Experiment three Assay test of ibuprofen tablets

Introduction: Ibuprofen is a non-steroidal anti-inflammatory agent, belongs to the aryl alkanoic acid derivatives, mainly used as analgesic and anti- inflammatory drug in rheumatoid arthritis and moderate pain.

physiochemical properties It is a white crystalline powder. insoluble in water, but freely soluble in organic solvents such as acetone, ether, methanol and chlorinated hydrocarbons. As an acid, it can react with bases such as sodium hydroxide to form the water soluble ibuprofen sodium salt. Its molecular weight equals 206.3 g/mole. melting point is 75 °C.

Available dosage forms: Exists as cream, gel, oral suspension and tablets or capsules.

Synthesis Ibuprofen begin with isobutylbenzene and use Friedel-Crafts acylation. The Boot process requires six steps, while the Hoechst process, with the assistance of catalysts, is completed in only three steps. the human body can convert the inactive (R) form into the (S) form, so eventually 100% of the ibuprofen taken becomes active. The process discovered by Cheminor is therefore unlikely to have commercial significance.

The 12 principles of green chemistry are prevent waste. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.(Atom Economy). Less Hazardous synthesis. Chemical products should be designed to preserve efficacy of function while reducing toxicity. The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used. Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure (energy efficiency). A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable. Reduce derivatives - Unnecessary derivatization (blocking group, protection/ deprotection, temporary modification) should be avoided whenever possible. Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products. Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances. Substances and the form of a substance used in a chemical process should be chosen to minimize potential for chemical accidents, including releases, explosions, and fires.

Identification tests Melting Point 75.0-78.0 By UV Exhibits 2 absorption maxima, at 264 nm and 272 nm. The ratio of the absorbance measured at the maximum at 264 nm to that measured at the shoulder at 258 nm is 1.20 to 1.30. The ratio of the absorbance measured at the maximum at 272 nm to that measured at the shoulder at 258 nm is 1.00 to 1.10. By IR The infra-red absorbance spectrum obtained from the sample should be concordant with spectrum obtained from the standard. By TLC The principal spot in the chromatogram obtained with the test solution is similar in position, color and size to the principal spot in the chromatogram obtained with the reference solution.

Assay Test: Weigh 20 tablets, and then grind them using a mortar and a pestle. From the powder, take equivalent amount containing 0.4 g ibuprofen; dissolve in 20 ml chloroform for 15 minutes. Filter the solution under reduced pressure, and wash the residue with two (5 ml) chloroform. Evaporate the filtrate to dryness under current air (inside the hood). Dissolve the solid residue in 80 ml absolute ethanol (previously neutralised with NaOH). Titrate with 0.1 M NaOH using phenolphthalein as indicator.

Weigh 20 tablets To decrease weight variation & increase accuracy of the assay.

Extraction Sample preparation for Elemental analysis . Solids are usually dissolved in a liquids to be extracted. separate the analyte from interferences. obtain the analyte(s) in a form that can be analyzed.

filtration Filtration is commonly used to separate a material in the solid phase from one in the liquid phase

Suction filtration vs gravity filtration Gravity filtration is the method of choice to remove solid impurities from an organic liquid. The impurity can be a drying agent or an undesired side product or leftover reactant. Gravity filtration can be used to collect solid product, although generally vacuum filtration is used for this purpose because it is faster. Vacuum filtration is used primarily to collect a desired solid, for instance, the collection of crystals in a recrystallization procedure. Vacuum filtration uses a Buchner funnel and a side-arm flask. Vacuum filtration is faster than gravity filtration, because the solvent or solution and air is forced through the filter paper by the application of reduced pressure.

Suction filtration vs. gravity filtration

Fluted filter paper vs. cone filter paper The major advantage of a fluted filter is that it increases the speed of filtration for two reasons: first, it increases the surface area of the filter paper through which the solvent seeps; second, it allows air to enter the flask along its sides to permit rapid pressure equalization

A rotary evaporator (or rotavap) is a device used in chemical laboratories for the efficient and gentle removal of solvents from samples by evaporation.

Rotary evaporator (or rotavap) Principle Components The principle is that Vacuum evaporators as a class function because lowering the pressure above a bulk liquid lowers the boiling points of the component liquids in it. A motor unit that rotates the evaporation flask or vial containing the user's sample. A vapor duct that is the axis for sample rotation, and is a vacuum-tight conduit for the vapor being drawn off of the sample. A vacuum system, to substantially reduce the pressure within the evaporator system. A heated fluid bath (generally water) to heat the sample. A condenser with either a coil passing coolant, or a "cold finger" into which coolant mixtures such as dry ice and acetone are placed. A condensate-collecting flask at the bottom of the condenser, to catch the distilling solvent after it re-condenses. A mechanical or motorized mechanism to quickly lift the evaporation flask from the heating bath.

Calculations

Calculations Note: Each 1 ml of 0.1 M NaOH is equivalent to 20.63 mg of Ibuprofen. According to BP, Ibuprofen tablets should contain not less than 95% and not more than 105% of the labelled amount of Ibuprofen. According to USP, Ibuprofen tablets should contain not less than 90% and not more than 110% of the labelled amount of Ibuprofen.

Source of errors Intrinsic errors (end point # eq. point) Systematic errors (vol. glassware accuracy) Instrumental errors( temp.) Method errors( nonideal chemical behavior) Personal errors (misreading the volume) Gross errors (personal carelessness) Indeterminate or random errors

think What could be the difference between the assay of tablets contain ibuprofen from powder of ibuprofen? When ibuprofen can not be given to a patient?