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Reagents & reactions in estimation of pharmaceuticals


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Reagents are used for the qualitative and quantitative determination of the pharmaceutical preparations, as they react with particular groups and increase their detectability by impart colour to the compounds.

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Reagents & reactions in estimation of pharmaceuticals

  1. 1. Reagents and Reactions E. Udaya Rajitha I M. Pharmacy 1
  2. 2. CONTENTS  Introduction  Reactions  Reagents  Preparation  Mechanism  Applications 2
  3. 3. Introduction Reagents are used for the qualitative and quantitative determination of the pharmaceutical preparations, as they react with particular groups and increase their detectability by impart colour to the compounds. 3 Reaction Reagent Diazo coupling reaction BM Oxidative coupling reaction MBTH Condensation reaction PDAB, PDAC Oxidation / Reduction reaction FC
  4. 4. 4 Preparation: 100mg of BM reagent powder 100ml of mixture [ acetone : water (7:3) ] Keep in dark place & protect from light Mechanism: Diazotization Coupling BM reagent: The compounds which contains primary aromatic amine groups are react with the BM regent and form red colour azo dye which shows λmax at 550nm. Diazo coupling reaction:
  5. 5. Diazotization: 5 NaNO2 HCL HNO2 HNO2 NH2 + 0-50C + Aromatic Ammonium molybdate+ Diazonium salt NHCH2 CH2 NH2 Diazonium salt + Red azo dye Coupling: BM reagent
  6. 6. Applications: 6 Analysis of sulphonamides, paracetamol, dapsone, isoniazid, procainamide, nifidipine, metronidazole…etc., OH N NCl NHCH2 CH2 NH2 NHCH2 CH2 NH2 N OHN + + Analysis of Paracetamol: OH NHCOCH3 OH NH2 NaNO2 +HCL OH N NCl Hydrolysis + Paracetamol Step:1 Para amino phenol Diazonium salt Step:2 BM reagent Red azo dye
  7. 7. 7 Oxidative coupling reaction: MBTH reagent: Compounds like phenols, amines, aldehydes, indoles, catechol amines reacts with the MBTH reagent and forms orange-red colour product. Preparation: 200mg of MBTH in 100ml of water It gives 0.2% strength Mechanism: Oxidation Coupling
  8. 8. 8 CH3 S N-NH2 N FeCl3 /CAS CH3 S N-NH N + CH3 S N-NH N OH CH3 S N N-N O + + Oxidation: Coupling: MBTH reagent Phenol Red azo dye
  9. 9. 9 CH3 S N-NH2 N FeCl3 /CAS CH3 S N-NH N + CH3 S N N-N CH3 S N-NH N HCHO C H H + + Applications: Analysis of aldehydes, indoles, carbazoles, nimesulide, diclophenac, oxiphenbutazole, primaquine, metronidazole…etc., Analysis of Formaldehyde: Step:1 Step:2 MBTH reagent Red azo dye Formaldehyde
  10. 10. Condensation reaction: 10 PDAB reagent: Compounds like primary aromatic amines, primary alkyl amines and compounds contains phenolic –OH groups react with the PDAB reagent and give yellow colour product. Preparation: Dissolve 125mg of PDAB reagent cool 65ml of conc.H2SO4, 35ml of water
  11. 11. Mechanism: 11 NC O H CH3 CH3 NC CH3 CH3 H Ar-NAr-NH2 H2 SO4 + Schiff's base formation: PDAB form coloured condensation products with primary aromatic amines in the presence of conc.H2SO4. Here C=O is converted to C=N. PDAB reagent Schiff's base
  12. 12. 12 NC O H CH3 CH3 NHNH2 NC CH3 CH3 NHN H + Analysis of phenyl hydrazine: Applications: Determination of phenyl hydrazine, nimesulide, nifidipine, indole and pyrrole derivatives, amoxicillin, metronidazole and estimation of urobilinogen…etc., PDAB reagent Phenyl hydrazine Schiff's base
  13. 13. Oxidation / Reduction reaction: 13 FC reagent: 10gm of sodium tungstate + 2.5gm of sodium molybdate add 70ml of water and 10ml of conc.HCl add 5ml of 80% phosphoric acid and 15g of lithium sulphate reflux for 10 hrs Add 5ml of water and 1 drop of bromine reflux for 15 min Cool to room temperature Preparation:
  14. 14. 14 FC reagent is a oxidising agent, so it itself reduces and oxidise the analyte, probably drug effects reduction of 1 or more oxygen atoms from tungstate or molybdate in the FC reagent, there by producing one or more possible reduced species which have characteristic intense blue colour. Mechanism: Drug + FC reagent Molybdenum blue / Tungstic green Alkali
  15. 15. Applications: 15 Estimation of Omeprazole, Aceclofenac, assay of Folic acid, Acyclovir, Diclofenac, Antibiotics…etc., + Omeprazole FC reagent ↓ Na2CO3 Blue colour complex
  16. 16. 16 Other reagents: • Folins reagent • Gibbs reagent • NBS • FeCl3, Potassium ferri cyanide, 1,10- Phenanthroline • Froehde Reagent • 4-(Dimethylamino) Cinnamaldehyde • Phosphomolybdic acid • Zwikker Reagent
  17. 17. 17 Common applications: Reagents Drugs BM, MBTH Procainamide BM, PDAB Nifidipine, Sulphonamides, Metronidazole PDAB, MBTH Indole, Nimesulide MBTH, Gibb’s Vitamin B6 Folins, PDAB, NBS Amoxicillin BM, NBS, FeCl3, K.Fe(CN)6, 1,10-phenanthroline Paracetamol PDAB, MBTH, FC, FeCl3, K.Fe(CN)6, 1,10-phenanthroline Diclofenac
  18. 18. Conclusion 18
  19. 19. References: 19 • Text book of pharmaceutical analysis by P. D. Chaithanya sudha, chapter VII (Reagents), Pg. no. 348-369. • A review article on Chemical derivatization methodologies for Uv‐Visible Spectrophotometric determination of pharmaceuticals by Olajire A. Adegoke. • A review article on Role of Chemical and Analytical Reagents in Colorimetric Estimation of Pharmaceuticals by K. Sushma, Somsubhra Ghosh et al.,
  20. 20. THANK YOU 20