Showing papers in "Journal of Analytical Chemistry in 2009"
TL;DR: The following methods for the determination of adenosine triphosphate reported in the past 25 years are considered: bioluminescence methods with the use of the firefly luciferase enzyme, and fluorescence, spectrophotometric, and electrochemical techniques, which are promising but not commonly used for thedetermination of adenine nucleotides.
Abstract: The following methods for the determination of adenosine triphosphate reported in the past 25 years are considered: bioluminescence methods with the use of the firefly luciferase enzyme (with sensitivity to 10−14 M); chromatographic methods (ion-exchange, thin-layer, and high performance liquid chromatography) for the determination of adenine nucleotides in mixtures with other nucleotides, nucleosides, and nitrogen bases; and fluorescence, spectrophotometric, and electrochemical techniques (including those with the use of sensors), which are promising but not commonly used for the determination of adenine nucleotides. The advantages and disadvantages of these methods are demonstrated.
95 citations
TL;DR: In this paper, the antihypertensive drug amlodipine has been characterized voltammetrically in a carbon paste electrode by means of anodic stripping voltammetry.
Abstract: The antihypertensive drug amlodipine has been characterized voltammetrically in a carbon paste electrode by means of anodic stripping voltammetry. An adsorptive stripping method in a carbon paste electrode for trace determination of amlodipine has been described. Cyclic voltammetric studies indicated the oxidation of amlodipine besylate at the electrode surface through a single two-electron irreversible step fundamentally controlled by adsorption. A study of the variation in the peak current with solution variables such as pH, ionic strength, concentration of amlodipine, possible interference, and instrumental variables, such as preconcentration time and accumulation potential, has resulted in the optimization of the oxidation signal for analytical purposes. By anodic adsorptive anodic stripping voltammetry, the calibration plot was linear in the range 9.9 × 10−9 − 1.4 × 10−7 M with a detection limit of 2 × 10−10 M in a carbon paste electrode at pH 11.0. The procedure was successfully applied to the assay of amlodipine besylate in some commercial products in the market (Amlopres®, Amlodipine, and Norvasc®). The percentage recoveries were in agreement with those obtained by the reference method.
62 citations
TL;DR: The state-of-the-art immunochemical methods for the determination of mycotoxins are considered in this article, and the principles of particular methods are considered, and the examples of the use of these methods are given; the main lines of development are discussed.
Abstract: The state-of-the-art immunochemical methods for the determination of mycotoxins are considered. Both instrumental (enzyme-linked immunosorbent assay, polarization fluoroimmunoassay, and sensor devices) and noninstrumental methods are presented. The principles of particular methods are considered, and the examples of the use of these methods for the determination of mycotoxins from various groups in food products and animal feeds are given; the main lines of development are discussed.
44 citations
TL;DR: In this paper, the main preconcentration techniques in capillary electrophoresis are considered and the use of these techniques makes it possible to increase sensitivity in the determination of analytes by a factor of 100 or higher.
Abstract: The main preconcentration techniques in capillary electrophoresis are considered. The use of these techniques makes it possible to increase sensitivity in the determination of analytes by a factor of 100 or higher.
42 citations
TL;DR: In this paper, a new solvent-free mode of liquid phase microextraction termed ionic liquid dispersive liquid-liquid extraction (IL-DLLME) was developed.
Abstract: In the present study, a new solvent-free mode of liquid phase microextraction termed ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) was developed. Four phenols were used as model compounds in the development and evaluation of the procedure. In this method, 50 µL of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) and 1.5 mL of sample aqueous solution were placed in a 2.2-mL glass test tube and mixed by aspirating and rapidly injecting by a syringe. This procedure produced a cloudy solution. In this process, phenols in the water sample were extracted into the IL phase. After centrifuging, the fine droplets of IL sedimented to the bottom of the glass test tube. The settled phase was injected into the high performance liquid chromatograph (HPLC) for separation and detection of phenols. Some parameters that might affect the extraction efficiency were optimized. The main advantages of the proposed method are high speed, high recovery, good repeatability and environmental friendliness.
41 citations
TL;DR: In this paper, it was shown that low-molecular chitosan can be fractioned by ultrafiltration and the types of membranes suitable for this purpose were determined.
Abstract: It was shown that low-molecular chitosan could be fractioned by ultrafiltration. The types of membranes suitable for this purpose were determined. The effect of ionic strength and the solvent nature on the molecular weight and polydispersity of the obtained samples was studied. The possibility of obtaining chitosan with low polydispersity was shown.
38 citations
TL;DR: In this paper, an on-line solid phase extraction method, linked to inductively coupled plasma optical emission spectrometry (ICP-OES), has been examined using octadecyl-bonded silica cartridge for determination of low levels of uranium and thorium in aqueous samples.
Abstract: An on-line solid phase extraction method, linked to inductively coupled plasma optical emission spectrometry (ICP-OES), has been examined using octadecyl-bonded silica cartridge for determination of low levels of uranium and thorium in aqueous samples. 2,3-dihydro-9,10-dihydroxy-1,4-anthracenedion forms a hydrophobic complex with cations and the resulted complex was retained on SPE. The retained complex was eluted using an acidic solution and introduced into ICP for determination. Various effective parameters and chemical variables such as sample pH, amount of ligand (as a complexing agent), sampling and eluting flow rates and concentration of the eluent were optimized. Under optimal conditions, calibration curves with dynamic linear ranges of 1–200 μg/L (r
2 = 0.9999) and 1–500 μg/L (r
2 = 0.9994) for U and Th were obtained, respectively. Detection limits based on three times of standard deviations of blank by 6 replicates were 0.69 μg/L and 0.84 μg/L for U and Th, respectively. Sample throughput was 10 samples/h. The interference effects of several metal ions on percentage of recovery of U and Th were also studied. The method was applied to the recovery and sequential determination of these actinide elements in different water samples.
35 citations
TL;DR: In this paper, the reaction between doxycycline, hydrogen peroxide and Cu(II) was investigated spectrophotometrically in aqueous solutions and the absorption spectra showed that the degradation of antibiotic drug occurs in weak alkaline aqueose solutions, and the kinetics of the reaction was studied by applying the initial rate method and the relative rate constants were calculated at different temperatures.
Abstract: The reaction between doxycycline, hydrogen peroxide and Cu(II) was investigated spectrophotometrically in aqueous solutions The absorption spectra show that the degradation of antibiotic drug occurs in weak alkaline aqueous solutions The kinetics of the reaction was studied by applying the initial-rate method and the relative rate constants were calculated at different temperatures The kinetic-spectrophotometric method for the determination of doxycycline based on the kinetics of pseudo-first order reaction at 20°C is proposed The effects of several molecules and ions usually present in pharmaceutical formulations were studied in order to assess their interference The calibration graph was applied to the determination of doxycycline in capsule dosage form The relative standard deviation was no greater than 380% The results were compared to those obtained by the official HPLC method
34 citations
TL;DR: Analytical perspectives related to the use of a mixing chamber such as time-based flow analysis, flow titrations, and analyte separation/concentration are discussed along with the examination of several ordinary manifold components that might act as mixing chambers.
Abstract: Inclusion of a mixing chamber in a flow system is critically rev—iewed in-relation to sample dilution, improvement of mixing conditions and exploitation of exponential concentration lessening. Analytical perspectives related to the use of a mixing chamber such as time-based flow analysis, flow titrations, and analyte separation/concentration are also discussed along with the examination of several ordinary manifold components that might act as mixing chambers. The possibility of using the mixing chamber in order to accommodate or to carry out the multiple steps inherent to the specific analytical procedure or, in other words, to behave as a mini-laboratory, is also highlighted. This aspect is foreseen as a logical evolution of the lab-on-a-valve and the flow-batch concepts. The article is published in the original.
30 citations
TL;DR: A simple ultraviolet spectrophotometric method for the estimation of montelukast in methanol has been devised and been compared with the existing pharmacopoeial RP-HPLC method for estimation of the drug.
Abstract: A simple ultraviolet spectrophotometric method for the estimation of montelukast in methanol has been devised and been compared with the existing pharmacopoeial RP-HPLC method for estimation of the drug. The limit of detection of montelukast at 283 nm was 75.2 ng/mL. The calibration was linear in the range of 3–45 μg/mL. Analytical parameters such as stability, selectivity, accuracy and precision have been established for the method in MONAKA® tablets and in human serum and evaluated statistically to assess the application of the method. The method was validated under the ICH and USP guidelines and found to comprise the advantages for simplicity, stability, sensitivity, reproducibility and accuracy for using as an alternate to the existing non-spectrophotometric methods for the routine analysis of the drug in pharmaceutical formulations and in pharmaceutical investigations involving montelukast.
29 citations
TL;DR: In this paper, a method is proposed for determining platinum-group elements, Ru, Pd, Os, Ir, Pt, and Re in geological samples by isotope dilution with mass spectrometric ending after sample decomposition with a mixture (1: 3) of conc. HCl + HNO3 in a microwave system and the chromatographic separation of the analytes from the matrix on an AG 50W × 8 cation exchanger.
Abstract: A method is proposed for determining platinum-group elements, Ru, Pd, Os, Ir, Pt, and Re in geological samples by isotope dilution with mass spectrometric ending after sample decomposition with a mixture (1: 3) of conc. HCl + HNO3 in a microwave system and the chromatographic separation of the analytes from the matrix on an AG 50W × 8 cation exchanger. The concentrations and isotope ratios are determined on high-resolution mass spectrometers ELEMENT and ELEMENT2. The attained detection limits range from 0.005 ng/g (Ir) to 0.2 ng/g (Pd) in solid samples. The use of isotope dilution improves the accuracy of determination and takes into account the matrix effect and changes in plasma parameters on the analytical signal. The method is tested in the analysis of standard samples of spinel lherzolite (GP-13) and serpentinite (UB-N). The relative standard deviation of the results of analysis is 5–22%, depending on the element and its concentration level (Ru, Pd, Re, Pt). In determining Os and Ir, a certain decrease in the accuracy and repeatability of the results is noticed.
TL;DR: In this article, a diclofenacselective electrode with a plasticized polyvinyl chloride membrane containing an ion associate of diclenac with Astrafloxin FF as an electrode-active substance was developed.
Abstract: A diclofenacselective electrode with a plasticized poly(vinyl chloride) membrane containing an ion associate of diclofenac with Astrafloxin FF as an electrode-active substance was developed. The linearity range of the electrode function varied from 5 × 10−5 to 5 × 10−2 M; the slope of the electrode function was 59.0 ± 1.2 mV/pc, and the working pH range was 9–12. The effectiveness of the use of this electrode for monitoring diclofenac in pharmaceutical preparations was demonstrated.
TL;DR: In this paper, a new method was proposed for the generation of vapor iodine from periodate ions using hydrogen peroxide as a reductant, which allowed the detection limit for iodine to be lowered by 3-4 orders of magnitude.
Abstract: Procedures of microwave oxygen combustion and microwave acid digestion of biological samples were optimized for the subsequent determination of iodine. A new method was proposed for the generation of vapor iodine from periodate ions using hydrogen peroxide as a reductant. Procedures were developed for determining iodine in biological samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) using oxidation and reduction vapor generation; these allowed the detection limit for iodine to be lowered by 3–4 orders of magnitude. The developed procedures were used to analyze certified reference materials of milk (Skim Milk Powder BCR 150) and seaweed (Sea Lettuce BCR 279) and a Supradyn vitamin complex.
TL;DR: In this article, two validated analytical methods have been developed to determine glimepiride in pharmaceutical formulations using HPLC and 1st order derivative spectrophotometric techniques, and the linearity range was found to be 20-140 μg/mL with mean recovery of 100.52 ± 0.33%.
Abstract: Two validated analytical methods have been developed to determine glimepiride in pharmaceutical formulations using HPLC and 1st order derivative spectrophotometric techniques. Employing reverse phase HPLC method, the drug was analyzed by pumping a mixture of acetonitrile and 2% formic acid solution, pH 3.5 (80: 20 v/v) through a C18 column (250 × 4.6 mm, 5 μm) and detecting the eluents at 228 nm. The linearity range was found to be 20–140 μg/mL with mean recovery of 100.52 ± 0.33%. The second method was based on the formation of a complex of the drug with 2,3,5-triphenyl-2H-tetrazolium chloride in basic media. 1st order derivative spectrum made it possible to detect the complex at 413.5 nm. The linearity range was found to be 40–160 μg/mL, with mean recovery of 100.33 ± 0.47%. Both the proposed methods can reliably be used for routine analysis of glimepiride in raw material as well as in pharmaceutical formulations.
TL;DR: In this paper, the reaction between telmisartan and congo red could form ionassociation complex, which has the maximum absorbance at 593 nm in the spectrophotometric experiment, under this wavelength, the Beer's law was obeyed within the concentration range of 1.08 × 10−6−2.
Abstract: In pH 2.50 HCl-NaAc buffer solution, the reaction between telmisartan and congo red could form ionassociation complex, which has the maximum absorbance at 593 nm in the spectrophotometric experiment. Under this wavelength, the Beer’s law was obeyed within the concentration range of 1.08 × 10−6−2.24 × 10−5 M. The linear regression equation was A = −0.1913 × 105c + 0.0286 (C: M). The regression coefficient r was 0.9986. The apparent molar coefficient ɛ593 was 1.63 × 104 L mol−1 cm−1 and the detection limit was 5.66 × 10−7 M. The established method having high sensitivity and good selectivity could be applied to the determination of telmisartan in pharmaceutical, urine and blood plasma samples with satisfactory results. The reaction mechanism was also discussed by using density functional theory methods. The result obtained was consilient with experimental data.
TL;DR: In this paper, a chelating resin, 1-(2-pyridylazo)-2-naphthol (PAN) coated Amberlite XAD-1180, was prepared and used for the preconcentration of Cd, Mn, Ni, Pb, and Zn, prior to their determination by flame atomic absorption spectrometry (FAAS).
Abstract: A new chelating resin, 1-(2-pyridylazo)-2-naphthol (PAN) coated Amberlite XAD-1180 (AXAD-1180), was prepared and used for the preconcentration of Cd(II), Mn(II), Ni(II), Pb(II) and Zn(II) ions prior to their determination by flame atomic absorption spectrometry (FAAS). The optimum pH for simultaneous retention of the elements and the best elution means for their simultaneous elution were pH 9.5 and 3 M HNO3, respectively. The sorption capacity of the resin was found to be 5.3 mg/g for Cd and 3.7 mg/g for Ni. The detection limits for Cd(II), Mn(II), Ni(II), Pb(II) and Zn(II) were 0.7, 10, 3.1, 29 and 0.8 μg/L, respectively. The effects of interfering ions for quantitative sorption of the metal ions were investigated. The preconcentration factors of the method were in the range of 10–30. The recoveries obtained were quantitative (≥95%). The standard reference material (GBW07605 Tea sample) was analysed for accuracy of the described method. The proposed method was successfully applied to the analysis of various water, urea fertilizer and tea samples.
TL;DR: In this article, conditions for the voltammetric determination of lipoic acid and unithiol at a glassy-carbon electrode modified with multiwalled carbon nanotubes were found.
Abstract: Conditions are found for the voltammetric determination of lipoic acid and unithiol at a glassy-carbon electrode modified with multiwalled carbon nanotubes. Possible mechanisms for the oxidation of lipoic acid and unithiol are proposed. As compared to an unmodified electrode, the use of the modified electrode allows the analyst to reduce overvoltage (ΔE = 0.1 V) and increase the oxidation current of lipoic acid. Unithiol is oxidized in the accessible range of potentials only at an electrode modified with carbon nanotubes. The determination limits for unithiol and lipoic acid are 4.1 × 10−5 and 1.9 × 10−5 M, respectively. Milligram amounts of these substances are determined in model solutions with RSD = 1–5%. Procedures for determining the active substances (lipoic acid and unithiol) in pharmaceuticals are proposed.
TL;DR: In this paper, a cloud point extraction process using the nonionic surfactant Triton X-114 for extraction and preconcentration of periodate and iodate ions from aqueous solution was investigated.
Abstract: A cloud point extraction process using the nonionic surfactant Triton X-114 for extraction and preconcentration of periodate and iodate ions from aqueous solution was investigated. The method is based on the extraction of triiodide ion, the colored product of the reaction of periodate and iodate with iodide in acidic media. The triiodide was concentrated in surfactant rich phase and then determined spectrophotometrically at 358 nm. For the determination of periodate and iodate in mixture, two sets of conditions were established. In one set of conditions only periodate reacted with iodide but in the other set both ions reacted with iodide. The data were evaluated by the method of proportional equations. The optimal extraction and reaction conditions (e.g., surfactant and reagent concentrations and centrifuge time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor, and enhancement factors) were obtained. Under the optimized conditions, the methods allowed the determination of periodate and iodate at concentrations between 2.0 and 1000 and 4.0 and 400 ng/mL, respectively. The proposed method was successfully applied to the determination of periodate and iodate in water samples.
TL;DR: An approach to fingerprinting and quantitative analysis of volatiles in Shexiang Baoxin Pill (SBP) was proposed by using gas chromatography (GC) with a flame ionization detector and a mass spectrometric detector (MS).
Abstract: An approach to fingerprinting and the quantitative analysis of volatiles in Shexiang Baoxin Pill (SBP) was proposed by using gas chromatography (GC) with a flame ionization detector and a mass spectrometric detector (MS). Using the proposed method, the chemical fingerprint of SBP extract was established, in which the separation of more than 30 volatiles was realized in about 30 min, and 26 peaks were identified by GC/MS analysis. Seven major volatiles, including borneol, isoborneol, isopropyl methylphenol, mascone, cinnamaldehyde, cinnamic acid, and benzyl benzoate, were further quantified. The linearity, precision, stability, repeatability, and accuracy were acceptable. The proposed method was successfully applied to the determination of volatiles in 11 batches of SBP samples. To evaluate their quality, principal components analysis (PCA) was performed on the basis of the data of chemical fingerprints, and the score plot clearly revealed the variations of samples produced in different years. Moreover, the results of the quantitative analysis of various samples were also comparatively studied. The results indicated that, to ensure the quality of SBP, more efficient storage and package techniques are needed. The proposed method enables chemical fingerprinting and the simultaneous determination of multicomponents to be performed in one run, and can be applied as a comprehensive quality control technique for traditional Chinese medicine containing volatile constituents.
TL;DR: In this paper, the effect of surfactant micelles and albumin on the fluorescence warfarin of and fluorescence of Eu3+ and Tb3+ sensitized by war-farin and the second ligand is studied.
Abstract: The effect of surfactant micelles and albumin on the fluorescence warfarin of and the fluorescence of Eu3+ and Tb3+ sensitized by warfarin and the second ligand is studied It was shown that sensitized fluorescence in the system Eu3+-tenoyltrifluoroacetone-warfarin allows a 3800-fold reduction of the detection limit for warfarin The developed procedure was used to determine warfarin in soil
TL;DR: In this article, a lidocaine ion-selective electrode was developed and used in pharmaceutical analysis, which was found to be very selective, precise, and usable within the pH range 5 − 9.5.
Abstract: A novel lidocaine ion-selective electrode is prepared, characterized and used in pharmaceutical analysis. The electrode incorporates PVC-membrane with lidocaine-sulfathiazole ion pair complex. The influences of membrane composition, temperature, pH of the test solution, and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a lidocaine concentration range from 1.0 ×10−5 to 1.0 × 10−1 mol L−1 with a slope of 60.1 ± 0.2 mV per decade at 25°C and was found to be very selective, precise, and usable within the pH range 5–9.5. The standard electrode potentials, E
o, were determined at 10, 15, 20, 25, 30, 35 and 40°C, and used to calculate the isothermal temperature coefficient (dE
o/dT=−0.0003 V °C−1) of the electrode. However, the electrode performance is significantly decreased at temperatures higher than 45°C. The electrode was successfully used for potentiometric determination of lidocaine hydrochloride in pharmaceutical products.
TL;DR: The individual sources of errors in procedures used for considering matrix effects were studied in this paper, where the ZAF and PRZ analytical programs provided good correction in the predominance of one of the matrix effects, namely absorption or the atomic number.
Abstract: The individual sources of errors in procedures used for considering matrix effects were studied. The ZAF and PRZ analytical programs provided good correction in the predominance of one of the matrix effects, namely, absorption or the atomic number. Their simultaneous occurrence increased the total error to 2–4 rel %. In the ZAF method, normalization to oxygen in terms of stoichiometry introduced errors if the sample simultaneously contained the test element in various oxide forms. The greatest error of up to 1–2 wt % appeared in simple and double oxides. In the analysis of the main rockforming silicates with the determination of total iron as FeO, the presence of Fe2O3 can change the concentration of components to ∼0.2%.
TL;DR: In this paper, a Solid Phase Extraction (SPE) method for preconcentration and determination of Cd(II, Pb(II), Co(II) and Ni(II)-aqueous samples by inductively coupled plasma optical emission spectrometry is described.
Abstract: Solid-phase extraction (SPE) method for preconcentration and determination of Cd(II), Pb(II), Co(II), Ni(II), and Cu(II) aqueous samples by inductively coupled plasma optical emission spectrometry is described. The preconcentration of analytes is accomplished by retention of their chelates with 1.10-phenanthroline in aqueous solution on a solid phase containing carboxylic acid (COOH) bonded to silica gel in a column. The limits of detection values (defined as “3s” where “s” is standard deviation of the blank determination) are 3.6 μg/L for Cd(II), 17.5 μg/L for Pb(II), 3.1 μg/L for Co(II), 2.1 μg/L for Ni(II), and 4.4 μg/L for Cu(II) and corresponding limit of quantification (6s) values are 7.2, 35, 6.2, 4.2 and 8.8 μg/L, respectively. As a result, a simple method was elaborated for the group concentration and determination of the above mentioned metals in reference material and in samples of plant material.
TL;DR: In this paper, three multielement methods: inductively coupled plasma mass spectrometry (ICP-MS), inductive coupled plasma atomic emission spectroscopy (AES), and Spark Source Mass Spectrometer (SSMS) were used for the determination of additives in the samples of germanium and germanIUM oxide.
Abstract: Three multielement methods: (1) inductively coupled plasma mass spectrometry (ICP-MS), (2) inductively coupled plasma atomic emission spectroscopy (ICP-AES), and (3) spark source mass spectrometry (SSMS) were used for the determination of additives in the samples of germanium and germanium oxide. The detection limits of direct SSMS and ICP-AES/ICP-MS were compared using the autoclave predissolution of germanium and germanium dioxide samples. It was shown that in the latter case, the detection limits could be significantly improved by the separation of germanium from analytes by distillation. In this case, the detection limits of such limiting elements like Th and U can reach the level n 10−10 wt %.
TL;DR: In this article, a unified procedure was developed for the cyclic-injection determination of phosphate and silicate ions simultaneously present in aqueous solutions; the analytical ranges were 1 −90 and 0.5 −25 mg/L, respectively.
Abstract: A unified procedure was developed for the cyclic-injection determination of phosphate and silicate ions simultaneously present in aqueous solutions. The analytical ranges were 1–90 and 0.5–25 mg/L, respectively; the procedure enabled 10 determinations per hour.
TL;DR: In this article, the detection of sulfanylamide drugs in environmental objects and foodstuffs is considered, including specific detection of individual substances, class-specific immunoassay of the whole group of sulfamide drugs, widely used ELISA methods; biosensors; fluorescence polarization immunoASSay; and new promising methods for the detection sulfamide drug, immunochromatographic test strips, the method using molecularly imprinted polymers, piezoelectric quartz immunosensors, etc.
Abstract: Recent achievements in the detection of sulfanylamide drugs in environmental objects and foodstuffs are considered. These are the specific detection of individual substances; class-specific immunoassay of the whole group of sulfamide drugs; widely used ELISA methods; biosensors; fluorescence polarization immunoassay; and new promising methods for the detection of sulfamide drugs, immunochromatographic test strips, the method using molecularly imprinted polymers, piezoelectric quartz immunosensors, etc.
TL;DR: A brief review of the most common techniques for microparticle fractionation (0.1-100 μm) is presented in this paper, where the main advantages and limitations of these methods are revealed and their outlooks and fields of applications are envisaged.
Abstract: The development of new methods for fractionating particles of a different nature is becoming more important in solving some scientific and technological problems. This paper presents a brief review in the theory and practice of the most common techniques for microparticle fractionation (0.1–100 μm). These are dry and wet sieving, elutriation, sequential filtration, split-flow thin fractionation (SPLITT system), field-flow fractionation (FFF), membrane filtration, and capillary electrophoresis. Special attention is paid to the FFF technique, which offers a unique potential for the separation of different materials, from biopolymers and microorganisms to colloidal and solid particles, and the estimation of their physical properties. An alternative version of sedimentation FFF is described, namely, the fractionation of microparticles in rotating coiled columns. The main advantages and limitations of the methods are revealed and their outlooks and fields of applications are envisaged.
TL;DR: In this article, the catalytic activity of gold, palladium, and rhodium particles and their binary systems electrodeposited on the surface of a glassy-carbon electrode in the oxidation of dopamine and ascorbic acid are compared.
Abstract: The catalytic activities of gold, palladium, and rhodium particles and their binary systems electrodeposited on the surface of a glassy-carbon electrode in the oxidation of dopamine and ascorbic acid are compared. As compared to individual noble metals, the Au-Pd binary system exhibits a higher catalytic activity that manifests itself in a multiple increase in the oxidation current of the mediator and in a decrease in the oxidation potential of the substrate. It is found that dopamine and ascorbic acid can be simultaneously determined by voltammetry at an electrode modified with the Au-Pd binary system. The catalytic currents of substrate oxidation are linear functions of the concentrations in the ranges from (1 × 10−3 to 1 × 10−7) M for dopamine and from (5 × 10−3 to 1 × 10−6) M for ascorbic acid.
TL;DR: The reduction of silver nitrate with sodium borohydrate in an aqueous medium in the presence of cetyl trimethylammonium bromide gives a stable sol of silver, which can adsorb nonpolar organic compounds, e.g., polycyclic aromatic hydrocarbons, on the surface of metal nanoparticles as mentioned in this paper.
Abstract: The reduction of silver nitrate with sodium borohydrate in an aqueous medium in the presence of cetyl trimethylammonium bromide gives a stable sol of silver, which can adsorb nonpolar organic compounds, e.g., polycyclic aromatic hydrocarbons, on the surface of metal nanoparticles. The subsequent luminescent determination demonstrated the effect of sensitized luminescence of silver nanoparticles, which could provide a basis for the determination of traces of polycyclic aromatic compounds in water.
TL;DR: In this article, second order derivative spectrophotometry was used for simultaneous determination of 2-ethylhexyl-4-methoxycinnamate (OMC) and oxybenzone (OB) in commercial sunscreen formulations.
Abstract: Simultaneous determination of 2-ethylhexyl-4-methoxycinnamate (OMC) and oxybenzone (OB) in commercial sunscreen formulations has been achieved by using second order derivative spectrophotometry. The analytical methodology described does not require elaborate pretreatment of samples. The results obtained could be validated by reverse phase HPLC assay by using isocratic methanol: water (88: 12) solvent system. The sensitivity of the developed derivative spectrophotometry method was determined to be 9.0 × 10−3 L/mg for OB and 9.56 × 10−3 L/mg for OMC. The limit of instrumental detection (LOD) was determined to be 0.6 mg/L for OB and 1.38 mg/L for OMC with relative standard deviation of 0.001 and 0.004 for OB and OMC respectively. The method developed can be used for quick assay of commercial sunscreens.