrode process of oxine may be divided into three groups according to the pH of the solution: pH < 3.5, 3.5 ≤ pH < 9, and pH ≥ 9. In the presence of oxine, only an anodic peak at+1.1 V vs. SCE was obtained for a 0.1 mol/l KNO3 solution of pH 4.1. The anodic peak current increased slightly with increasing oxine concentration. The result of the controlled-potential electrolysis showed that the chemical reaction of oxine and PbO2 in the cathodic process was the rate-determining step in the total electrode reaction.

Simplified cell labelling with indium-111 acetylacetone.

Isolated cells labelled by means of 111 In-oxine (8-hydroxyquinoline) have been found clinically acceptable for the diagnosis of abscesses (Thakur et al., 1977) and vascular thrombi (Goodwin et al., 1978), as well as useful in research on cell migration and survival in animals (Rannie et al., 1977) and man (Lavender et al., 1977). Attention has recently been drawn to the detrimental effect this method of labelling may have on cells (Segal et al., 1978; Danpure et al., 1979; Silvester 1979). In part, damage is attributable to the soft radiation (Auger electrons) emitted in the decay of intra-cellular 111In, but further damage may also be caused by a too-high oxine concentration, or by the presence of heavy-metal impurities. With care these problems may be overcome, but a further hazard remains: the 111In-oxine complex is prepared and dispensed in ethanol solution, which itself can be toxic when added to the washed-cell suspensions (Atkinson et al., and which it is inconvenient to store and handle.

Labelling of human and rabbit platelets with 111Indium-oxine complex.

Platelets suspended in buffer were labelled with 111Indium-xoine. In the isolation procedure the platelets and a fraction of the erythrocytes are processed simultaneously, whereby the erythrocytes serve as a supporting cushion in the centrifugation steps. Various factors which influence the labelling effectiveness were examined, and the method's utility was estimated by in vivo studies in rabbits. A platelet concentration of more than 800 x 10(9)/1 and an oxine concentration of approximately 6 micrograms/ml in a plasma-poor system (transfer of platelets from plasma to buffer without further washing steps) will yield a high labelling efficiency. If the platelet isolation yield is to be large, a slight erythrocyte-leucocyte contamination must be accepted. Our experimental results indicated that this is permissible. In vivo investigations of 5 rabbits showed in vivo recoveries of platelets from 61--74% and mean survival times from 69 h to 110 h. This supports the assessment that the method of platelet isolation and labelling is gentle.

Systematic study of the solvent extraction of metal oxinates

The extraction of 32 metals (Be, Mg, Ca, Sr, Ba, Sc, La, Ti, Zr, Th, V, Nb, Cr, Mo, W, U, Mn, Fe, Co, Ni, Pd, Cu, Ag, Zn, Cd, Hg, Al, Ga, In, Tl, Pb and Bi) with oxine solution has been studied. The effects of pH, oxine concentration and water-soluble complexing agents (oxalic acid, tartaric acid, hydrocyanic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid and 1,2-diaminocyclohexanetetraacetic acid) have been investigated. From these results the extraction constants and stability constants ot the metal complexes with the various complexing agents investigated have been calculated.

Studies of the solvent extraction of indium oxinate

An investigation of the extraction of radio-labelled 2.10 -5 M indium from various aqueous solutions into a number of organic solvents containing oxine has been carried out. The effects of pH value, oxine concentration, masking agents, different organic phases, and temperature have been studied. Extraction constants and pH values of 50% extraction have been measured and compared with theoretically-calculatud values.

Studies of the solvent extraction of silver oxinate

Summary A study of the extraction of 10 −7 M silver ion from various aqueous solutions into various organic solvents containing oxine has been carried out. The effects of pH, the presence of water-soluble complexing agents, oxine concentration, and temperature have been investigated. Extraction constants have been calculated and theoretical interpretations of the data are offered.