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Title:1)To identify and calculate the content of

Chlorpromazine hydrochloride in a tablet

dosage form using UV/Vis

Spectrophotometer.

2)To measure the light absorbing impurities in

Doxycyline hydrochloride capsules

Apparatus required:

1)A double beam UV/Vis Spectrophotometer , 2)Volumetric flasks. 3)Pipettes ,4)Funnels, 5)Filter papers , 6)Spatula,7)Watch glass or butter paper .

Chemicals required:

1) Chlorpromazine hydrochloride tablets, 2) Dil. Hydrochloric acid , 4)Methanol.

Theory:

UV/Vis Spectrophotometry is the measurement of the absorption of monochromatic radiation by solutions of chemical substances in the range of 180nm to 380nm (uv) and 380 to 780nm (Vis.) of the spectrum respectively.

According to the modified Beer-Lambert’s equation

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A = log10 1/T = log10 I0/I = a1%1cm * b * c

Measurement of light absorption (in the form of absorbance) in the visible and ultraviolet range is widely used as a mean of identification or a supplementary evidence of identification. It is especially useful when the observed spectrum shows more than one characteristic maximum and when pH influences position of maxima. The ratio of the absorbances at two maxima also provide a useful criterion of identity. More over , in some cases, the absorbance at specified wavelength though may not maxima, is used as the basis of limit tests to exclude known or unknown impurities.

Procedure:

1)For Chlorpromazine hydrochloride identification and assay.

a)Dil. Hydrochloric acid( 50ml):

Weigh accurately about 5.0g of Conc. Hydrochloric acid and dilute to 50ml

with water.

b)Sample preparation:

Each tablet claims to contain Chlorpromazine Hydrochloride =

Weigh 20 tablets =

Average weight of each tablet=

Then pulverize the tablets.

i)For assay:(92.5-107.5)% of the stated amount of Chlorpromazine hydrochloride.

Weigh accurately a quantity of the powder containing about 0.0625 g of Chlorpromazine Hydrochloride, add 5 ml of dilute hydrochloric acid and 100 ml of water. Shake for l5 minutes and add sufficient water to produce 250.0 ml. Centrifuge about 15 ml and to 5.0 ml of the clear, supernatant liquid add l0 ml of dilute hydrochloric acid and sufficient water to produce 250.0ml. Measure the absorbance of the resulting solution at the maximum at about 254nm. Calculate the content of Chlorpromazine hydrochloride taking 915 as the specific absorbance at

254nm.

Wt.of sample taken=

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ii)For identification:

Examine the sample solution in the range 230nm to 360nm , it should show absorption maxima at about 254nm and 306 nm; absorbance at about 254nm should be 0.45 to 0.48.

Observation:

For identification absorption maxima recorded at:

Absorbance recorded at 254nm:

For assay, absorbance measured at 254nm:

2)For the measurement of light absorbing impurities in Doxycycline hydrochloride

capsules.

a)1M Hydrochloric acid(50ml):

Dilute about 4.4ml of Conc. Hydrochloric acid to 50ml with water.

b)Sample preparation:

Each capsule claims to contain Doxycycline hydrochloride =

Weigh 10 capsules=

Average weight of each capsule=

Then mix the contents of the capsules.

Weigh accurately a quantity of the powder equivalent to 0.250g of Doxycycline and transfer quantitatively into a 25ml volumetric flask. Dissolve the powder in a mixture of 1volume of 1M Hydrochloric acid and 99 volume of methanol. Dilute to 25ml with the same solvent so that concentration of anhydrous Doxycycline becomes 1% w/v. Filter the solution. The absorbance of the filtrate at 490nm , not greater than 0.2. This value should be measured with reference to the dried contents of the capsules.