High-performance liquid chromatographic analysis of codeine in syrups using ion-pair formation

Morphine and its metabolites: Analytical methodologies for its determination

The present article reviews the methods of determination published for morphine and its metabolites covering the period from 1980 until at the first part of 2006. The overview includes the most relevant analytical determinations classified in the following two types: (1) non-chromatographic methods and (2) chromatographic methods.

Morphine metabolism in the opium poppy and its possible physiological function. Biochemical characterization of the morphine metabolite, bismorphine

We identified a novel metabolic system of morphine in the opium poppy (Papaver somniferum L.). In response to stress, morphine is quickly metabolized to bismorphine consisting of two morphine units, followed by accumulation in the cell wall. This bismorphine binds predominantly to pectins, which possess high galacturonic acid residue contents, through ionical bonds. Our newly developed method using artificial polysaccharides demonstrated that bismorphine bridges are formed between the two amino groups of bismorphine and the carboxyl groups of galacturonic acid residues, resulting in cross-linking of galacturonic acid-containing polysaccharides to each other. The ability of bismorphine to cross-link pectins is much higher than that of Ca2+, which also acts as a cross-linker of these polysaccharides. Furthermore, we confirmed that cross-linking of pectins through bismorphine bridges leads to resistance against hydrolysis by pectinases. These results indicated that production of bismorphine is a defense response of the opium poppy. Bismorphine formation is catalyzed by anionic peroxidase that pre-exists in the capsules and leaves of opium poppies. The constitutive presence of morphine, together with bismorphine-forming peroxidase, enables the opium poppy to rapidly induce the defense system.

High-performance liquid chromatographic determination of morphine and its 3- and 6-glucuronide metabolites by two-step solid-phase extraction

To provide more accurate measurement of morphine and its metabolites for a study of the genetic differences on morphine response, a method for the analysis of morphine and its metabolites is described which has the advantages of increased sensitivity and specificity by using a cleaner extraction. The new extraction method involves both the hydrophobic isolation on a carbon cartridge and ion-exchange isolation on ion-exchange resin which has not preliminary been described for morphine analysis. The combination of these two steps successfully purified drugs from human plasma with maximum removal of interfering substance comparing with a conventional C18 cartridge alone. The analytes are quantified by high-performance liquid chromatography on a reversed-phase C18 column employing a mobile phase consisting of 25% acetonitrile in 0.05 M phosphate buffer (pH 2.1), and 2.5 mM sodium dodecyl sulfate as the pairing ion with a combination of electrochemical and fluorometric detections. The recoveries for morphine (M), morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G) and hydromorphone after the SPE procedure were 86+/-7.1%, 82+/-6.9%, 79+/-6.0% and 85+/-6.0%, respectively. Limits of detection for this method are 0.1 ng/ml for M, and 0.18 ng/ml for M3G and M6G. Limits of quantitation were approximately 0.25 ng/ml for M, and 0.45 ng/ml for M3G and M6G. The present assay was applied to measure M, M3G and M6G content in human plasma to test the applicability and suitability of this method for clinical and research use.

Reversed-phase high-performance liquid chromatography--photodiode-array analysis of alkaloid drugs of forensic interest

A reversed-phase high-performance liquid chromatography-photodiode-array method for the analysis of 23 drugs of forensic interest is presented. The separation method development was based on mobile-phase optimisation, temperature control and use of three ODS stationary phases. Multiwavelength detection and quantitation was performed at 225, 232, 239, 254, 275 and 289 nm. Absorbance rationing proved to be very helpful for the identification of these drugs. Recognition of the analysed compounds was achieved by means of correlation of retention time and absorbance ratios. The method was directly applied to the analysis of illicit heroin and cocaine samples and to the analysis of pharmaceutical preparations containing codeine.

Determination of isomeric N-oxide metabolites of some substituted 2,4-diaminopyrimidines by reversed-phase ion-pair high-performance liquid chromatography

Reversed-phase ion-pair high-performance liquid chromatography has been investigated for the separation, detection, identification and quantitation of the isomeric 1N- and 3N-oxide metabolites of metoprine, pyrimethamine and trimethoprim. A rapid and sensitive analytical method for the simultaneous determination of the isomeric 1N- and 3N-oxides of metoprine and pyrimethamine was devised for in vitro metabolic studies by optimisation of mobile phase pH, pairing-ion concentration, secondary-ion concentration and percentage organic modifier.

Liquid chromatographic methods validation for pharmaceutical products

The current status of validation in LC methods for the analysis of pharmaceuticals has been reviewed with special reference to compatibility testing methods. Validation data were provided in terms of method linearity, accuracy, precision, system suitability, specificity, use of alternate methods, injection order, application of peak height or area measurements and of internal or external standards.

Solubility behavior of narcotic analgesics in aqueous media: solubilities and dissociation constants of morphine, fentanyl, and sufentanil

The pH dependence of the aqueous solubility of morphine, fentanyl, and sufentanil was investigated at 35 degrees C. Dissociation constants and corresponding pKa' values of the drugs were obtained from measured free-base solubilities (determined at high pH's) and the concentrations of saturated solutions at intermediate pH's. Morphine, fentanyl, and sufentanil exhibited pKa' values of 8.08, 8.99, and 8.51, respectively. Over the pH range of 5 to 12.5 the apparent solubilities are determined by the intrinsic solubility of the free base plus the concentration of ionized drug necessary to satisfy the dissociation equilibrium at a given pH. Consequently, the drug concentrations of saturated aqueous solutions fall off precipitously as the pH is raised and ionization is suppressed. Further, at low pH's the aqueous solubility of morphine increased in a linear fashion with increases in the molar strength of citric acid which was added to acidify the medium, suggesting the formation of a soluble morphine-citrate complex.

The simultaneous determination of active ingredients in cough-cold mixtures by isocratic reversed-phase ion-pair high-performance liquid chromatography

A simple, rapid and accurate method for the simultaneous determination of active ingredients in cough-cold mixtures using isocratic reversed-phase ion-pair high-performance liquid chromatography has been developed. It involves the use of an octadecylsilane column as the stationary phase with methanol, water, tetrahydrofuran, phosphoric acid mixtures as mobile phase including sodium dioctylsulphosuccinate as the ion-pair agent. The pH of the mobile phase was adjusted to 4.6 by means of phosphoric acid and ammonium hydroxide solutions. The proposed method involves the simple dilution of the samples with the mobile phase and the addition of metoclopramide hydrochloride as the internal standard. The active ingredients under investigation were chlorpheniramine, codeine, diphenhydramine, ephedrine, ethylmorphine, phenylephrine, phenylpropanolamine and pholcodine, which exist as various combinations in cough-cold mixtures. The optimum composition of the mobile phase and the optimum flow rate were determined and are reported. The method was applied to the determination of active ingredients in seven commercially available cough-cold mixtures.

Stability of morphine solutions in plastic syringes determined by reversed-phase ion-pair liquid chromatography

A reversed-phase ion-pair HPLC assay has been developed for quantitating morphine, codeine, apomorphine, and pseudomorphine in aqueous solutions. Using two types of plastic syringes, the effect of light (25 W) and temperature (22 and 3 degrees C) on the stability of morphine, over a 12-week period, has been investigated in the presence and absence of preservative and antioxidant. The leaching of contaminants from the plastic syringes to water stored in them, for a period of up to 12 weeks, has also been investigated. The results indicate that less than 3% of the morphine is degraded in both types of plastic syringes, stored in light at 22 +/- 2 degrees C. The degradation is even less prominent in the dark or at 3 degrees C. Pseudomorphine has been identified as the major degradation product. Using 5% degradation of drug as the criterion for the determination of the shelf-life of morphine, it was found that in one brand of plastic syringes, morphine has a shelf-life of the order of 20 and 33 weeks, in the absence and presence of preservative and antioxidant, respectively. In the other brand of plastic syringe, the drug has a shelf-life of greater than 1 year. Some unidentified leached contaminants have been detected in water stored in both brands of syringes.

Simultaneous high-performance liquid chromatographic stability-indicating analysis of acetaminophen, codeine phosphate, and sodium benzoate in elixirs

A stability-indicating high-performance liquid chromatographic method has been developed for the simultaneous determination of acetaminophen, codeine phosphate and sodium benzoate in an elixir formulation. The reversed-phase paired-ion method utilizes UV detection at 214 nm, a C18 column at 50 degrees C and requires ca. 10 min per analysis. The method has been validated for use with elixirs containing 120 mg of acetaminophen, 12 mg of codeine phosphate and 7.5 mg sodium benzoate preservative per 5 ml. The known potential degradation products p-aminophenol, codeine N-oxide and codeinone are separated for quantitation simultaneous with the parent compounds. The method has been shown to be linear, reproducible, specific, sensitive and rugged.

Analysis of iodochlorhydroxyquin in cream formulations and bulk drugs by high-performance liquid chromatography

A high-performance liquid chromatographic method for the analysis of iodochlorhydroxyquin in creams and as bulk drugs has been developed. Iodochlorhydroxyquin was acetylated in the 8-position by reaction with acetic anhydride in pyridine. The resulting ester was mixed with the internal standard and chromatographed on a microparticulate silica column. Recovery was quantitative and the method was shown to be applicable to cream formulations from several manufacturers.

High-performance liquid chromatographic determination of hydrocortisone cypionate: method development and characterization of chromatographic behavior

A reversed-phase high-performance liquid chromatographic method for hydrocortisone cypionate bulk drug and oral solution was developed that avoids the use of a heated column as described in USP XX. A study of the effect of the organic modifier concentration on the capacity factor suggests that mixed partition and adsorption phenomena are responsible for the retention of several steroids when acetonitrile is used in the mobile phase. Evidence is presented that hydrogen bonding of the solute molecule with silane hydroxyl groups may be responsible for the adsorption.

Determination of dextromethorphan hydrobromide by high-performance liquid chromatography using ion-pair formation

The chromatographic retention behavior of dextromethorphan hydrobromide on an octadecylsilane column was investigated as a function of the pairing ion and the mobile phase composition. Dramatic increases in the capacity factor were observed with pairing ions containing more than eight carbons and with decreasing organic modifier (acetonitrile) concentration. Several pharmaceutically important amines exhibited similar behavior with respect to acetonitrile concentration. An analytical method was developed for dextromethorphan hydrobromide bulk drug and syrups and was applied to commercial preparations.