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.     

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.     

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.     

Spectrophotometric determination of trace amounts of beryllium using 1,8-dihydroxyanthrone as a new chromogenic reagent

A simple, rapid, and sensitive spectrophotometric method for the trace level determination of beryllium based on the formation of a 1:2 complex with anthralin (1,8-dihydroxyanthrone) as a new reagent is developed. A spectrophotometric method was used to determine the acidity constant and stepwise proton dissociation of the reagent. The experimental conditions for determining beryllium including the influences of pH, reagent concentration and time were evaluated and optimized. Under the optimum experimental conditions, the molar absorptivity of the complex is 0.47 × 10⁴ l mol^?1 cm^?1 at 545 nm. Calibration graph was linear in the range of 0.04–1.04 μg ml^?1 with a detection limit of 0.012 μg ml^?1 and a %RSD of 0.43%, for 5 replicate determinations at 0.48 μg ml^?1 of Be(II). The interferring effect of some cations and anions was also studied. The method was applied for the determination of beryllium in beryl, silicate rock and alloys. Ethylenediaminetetraacetic acid (EDTA) was used for masking interfering ions.     

Fluorimetric assay of ergotamine

Studies on the fluorescence properties of ergotamine in water at various pH values, and in several organic solvents are described. An assay procedure for ergotamine, based on its intense fluorescence in ethanol, is presented. Extraction of ergotamine into benzene from basic aqueous solution is followed by transfer of the extract to ethanol for fluorescence determination. The plot of fluorescence intensity vs. concentration is linear up to 5 μg ml^?1, and the assay has a limit of detection of 0.002 μg ml^?1. Reproducibility data at the 2.5-μg ml^?1 level are given.     

Direct detection of acetaminophen in urine by liquid chromatography with electrochemical detection using dual electrodes. Preliminary application to a single-dose pharmacokinetic study

A method for the direct determination of acetaminophen in urine based on liquid chromatography with series dual-electrode detection has been developed. No sample pretreatment steps are required except for filtration. The method gives a linear range from 0.5 to 300 μg ml^?1 and a detection limit of 0.2 μg ml^?1 (10 μl). The analysis time of the assay is less than 7 min. The pharmacokinetics of acetaminophen in urine from a subject who had orally ingested 450 mg (table form) of the drug were studied and various pharmacokinetic parameters were determined.     

Flow-injection spectrophotometric determination of cobalt by extraction as tetrathiocyanatocobaltate(II) with the ethylenebis(triphenylphosphoniu) cation

Cobalt (0–10 μg) may be determined spectrophotometrically at 625 nm after flow-injection extraction into chloroform of the ion associate ethylenebis(triphenylphosphonium) tetrathiocyanatocobaltate(II). The carrier stream contained 10% (w/v) ammonium fluoride and the reagent stream contained 0.5% (w/v) ethylenebis (triphenylphosphonium) bromide and 5% (w/v) ammonium thiocyanate. The injection rate was 20 h^?1. The calibration graph is linear up to 20 μg ml^?1 and detection limit is 0.23 μg ml^?1 cobalt, based on injection volumes of 500 μl. The system has been applied to the determination of cobalt in a range of tool steels.     

Spectrophotometric Determination of Uranium(VI) with Chlorophosphonazo-mN by Flow Injection Analysis

Abstract

A sensitive and selective spectrophotometric flow injection analysis (FIA) method with chlorophosphonazo-mN has been developed for the determination of uranium(VI) in standard ore samples. Most of interfering ions are effectively eliminated by the masking reagent of diethylenetriaminepentaacetic acid (DTPA). In the U(VI)-chlorophosphonazo-mN system, the maximum absorption wavelength is at 680 nm and Beer's law is obeyed in the range of 1 to 15 μg ml^?1. The correlation coefficient of the calibration curve is 0.9998, the sampling frenquency is 60 h^?1, and the detection limit for uranium(VI) is 0.5 μg ml^?1. The composition of the U(VI)-chlorophosphonazo-nN complex was established to be 1:2 by flow-through spectrophotometric and conventional molar ratios methods.     

Novel Method for Selective Spectrophotometric Determination of Titanium(IV) with Water Extract of Slippery Elm Leaf as a New Reagent

Abstract

A novel spectrophotometric method for the determination of titanium(IV) by using a new reagent, water extract of slippery elm leaf is developed. In 0.05 M hydrochloric acid, titanium(IV) reacts with this reagent to form a yellow product. The formed product shows maximum absorbance at 415 nm with a molar absorptivity value of 0.68×10⁴ l mol^–1 cm^–1 and the method was linear in the 0.2–6 µg ml^?1 concentration range. The detection limit value was found to be 0.0131 µg ml^?1. The proposed method was simple, low cost, selective, and sensitive. It was applied to the analytic samples with satisfactory results.     

Kinetic-Spectrophotometric Determination of Molybdenum(VI) Based on Its Catalytic Effect on the Thionine-Hydrazine Reaction

Abstract

A kinetic method for the determination of trace amounts of Mo(VI) (0.05-4 μg ml^?1) based on its catalytic effect on the reduction of thionine by hydrazine monochloride in strongly acidic media is reported. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 605 nm after a fixed time (5 min.). The detection limit of the method is 23 ng ml^?1 and the relative standard deviation (RSD) for 0.05 μg ml^?1 of Mo(VI) is 1.2% (n=7). The method is almost free from interferences, especially from large amounts of tungsten. The procedure was successfully applied to the determination of trace amounts of molybdenum in steel.     

Chemiluminescence determination of bufrenorphine hydrochloride by flow injection analysis

A direct, simple and rapid flow-injection method is described for determining buprenorphine hydrochloride (10^?8–10^?4 M) based on its chemiluminescent oxidation with potassium permanganate in polyphosphoric acid. The limit of detection is 1 × 10^?8 M (0.5 pmol per injection) and the log-log calibration is linear up to 1 × 10^?4 M; the r.s.d. is 0.7% for a 10 μg ml^?1 solution (n = 10). The method is directly applicable to aqueous solutions of tablets containing the drug (0.2 mg/tablet).     

Flow-injection extraction spectrophotometric determination of dichromate with the tetramethylenebis(triphenylphosphonium)cation

Chromium(VI) (0–5 μg) can be determined spectrophotometrically at 365 nm after flow-injection extraction into chloroform of the ion-associate, tetramethylenebis(triphenylphosphonium) dichromate. The carrier stream is distilled water and the reagent stream contains 1 M sulphuric acid and 0.5% (w/v) tetramethylenebis(triphenylphosphonium) bromide. The sampling rate is 24 h^?1. The calibration graph is linear up to 20 μg ml^?1 and the detection limit is 0.44 μg ml?1 chromium, based on injection volumes of 250 μl. The system has been applied to the determination of chromium in a range of steels.     

Flow-injection determination of proteins based on the lowry spectrophotometric method

The flow-injection system is based on the use of Folin-Ciocalteus reagent, with 1,4-dithio-D,L-threitol to accelerate the formation of the coloured complex. The calibration graph for bovine serum albumin is linear between 0.01 and 0.1 mg ml^?1; the detection limit is 0.005 mg ml^?1 albumin and up to 0.5 mg ml^?1 can be determined. The injection frequency is 20 h^?1. The results obtained by the flow-injection method and by the manual Lowry procedure show excellent correlation. Egg lysozyme, alkaline phosphatase and β-lactoglobulin are also tested.     

Flow-injection extraction-spectrophotometric determination of permanganate with the ethylene-bis(triphenylphosphonium) cation

Permanganate is determined spectrophotometrically at 545 nm after extraction into chloroform of the ion-associate, ethylene -bis (triphenylphosphonium) permanganate. The carrier stream is pH 6 buffer containing 10% (w/v) ammonium fluoride and the reagent stream is 0.25% (w/v) ethylene-bis (triphenylphosphonium) bromide. The injection rate is 24 h^?1. Th calibration graph is linear up to 25 μg ml^?1 and the detection limit is 0.58 μg m^?1 Mn (VII), based on 250- μl injections. The system is applied to the determination of manganese in a range of steels.     

Selective Kinetic Spectrophotometric Determination of Nitrite in Food and Water

Abstract

A highly selective and sensitive method for the kinetic spectrophothometric determination of sub-microgram amounts of nitrite has been development based on its reaction with Nile blue 2B in acidic medium. The reaction is monitored spectrophotometrically at 595 nm at a fixed time of 4.5 min. The change in absorbance at 595 nm is related to the concentration of nitrite in the range 0.005 - 1.100 μg.ml^?1 The detection limit is 0.001 μg.ml^?1. The relation standard deviation is 1% for 0.020 μg.ml^?1 of nitrite for ten replicate measurements. Most common anions and cations do not interfere. The procedure was applied to the determination of trace amounts of nitrite in sausage and water.     

Phosphorescence detection in flowing systems: selective determination of aluminium by flow-injection liquid room-temperature phosphorimetry

The concept of the micelle stabilized liquid room-temperature phosphorescence (MS-LRTP) was applied to the determination of a metal (aluminium) in a flowing system. A three-line flow-injection manifold was developed and various parameters were optimized. A linear calibration graph was obtained for 0–4 μg ml^?1 aluminium. The limit of detection was 50 ng ml^?1 and the relative standard deviations for 0.1 and 1.0 μg ml^?1 aluminium were 2.7 and 1.3% respectively. The proposed procedure is fairly selective. More than 20 common ions studied did not interfere with the determination of aluminium or could be masked by appropriate reagents. The flow-injection method proposed was applied without any preliminary separation to the determination of aluminium in simulated synthetic samples in water and in clinical samples of particular importance in the control of aluminium toxicity in renal failure patients.     

Determination of Biacetyl by Sensitized Photochemical Kinetic Fluorimetry

Abstract

A new in-situ photochemical kinetic fluorimetric method was proposed for the determination of biacetyl (BI). It is based on the sensitization of BI on the photochemical reaction of amaranth (AM). AM, a nonfluorescent compound was converted into an intensively fluorescent compound in a slightly alkaline medium by the sensitized photochemical reaction, and BI was indirectly determined by monitoring the change of the fluorescence intensity. The determination can be carried out by fixed-time method or tangent method. The kinetic behavior of the reaction and the effects of some experimental conditions were investigated and discussed. The calibration graph was rectilinear from 1.0 μg ml^?1 to 10.0 μg ml^?1 of BI (r = 0.999), the limit of detection was 1.0 ng ml^?1, and the coefficient of variation was 0.44% for 0.90 μg ml^?1 of BI (n = 6). The mechanism for the sensitization of BI was examined and the triplet-triplet energy transfer, in which BI acted as the energy donor and AM as the energy acceptor, was suggested to be the main cause. Its application to real samples has been tested.     

Determination of phosphorus in biological tissues by aluminium block digestion and flow-injection spectrophotometry

Biological tissues are digested with nitric and perchloric acids in a heated aluminium block. Flow-injection spectrophotometry is then used to measure phosphate via the phosphovanadomolybdate complex at 413 nm. The detection limit is 0.3 μg ml^?1 phosphorus; relative standard deviations are 0.7% and 0.4% at 1 μg ml^?1 and 25 μg ml^?1 phosphorus, respectively. Interferences are discussed. The decomposition procedure is evaluated for model compounds and standard reference materials.     

Atomic absorption spectrometric studies of the atomization of boron from a carbon rod atomizer

Boron (<20 μg ml^?1) in aqueous solutions gives no absorbance but addition of ascorbic acid, especially with titanium greatly enhances the signal, leading to a detection limit of 0.2 μg ml^?1 boron. The presence of uranium (<10 mg ml^?) only slightly decreases the boron signal.     

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.