Fluorescent Complexes of Nucleic Acids/8-Hydroxyquinoline/Lanthanum(III) and the Fluorometry of Nucleic Acids

Abstract

The ternary fluorescent complexes of nucleic acids/8-hydroxyquinoline/ lanthanum (III) were studied. Nucleic acids in the study involve natured and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of pH 8.0–8.4 (controlled by NH₃-NH₄Cl buffer) ternary fluorescent complexes are formed which emit at 485.0 nm for calf thymus DNA and at 480.0 nm for yeast RNA (when excited at 267.0 nm) and emits at 483.0 nm for fish sperm DNA when excited at 265.0 nm. Based on the fluorescence reactions sensitive fluorometric methods for nucleic acids were proposed. Using optimal conditions, the calibration curves were linear in the range of 0.4–3.6 μg˙ml^?1 for calf thymus DNA, 0.4–4.0 μg-ml^?1 for fish sperm DNA and 0.4–4.0 μg˙ml^?1 for yeast RNA, respectively. The limits of determination (3σ) were 0.076 μg˙ml^?1 for calf thymus DNA, 0.068 μg˙ml^?1 for fish sperm DNA and 0.329 μg˙ml^?1 for yeast RNA, respectively. Five synthetic samples were determined with satisfaction.

     

Colorimetric Determination of Propofol in Bulk form,Dosage Form and Biological Fluids

ABSTRACT

Propofol is coupled with 2, 6-dichloroquinone-4-chlorimide (DCQ) in a reaction buffered at pH 9.6 to give a colored product having an analytically useful maximum at 635 nm. The factors affecting the color generation were optimized and incorporated in the procedure. The reacted propofol has a molar absorptivity of 3.9 × 10^?4 L mol^?1 cm^?1, and Beer's law is obeyed for concentrations 1-5 μg ml^?1 with detection limit 0.25 μg ml^?1. The method was found applicable to biological fluids (plasma and urine) spiked with propofol at concentration levels 1-5 μg ml^?1 for plasma and 1-5 μg 0.5 ml^?1 urine (less sensitivity is obtained with urine volumes above 0.5 ml) with detection limits 0.28 μg ml^?1 for plasma and 0.4 μg 0.5 ml^?1 urine. The average recovery for the commercial preparation (1% w/v propofol emulsion intravenous injection for infusion) was 99.54% with an RSD of 1.05%. The method was validated by an adopted HPLC method. The results obtained by the HPLC method for the commercial preparation were statistically compared with the proposed method and evaluated at the 95% confidence limits.     

Assay of mixtures of chlorpheniramine maleate,pyrilamine meleate and phenylpropanolamine hydrochloride in cold-allergy tablets by difference spectrophotometry

Mixtures of chlorpheniramine maleate (CPM) and phenylpropanolamine hydrochloride (PPA), with and without pyrilamine maleate (PRM), are assayed by u.v. difference spectrophotometry without prior separation. The spectra for CPM and PRM in solutions at pH 1 and pH 6 show differences whereas the spectra for PPA remain the same at pH 1 and 6. For PPA, quantitation is based on the spectral change on oxidation to benzaldehyde with metaperiodate; this oxidation does not affect CPM and PRM. Calibration plots are linear for 6.7–99.9 μg ml^?1 CPM (r = 0.9992), 12.7–50.6 μg ml^?1 PRM (r = 0.9997) and 25–115.3 μg ml^?1 PPA (r = 0.9980) in the presence of one another. Average recoveries (± RSD) from simulated PPA/CPM tablets were: PPA, 98.4 ± 0.4% (without PRM, n = 3), 99.8 ± 0.4% (with PRM, n = 5); CPM, 99.3 ± 0.6% (without PRM, n = 3), 99.2 ± 0.4% (with PRM, n = 5); and PRM, 99.5 ± 0.2% (in PPA/CPM/PRM tablets, n = 5). The method was successfully applied to commercial cold-allergy tablets containing these compounds.     

Versatile automatic stopped-flow system for routine analysis

A versatile, automatic stopped-flow system featuring a mixing module and real-time data collection and treatment is presented. The mixing module is compatible with a number of spectrophotometers and spectrofluorimeters. The fast reaction between iron(III) and thiocyanate is used to evaluate the performance of the system and to develop a routine procedure for the determination of iron in wines, with a reaction time of 3 s. The calibration is linear over the range 1–30 μg ml^?1, with a r.s.d. of 0.9% (n = 11) for 10 μg Fe ml^?1 and a high sample throughput (120 h^?1) is achieved.     

Determination of technetium based on quenching of the fluorescence of some organic compounds,with application to vegetation

Technetium is an effective quencher of the fluorescence produced by 2,5-diphenyloxazole (PPO), 1,4-bis(4-methyl-5-phenyl-2-oxazolyl)benzene (POPOP) and 2,2′-pyridil [1,2-dioxo-1,2-bis(2-pyridyl)ethane]. Spectrofluorimetric procedures for 0.01–12 μg Tc ml^?1 with PPO and 0.1–12 μg ml^?1 with 2,2′-pyridil, and a spectrophotometric method for 1–15 μg ml^?1 are described. The distribution of technetium in vegetation is measured by applying the PPO method.     

Cathodic stripping voltammetry of pipemidic acid and ofloxacin in pharmaceutical dosages and human urine

Sensitive cathodic stripping voltammetric methods have been developed for two quinolone antibacterial drugs, pipemidic acid (PIP) and ofloxacin (OFL) using hanging mercury drop electrode as working electrode vs. Ag/AgCl reference electrode. The methods were developed for the determination of drugs individually as well as simultaneously. 0.1 M and 0.01 M hydrochloric acid was used as medium for PIP and OFL, respectively, 0.1 M potassium chloride was used as base electrolyte. Reduction waves were observed for PIP within ?700 mV to ?800 mV and for OFL within ?1100 mV to ?1200 mV. Linear calibration ranges for PIP and OFL were observed within 10–100 μg ml^?1 with detection limits of 50 ng ml^?1 and 1 μg ml^?1, respectively. Relative standard deviations (RSD) for the analysis of 10 gµg ml^?1 of PIP and OFL (n = 6) were 0.5% and 1.4%, respectively. The presence of glucose, lactose, sorbitol, gum arabic, starch, magnesium stearate, methylparaben and propylparaben did not affect the determinations of both PIP and OFL. The methods were used for the analysis of pharmaceutical preparations and the results indicated relative deviation of 0.5–5.5% from labeled values with RSD within 0.49–2.5%. PIP and OFL could also be determined simultaneously, and were determined from spiked human urine.     

Determination of vanadium and titanium in steel by inductively coupled plasma atomic emission spectrometry with modified use of a tungsten boat furnace atomizer for atomic absorption spectrometry

For electrothermal sample introduction, a commercially available tungsten boat atomizer for atomic absorption spectrometry (AAS) was transferred to a vaporizer for inductively coupled plasma atomic emission spectrometry (ICP-AES). The modification retained as much of the original design of the atomizer as possible, so that the apparatus could be switched easily between conventional tungsten boat furnace (TBF)-AAS and TBF-ICP-AES. By using this system, a procedure for the determination of vanadium and titanium in steel was investigated. The detection limits (S/N=3) of vanadium and titanium were 3.9 and 1.5 ng ml^?1, respectively. The relative standard deviations for five replicate determinations were ca. 3% for both elements. The calibration graphs were linear up to 100 μg ml^?1 vanadium(V) and 10 μg ml^?1 titanium(IV). Results of analyses of some low-alloy steel samples are given.     

Magnetic solid-phase extraction of rose bengal using iron oxide nanoparticles modified with cetyltrimethylammonium bromide

Magnetic solid phase extraction (MSPE) based on cetyltrimethylammonium bromide (CTAB)-coated magnetic iron oxide nanoparticles (C-MIONPs) was investigated for the separation, preconcentration and determination of Rose Bengal (RB) in aqueous solutions. The influences of different analytical parameters such as pH, temperature, ionic strength, volume of desorbent solvent, amount of adsorbent and interfering ions in the adsorption of RB on C-MIONPs were investigated. The RB adsorption on C-MIONPs follows Langmuir isotherm. The sizes of C-MIONPs were in the range of 20–80 nm. The method was capable of determining RB concentration in the range of 0.01–1.20 μg ml^?1. The limit of detection (LOD) of RB based on three times the standard deviation of the blank (3Sb) was found to be 5.91 × 10–3 μg ml^?1 (n = 8). The relative standard deviation (RSD) for 0.3 μg ml^?1 and 0.8 μg ml^?1 of RB were 4.1% and 1.1%, respectively. The proposed method was applied to the determination of RB in Brucella Antigen solution and water samples from the Karoon River.     

The determination of chromium(VI) in natural waters by differential pulse polarography.

A method utilizing differential pulse polarography for the determination of chromium(VI) in natural water is described. Additions of 0.62 μg Cu(II) ml^-1 and 0.55 μg Fe(III) ml^-1 did not interfere with the determination of 0.050 μg Cr(VI) ml^-1. The natural water samples containing chromium(VI) were buffered to approximately pH 7 with 0.1 M ammonium acetate and 0.005 M ethylene diamine and analyzed. Natural water samples of chromium content from 0.035 μg ml^-1 to 2.0 μg ml^-1 may be analyzed directly without further preparation. The detection limit is 0.010 μg ml^-1.     

On-line preconcentration of trace copper for flame atomic absorption spectrometry using a spherical cellulose sorbent with chemically bound quinolin-8-ol

Preconcentration was effected using a 50 mm × 2 mm i.d. minicolumn packed with a spherical cellulose sorbent with chemically bound quinolin-8-ol function groups (Ostorb Oxin). The column was connected to the nebulizer of the atomic absorption spectrometer and the sample solution and eluent (2 M hydrochloric acid) were sucked through it at a flow-rate of 2–3 ml min^?1 by utilizing the negative pressure of the nebulizer. The experimental design was tested with the determination of traces of copper. Peak-area and peak-height measurements were compared. Owing to the simple calibration, the former method was used for quantification. The dynamic range was from 0.3 ng ml^?1 (detection limit) to 5 μg ml^?1 (breakthrough). The reproducibility in the concentration range 25 ng ml^?1-5 μg ml^?1 was better than 5%. Water-soluble inorganic salts, ammonia and sodium hydroxide were analysed. The accuracy of the results was checked by anodic-stripping voltammetry and by electrothermal AAS.     

Spectrophotometric determination of nitrite in polluted waters using 3-nitroaniline

Nitrite reacts with 3-nitroaniline in the presence of hydrochloric acid to form a diazonium cation, which is subsequently coupled with N-(1-naphtyl)ethylenediammonium chloride to form a stable purple azo dye. The method is suitable for the determination of 0.01–0.80 μg ml^?1 nitrite. The reactions are very fast and require no control of temperature. The observed molar absorptivity and Sandell's sensitivity of the azo dye are 4.9 × 10⁴ l mol^?1 cm^?1 and 9.4 × 10^?4 μg cm^?2, respectively. The method is free from most interferences. The method has been applied successfully to polluted river water.     

Integrated Retention/Spectrophotometric Detection Method for the Determination of Formaldehyde

Abstract

An integrated-sensor method for the determination of formaldehyde based on retention of the reaction product of the analyte with p-rosaniline and sulfite in a flow-cell packed with Dowex 1-X-8 anion exchange resin was developed. The method has a good selectivity with a detection limit of 0.3 μg ml^?1 (1 ml sample) or 75 ng ml^?1 (2 ml sample), and a linear range between 1–30 μg ml^?1. The relative standard deviations (n = 11) were 2.8 and 1.3% for 2 and 20 μg ml^?1 formaldehyde, respectively. Depending on the working conditions, the sampling frenquency ranged between 10 and 18 h^?1. The method was applied to the determination of formaldehyde in well water.     

High performance liquid chromatographic determination of sodium benzoate, methylparaben and propylparaben as preservative components in nystatin suspensions

A simple and sensitive method was developed for the analysis of preservatives sodium benzoate, methylparaben and propylparaben in nystatin suspensions by reversed-phase high performance liquid chromatography (HPLC), equipped with a C18 column and PDA detector. The mobile phase was a mixture of acetonitrile and acetate buffer of pH 4.4 (35:65 v/v). Under the optimized experimental conditions, separation of the preservatives was achieved in less than 20 min. The limits of quantifications (LOQs) and the linear dynamic ranges (LDRs) of sodium benzoate, methylparaben and propylparaben were 0.3 and 50–1000 μg Ml^?1, 0.5 and 50–600 μg ml^?1 and 0.3 and 50–900 μg ml^?1, respectively; the respective precisions (%RSD) at 500 μg ml^?1 level were 0.72%, 0.73% and 0.51% (n = 6). The average recoveries of sodium benzoate, methylparaben and propylparaben for spiked nystatin samples were obtained as 98%, 97% and 98%, respectively.     

Flow-injection spectrophotometric determination of ascorbic acid by reduction of vanadotungstophosphoric acid

Ascorbic acid may be determined spectrophotometrically at 360 nm based on reduction of vanadotungstophosphoric acid using flow-injection analysis. The carrier stream was distilled water and the reagent streams were buffer solution (pH 3.0), 1.735 × 10^?3 M dodecatungstophosphoric acid and 1.735 × 10^?3 M sodium vanadate. The injection rate was 80 h^?1. The calibration graph was linear up to 80 μg ml^?1 ascorbic acid and the relative standard deviation for the determination of 20 μg ml^?1 ascorbic acid was 1.5% (n=10). The detection limit was 1.0 μg ml^?1 ascorbic acid, based on an injection volume of 250 μl. The system was applied to the determination of ascorbic acid in vitamin C tablets.     

Modular stopped-flow/diode-array detection system for simultaneous kinetic analysis

The coupling of a stopped-flow module to a diode-array spectrophotometric detector has been exploited for the simultaneous kinetic resolution of mixtures. The analytical possibilities are shown with the resolution of a mixture of two analytes (hydrazine and phenylhydrazine), yielding products with different spectral features (after reaction with p-dimethylaminobenzaldehyde), so that only the simultaneous measurement of their respective initial rates at their corresponding maximum absorption wavelengths is possible. The method allows 0.02–30 μg ml^?1 hydrazine and 8–2200 μg ml^?1 phenylhydrazine to be determined simultaneously.     

Simultaneous Determination of Valsartan and Hydrochlorothiazide in Tablets by High-Performance Liquid Chromatography

ABSTRACT

A method for the simultaneous determination of valsartan and hydrochlorothiazide in tablets is described. The procedure, based on the use of reversed-phase high-performance liquid chromatography, is linear in the concentration range 5.0-10.0 μg ml^?1 for valsartan and 0.5-2.0 μg ml^?1 for hydrochlorothiazide, is simple and rapid and allows accurate and precise results. The limit of detection was 1.0 μg ml^?1 for valsartan and 0.05 μg ml^?1 for hydrochlorothiazide.     

Automated stopped-flow system in pharmaceutical and clinical analysis : Kinetic determination of acetaminophen in formulations and serum by using the iron(II)—2,4,6-tris(2-pyridyl)-s-triazine

The development of automated stopped-flow spectrophotometric systems, their potential in automated routine determinations using kinetic and fast equilibrium techniques and several examples of applications are briefly reviewed. The use of a compact, inexpensive laboratory-made stopped-flow system for the measurement of reaction rates and a fast equilibrium method for the determination of acetaminophen in formulations and serum are described. The reaction-rate method is based on monitoring the oxidation of acetaminophen by iron(III) in the presence of the chelating agent 2,4,6-tris(2-pyridyl)-s-triazine to form a highly absorbing complex of iron(II). The calibration graph is linear in the range 20–200 μg ml^?1, with a precision of 0.8–2.6%, a detection limit of 5.5 μg ml^?1 and a measurement throughput of 120 per hour. Common excipients do not interfere and the analysis of commercial formulations gave results similar to those of a reference method. The optimization of the experimental conditions was done by a kinetic study of the reaction and some kinetic parameters are given.The method for the determination of acetaminophen in serum is based on a rapid measurement of the absorbance of the reaction mixture after a delay time of 15 s in the presence of chlorpromazine, which catalyses the reaction. Acetaminophen is isolated by extraction with ethyl acetate and the calibration graph is linear in the range 0.5–6 μg ml^?1 with a detection limit of 0.04 μg ml^?1 and a precision of 1.5%. The proposed method showed a decreased interference from drugs that also react with iron(III).     

Flow-injection determination of europium after on-line reduction

A zinc reductor minicolumn is used in a flow-injection system for reduction of europium(III) to europium(II). Europium(II) is indirectly determined either spectrophotometrically by oxidation with iron(III) and reaction of the iron(II) formed with 1,10- phenanthroline, or spectrofluorimetrically by reaction with cerium(IV) and measurement of the cerium(III) produced. The reductor functions efficiently at flow rates up to 1 ml min^?1, which allows sample injection rates up to 100 h^?1. Linear calibration is achieved for 10–200 and 0.5–4 μg ml^?1 with detection limits of 2.5 and 0.25 μg ml^?1, by spectrophotometry and spectrofluorimetry, respectively.     

Spectrophotometric determination of iron(III) with EDTA tetrahydrazide

The tetrahydrazide of ethylenediamine tetraacetic acid (NH₂NH)₄-EDTA was synthesized from the EDTA ester and hydrazine hydrate in ethanolic solution, the resulting (NH₂NH)₄-EDTA being recrystallized in 60% ethanol. When the spectrophotometric study of the iron(III) (NH₂NH)₄-EDTA complex in aqueous solution was made two absorption maxima at 530 and 450 nm at pH 4.5 and 11.0, respectively, were found. Beer's law is obeyed in the range 1.0–20.0 μg Fe(III) ml^?1 at 530 nm and pH 4.5 and 0.5–12.0 μg Fe(III) ml^?1 at 450 nm and pH 11.0, the molar absorptivities being 1.95 × 10³ 1 mol^?1 cm^?1 at 530 nm and 3.35 × 10³ 1 mol^?1 cm^?1 at 450 nm, respectively. The Ringbom optimal interval falls between about 3 and 18 μg Fe(III) ml^?1 at 530 nm and about 2–14 μg Fe(III) ml^?1 at 450 nm. The reaction between the metal and the ligand was also investigated. The method has been successfully applied to the determination of iron in talcs.     

Fluorimetric determination of danthron in pharmaceutical tablets and in urine

A simple, rapid determination is reported for danthron (1,8-dihydroxyanthraquinone) in pharmaceutical tablets. In a flow-injection system, danthron is reduced by sodium dithionite in $\text{1}\text{1}$ methanol/borate buffer to give a fluorescent complex. Linearity ranges from 30 μg ml^?1 to below 0.1 μg ml^?1. In urine samples, danthron is separated from other fluorescing species by reversed-phase high-performance liquid chromatography before its reduction by dithionite in a post-column reactor. Urine preparation requires no extraction. Spiked urine samples were studied in the working range of 0.02–2.0 μg ml^?1 danthron.