A mixed complex Fe(bpy)(phen)(2+) was synthesized and resonance light-scattering (RLS) characteristics of a triple complex Fe(bpy)(phen)SO4-Myristylpyridinium bromide-bovine serum albumin were studied. When albumin was added, Fe(bpy)(phen)(2+) aggregated on the surface of albumin molecules at pH 5.5-7.0. As a result. RLS peaks at 400 nm and 470 nm were enhanced. The intensity of RLS signals was proportional to the concentration of bovine serum albumin. It was observed that the presence of myristylpyridinium sensitized the system. Determination limit was 0.02 mg L-1.
A simple testis proposed for short-lived organopotassium and organosodium intermediates formed during some organic processes. It is based on the use of 15-crown-5 or 18-crown-6 as the additional reagent and identification of its ring opening product, i.e. alkali metal tetraethylene glycoxide vinyl ether or alkali metal pentaethylene glycoxide vinyl ether, respectively.
The widespread use of autocatalysts containing platinum as one of active components generates an ecological awareness on the introduction of the metal into the environment. The evaluation of the level of the metal emission and a risk to living organisms from catalyst technology requires the examination of a large variety of environmental samples for the content ofultra-traces (pg g ―1 and ng g ―1 ) of platinum. Inductively coupled plasma―mass spectrometry is the most promising instrumental technique for the detection of low concentrations of the elements in complex matrices. The application of the technique to the detection of platinum in environmental materials is seriously hampered by hafnium which can occur in such samples. The ICP-MS signals of platinum isotopes are overlapped by the signals of HfO + ions generated under plasma conditions. Methods developed for the elimination of the effect of hafnium on the detection of platinum by ICP―MS technique are presented in the paper. Possibilities and limitations of mathematical correction; modifications in sample introduction techniques; the use of dynamic reaction cells, double-focusing sector field mass spectrometers and chemical separation procedures are discussed in detail.
A novel DNA probe based on the measurement of enhanced resonance light-scattering (RLS) resulting from the interaction of the functionalized L-cysteine capped CdS nanoparticles (nano-L-cysteine-CdS) with DNA has been proposed. The RLS signals ofnano-L-cysteine-- CdS were greatly enhanced by DNA at the wavelength of c a 415 nm. The relationship between the measured signal magnitude and DNA content was linear in the concentration range of 20―700 ng mL -1 for calf thymus DNA and 30-800 ng mL -1 for fish sperm DNA. Detection limits (S/N = 3) were 1.5 and 1.9 ng mL -1 , respectively. Based on these results, a new direct quantitative method for determination of DNA was established. This procedure has higher sensitivity and better selectivity than most of other similar methods, due to the nature ofnanoparticles.
A new micelle-mediated phase separation method using mixed micelles of anionic surfactant sodium dodecyl sulfate and non-ionic surfactant Triton X-114 has been developed for preconcentration of ultratrace amounts of 1,1-dimethylhydrazine (UDMH) as a prior step to its spectrophotometric determination. The method was based on extraction of dimethylhydrazone - the coloured product of reaction of UDMH with p-nitrobenzaldehyde in the presence of electrolyte as phase separation inducing agent. Dimethylhydrazone concentrated in a surfactant-rich phase was then determined spectrophotometrically at 404 nm. Optimal extraction and reaction conditions (e.g. surfactant and reagent concentrations, temperature) were studied and analytical characteristics of the method (e.g. limit of detection, linear range, preconcentration and enhancement factors) were determined. Linearity was observed in the range 10-500 ng mL(-1) UDMH and detection limit of the method was 5.0 ng mL(-1). Interfering effects from some cations, anions, and organic compounds were also investigated. The proposed method was successfully applied to the determination of UDMH in water and soil samples.
In this paper, a capillary electrophoresis-electrochemiluminescence method for simultaneous detection of three macrolide antibiotics: azithromycin (ATM), roxithromycin (RTM) and erythromycin ethylsuccinate (ETMES) has been presented. The method is based upon the enhancement effect of these compounds on electrochemiluminescence of tris(2,2-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+)). Under the optimized conditions. complete separation of ATM, WIN and ETMES was achieved within 6 min using 20 mmol L-1 phosphate buffer of pH 7.3 as a background electrolyte and applying a separation voltage of 20 kV. Detection limits were 0.1 mu mol L-1 for ATM, 0.2 mu mol L-1 for WIN, and 0.4 mu mol L-1 for ETMES (S/N = 3). Relative standard deviations for all analytes were below 5%. The proposed method has been successfully applied to the determination of the content of the studied compounds in spiked human plasma and urine samples.
A newly constructed electrochemical multisensor containing 8 different sensors (5 different solid amalgam electrodes, platinum, gold and glassy carbon electrodes) for analysis of small sample volumes (5-200 mu L) was developed. The multisensor was connected to the specially constructed and developed electrochemical multichannel device for sequential autonomous measurements. This device consisted of a computer (PC or notebook), an interface card, and a control box: it was able to control up to 1; sensors (i.e. electrode sets) in it selected sequence, in which each sensor could utilize different detection mode (e.g. DCV DPV, coulometry, chronopotentiometry, square-wave voltammetry) and operate at different parameters. The analysis of a mixture of ferrocene and nucleic acid bases: adenine and guanine was used to demonstrate the possibilities of this device.
A sensitive chemiluminescence method for determination of loratadine has been presented. The method is based on the inhibitory effect of loratadine on the chemiluminescence reaction between luminol and myoglobin. The decrement in chemiluminescence intensity changed linearly with the logarithm of loratadine concentration over the range 0.1-100.0 ng mL(-1) (R-2 = 0.9992) with a detection limit of 0.03 ng ml(-1) (3 sigma). At a flow rate of 2.0 ng min(-1), the complete analytical process could be performed within 30 s including sampling and washing, with a relative standard deviation of less than 3.0% (n = 7). Without any pretreatment the proposed procedure was applied to the determination of loratadine in tablets, human serum, and urine samples with recoveries of 91.7-108.3%, 90.1-103.3%, and 94.6-107.6%, respectively.
The influence of Cr2O72- on the B-Z oscillating reaction has been studied. The research results have shown that B-Z oscillating reaction can be paused by Cr2O72- and the pause time can be used as a kinetic parameter in determination of Cr2O72- (when perturbed by particular chemicals, stable oscillating reaction is inhibited or paused; pause duration of the oscillation phenomenon is defined as a pause time). Under optimum experimental conditions. the pause time was linearly proportional to the concentration of Cr2O72- in the range 4.74 x 10(-6-)1.20 x 10(-4) mol L-1 (r = 0.999), detection limit was 1.32 x 10 mol L-1. The influence of more than 15 coexisting ions on determination of Cr2O72- was investigated in details. Most cations and anions had little effect on the determination results of Cr2O72-. A possible disturbance mechanism of Cr2O72- on the oscillating system was discussed. As a particularly efficient oxidant. Cr2O72- could consume Br- quickly. Due to the extra consumption of Br-. the B-Z oscillating reaction was inhibited, and therefore paused for a particular time (pause time). The higher the concentration of Cr2O72- was, the longer the pause time became, until the B-Z oscillating reaction was quenched completely.
Binding reaction of methylene blue (MB) with human serum albumin (HSA) in the presence of sodium dodecyl sulfate (SDS) was studied. It was found that at pH = 2.87 positively charged MB bound firstly to HSA via hydro.-en and hydrophobic bonds to form MB-HSA aggregate. The aggregate contained many positive charges and attracted negatively charged SDS to form macromolecules, which induced a great enhancement of RLS intensity. RLS intensity was directly proportional to the concentration of HSA. This phenomenon was utilised in a new method for quantitative determination of HSA protein.
A rapid and selective chromatographic method for determination of fluoxetine in blood samples has been developed. The method is based on a selective reaction between 7,7,8.8-tetracyanoquinodimethane (TCNQ) and molecules with a secondary amine moiety, resulting in a purple solution. Blood samples were spiked with fluoxetine and nortriptyline as an internal standard. then. both compounds were extracted applying a microwave-assisted extraction - a novel technique for isolation of an analyte from biological matrix After extraction, dried residues were dissolved in acetonitrilic solution of TCNQ and heated for 30 minutes at 80 degrees C. The obtained intense purple-blue colored solutions were then analyzed by high performance liquid chromatography with diode-array detection Chromatograms were recorded at 567 nm. Limits of detection and quantification of fluoxetine in blood were 0,03 and 0,10 mu g mL(-1). respectively It was concluded therefore that fluoxetine can be determined in blood in the therapeutic concentration range. The developed method has been applied to the analysis of whole blood samples collected from a female patient treated with Seronil (R) 20 (20 mg of fluoxetine)
A rapid, accurate, and precise ICP-OES procedure for determination of lead sulfate in lead-acid batteries plates was elaborated based on the measurement of the sulfur emission line. Optimal parameters of spectrometric measurements were selected and accuracy, repeatability, and reproducibility were estimated. The proposed analytical ICP-OLS procedure was validated through the analysis of certified reference materials, and it good agreement between the ICP-OES results and the reference values was obtained. It was proved that the ICP-OES method is more accurate and precise than the routine gravimetric method. Additional advantages of the elaborated method over the routine one are high speed of total analysis and elimination of toxic barium chloride.
A sensitive, selective, precise and stability-indicating high-performance thin layer chromatographic (HPTLC) method for analysis of donepezil hydrochloride (DH) as bulk drug and in formulations was developed and validated. TLC aluminum plates pre-coated with 60 F-254 silica gel (20 x 10 cm) were used as the stationary phase. The solvent system consisted of butanol water glacial acetic acid (5:4:1, v/v/v). Densitometric analysis of DH was carried out in the absorbance mode at 260 nm. This system was found to give compact spots for DH (R(F) = 0.53 +/- 0.03 for six replicates). DH was subjected to acidic and alkaline hydrolysis, oxidation, dry and wet heat treatment, and photodegradation; under all these conditions the drug underwent degradation. Degradation products had significantly different RE values and thus were well separated from the pure drug. The method was validated with respect to linearity, precision, robustness, limit of detection (LOD), limit of quantification (LOQ), ruggedness and accuracy. Linearity was observed in the range 50-1000 ng per spot with a significantly high value of the correlation coefficient r(2) = 0.9979; 95% confidence interval of r(2) was 0.9908-0.9995. The mean S.E. value of the slope was 0.1316 with respect to the peak area. LOD and LOQ were 15.40 and 50.90 rig per spot, respectively. Statistical analysis proved that the method was repeatable and specific for the estimation of the studied drug. As the method could effectively separate the drug from its degradation products, it can be employed as a stability-indicating procedure.
In this review we compare the glass electrode to the ion-sensitive field-effect transistor (ISFET) with regard to the determination of pH. A brief overview of electrochemical methods to determine pH is given to put both devices in historical context. The "dissociation mechanism" is discussed as the most appropriate theoretical description of the phase boundary potential generation at the glass electrode. This model bears remarkable similarities to the "site-dissociation model" which is presented for the charging mechanism at the ISFET/solution interface. It is concluded that the theories behind both devices primarily differ from each other by the charge balancing mechanism. From the discussion of the device properties it is interred that the ISFET exhibits some advantages (e.g. size, robustness, response time) over the glass electrode, but also suffers from packaging challenges and a more complex temperature dependence. Nevertheless, with regard to application fields the glass electrode remains the undisputed gold standard. The ISFET is only slowly gaining ground in the market with special robust devices, e.g. for the food industry, as well as miniaturized systems in biomedical applications.
A column with a novel monolithic molecularly imprinted polymer (MIP)-based stationary phase with malachite green (MG) as template molecules was prepared. The synthesized MIP was characterized by IR and SEM. Extraction conditions on MIPs were optimized. MG and some other compounds were employed for selectivity tests. River water samples were spiked with MG at the concentration 20-500 ng mL -1 ; extraction was performed using a MISPE column and detection was accomplished by HPLC. The achieved recoveries were in the range 95.06-100.13%; relative standard deviation was 0.025-6.63%. MG concentrations in three natural water and fish samples were 2.65, 2.60, 2.36 and 5.63 ng mL -1 , respectively.
Formation of Os(IV)-Orange G (OG) complex was investigated. The following optimum conditions for the reaction were established: pH = 5.80 (0.20 mol L -1 acetate buffer solution) ; heating time on a boiling water bath: 30 min; excess of reagent: 2-fold. Effective molar absorptivity e at 540 nm was 1.1 × 10 4 L mol -1 cm -1 . Stoichiometric ratio of the components of Os(IV)-OG compound was determined applying mole ratio and continuous variations methods. Linear range for Os(IV) determination was 0.01-7.70 μg mL -1 . Selectivity of spectrophotometric determination of Os(IV) using Orange G was investigated in the presence of platinum and other metal ions after elimination of the effect of interfering components using masking agents.
TLC densitometric method for simple and sensitive stability assessment of modafinil has been developed. The objective was to provide a rapid, precise, robust, and reproducible technique for the analysis of modafinil. The method was validated for bulk drug and tablet formulations. It could be used to separate the drug from its degradation products. The procedure employed TLC aluminum plates precoated with 60F-254 silica gel as the stationary phase. The solvent system consisted of toluene-chloroform-methanol (1: 1 0.5, v/v/v) mixture. It provided well-resolved compact spots for modafinil (R-f value 0.46 +/- 0.01) and allowed for separation of the excipients and degradation products. Densitometric scanning interegation was performed at the wavelength of 220 nm. Calibration plot was linear r(2) = 0.999) in the analyte concentration range 100-5000 ng per spot. The method was validated with respect to linearity, accuracy recovery, precision, ruggedness. and specificity. The limit of detection and quantification were 20.54 ng per spot and 62.26 ng per spot, respectively. The determined drug content was within the +/-5% range of the labeled content. The drug was analyzed tinder different stress conditions in order to Study its degradation in the presence of acid, base, and peroxide.
In this study, gradient and isocratic elution of 11 phenothiazine derivatives in the reversed-phase systems controlled by chaotropic effect was compared. Potential applicability of the Chromsword software for retention data prediction either under isocratic or gradient conditions was studied. Simulations were performed on the basis of previously conducted experiments concerning retention measurements at different concentrations of organic modifiers (methanol, acetonitrile) in the mobile phase. Eluent systems were acidified with perchloric acid and modified with chaotropic additives (sodium perchlorate and sodium hexafluorophosphate) at the constant concentration. An agreement between the predicted and experimental retention parameters was estimated statistically Optimal gradient profile for the separation of all examined compounds was selected.
A highly sensitive flow injection chemiluminescent method for determination of indomethacin has been proposed. During oxidation of indomethacin by KMnO4 in polyphosphoric acid medium, chemiluminescence emission was observed, which could be enhanced more than 100 times in the presence of 4% formaldehyde. The chemiluminescence mechanism was investigated and two emitters were identified. The proposed strategy allowed for sample assay rate of 100 per I h in an automatic mode in combination with flow injection analysis. Indomethacin could be determined over the concentration range 1.0 x 10(-9)-1.0 x 10(-6) g mL(-1) with the detection limit (3 sigma) of 6.0 x 10(-10) g mL(-1). The relative standard deviation for determination of 1.0 x 10(-8) g mL(-1) indomethacin (n = 11) was 2.3%. The proposed method has been successfully applied to the analysis of a commercial pharmaceutical formulation without any sample pretreatment and to biological samples after their clean-up by solid phase extraction.
