pharmaceutical reagents

1. PRINCIPLES & PROCEDURES INVOLVED IN
USAGE OF REAGENTS IN PHARMACEUTICAL
ANALYSIS
Presented By
Y.Divya
M.Pharmacy First year-I sem
SPMVV

2. CONTENTS
• Introduction to reagents
• Reagents
a) PDAB
b)Folin Ciocalteau
c)MBTH
• Reagent Profile
• Principle & Mechanism
• Procedure
• Examples
• Applications
• Conclusion
• References

3. oThe Reagents are mainly used for qualitative & quantitative analysis.
oThere are a number of reagents which are mainly used for determination
of pharmaceuticals.
•MBTH
•2,4,6-tripyridyl-S-
thiazine(TPTZ)
•1,2-naphthaquinone-4-sulphonate
sodium(NQS)
•PDAB/PDAC
•Ninhydrin reagent
•Bratton marshall reagent
•Folin ciocalteau reagent
•Gibb’s reagent
INTRODUCTION

4. •It is an aromatic compound and chromogenic in nature.
•Used for colorimetric estimation of amine group containing drugs.
Reagent Profile:
Synonym : Ehrlich’s reagent
IUPAC Name : 4-(dimethyl amino)-benzaldehyde
Molecular Formula : C9H11NO
Molecular Weight : 149.9
Color : White or offwhite
Solubility : soluble in alcohol, 0.1N HCl, water

5. The primary amine group which is present in the structure of
drug reacts with carbonyl group in the PDAB reagent and
forms schiff base which can be measured colorimetrically.
The principle in the formation of schiff’s base is nucleophilic
addition reaction. Here the nucleophile is amine group.

6. General Reaction
•More suitable for amines
oximes.
•NH2, NR2, NR3 are strong auxochromes.
•But in aromatic compounds it is 100% colored.

7. Example:

9. Preparation Of PDAB Reagent:
To 400mg of PDAB
+2ml of conc H2SO4
+10ml alcohol
Finally, make upto 100ml
with distilled water

10. PROCEDURE:
1. Stability of color
2. Optimisation of reagent concentration and volume
3. Quantification methods:
o Calibration plot by
Interpolation
Regression
y=mx + c
o Single point standardization
o Double point standardization

11. 1. Stability of color:
The color formation depends upon:
PH
Temperature
Catalyst
In case of PDAB, color formation is more favourable in acidic PH
Conc of drug
10-50mcg/ml
X conc of
reagent
Colored compound.
Mini stability:
30min
Max stability: 1hr
Time(min)
Opticaldensity

12. 2.Optimization Of Reagent Concentration And
Volume:
•The point beyond which there is no change in OD, corresponding to
the volume of reagent is optimized volume of reagent.
•Preferably it is below 3ml.
•Here conc of drug & % strength of reagent is kept constant.
•Where as for optimized concentration of reagent, volume of reagent
and conc of drug are kept constant
OD
Vol. of reagent (ml)
OD
Conc of reagent (mcg/ml)

13. 3.Quantification Procedure:
a) Calibration Plot by:
Interpolation
Regression
y = mx + c
b) Single point standardization:
c) Double point standardization:

14. Applications Of PDAB Reagent
PDAB reagent is used in:
•Micro determination of urea in urine
samples.
•Detection of sulphonamides
Amines
Ergot alkaloids
•Used as TLC stain.
•Used for spectrophotometric determination
of Ranitidine, Chloramphenicol,
Metronidazole, Sulphamethoxazole.

15. Example:
Estimation of Chloramphenicol in given
pharmaceutical formulation:
Principle:
The aromatic nitro group present in the
chloramphenicol is reduced to aromatic amine
group by refluxing with zinc dust in presence of
HCl for 10mins.
The resultant amine group of chloramphenicol
reacts with the carbonyl group of PDAB reagent
and forms schiff base that is estimated
colorimetrically at 441nm.

16. Reaction:

17. PPn of stock soln
•To100 mg ofdrug
•+500mg of zinc dust
+2ml of 5N HCl,
boil for 30mins
•Filterate was made
upto 10ml with
methanol
Determination
of λmax
• Pipette out 0.1ml
from stock soln +
2ml of PDAB
reagent
• Make upto 10ml
with methanol
•Scan from 400-
800nm, and λmax
was found to be at
441nm
PPn of
calibration std
•From stock pipette
out 0.5, 1.5, 2.0, 2.5
ml
•+2ml of PDAB
reagent
•Make upto 10ml
with methanol

18. Assay Of Chrloramphenicol Capsules
To 100mg of capsule powder
+500mg of Zinc dust
+2ml of 5N HCl, boil for 30mins
Cool & make to 100ml with
methanol & filter
From filterate 1ml was
pipetted out
+2ml of reagent
Make to 10ml with methanol,
measure abs at 441nm
PPn of stock soln Ppn of test sample

19. •Chemically it is Phosphomolybdotungistic acid
•Also known as hetero polyacids
•Used for colorimetris estimation of drugs containing phenols or
amines
•It consists of:
•Sodium tungstate
•Sodium molybdate
•85% Phosphoric acid
•Lithium sulphate
•Bromine

20. Reagent Profile:
Synonym : Phosphomolybdotungistic acid
Color : Clear bright yellow
Storage : Tightly capped at RT. The can be
diluted with deionized water
1 Hexavalent phosphomolybdotungistic acid complexes with the
following structures formed in the solution.
3H2O.P2O5 13WO3. 5MoO3. 10H2O
3H2O xP2O5. 14WO3. 4MoO3. 10H2O

21. Cool to RT, make to 100ml with water
+15g Lithium sulphate +5ml water + 1drop Bromine, reflux
for 15min
+5ml 85% Phosphoric acid + 10ml Conc HCl, Reflux for
1ohr.
Dissolve 10g Sodium tungstate and 2.5g sodium molybdate in
70ml water

22. Orthophosphoric
acid
Converted to
peiodic/ vanaldic
acid, molybdic acid
Results in Heteroyl
acid mixture
Undergoes
reduction if analyte
has oxidizing nature
Molybdenum
Blue
Estimated
colorimetrically at
400-800nm

23. APPLICATIONS OF FC REAGENT
•Used as spray reagent in many chromatographic
procedures.
•Used in Lowry method for determining protein
concentration.
•It is also reactive towards thiols and many vitamins.
•Several drugs like:
Aspirin
Piroxicam
Acetazolamide
Sparfloxacin
Pyridoxine HCl
are estimated using this FC reagent

24. Example:
Estimation of Omeprazole in given pharmaceutical formulation
Principle:
Omeprazole affects reduction of 1, 2 & 3 oxygen atoms from tungstate and
molybdate in Fc reagent, thereby producing one or more of possible reduced
species which have a characteristic blue color, that can be estimated
colorimetrically at 742nm
+
3H2O.P2O5 13WO3. 5MoO3. 10H2O
3H2O xP2O5. 14WO3. 4MoO3. 10H2O
Blue colored complex

25. Preparation Of Standard Stock Solution
To 100mg of crude drug + 10ml of 0.1N NaOH, made upto 100ml
with distilled water (1000mcg/ml) SOLUTION -1
From above solution, pippete out 10ml and make to 100ml with distilled
water(100mcg/ml) SOLUTION-2
From solution-2 pipette out 0.2, 0.8, 1.4, 2.0, 2.6 ml of solution +
2ml of Fc reagent + 9ml of sod. Carbonate, make to 25ml with
distilled water
Keep aside for 10mins. Measure Abs at 742 nm

26. Assay Of Omeprazole Capsules:
Weight of powder equivalent to 10mg was dissolved in 10ml
0f sodium hydroxide solution
From above solution pipette out 2ml and add 2ml of FC
reagent, 9ml of Sod. Carbonate, make to 25ml with distilled
water
Keep aside for 10mins. Measure absorbance at 742nm

27. MBTH is a chromogenic reagent used for colorimetric
estimation of drug containing phenolic, aromatic amines
and active methylene groups

28. Reagent Profile:
IUPAC name : 3-methyl-2-
benothiazolinone hydrazone
Molecular Formula : C8H10N3S. H2O
Molecular Weight : 233.72
Color :White to half white powder
Solubility : freely soluble in distilled water

29. MBTH first reacts with aldehydes to form azine. Only if there is
remaining MBTH, it is oxidized to another species which combines
with the azine to form formazan.
However if there is enough aldehyde, all the MBTH is converted to
azine and there is no formation of blue color.
Thus by using the limiting agent MBTH, the amount of aldehyde
can be tested.
Less aldehyde produce more blue color
More aldehyde produce less blue color

30. With Phenols
With phenols under suitable conditions MBTH loses two
electrons and one proton to form the electrophilic intermediate.
This undergoes electrophilic substitution with phenols and other
groups to form the colored product
Mechanism Involved
1. Oxidative coupling
2. Dehydration

31. Oxidative Coupling Reactions:
Step-I
Formation of oxidation form of MBTH as an
Intermediate

32. STEP-2
Formation Of ColoredComplexes:
a) Reaction With Aldehydes:

33. b) Reaction With Phenols
CH3

34. c) Reaction with Amines:

35. a) Reaction With aldehydes:

36. b) Reaction With Citrals:

37. •Applicable for analysis of drinking surface and saline
water, industrial and dosmetic water
•Applicable for measuring Phenolic material at
2mcg/ml.
•Used for determination of drugs like acylovir,
ceftazidine, cefadroxil, nicorandil, methyldopa etc.,
•Used for estimation of samples that contain high
conc of aldehydes Eg: Disinfectants
Applications of MBTH Reagent:

38. Example
Estimation of Lamotriginein givenpharmaceutical formulation
Principle:
The principle involved in this method is Ion catalysed coupling reaction
of MBTH. In presence of FeCl3, MBTH loses 2 electrons and one
proton forming an electrophilic intermediate and which is proton active
coupling species.
The intermediate formed undergoes electrophilic substitution with the
drug to form green colored product, that is estimated colorimetrically
at 663nm.

40. PPn of stock soln
• Dissolve 100mg of
crude drug in 100ml of
methanol(100mcg/ml)
Construction of
calibration curve
• From std soln pipette
out 0.2, 0.4, 0.6, 0.8 ml
• +2ml of 0.2%
MBTHreagent +2ml of
0.2% FeCl3
• Keep aside for 20mins
• Make upto 10ml with
distilled water
• Measure abs at 663nm
Procedure

41. Assay Of Lamotrigine Tablets
Dissolve equivalent to 10mg powder in 10ml methanol
From above solution 60mcg/ml of solution was taken, to
this +2ml of 0.2% MBTH +2ml of 0.2% FeCl3. Allow
to stand for 20mins
Make up the volume to 10ml with distilled water.
Measure absorbance at 663nm

42. Conclusion….
Here by it can be concluded that
when reagents are used in optimized
volume and optimized concentration
they be successfully used for the
estimation of drugs in
pharmaceutical preparations both
quantitatively and qualitatively

43. 1. Textbook of Pharmaceutical analysis by P.D.Chaithanya Sudha
2. Peterson, G.L., Anal. Biochem. 100, 201-220 (1979).
3. Bray, H.G., and Thorpe, W.V., Meth. Biochem. Anal. 1, 27-52
(1954).
4. Lowry, O.H., et al., Protein measurement with the Folin phenol
reagent J. Biol. Chem. 193, 265-275 (1951)
5. Eberhardt et al. (1985) Marine Chemistry vol. 17: 199–212