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.     

Synthesis and In Vitro Anti-HIV Activity of Some New Schiff Base Ligands Derived from 5-Amino-4-phenyl-4H-1,2,4-triazole-3-thiol and Their Metal Complexes

New Schiff base ligands (6–9) derived from 5-amino-4-phenyl-4H-1,2,4-triazole-3-thiol 1 and substituted benzaldehydes (2–5) as well as their metal complexes with Cu(II), Fe(II), Au(III), and Mn(II) (12–17) have been synthesized. A new benzothiazole derivative (11) was prepared from coupling of 7 with N-(benzothiazol-2-yl)-2-chloroacetamide 10. Their spectral properties were investigated. The newly designed and synthesized Schiff base ligands and the metal complexes were assayed for anti-HIV-1 and HIV-2 activity by examination of their inhibition of HIV-induced cytopathogenicity in MT-4 cells. Compounds 11 and 16 were found to be the most active inhibitors in cell culture (EC₅₀ = 12.2 μg/mL (SI = 4) and > 2.11 μg/mL (SI = > 1), respectively) against HIV-1, whereas 11 showed inhibition against HIV-2 of EC₅₀ > 10.2 μg/mL with SI = 9, which provided a good lead for further optimization.     

Assay of Brain Tocopherols Using High Performance Liquid Chromatography

Abstract

The four natural tocopherols were separated using a μ-Bondapak-NH₂ column. For the analysis of brain tocopherols 5,7-dimethyltocol was used as an internal standard. α-Tocopherylquinone and other tocopherols than α-tocopherol were not detected. Rat cerebral cortex and cerebellum contained 19.3 μmol/g and 11.2 μmol/g of α-tocopherol, respectively. A chromatographic system with a reversed-phase column proved less suitable.     

Ion-Associates of Alkaloids and Synthetical Psychopharmaca With Cresol Red.

Abstract

Ethylmorphine, morphine, codeine, cocaine, sernyl (PCP), LSD, 3-quinuclidinyl benzilate (BZ) provide, together with Cresol Red, ion-associates that are extractable by chloroform. The extracts of the ion-associates prove the absorption maxima in the interval 405 to 415 nm. Maximum extraction of the analytes of the ion-associates is reached after 4 minutes, taking readings of different pH values in 4 intervals of 1.5. This method allows detect of alkaloids and synthetical psychopharmaca row of quantities between 0.45 μg.ml^?1 and 1.55 μg.ml^?1 and to determine 1.05 μg.ml^?1 to the amount 2.99 μg.ml^?1 of the analytes in the aqueous solutions.     

Gas Chromatographic Determination of Urinary Androstanediol in Cases of Idiopatic Hirsutism

Abstract

The urinary androstanediol was determined in cases of idiopatic hirsutism by means of GLC. The determination was carried out on urines of 9 women before the beginning of a treatment with placebo and after three and six months of estrogen treatment. The initial range of values was between 39 and 99 μg/24h; at the end of the treatment the values ranged between 13 and 25 μg/24 h.

The yield of the whole procedure of determination was 70% and the detection limit was about 0.2 μg of androstanediol in urine.     

Spectrophotometric Determination of Phenols and Cyanides After Distillation from Natural Waters

Abstract

Total phenols were determined by molecular spectrophotometry, after distillation, complexation with 4-aminoantipyrine and extraction into chloroform. Cyanides were also determined spectrophotometrically after distillation from the acidified samples, and complexation in moderate acidic solution with barbituric acid. The dynamic ranges were 0 – 100 μg L^?1 for total phenols and 0 – 30 μg L^?1 for cyanides. The above methods were applied in the analysis of river, lake and stream waters collected from Northern Greece. The seasonal and spatial variation of concentrations was evaluated by two-way ANOVA. Background levels (4 – 12 μg L^?1 for total phenols and 0.3 – 3 μg L^?1 for cyanides), were found in almost all surface waters, with some exceptions.     

Isolation of Glycoalkaloids with the Chromatotron and Their Determination by High-Performance Liquid Chromatography

Abstract

An extract of Solanum laciniatum leaves was fractionated with the Chromatotron. The glycoalkaloid fraction thus obtained was analyzed by reversed-phase HPLC. The load capacity of the Chromatotron with a 2-mm layer thickness is 600 mg (as determined with cholesterol) and the recovery of solasonine from the plant extract (as determined by HPLC) is 93–96%. The HPLC method permits the detection of as little as 1.5 μg solasonine or 3.5 μg solamargine with a linear detector response up to 375 μg for the former and 250 μg for the latter.     

Flow-Injection Chemiluminescence Determination of Fluoroquinolones

ABSTRACT

A new flow-injection CL method was developed for the determination of fluoroquinolones including ofloxacin, norfloxacin, ciprofloxacin and lomefloxacin in pharmaceutical preparations, based on the chemiluminescence reaction of sulphite with cerium(IV) sensitized by these compounds. The linear ranges are 0.04 to 4.0 μg ml^?1 for ofloxacin and 0.4 to 40.0 μg ml^?1 for norfloxacin, ciprofloxacin and lomefloxacin, respectively. The detection limits are 0.016 μg ml^?1 for ofloxacin and 0.16 μg ml ^?1 for norfloxacin, ciprofloxacin and lomefloxacin, respectively. The relative standard deviations (RSD) are 2.1 to 2.6% (n=10) for these fluoroquinolones. The analytical procedure has been applied to the determination of the fluoroquinolones in pharmaceutical commercial formulations. The results are in agreement with those obtained by the official methods.     

Spectrophotometric Determination of Trimethoprim in Pure Form and in Pharmaceutical Preparations using Bromothymol Blue,Bromocresol Green and Alizarin Red S

ABSTRACT

Simple, sensitive and selective methods for the determination of trimethoprim (TMP) in pure form and in pharmaceutical formulations are described. The methods are based on the reaction of TMP as a π-electron donor with bromothymol blue (BTB), bromocresol green (BCG) and alizarin red S (ARS) as electron acceptors. The coloured products are quantified spectrophotometrically at their corresponding λ_max.

Beer's law is obeyed in case of BTB in the range 2.9-23.2 μg/ml (CHCl₃), 2.9-20.0 μg/ml (CH₂Cl₂) and 5.0-29.0 μg/ml (ClC₆H₅), in the case of BCG 2.9-27.5 μg/ml (H₂O/alc.), 2.9-18.3 μg/ml (CHCl₃) and 2.9-20.3 μg/ml (CH₂Cl₂) and for ARS in the range 3.0-12.0 μg/ml in H₂O/alc medium.

The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations and percent recoveries are evaluated. Application of the suggested methods to dosage forms is presented and compared with the pharmacopoeial method. The interference from additives and sulfa compounds, especially sulfamethoxazole, has been overcome by extraction into chloroform or methylene chloride.     

Detection and Spectrophotometric Determination of Microgram Quantities of Ethylenediaminetetraacetic Acid with Phosphomolybdic Acid

Abstract

A simple, rapid and accurate method for the detection and determination of microgram quantities of EDTA is based on the absorbance of the complex formed by its reaction with phosphomolybdic acid at pH 2. Absorbance is measured against a phosphomolybdic acid reference solution at a wave length of 690 am. The effect of time, temperature and amount of phosphomolybdic acid is studied and optimum operating conditions established. Beer's law is obeyed in the concentration range 18.6–186.0 μg ml^?1 of EDTA. Its detection limit is 18.6 μg in the solution phase and 3.72 μg in the resin phase. The relative standard deviation is ±0.445 μg. Ion exchange resin beads act as a catalyst and detection medium to improve the sensitivity and selectivity of the test.     

Organic Compounds In Cloud And Rain Water

Abstract

Cloud and rain water samples have been collected in spring 1991 in the Vosges mountains (France) and analyzed for aldehydes, phenols and polycyclic aromatic hydrocarbons (PAHs). Both passive and active cloud collectors have been employed. A mean concentration of formaldehyde of 197 μg/l (6.6 μM) has been found in cloud water while on the average only 100 μg/l (3.3 μM) were observed in rain water. The average phenol concentration was 3.5 μg/l (37 nM), but only 1.6 μg/l (17 nM) in rain water. Finally, the mean concentration of PAHs (only determined in cloud water) amounts to 0.37 μg/l. The PAH profile is similar to that observed for rain water sampled in Hannover (Germany).     

Determination of Lacinilene C 7-Methyl Ether by High Performance Liquid Chromatography

Abstract

An HPLC method is presented for the quantization of lacinilene C 7-methyl ether in cotton dusts. A standard of lacinilene C 7-methyl ether was isolated from extracts of gin trash and a new extraction procedure was developed that effected complete removal of lacinilene C 7-methyl ether from cotton dust. Total dust contains an average of 48.64 μg/g of lacinilene C 7-methyl ether, and the below 20 μm fraction contains 35.9 μg/g of lacinilene C 7-methyl ether.     

Simultaneous Analysis of Pyridoxine and Melatonin in Tablet Formulation by Derivative Ultraviolet Spectroscopy

Abstract

A method for simultaneous analysis of pyridoxine and melatonin by second and third derivative UV - spectroscopy, the “zero - crossing” technique, is described. The determination has been carried out in 0.1 mol dm^?3 hydrochloric acid solution and the concentration range of 2 – 10 μg/ml pyridoxine and 0.5 – 3.5 μg/ml melatonin. Lower limits of detection at the 95% confidence level were 0.26 μg/ml for pyridoxine and 0.05μg/ml for melatonin The advantages of the proposed method include its application for the assay and in-vitro dissolution studies of pyridoxine and melatonin from two different tablet formulations.     

Separation of the α-Tocopherol Model Compound 2,2,5,7,8-Pentamethyl-6-Chromanol from its Oxidation Products by High Performance Liquid Chromatography

Abstract

A rapid method is described for the separation of the α-tocopherol model compound, 2,2,5,7,8-pentamethyl-6-chromanol (6), from 9 of its oxidation products in a single 35 minute run. Separated derivatives of 6, in order of elution, included the 5-cholesteroxymethyl (1), spirotrimer (2), spirodimer (3), 5-formyl (4), 5-ethoxymethyl (5), dihydroxydimer (7), chroman dione (8), quinone (9) and pyrano xanthene (10). A normal phase system, using gradient elution is employed, the eluent being monitored at 290 nm. The minimum detection limit for compounds 1–8 was 0.1 μg per injection and for compounds 9 and 10 it was 0.3 μg per injection.     

The Determination of The Herbicide Linuron in Saskatoon Berries Using HPLC with Column Switching

Abstract

A sensitive method for the determination of residues of the herbicide linuron [3-(3, 4-dichlorophenyl)-l-methoxy-l-methylurea] in saskatoon berries (Amelanchier anifolia Nutt.) is described. Use of column switching techniques permitted a limit of quantification of 10 μg/kg. Recoveries at the 10 μg/kg fortification level were in the order of 86%.     

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.     

Simultaneous Trace Determination of Nickel and Cobalt in Natural Waters by Differential Pulse Polarography

Abstract

A differential pulse polarographic method has been developed for the simultaneous low level determination of nickel and cobalt in the presence of furildioxime in natural waters. The nature of the electrode processes was studied with cyclic voltammetry. Limits of determination of 0.4 μg/L and 0.15 μg/L were achieved for nickel and cobalt respectively     

A Fluorosensor with Immobilized Cyclodextrin As A Substrate

Abstract

A flow-through optosensor for phenylalanine and tyrosine is described in this paper. The sensor is developed in conjunction with a flow-injection analysis system and uses immobilized β-cyclodextrin as the sensing agent. The analytical performance characteristics of the proposed sensor for analysis of very low levels of phenylalanine and tyrosine were as follows: the detection limits for phenylalanine and tyrosine were 0.20 μg ml^?1 and 8.9 ng ml^?1, respectively. The observed relative standard deviations were 1.03% for 50 μg ml^?1 of phenylalanine (n = 7) and 3.6% for 0.1 μg ml^?1 of tyrosine (n = 7), respectively.     

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.     

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.