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PRE-FORMULATION STUDIES

43 Institute of Pharmaceutical Sciences & Research Centre, Bhagwant University, Ajmer

Preformulation Studies: - 100-102

The following Preformulation studies were carried out,

Identification of the drug

Analytical method for satranidazole

Solubility studies

Loss on drying

Partition coefficient

Particle size determination

Thin layer chromatography

Drug – Excipient interaction

IDENTIFICATION OF DRUG

Colour : pale yellow or yellow colour

Nature : Crystalline

Odour : Odorless

Taste : Bitter

Melting point:

The drug (Satranidazole) was taken into melting point capillary tube and melting point

was determined by using digital auto melting point apparatus.

The melting point of the drug was found to be 185-191 oC.



IR Study7

Fig-2 Infra red spectral characteristics of Satranidazole



Table 6: Infra red spectral characteristics of Satranidazole

S.No. Wave number (cm-1) Interpretation

1 1740.44 C = O Stretching

2 1533.13 Asymmetric NO2 Stretching

3 1384.64 Symmetric NO2 Stretching

4 1330.64 Asymmetric SO2 Stretching

5 1167.69 Symmetric SO2 Stretching

6 3114.47 C-H Stretching for Pyrazine

7 3014.19 C-H Asymmetric Stretching for Methyl group

8 2926.45 C-H Symmetric Stretching for Methyl group

9 2976.81 C-H Asymmetric Stretching for Methylene group

ANALYTICAL METHOD FOR SATRANIDAZOLE

UV spectrum of Satranidazole in methanol

Satranidazole can be estimated by UV Spectrophotometrically in solvent. A solution of

Satranidazole was prepared in methanol gives maximum absorbance at ٨ max of 318 nm.

Preparation of Calibration Curve

1000 µg/ml (10mg/10ml) stock solution of drug was prepared in methanol solution and

suitable dilutions were made i.e.5 µg /ml, 10 µg /ml, 15µg /ml, 20 µg /ml and 25 µg /ml

respectively. The sample was scanned at ٨max 318nm. The absorbance of samples of

different concentration at the previously measured ٨max (at 318 nm). The graph was

plotted between the absorbance and concentration. The graph obeyed the Beer-Lambert’s

law in the selected concentration range.



Table 7: Calibration curve in Methanol

S.No. Conc.(µg/ml) Absorbance Absorbance after regression

1. 0 0 0

2. 5 0..173 0.150

3. 10 0.346 0.301

4. 15 0.525 0.452

5. 20 0.620 0.603

6. 25 0.790 0.754

y = 0.0323x

00.20.4

0.60.8

1

0 10 20 30Concentration (mcg/ml)

Abs

orba

nce

Fig.3 Calibration curve of Satranidazole in methanol



UV spectrum of Satranidazole in phosphate buffer

1000 µg/ml (10mg/10ml) stock solution of drug was prepared in phosphate buffer

solution (pH 7.4) and suitable dilutions were made i.e.5 µg/ml, 10 µg/ml, 15 µg/ml, 20

µg/ml and 25 µg/ml respectively. The sample was scanned at ٨max 318nm. The

absorbance of samples of different concentration at the previously measured ٨max (at

318 nm). The graph was plotted between the absorbance and concentration. The graph

obeyed the Beer-Lambert’s law in the selected concentration range.

Table 8: Calibration curve of Satranidazole in pH 7.4 phosphate buffer

S.No. Conc.(µg/ml) Absorbance Absorbance after

regression

1. 0 0 0

2. 5 0.234 0.205 3. 10 0.464 0.41 4. 15 0.627 0.615 5. 20 0.867 0.82 6. 25 1.124 1.025

y = 0.0441x

00.20.40.60.8

11.2

0 10 20 30Concentration (mcg/ml)

Abs

orba

nce

Fig.4 Calibration curve of Satranidazole in pH 7.4 phosphate buffer



SOLUBILITY STUDIES105: Equilibrium solubility of the drug in various selected

solvents was determined like water, ethanol, methanol, isopropyl alcohol, chloroform,

PEG400, and dimethyl formamide. Excessive quantity of drug was dissolved in 5.0ml of

solvents in volumetric flask and kept in a shaker for the period of 5 hours. The resulting

saturated solutions were kept aside for 24 hours, filtered through sintered glass filter and

was analyzed by UV spectrophotometer.

Table 9: Solubility of Satranidazole in the different solvents

S.No.

Solvents Solubility Solubility as per I.P

1

2

3

4

5

6

7

Water

Methanol

Ethanol

Isopropyl alcohol

Chloroform

PEG 400

Dimethyl formamide

2127

398

2583

6896

1879

147

85

Very Slightly Soluble

Slightly Soluble




Slightly Soluble

Freely soluble



SOLUBILITY IN DIFFERENT pH BUFFER SOLUTION

The solubility of the drug was determined in different pH solutions like pH 1.2, pH 4.0,

pH 5.8, pH 7.0 and pH 7.4 phosphate buffer. The saturated solution of drug was prepared

in these pH solutions, filtered and assayed spectrophotometrically.

Table 10: pH- solubility profile of Satranidazole

S. No.

Different pH phosphate

buffer solution

Solubility Solubility as per

I.P

1

2

3

4

5

1.2

4.0

5.8

7.0

7.4

2096

1785

2232

2358

2331

Very Slightly

Soluble

pH of drug solution: The pH of 1% (w/v) of Satranidazole was determined by using

digital pH meter at 25 oC and was found to be 4.5- 5.2

LOSS ON DRYING (LOD)

1gm sample was taken in pre weighed aluminum foil and put it into moisture balance for

3 hrs at 105°C. Then note the weight of the sample.

The LOD is calculated as per the given formula.

LOD % = (A-B)/ A X 100

Table11: Loss on drying of Satranidazole

S.No. Wt. of drug

before drying

(gm)

Wt. of drug

after drying

(gm)

LOD

(%w/w)

Average

LOD

(%w/w)

1. 1.001 0.9881 0.0129

0.013 2. 0.9999 0.9868 0.0131



PARTICLE SIZE:

The particle size of Satranidazole sample was estimated by optical microscope method.

The drug was taken on glass slide and mounted under optical microscope initially at 10X

magnification. After the adjustment for view, magnification was increased to 50X.

Particle size analyses were carried out by Photomicroscope and USB digital scale

computer program (software).

Table 12: Particle size distribution of Satranidazole

S.No. Size Range in

µm

Mean Diameter

(d) in µm

Number of

particles (n)

nd

1 0-1 0.5 7 3.5

2 1-2 1.5 21 31.5

3 2-3 2.5 10 25

4 3-4 3.5 11 38.5

5 4-5 4.5 5 22.5

6 5-6 5.5 1 5.5

7 6-7 6.5 3 19.5

8 7-8 7.5 2 15

Σn = 60 Σnd = 161

The average particale size can be calculated as-

average particale size = Σnd/ Σn

= µm



Particle Size Distribution

0

5

10

15

20

25

1 2 3 4 5 6 7 8Particle Size

Freq

uenc

y

Fig.5: Particle Size Distribution of Satranidazole

THIN LAYER CHROMATOGRAPHY 106

Thin layer chromatography is an important analytical tool in the separation, identification

and estimation of different drugs. In this technique the different compounds are separated

by the different migration of solute between two phases, a stationary phase and a mobile

phase. The principle of separation is adsorption and the stationary phases act as an

adsorbent.

APPLICATION OF THE SAMPLE: -

The solution of Satranidazole was made in methanol. About 5µl sample was spotted by

capillary tube on the pre coated TLC plates by keeping a distance of about 2 cm above

the base of the plate.

DEVELOPMENT OF THE CHROMATOGRAM: -

The plate was then placed in TLC chamber previously saturated with appropriate solvent

system, ethyl acetate: methanol: diethyl amine (85:10:5v/v) development of

chromatogram, the plate was removed and the spot was observed under the UV chamber

at the short wavelength 254nm. The Rf value was calculated and tabulated.



Stationary phase = pre coated silica gel- G plate

Mobile phase = ethyl acetate: methanol: diethyl amine (85:10:5v/v)

Table 13: The Rf values of the TLC studies of Satranidazole: -

Drug Rf Value

Satranidazole 0.81


A 50mg quantity of the drug (Satranidazole) was accurately weighed and dissolved in 50

ml of distilled water. The resulting solution was shaken with equal volume of n- octanol

for 30 minutes in a separating funnel and allowed to stand for 24 hours. The majority of

lower aqueous phase was run off and the drug content was determined in both solutions

by measuring the absorbance at max of 318 nm by UV spectrophotometer.

The partition coefficient was determined by formula:

Table 14: Partition coefficient

S.No Conc. of drug in

water (g/ml)

Conc. of drug in

n-octanal (g/ml)


(log P)

1 0.0398 0.1684 4.23

Drug – Excipient interaction by DSC Study

In the DSC spectra of Satranidazole and Eudragit L & S mixture, a sharp endothermic

peak of fusion of Satranidazole is observed at 186.92OC & 184.45OC which is

corresponding to its melting point and shows no interaction.



Fig. 6: Drug – Excipient interaction by DSC method

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