Chapter 4 Identification of Drugs

Nilam Patel PhD Thesis 65

Title Section Page No.

4.1 Identification of cilnidipine 66

4.2 Identification of telmisartan 68

4.3 Identification of azelnidipine 70

4.4 Identification of olmesartan 72

4.5 Identification of ambrisentan 74

4.6 Identification of tadalafil 76

4.7 Results 78

4.8 References 79

Chapter 4 Identification of Drugs

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4.1 Identification of cilnidipine

4.1.1 Melting range determination

Cilnidipine melting range was found to be 115-116°C.

4.1.2 Determination of λmax by UV spectroscopy

4.1.2.1 Standard stock solutions

Standard stock solution was prepared by dissolving 10 mg of cilnidipine working

standard in to separate 100 mL of methanol to get concentration of 100 µg. Aliquots

of stock solutions were further diluted with methanol to get working solution of 10

µg/mL and the working standard was scanned between 200-400 nm to find λmax of

solution.

Figure 4.1: UV absorption maxima of cilnidipine

4.1.3 Characterization by IR spectroscopy

4.1.3.1 Standard Pellet Preparation

First of all grind a quantity of the working standard with a specially purified salt potassium

bromide finely. This powder mixture is then pressed in a mechanical die press to form a

translucent pellet through which the beam of the spectrometer can pass.

Chapter 4 Identification of Drugs

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Figure 4.2: FTIR spectrum of cilnidipine

Table 4.1: Characteristic peaks of cilnidipine

Functional group FTIR frequency (cm-1)

Theoretical peak

FTIR frequency (cm-1)

Practical peak

Aromatic 2°amine (N-H

stretch) ~3450 3458

C-N (Aromatic 2°amine,

CN stretch) 1370-1280 1376

Nitro(-N-O) 1355-1320 1349

Methoxy (-OCH3) 2850-2815 2801

Chapter 4 Identification of Drugs

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4.2 Identification of telmisartan

4.2.1 Melting range determination

Telmisartan melting range was found to be 115-116°C.

4.2.2 Determination of λmax by UV spectroscopy

4.2.2.1 Standard stock solutions

Standard stock solution was prepared by dissolving 10 mg of telmisartan working

standard in to separate 100 mL of methanol to get concentration of 100 µg. Aliquots

of stock solutions were further diluted with methanol to get working solution of 10

µg/mL and the working standard was scanned between 200-400 nm to find λmax of

solution.

nm.

200.00 250.00 300.00 350.00 400.00

Ab

s.

2.108

2.000

1.500

1.000

0.500

0.000

-0.191

Figure 4.3: UV absorption maxima of telmisartan

4.2.3 Characterization by IR spectroscopy

4.2.3.1 Standard Pellet Preparation

First of all grind a quantity of the working standard with a specially purified salt potassium

bromide finely. This powder mixture is then pressed in a mechanical die press to form a

translucent pellet through which the beam of the spectrometer can pass.

Chapter 4 Identification of Drugs

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Figure 4.4: FTIR spectrum of telmisartan

Table 4.2: Characteristic peaks of telmisartan

Functional group FTIR frequency (cm-1)

Theoretical peak

FTIR frequency (cm-1)

Practical peak

Carboxylic acid 1750-1700 1762

-O-H stretch(-CO stretch

in carboxylic acid 3300-2500 2807

Aromatic 3°amine (N-H

stretch) 3500-3300 3311

C-N (Aromatic 3°amine,

CN stretch) 1360-1310 1349

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4.3 Identification of azelnidipine

4.3.1 Melting range determination

Azelnidipine melting range was found to be 115-116°C.

4.3.2 Determination of λmax by UV spectroscopy

4.3.2.1 Standard stock solutions

Standard stock solution was prepared by dissolving 10 mg of azelnidipine working

standard in to separate 100 mL of methanol to get concentration of 100 µg. Aliquots

of stock solutions were further diluted with methanol to get working solution of 10

µg/mL and the working standard was scanned between 200-400 nm to find λmax of

solution.

nm.

200.00 250.00 300.00 350.00 400.00

Ab

s.

2.216

2.000

1.500

1.000

0.500

0.000

-0.203

Figure 4.5: UV absorption maxima of azelnidipine

4.2.3 Characterization by IR spectroscopy

4.2.3.1 Standard Pellet Preparation

First of all grind a quantity of the working standard with a specially purified salt potassium

bromide finely. This powder mixture is then pressed in a mechanical die press to form a

translucent pellet through which the beam of the spectrometer can pass.

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Figure 4.6: FTIR spectrum of azelnidipine

Table 4.3: Characteristic peaks of azelnidipine

Functional group FTIR frequency (cm-1)

Theoretical peak

FTIR frequency (cm-1)

Practical peak

Aromatic 3°amine (N-H

stretch) 3500-3300 3315

C-N (Aromatic 3°amine,

CN stretch) 1360-1310 1378

Aromatic 2°amine (N-H

stretch) ~3450 3182

C-N (Aromatic 2°amine,

CN stretch) 1370-1280 1391

Nitro(-N-O) 1355-1320 1351

Ester 1750-1725 1715

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4.4 Identification of olmesartan

4.4.1 Melting range determination

Olmesartan melting range was found to be 115-116°C.

4.4.2 Determination of λmax by UV spectroscopy

4.4.2.1 Standard stock solutions

Standard stock solution was prepared by dissolving 10 mg of olmesartan working

standard in to separate 100 mL of methanol to get concentration of 100 µg. Aliquots

of stock solutions were further diluted with methanol to get working solution of 10

µg/mL and the working standard was scanned between 200-400 nm to find λmax of

solution.

nm.

200.00 250.00 300.00 350.00 400.00

Ab

s.

1.228

1.000

0.500

0.000

-0.116

Figure 4.7: UV absorption maxima of olmesartan

4.4.3 Characterization by IR spectroscopy

4.4.3.1 Standard Pellet Preparation

First of all grind a quantity of the working standard with a specially purified salt potassium

bromide finely. This powder mixture is then pressed in a mechanical die press to form a

translucent pellet through which the beam of the spectrometer can pass.

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Figure 4.8: FTIR spectrum of olmesartan

Table 4.4: Characteristic peaks of olmesartan

Functional group FTIR frequency (cm-1)

Theoretical peak

FTIR frequency (cm-1)

Practical peak

Aromatic 3°amine (N-H

stretch) 3500-3300 3301

C-N (Aromatic 3°amine,

CN stretch) 1360-1310 1345

Aromatic 2°amine (N-H

stretch) ~3450 3401

C-N (Aromatic 2°amine,

CN stretch) 1370-1280 1378

C=O stretch 1760-1690 1612

Cyclic C-O-C 1140-1070 1109

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4.5 Identification of ambrisentan

4.5.1 Melting range determination

Ambrisentan melting range was found to be 115-116°C.

4.5.2 Determination of λmax by UV spectroscopy

4.5.2.1 Standard stock solutions

Standard stock solution was prepared by dissolving 10 mg of ambrisentan working

standard in to separate 100 mL of methanol to get concentration of 100 µg. Aliquots

of stock solutions were further diluted with methanol to get working solution of 10

µg/mL and the working standard was scanned between 200-400 nm to find λmax of

solution.

nm.

200.00 250.00 300.00 350.00 400.00

Ab

s.

1.764

1.500

1.000

0.500

0.000

-0.182

Figure 4.9: UV absorption maxima of ambrisentan

4.5.3 Characterization by IR spectroscopy

4.5.3.1 Standard Pellet Preparation

First of all grind a quantity of the working standard with a specially purified salt potassium

bromide finely. This powder mixture is then pressed in a mechanical die press to form a

translucent pellet through which the beam of the spectrometer can pass.

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Figure 4.10: FTIR spectrum of ambrisentan

Table 4.5: Characteristic peaks of ambrisentan

Functional group FTIR frequency (cm-1)

Theoretical peak

FTIR frequency (cm-1)

Practical peak

Aromatic 3°amine (N-H

stretch) 3500-3300 3368

O-H stretch 3300-2500 2925

C-N (Aromatic 3°amine,

CN stretch) 1360-1310 1348

C-O-C (alkyl substituted

ether, C-O stretch) 1150-1050 1119

Carboxylic acid 1725-1650 1685

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4.6 Identication of tadalafil

4.6.1 Melting range determination

Tadalafil melting range was found to be 115-116°C.

4.6.2 Determination of λmax by UV spectroscopy

4.6.2.1 Standard stock solutions

Standard stock solution was prepared by dissolving 10 mg of tadalafil working

standard in to separate 100 mL of methanol to get concentration of 100 µg. Aliquots

of stock solutions were further diluted with methanol to get working solution of 10

µg/mL and the working standard was scanned between 200-400 nm to find λmax of

solution.

nm.

200.00 250.00 300.00 350.00 400.00

Ab

s.

1.865

1.500

1.000

0.500

0.000

-0.157

Figure 4.11: UV absorption maxima of tadalafil

4.6.3 Characterization by IR spectroscopy

4.6.3.1 Standard Pellet Preparation

First of all grind a quantity of the working standard with a specially purified salt potassium

bromide finely. This powder mixture is then pressed in a mechanical die press to form a

translucent pellet through which the beam of the spectrometer can pass.

Chapter 4 Identification of Drugs

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Figure 4.12: FTIR spectrum of tadalafil

Table 4.6: Characteristic peaks of tadalafil

Functional group FTIR frequency (cm-1)

Theoretical peak

FTIR frequency (cm-1)

Practical peak

Aromatic 3°amine (N-H

stretch)

3500-3300 3449

C-N (Aromatic 3°amine,

CN stretch)

1360-1310 1348

Aromatic 2°amine (N-H

stretch)

~3450 3513

C-N (Aromatic 2°amine,

CN stretch)

1350-1280 1350

Amide 1680-1630 1578

C=O stretch 1760-1690 1635

Cyclic C-O-C 1140-1070 1124

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4.7 Results

Table 4.7: Result of identification tests for drugs

Drugs Parameter Literature

reporting

Observation/

Comment

Cilnidipine

Melting point (°C) 115.5-116.5 115.5-116.5

λmax (nm) 240.2 Complies

IR spectra Peak matches Complies

Telmisartan

Melting point (°C) 261-263 261-262

λmax (nm) 296 Complies

IR spectra Peak matches Complies

Azelnidipine

Melting point (°C) 122-123 122-123

λmax (nm) 255.6 Complies

IR spectra Peak matches Complies

Olmesartan

Melting point (°C) 180-182 180-181

λmax (nm) 256.4 Complies

IR spectra Peak matches Complies

Ambrisentan

Melting point (°C) 190-191 190-191

λmax (nm) 266 Complies

IR spectra Peak matches Complies

Tadalafil

Melting point (°C) 302-303 302-303

λmax (nm) 284.2 Complies

IR spectra Peak matches Complies

Chapter 4 Identification of Drugs

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4.8 References

1. Silverstein RM, Bassler GC, Morrill TC. Spectrometric identification of organic

compounds. 4th ed. New York: John Wiley and Sons. 1981, 272.S5-S6

2. John Coates. Interpretation of Infrared spectra, a practical approach. Encyclopedia in

Analytical Chemistry. New York: John Wiley and Sons. 2000, 10815-10837