盐酸二甲双胍Metformin Hydrochloride（BP2010）General Notices(Ph Eur monograph 0931)C 4H11N5,HCl 165.6 1115-70-4Action and useBiguanide; treatment of diabetes mellitus. PreparationMetformin TabletsPh EurDEFINITION1,1-Dimethylbiguanide hydrochloride.Content98.5 per cent to 101.0 per cent (dried substance).CHARACTERSAppearanceWhite or almost white crystals.SolubilityFreely soluble in water, slightly soluble in alcohol, practically insoluble in acetone and in methylene chloride.IDENTIFICATIONFirst identification B, E.Second identification A, C, D, E.A. Melting point(2.2.14): 222 °C to 226 °C.B. Infrared absorption spectrophotometry(2.2.24).Preparation Discs of potassium chloride R.Comparison metformin hydrochloride CRS.C. Thin-layer chromatography(2.2.27).Test solution Dissolve 20 mg of the substance to be examined in water R and dilute to 5 ml with the same solvent.Reference solution Dissolve 20 mg of metformin hydrochloride CRS in water R and dilute to 5 ml with the same solvent.Plate TLC silica gel G plate R.Mobile phase Upper layer of a mixture of 10 volumes of glacial acetic acid R, 40 volumes of butanol R and 50 volumes of water R.Application 5 µl.Development Over a path of 15 cm.Drying At 100-105 °C for 15 min.Detection Spray with a mixture of equal volumes of a 100 g/l solution of sodium nitroprusside R, a 100 g/l solution of potassium ferricyanide R and a 100 g/l solution of sodium hydroxide R, prepared 20 min before use.Results The principal spot in the chromatogram obtained with the test solution is similar in position, colour and size to the principal spot in the chromatogram obtained with the reference solution.D. Dissolve about 5 mg in water R and dilute to 100 ml with the same solvent. To 2 ml of the solution add 0.25 ml of strong sodium hydroxide solution R and 0.10 ml of α-naphthol solution R. Mix and allow to stand in iced water for 15 min. Add 0.5 ml of sodium hypobromite solution R and mix. A pink colour develops.E. It gives reaction (a) of chlorides(2.3.1).TESTSSolution SDissolve 2.0 g in water R and dilute to 20 ml with the same solvent.Appearance of solutionSolution S is clear (2.2.1) and colourless (2.2.2, Method II).Related substancesLiquid chromatography(2.2.29).Test solution Dissolve 0.50 g of the substance to be examined in the mobile phase and dilute to 100.0 ml with the mobile phase.Reference solution (a) Dissolve 20.0 mg of cyanoguanidine R in water R and dilute to 100.0 ml with the same solvent. Dilute 1.0 ml to 200.0 ml with the mobile phase.Reference solution (b) Dilute 1.0 ml of the test solution to 50.0 ml with the mobile phase. Dilute 1.0 ml of this solution to 20.0 ml with the mobile phase.Reference solution (c) Dissolve 10.0 mg of melamine R in about 90 ml of water R. Add 5.0 ml of the test solution and dilute to 100.0 ml with water R. Dilute 1.0 ml of this solution to 50.0 ml with the mobile phase.Column:∙— size: l = 0.25 m, Ø = 4.6 mm;∙— stationary phase: irregular, porous silica gel to which benzenesulphonic acid groups have been chemically bonded (10 µm); Or∙— size: l = 0.11 m, Ø = 4.7 mm;∙— stationary phase: regular, porous silica gel to which benzenesulphonic acid groups have been chemically bonded (5 µm).Mobile phase 17 g/l solution of ammonium dihydrogen phosphate R adjusted to pH 3.0 with phosphoric acid R.Flow rate 1 ml/min.Detection Spectrophotometer at 218 nm.Injection 20 µl.Run time Twice the retention time of metformin hydrochloride. System suitability Reference solution (c):∙—resolution: minimum of 10 between the peaks due to melamine and to metformin hydrochloride.Limits:∙—impurity A: not more than the area of the corresponding peak in the chromatogram obtained with reference solution (a) (0.02 per cent);∙—any other impurity: not more than the area of the principal peak in the chromatogram obtained with reference solution (b) (0.1 per cent).Heavy metals(2.4.8)Maximum 10 ppm.12 ml of solution S complies with limit test A. Prepare the standard using lead standard solution (1 ppm Pb) R.Loss on drying(2.2.32)Maximum 0.5 per cent, determined on 1.000 g by drying in an oven at 105 °C for 5 h.Sulphated ash(2.4.14)Maximum 0.1 per cent, determined on 1.0 g.ASSAYDissolve 0.100 g in 4 ml of anhydrous formic acid R. Add 80 ml of acetonitrile R. Carry out the titration immediately. Titrate with 0.1 M perchloric acid, determining the end-point potentiometrically(2.2.20).1 ml of 0.1 M perchloric acid is equivalent to 16.56 mg of C4H12ClN5.IMPURITIESSpecified impurities A.Other detectable impurities (The following substances would, if present at a sufficient level, be detected by one or other of the tests in the monograph. They are limited by the general acceptance criterion for other/unspecified impurities and/or by the general monograph Substances for pharmaceutical use(2034). It is therefore not necessary to identify these impurities for demonstration of compliance. See also 5.10. Control of impurities in substances for pharmaceutical use): B, C, D, E, FAppendix I E. Chemical and Biological Reference MaterialsWhere the letters BPCRS appear after the name of a substance in a test or assay, the British Pharmacopoeia Chemical Reference Substance is to be used. A comprehensive and up-to-date list of British Pharmacopoeia Chemical Reference Substances, together with terms of trade and supply, is available on the website at. A printed catalogue and the substances are obtainable from the BPCRS Sales Office, Market Towers, 1 Nine Elms Lane, London SW8 5NQ, United Kingdom (telephone +44(0)20 7084 2561, facsimile +44 (0)20 7084 2566,e-mail: bpcrs@).In addition to BPCRS, monographs of the British Pharmacopoeia may also refer to reference substances available from other suppliers. These are denoted by the letters CRS.Where the letters CRS or EPCRS appear, the chemical reference substance issued by the European Pharmacopoeia Commission is to be used; where the letters BRP or EPBRP appear, the Biological Reference Preparation issued by the European Pharmacopoeia Commission is to be used. A printed catalogue and the substances, as well as European Pharmacopoeia infrared reference spectra, are obtainable from the Council of Europe, European Directorate for the Quality of Medicines & Healthcare, CRS Sales Team, 7 allée Kastner, CS 30026, F-67081, Strasbourg Cedex, France (facsimile +33 (0)3 88 41 27 71, e-mail: crs@).Other sources of specific reference substances are shown below.Astragaloside I CRS , Astragaloside II CRS , Astragaloside IV CRS , Paeonol CRS , Rosmarinic acid CRS , Salvianolic Acid B CRS ,CRS , Withaferin A CRS , Withanolide A CRS , Tanshinone IIAWithanolide B CRS , Z-Ligustilide CRS may be obtained from the Office of Reference Materials, LGC Standards, Queen's Road, Teddington, TW11 0LY, United Kingdom (telephone +44 (0)20 8943 8480, facsimile +44 (0)20 8943 7554,e-mail: uksales@).Opacity, Standard Preparation of The Standard Preparation is the 5th International Reference Preparation, established in 1975, and consists of a rod of plastic simulating the optical properties ofa bacterial suspension (10 Units of opacity). It may be obtained from the National Institute for Biological Standards and Control (NIBSC), Blanche Lane, South Mimms, Potters Bar, Hertfordshire, EN6 3QG, United Kingdom (telephone +44 (0)1707 641000,e-mail: enquiries@).Piperonyl Butoxide CRS may be obtained from the Office of Reference Materials, LGC Promochem, Queen's Road, Teddington, TW11 0LY, United Kingdom (telephone +44 (0)20 8943 8480,facsimile +44 (0)20 8943 7554,e-mail: uksales@).© Crown Copyright 2009Appendix III D. Liquid Chromatography(Ph. Eur. method 2.2.29)Liquid chromatography (LC) is a method of chromatographic separation based on the difference in the distribution of species between two non-miscible phases, in which the mobile phase is a liquid which percolates through a stationary phase contained in a column.LC is mainly based on mechanisms of adsorption, mass distribution, ion exchange, size exclusion or stereochemical interaction.ApparatusThe apparatus consists of a pumping system, an injector, a chromatographic column (a column temperature controller may be used), a detector and a data acquisition system (or an integrator or a chart recorder). The mobile phase is supplied from one or several reservoirs and flows through the column, usually at a constant rate, and then through the detector.Pumping systemsLC pumping systems are required to deliver the mobile phase at aconstant flow rate. Pressure fluctuations are to be minimised, e.g. by passing the pressurised solvent through a pulse-dampening device. Tubing and connections are capable of withstanding the pressures developed by the pumping system. LC pumps may be fitted with a facility for "bleeding" the system of entrapped air bubbles.Microprocessor controlled systems are capable of accurately delivering a mobile phase of either constant (isocratic elution) or varying composition (gradient elution), according to a defined programme. In the case of gradient elution, pumping systems which deliver solvent(s) from several reservoirs are available and solvent mixing can be achieved on either the low or high-pressure side of the pump(s).InjectorsThe sample solution is introduced into the flowing mobile phase at or near the head of the column using an injection system which can operate at high pressure. Fixed-loop and variable volume devices operated manually or by an auto-sampler are used. Manual partial filling of loops may lead to poorer injection volume precision.Stationary phasesThere are many types of stationary phases employed in LC, including: ∙— silica, alumina or porous graphite, used in normal-phasechromatography, where the separation is based on differences in adsorption and/or mass distribution,∙— resins or polymers with acid or basic groups, used in ion-exchange chromatography, where separation is based oncompetition between the ions to be separated and those in the mobile phase,∙— porous silica or polymers, used in size-exclusion chromatography, where separation is based on differencesbetween the volumes of the molecules, corresponding to steric exclusion,∙— a variety of chemically modified supports prepared from polymers, silica or porous graphite, used in reversed-phase LC, where the separation is based principally on partition of the molecules between the mobile phase and the stationaryphase,— special chemically modified stationary phases, e.g.cellulose or amylose derivatives, proteins or peptides,cyclodextrins etc., for the separation of enantiomers (chiral chromatography).Most separations are based upon partition mechanisms utilising chemically modified silica as the stationary phase and polar solvents as the mobile phase. The surface of the support, e.g. the silanol groups of silica, is reacted with various silane reagents to produce covalently bound silyl derivatives covering a varying number of active sites on the surface of the support. The nature of the bonded phase is an important parameter for determining the separation properties of the chromatographic system.Commonly used bonded phases are shown below:octyl = Si-[CH2]7-CH3C8octadecyl = Si-[CH2]17-CH3C18phenyl = Si-[CH2]n-C6H5C6H5cyanopropyl = Si-[CH2]3-CN CNaminopropyl = Si-[CH2]3-NH2NH2diol = Si-[CH2]3-O-CH(OH)-CH2-OHUnless otherwise stated by the manufacturer, silica based reversed-phase columns are considered to be stable in mobile phases having an apparent pH in the range 2.0 to 8.0. Columns containing porous graphite or particles of polymeric materials such as styrene-divinylbenzene copolymer are stable over a wider pH range.Analysis using normal-phase chromatography with unmodified silica, porous graphite or polar chemically modified silica, e.g. cyanopropyl or diol, as the stationary phase with a non-polar mobile phase is applicable in certain cases.For analytical separations, the particle size of the most commonly used stationary phases varies between 3 µm and 10µm. The particles may be spherical or irregular, of varying porosity and specific surface area. These parameters contribute to the chromatographic behaviour of a particular stationary phase. In the case of reversed phases, the nature of the stationary phase, the extent of bonding, e.g. expressed as the carbon loading, and whether the stationaryphase is end-capped (i.e. residual silanol groups are silylated) are additional determining factors. Tailing of peaks, particularly of basic substances, can occur when residual silanol groups are present.Columns, made of stainless steel unless otherwise prescribed in the monograph, of varying length and internal diameter (Ø) are used for analytical chromatography. Columns with internal diameters of less than 2 mm are often referred to as microbore columns. The temperature of the mobile phase and the column must be kept constant during an analysis. Most separations are performed at room temperature, but columns may be heated to give higher efficiency. It is recommended that columns not be heated above 60 °C because of the potential for stationary phase degradation or changes occurring to the composition of the mobile phase.Mobile phasesFor normal-phase chromatography, less polar solvents are employed. The presence of water in the mobile phase is to be strictly controlled to obtain reproducible results. In reversed-phase LC, aqueous mobile phases, with or without organic modifiers, are employed.Components of the mobile phase are usually filtered to remove particles greater than 0.45 µm. Multicomponent mobile phases are prepared by measuring the required volumes (unless masses are specified) of the individual components, followed by mixing. Alternatively, the solvents may be delivered by individual pumps controlled by proportioning valves by which mixing is performed according to the desired proportion. Solvents are normally degassed before pumping by sparging with helium, sonication or using on-line membrane/vacuum modules to avoid the creation of gas bubbles in the detector cell.Solvents for the preparation of the mobile phase are normally free of stabilisers and are transparent at the wavelength of detection, if an ultraviolet detector is employed. Solvents and other components employed are to be of appropriate quality. Adjustment of the pH, if necessary, is effected using only the aqueous component of the mobile phase and not the mixture. If buffer solutions are used, adequate rinsing of the system is carried out with a mixture of water and the organic modifier of the mobile phase (5 per cent V/V) to prevent crystallisation of salts after completion of the chromatography.Mobile phases may contain other components, e.g. a counter-ion for ion-pair chromatography or a chiral selector for chromatographyusing an achiral stationary phase.DetectorsUltraviolet/visible (UV/Vis) spectrophotometers, including diode array detectors, are the most commonly employed detectors. Fluorescence spectrophotometers, differential refractometers, electrochemical detectors, mass spectrometers, light scattering detectors, radioactivity detectors or other special detectors may also be used.MethodEquilibrate the column with the prescribed mobile phase and flow rate, at room temperature or at the temperature specified in the monograph, until a stable baseline is achieved. Prepare the solution(s) of the substance to be examined and the reference solution(s) required. The solutions must be free from solid particles.Criteria for assessing the suitability of the system are described in the chapter on Chromatographic separation techniques (2.2.46). The extent to which adjustments of parameters of the chromatographic system can be made to satisfy the criteria of system suitability are also given in this chapter.Additional points for monographs of the British PharmacopoeiaThe composition and flow rate of the mobile phase are stated in the monograph. It is advisable to use as the mobile phase solvent mixtures that have been de-aerated using a vacuum pump or other suitable means of de-aeration that has no effect on the composition of the mixture.In quantitative work, particularly where the use of an internal standard is not specified in the monograph, the use of a fixed-volume loop injector is recommended. In certain exceptional cases the use of peak heights alone is prescribed in the monograph; where this is the case peak heights should be used irrespective of the symmetry factor.The column is usually made of stainless steel and its dimensions are stated in the monograph. The dimensions are stated as (length × internal diameter). When the monograph prescribes the use of a stationary phase designated by a letter, the relevant stationary phase defined below is intended. The nominal diameter of theparticles of the stationary phase is stated in parentheses immediately following the designating letter. In most cases reference is made to a particular commercial brand that has been found to be suitable for the purpose, but such statements do not imply that a different but equivalent commercial brand may not be used. The separation should be carried out at a constant ambient temperature unless otherwise specified in the monograph. When using mobile phases of high pH with a silica-based column, it is advisable to use a pre-column before the analytical column.Unless otherwise specified in the monograph the detector consists of a photometric detector fitted with a low-volume flow cell (about 10 µl i s suitable); the wavelength setting is specified in the monograph.The design of a particular chromatograph may require modification of the conditions detailed in the monograph. In such a case the analyst should be satisfied that the modified conditions produce comparable results.injection volumeWhere no injection volume is specified in the monograph, the analyst should select an appropriate volume for their specific application. The volume chosen is dependent on the response of the analyte, the detector used, the efficiency of the column and the overall performance of the chromatographic system. Where a volume is not indicated, 20 µl is usually appropriate; however this should be checked for suitability under the local operating conditions.run timeWhere no run time is specified in the monograph, the analyst should select an appropriate run time for their specific application. The run time chosen is dependent on the type of test. For example, where a run time is not indicated in a Related substances test the analyst should ensure that the run time is greater than all known or likely secondary peaks; similarly in an Assay the run time should be chosen to allow the baseline to stabilise following the elution of the peak of interest.secondary peaksReference may be made to secondary peaks. A secondary peak is a peak in the chromatogram other than the principal peak and any peak dueto internal standard, solvent or derivatising agents. Peaks identified as being due to the counter-ion and/or other excipients including preservatives in the material being examined may also be excluded.materialsSolvents and reagents used in the preparation of solutions for examination should be of a quality suitable for use in liquid chromatography.© Crown Copyright 2009Appendix VIII B. Amperometric and Potentiomeric TitrationsAmperometric Titration(Ph. Eur. method 2.2.19)In amperometric titration the end-point is determined by following the variation of the current measured between 2 electrodes (either one indicator electrode and one reference electrode or 2 indicator electrodes) immersed in the solution to be examined and maintained at a constant potential difference as a function of the quantity of titrant added.The potential of the measuring electrode is sufficient to ensure a diffusion current for the electroactive substance.Apparatus The apparatus comprises an adjustable voltage source and a sensitive microammeter; the detection system generally consists of an indicator electrode (for example, a platinum electrode, a dropping-mercury electrode, a rotating-disc electrode or a carbon electrode) and a reference electrode (for example, a calomel electrode or a silver-silver chloride electrode).A three-electrode apparatus is sometimes used, consisting of an indicator electrode, a reference electrode and a polarised auxiliaryelectrode.Method Set the potential of the indicator electrode as prescribed and plot a graph of the initial current and the values obtained during the titration as functions of the quantity of titrant added. Add the titrant in not fewer than 3 successive quantities equal to a total of about 80 per cent of the theoretical volume corresponding to the presumed equivalence point. The 3 values must fall on a straight line. Continue adding the titrant beyond the presumed equivalence point in not fewer than 3 successive quantities. The values obtained must fall on a straight line. The point of intersection of the 2 lines represents the end-point of the titration.For amperometric titration with 2 indicator electrodes, the whole titration curve is recorded and used to determine the end-point.Potentiometric Titration(Ph. Eur. method 2.2.20)In a potentiometric titration the end-point of the titration is determined by following the variation of the potential difference between 2 electrodes (either one indicator electrode and one reference electrode or 2 indicator electrodes) immersed in the solution to be examined as a function of the quantity of titrant added.The potential is usually measured at zero or practically zero current.Apparatus The apparatus used (a simple potentiometer or electronic device) comprises a voltmeter allowing readings to the nearest millivolt.The indicator electrode to be used depends on the substance to be determined and may be a glass or metal electrode (for example, platinum, gold, silver or mercury). The reference electrode is generally a calomel or a silver-silver chloride electrode.For acid-base titrations and unless otherwise prescribed, aglass-calomel or glass-silver-silver chloride electrode combination is used.Method The solvent mixture is neutralised, if necessary, before dissolution of the substance to be examined. Plot a graph of the variation of potential difference as a function of the quantity ofthe titrant added, continuing the addition of the titrant beyond the presumed equivalence point. The end-point corresponds to a sharp variation of potential difference.Determination of Primary Aromatic Amino-nitrogen(Ph. Eur method 2.5.8)Dissolve the prescribed quantity of the substance to be examined in50 ml of dilute hydrochloric acid R or in another prescribed solventand add 3 g of potassium bromide R. Cool in ice-water and titrateby slowly adding 0.1 M sodium nitrite with constant stirring.Determine the end-point electrometrically or by the use of the prescribed indicator.© Crown Copyright 2009Substances for Pharmaceutical UseGeneral Notices(Ph Eur monograph 2034)Ph EurDEFINITIONSubstances for pharmaceutical use are any organic or inorganic substances that are used as active substances or excipients for the production of medicinal products for human or veterinary use. They may be obtained from natural sources or produced by extraction from raw materials, fermentation or synthesis.This general monograph does not apply to herbal drugs, herbal drugs for homoeopathic preparations, herbal drug preparations, extracts, or mother tinctures for homoeopathic preparations, which are the subject of separate general monographs (Herbal drugs (1433), Herbal drugs forhomoeopathic preparations (2045), Herbal drug preparations (1434), Extracts (0765), Mother tinctures for homoeopathic preparations (2029)). It does not apply to raw materials for homoeopathic preparations, except where there is an individual monograph for the substance in thenon-homoeopathic part of the Pharmacopoeia.Where a substance for pharmaceutical use not described in an individual monograph of the Pharmacopoeia is used in a medicinal product prepared for the special needs of individual patients, the need for compliance with the present general monograph is decided in the light of a risk assessment that takes account of the available quality of the substance and its intended use.Where medicinal products are manufactured using substances for pharmaceutical use of human or animal origin, the requirements of chapter 5.1.7. Viral safety apply.Substances for pharmaceutical use may be used as such or as starting materials for subsequent formulation to prepare medicinal products. Depending on the formulation, certain substances may be used either as active substances or as excipients. Solid substances may be compacted, coated, granulated, powdered to a certain fineness, or processed in other ways. A monograph is applicable to a substance processed with an excipient only where such processing is mentioned in the definition section of the monograph.Substance for pharmaceutical use of special grade Unless otherwise indicated or restricted in the individual monographs, a substance for pharmaceutical use is intended for human and veterinary use, and is of appropriate quality for the manufacture of all dosage forms in which it can be used.Polymorphism Individual monographs do not usually specify crystalline or amorphous forms, unless bioavailability is affected. All forms of a substance for pharmaceutical use comply with the requirements of the monograph, unless otherwise indicated.PRODUCTIONSubstances for pharmaceutical use are manufactured by procedures that are designed to ensure a consistent quality and comply with the requirements of the individual monograph or approved specification.The provisions of general chapter 5.10 apply to the control of impurities in substances for pharmaceutical use.Whether or not it is specifically stated in the individual monograph that the substance for pharmaceutical use:∙— is a recombinant protein or another substance obtained as a direct gene product based on genetic modification, where applicable, the substance also complies with the requirements of the general monograph Products of recombinant DNA technology (0784);∙—is obtained from animals susceptible to transmissible spongiform encephalopathies other than by experimental challenge, whereapplicable, the substance also complies with the requirements of the general monograph Products with risk of transmitting agents of animal spongiform encephalopathies (1483);∙— is a substance derived from a fermentation process, whether or not the micro-organisms involved are modified by traditionalprocedures or recombinant DNA(rDNA) technology, where applicable, the substance also complies with the requirements of the general monograph Products of fermentation (1468).If solvents are used during production, they are of suitable quality. In addition, their toxicity and their residual level are taken into consideration (5.4). If water is used during production, it is of suitable quality.If substances are produced or processed to yield a certain form or grade, that specific form or grade of the substance complies with the requirements of the monograph. Certain functionality-related tests may be described to control properties that may influence the suitability of the substance and subsequently the properties of dosage forms prepared from it.Powdered substances may be processed to obtain a certain degree of fineness (2.9.35).Compacted substances are processed to increase the particle size or to obtain particles of a specific form and/or to obtain a substance with a higher bulk density.Coated active substances consist of particles of the active substance coated with one or more suitable excipients.Granulated active substances are particles of a specified size and/or form produced from the active substance by granulation directly or with one or more suitable excipients.。
