Category Archives: First semester

INDIAN PHARMACOPOEIA

Introduction to Pharmacopoeia

—The term Pharmacopoeia is derived from a Greek word Pharmakon meaning drug and Poietn meaning make. So, Pharmacopoeia is defined as any receipe or formula or other standard required to make or prepare a drug.

—In the united states, the first Pharmacopoeia was published in December 1820.

—The first International Pharmacopoeia was published by the World Health Organization in 1951 (volume I) and in 1955 (volume II).

—A Pharmacopoeia is issued under the authority of the Govt. of a country. The countries which have not developed their own Pharmacopoeias allow the standards laid down by Pharmacopoeias of some other countries.

—Indian Pharmacopoeia is the authorized book of standards in India but other Pharmacopoeias have also been recognized under the drugs and cosmetic rules.

—In addition, the Govt. of India also publishes the Ayurvedic and the Homeopathic Pharmacopoeias.

Indian Pharmacopoeia

—Indian Pharmacopoeia Commission (IPC) is an autonomous institution of the Ministry of Health and Family Welfare which sets standards for all drugs that are manufactured, sold and consumed in India.

—The set of standards are published under the title Indian Pharmacopoeia (IP) which has been modelled over and historically follows from the British Pharmacopoeia.

—The first edition of Pharmacopoeia of India was published in 1955.

—The second edition of Pharmacopoeia of India was published in 1966  and later on its supplement was published in 1975.

—The third edition of Indian Pharmacopoeia was published in 1985 by Govt. of India.

—The fourth edition was published by Govt. of India in 1996.

—The fifth edition of Indian Pharmacopoeia was published in 2007 by Govt. of India and later amended in 2008.

—The sixth edition of Indian Pharmacopoeia was published in 2010 by Govt. of India and later amended in 2012.

—The latest Indian pharmacopoeia is the seventh edition i.e. IP 2014. The Pharmacopoeia 2014 was released by Health Minister Ghulam Nabi Azad on November 4, 2013.

Description about the IP-2014, VII edition

—The IP 2014 is presented in four volumes.

—The IP 2014 incorporates 2548 monographs of drugs out of which 577 are new monographs consisting of APIs, excipients, dosage forms and herbal products etc., 313 new monographs on drug substances, dosage forms and pharmaceutical aids (A to Z) , 43 new drug substances monographs, 10 antibiotic monographs, 31 herbal monographs, 05 vaccines and immunosera for human use, 06 insulin products, 07 Biotechnology products etc. along with the 19 new general chapters. 19 new radiopharmaceutical monographs and 01 general chapter is first time being included in this edition.

PRACTICAL-ASSAY OF AMMONIUM CHLORIDE BY ACID BASE TITRATION

Object – To perform the assay of Ammonium chloride by acid base titration

Reference – 1. Siddiqui A.A. & Ali M., Practical Pharmaceutical Chemistry, CBS publishers and distributors, New Delhi, I edition, 1997, 22-23

  1. Rao G.D., Practical pharmaceutical analysis, Birla publications Pvt. Ltd., Delhi, II edition, 2007-08, 33

Glasswares & apparatus required – digital balance, pipette, burette, burette stand, conical flask

Chemicals required – ammonium chloride, distill water, formaldehyde solution, phenolphthalein indicator, sodium hydroxide solution

Theory – Acid base titration or neutralization titration involves neutralization of acid with base or base with acid and the end point is determined by means of indicator.

Acidimetry titration – it is a direct or residual volumetric analysis of a base with a standard acid. Direct titration is performed by introducing a standard acid solution gradually from a burette into a solution of base being assayed till the end point is obtained e.g. assay of sodium bicarbonate. Residual titration is used when the rate of reaction between a basic compound with an acid is slow. In this, the solution of the base is treated with an excess of accurately measured standard acid and excess acid is subsequently titrated with standard base e.g. assay of zinc oxide.

Alkalimetry titration – it is an estimation of acid/acidic drugs by titration with standard alkali. It also includes direct titration and residual/back titration methods as in acidimetry. Assay of ammonium chloride comes under direct titration method of Alkalimetry titration.

Ammonium chloride is an example of diuretic and systemic acidifier. The assay of ammonium chloride is based on the principle of formal titration. The formal titration is done in the presence of formaldehyde. When ammonium chloride is treated with formaldehyde (HCHO), HCl is liberated. The liberated hydrochloric acid is btitrated with a standard solution of sodium hydroxide using phenolphthalein indicator.

Procedure

  1. 1 gm of ammonium chloride was accurately weighed and dissolved in 20 ml water.
  2. 5 ml formaldehyde solution was added.
  3. After two minutes, titration was started slowly with 0.1 N Sodium hydroxide (given below) solution by using phenolphthalein indicator till pink color was obtained.
Preparation of 100 ml 0.1 N NaOH
Normality Volume Amount Dissolved in
1 N 1000 ml 40 gm 1000 ml
0.5 N 1000 ml 20 gm 1000 ml
0.1 N 1000 ml 4 gm 1000 ml
0.1 N 500 ml 2 gm 500 ml
0.1 N 100 ml 0.4 gm = 400 mg 100 ml

 

The reaction involved is-

HCl + NaOH           →      NaCl + H2O

Equivalent Factor – 1 ml of 0.1 N NaOH is equivalent to 0.005349 g of NH4Cl

Observation table –

S.NO. VOLUME OF AMMONIUM CHLORIDE SOLUTION IN ML INITIAL BURETTE READING FINAL BURETTE READING VOLUMJE OF 0.1 N SODIUM HYDROXIDE CONSUMED IN ML
1 25 50 33 (suppose) 17 (suppose)

 

 

Calculation –

Percentage purity of ammonium chloride =

Volume of 0.1 N sodium hydroxide x equivalent factor x 100 x normality of sodium hydroxide (actual)

Weight of ammonium chloride in grams x normality of sodium hydroxide (expected)

17 x 0.005349 x 100 x 0.1

=   ———————————-

  • x 0.1

= 0.05349 x 17 / 0.01 = 0.909 / 0.01 = 90.9%

Result – Assay of Ammonium chloride by acid base titration was carried out and the percentage purity was found 90.9%.

PRACTICAL-TITRATION OF STRONG ACID (0.1 N HCl) WITH STRONG BASE (0.1 N NaOH) BY POTENTIOMETRY

Object – Determination of Normality by electrochemical methods [Potentiometric titration of strong acid (0.1 N HCl) against strong base (0.1 N NaOH)]

Reference – Rao G.D., Practical pharmaceutical analysis, Birla publications Pvt. Ltd., Delhi, II edition, 2007-08, 136

Materials required-

Chemicals – 0.1 N HCl, 0.1 N NaOH, Distill water

Glassware & Apparatus/Instumentation – Potentiometer or PH meter, Magnetic stirrer, burette, beaker, pipette.

Theory – Potentiometric determination of the end point depends on the fact that the potential cross the two electrodes (reference and indicator) immersed in the solution changes sharply at the equivalence or end point. This change is similar to the color change by an indicator in usual method. But the potentiometric method is more accurate. These ti0trations are useful when no suitable color indicators are available. Equivalence point can be accurately found out after plotting normal plot (i.e. volume of Titrant Vs potential).

Procedure –

  1. In a 250 ml beaker, 10 ml of 0.1 N HCl was taken and then 100 ml of water was added to it, so that the electrodes can dip properly.
  2. The beaker was now kept on magnetic stirrer.
  3. Potential was noted down without adding alkali.
  4. Now potential was noted down with adding known volume of 0.1 N NaOH Solution.
  5. Now from the obtained data, a graph was plotted between volume of titrant and potential.
  6. From the graph end point was calculated.

Observation –

S.NO. VOLUME OF TITRANT ADDED POTENTIAL
1 1 ML
2 1 ML
3 1 ML
4 1 ML
5 1 ML
6 1 ML
7 1 ML
8 1 ML
9 1 ML
10 1 ML

 

Result – The end point in the titration of strong acid (0.1 N HCl) with strong base (0.1 N NaOH) was found ……………………….

PRACTICAL-PREPARATION & STADARDIZATION OF 0.1 N SULPHURIC ACID

Object – Preparation & standardization of Sulphuric acid (0.1 N)

Reference – 1. Kasture A.V. etal, Practical Pharmaceutical Chemistry-I, Nirali Prakashan, Pune, XI edition, 2005, 47

  1. Rao G.D., Practical pharmaceutical analysis, Birla publishers Pvt. Ltd., Delhi, II edition, 2007-08, 25

Glasswares & apparatus required – Volumetric flask, burette, burette stand, pipette, conical flask, digital balance, heating mantle.

Chemicals required – standard 0.1 N sodium carbonate solution (prepared by dissolving 530 mg of sodium carbonate in 100 ml of distill water), conc. Sulphuric acid, methyl orange solution

Theory – Sulphuric acid is a diprotic acid and 1 N solution contain 98.08/2 = 49.04 g H2SO4. Taking into consideration specific gravity (1.83) of sulphuric acid about 49.0 ml of conc. Sulphuric acid is required to prepare 1000 ml solution.

It is an example of alkalimetry. When a strong acid is titrated with a strong base, the salt produced in the reaction is not hydrolysed and therefore the ph of the resultant solution at the end point is exactly 7.0. sulphuric acid is a strong acid, is standardized by titrating with a strong base i.e. sodium carbonate (primary standard). The following reaction takes place when sodium carbonate is titrated with sulphuric acid. In this titration, end point detection is carried out by using methyl orange indicator.

Procedure –

In a volumetric flask, 4.9 ml of conc. Sulphuric acid was taken and 900 ml water was slowly added, cooled and then the volume was made upto 1000 ml with water.

Standardization –

  1. 10 ml of 0.1 N Sodium carbonate solution was pipette out into a clean and dried conical flask.
  2. 2 drops of methyl orange indicator was added to it.
  3. The contents of the flask was now titrated with sulphuric acid until red color was obtained.
  4. Burette reading was taken.

Observation table –  

S.NO. VOLUME OF 0.1 N SOD. CARBONATE SOLUTION TAKEN INITIAL BURETTE READING FINAL BURETTE READING VOLUME OF 0.1 N SULPHURIC ACID CONSUMED
1 10 ML 50 38 12 (SUPPOSE)

 

 

Calculation – Normality of H2SO4  is calculated by-

N1V1 = N2V2

N1 = 0.1 N = Normality of Na2CO3 Solution, N2 = ? = Normality of H2SO4

V1 = 10 ml = Volume of Na2CO3 Solution, V2 = 30 ml = Volume of H2SO4

0.1 X 10 = N2  X 12

Or N2 = 1 / 12 = 0.08 N

Result – Sulphuric acid (0.1 N) was prepared and standardized. The exact normality was found to be 0.08 N

COMMUNICATION, COMMUNICATION PROCESS, IMPORTANCE OF COMMUNICATION, FEEDBACK

COMMUNICATION –

Communication is derived from a Latin word ‘communicare’ which means to share or to give. So, communication is defined as the process of transferring or exchange of information from one source to another or from one person to another. Transfer of information includes emotions, values and feelings. Communication is a continuous process, there may be a time gap but it never stops. Communication is a process of exchange of messages both verbal and non-verbal. The basic requirement of communication is message. Message must be conveyed to the recipient through some medium. It is essential that the message must be understood be the recipient in the same terms as intended by the sender. The communication is a two way process and is incomplete without a feedback from the recipient to the sender on how well the message is understood by him.

DEFINITIONS OF COMMUNICATION-

  1. William Newman defined communication as – ‘communication is exchange of facts, ideas, opinion or emotions by two or more persons’.
  2. Keith & Davis defined communication as – ‘communication is the process of passing information and understanding from one person to another person.

IMPORTANCE OF COMMUNICATION-

  1. To present yourself in a better way.
  2. To develop good interpersonal relation.
  3. To prove yourself the best amongst all in a highly competitive environment.
  4. To transfer the information
  5. To deal with complexity of technical information
  6. A tool to get job
  7. Essential to job success
  8. For motivating counseling
  9. To impart education
  10. To impart education
  11. To improve discipline
  12. To receive messages
  13. To provide advice
  14. To issue order and instructions
  15. To facilitate coordination
  16. To establish effective leadership
  17. For job satisfaction
  18. To develop democratic environment in any organization.

THE COMMUNICATION PROCESS –

Flow chart below shows the process of communication

The goal of communication is to convey information and the understanding of that information from one person or group to another person or group. This communication process is divided into three basic components – sender, channel and receiver.

The above flow chart shows a sender transmits a message through a channel to the receiver. The sender first develops an idea which is composed into a message and then transmitted to the other party who interprets the message and receives meaning. Developing a message is called encoding and interpreting the message is called decoding.

FEEDBACK –   When two people interact, communication is rarely one-way only. When a person receives a message, she responds to it by giving a reply. Otherwise, the sender can’t know whether the other parties properly interpreted the message or how they reacted to it. Example – The supervisor has to know how subordinates respond to directives and plans.

REFERENCE-

  1. Pandey M., Communication skills, Nirali prakashan, Pune, I edition, 2017, 1.1-1.6
  2. www.cliffsnotes.com

PRACTICAL-INORGANIC CHEMISTRY-LIMIT TEST OF SULPHATE

Object – To perform the limit test for Sulphate as per I.P..

Reference – Sharma N. etal, Practical Inorganic Pharmaceutical Chemistry & Viva voce, Birla publications Pvt. Ltd., Delhi, I Edition, 2007-08, 96.

Materials required –

Chemicals – Barium sulphate reagent, dilute hydrochloric acid, Sodium Chloride, Potassium sulphate, Distill water

Glasswares & Apparatus – Nessler cylinder, Measuring cylinder, Pipette, Glass rod, Spatula, Weighing balance

Theory – Limit tests are quantitative or semi quantitative tests designed to identify and control small quantities of impurity which are likely to be present in the substance. The limit tests for sulphates is based on the reaction between sulphate and barium chloride in presence of hydrochloric acid.

Reaction involved-

BaCl2 + So42-  →  BaSO4 + 2Cl

Hydrochloric acid prevents precipitation of other acid radicals with barium chloride, and in presence of hydrochloric acid only sulphate get precipitated. The turbidity produced in each nessler cylinder was compared transversely. If the turbidity from the sample is less than the standard turbidity, the sample will pass the limit test and vice versa.

Fig : Nessler cylinder

Procedure –

Test solution –

  1. First of all, cleaned and dried Nessler cylinder was taken.
  2. In the Nessler cylinder, 2 gram of sample (NaCl) was taken.
  3. Then, 2 ml of dilute hydrochloric acid was added to it.
  4. Now, 45 ml with water was added.
  5. Then, 5 ml of Barium sulphate reagent was added.
  6. It was stirred well.
  7. Finally it was kept aside for 5 minutes and then turbidity or opalescence was observed.

Standard solution –

  1. First of all, cleaned and dried Nessler cylinder was taken.
  2. In the Nessler cylinder, 1 ml of 0.01089% w/v solution of potassium sulphate and 9 ml of distill water was taken.
  3. Then, 2 ml of dilute hydrochloric acid was added to it.
  4. Now, 45 ml with water was added to it.
  5. Then, 5 ml of barium sulphate reagent was added.
  6. It was stirred well.
  7. Finally it was kept aside for 5 minutes and then turbidity or opalescence was observed.

Inference –

  1. Turbidity of test solution > turbidity of standard solution – test failed
  2. Turbidity of test solution < turbidity of standard solution – test passed
  3. Turbidity of test solution = turbidity of standard solution – test passed

Result – On comparing the turbidity / Opalescence of test solution and standard solution, it was found that the turbidity of test solution is…………………………….. (more than/ less tan / equal to) the standard solution. Hence the sample ……………………………..(passed / failed) the limit test for sulphate.

PRIMARY AND SECONDARY STANDARDS

PRIMARY AND SECONDARY STANDARD

INTRODUCTION

In life, we always hear and use the word ‘standard’ e.g. the standard of rail service or the standard of education. What is the meaning of this word? Here we will discuss the standard, its types and properties and its uses.

STANDARDS

In pharmaceutical analysis, the word standard means a material which contains a substance of our interest with a known concentration. By using definite numbers with proper units we can express this. By using this standard we can determine the concentration of that substance in a new material. Therefore, primary standard is used as primary calibrator or primary reference material.

  1. Functions

Therefore, standard has the following uses in pharmaceutical analysis laboratory-

(a)   The standard is used as a reference by which we can determine unknown concentration

(b)  Used for standardization of  volumetric solutions

(c)  Used in the Preparation of secondary standard

(d)  Used to calibrate an instrument.

  1. Types

Standards can be divided into two types:

  1. Primary standard
  2. Secondary standard

Primary standard

A primary standard is a chemical or reagent which has certain properties such as-

(a)   It is extremely pure – A primary standard material should be extremely pure which means that it should be a chemical of high grade of purity, preferably 99.98%. In a pahramceutical analysis laboratory we  come across chemicals of different grade of purity. If we check the label we will notice a number with percentage termed as purity. So when a chemical has purity of 99.98% or more it is a suitable material to be used as  primary standard.

(b)  It is highly stable – It should be highly stable which means it usually does not react easily when kept in its pure form or it should have very low reactivity. This is important because if a reagent reacts easily with atmospheric oxygen or water or changes its property over time then it is unreliable and such a unstable and unreliable chemicals can never be used as standard.

(c)   It is anhydrous- It should be anhydrous which means that it does not contain any water molecule in its molecular structure. For example, in a pharmaceutical analysis laboratory we come across same chemical with different number of water molecules attached with it e.g. magnesium sulphate (MgSO4), which is also called Epsom salt. The Epsom salt which is found in drug store is a chemical with formula MgSO4.7H2O. Therefore if we want to prepare a primary standard of magnesium sulphate we should purchase an anhydrous MgSO4 preferably an analytical reagent grade chemical and with purity greater than 99.98%.

(d)  It is less hygroscopic  in nature-  The chemical preferably should be less hygroscopic  i.e. on opening the container it should not absorb water molecules from atmosphere.

(e)   It has very high molecular weight- It has very high molecular weight compared to its other similar forms. For example Epsom salt. Take 1 gram of MgSO4 for making a primary standard and name it as salt A. Now take 1 gram of MgSO4.7H2O for common uses and name it as salt B. Now if we compare the actual weight (Molecular weight) of magnesium sulphate to make a standard solution for both chemicals then it is found that-

CHEMICALS MOLECULAR WEIGHT
MgSO4 108
MgSO4.7H2O 234

 

In first case, molecule of salt A the weight of actual MgSO4 will be 108 atomic mass unit. But in second case, molecule of salt B the weight of actual MgSO4 will be 108 out of its total weight of 234 atomic mass unit.

108 gram salt A (MgSO4) will give 108 gram of MgSO4

So, 1 gram MgSO4 salt will give = 108/108 = 1 gram of MgSO4

But 234 gram salt B (MgSO4.7H2O) will give 108 gram of MgSO4

So, 1 gram MgSO4.7H2O salt will give = 108/234 = 0.461 gram of MgSO4

– Therefore if by mistake we make a standard out of salt B, actually we are taking 0.461 gram of MgSO4 and calculating it as 1 gram. So with this faulty standard estimation of MgSO4 in other unknown solution will give less result than the actual concentration. Hence it is important that primary standards must be anhydrous and of high molecular weight.

(f)   It can be weighed easily – It can be weighed easily because it is so pure that its weight is in fact a true representative of number of moles present in its actual weight.

(g)  It should be ready to use and available

(h)  It should be preferably non toxic

(i)   It should not be expensive

Uses – Primary standard is used to standardize a volumetric solution i.e. they are used for standardization of titration of solutions. It can be used for titration of acids as well as bases. In a pharmaceutical analysis laboratory, for acid titration the most common basic chemical standard is sodium carbonate (Na2CO3), (TRIS) Trisaminomethane [(CH2OH)3CNH2] etc. For base titration, potassium hydrogen phthalate [(KHP): KHC8H4O4] etc. For redox titration, potassium dichromate (K2Cr2O7) & Sodium oxalate (Na2C2O4) are very often used as primary standard.

– The primary standard is used for calibration of secondary standard or for method validation using a  specific method.

Secondary standard

A secondary standard is involved in preparation of reagents and kits or laboratories responsible for producing quality control material for other laboratories. They use primary standard as the primary calibrator or primary reference material. Secondary standard is used for the purpose of calibration of control material in laboratory for analysis of unknown concentration of a substance. So basically, secondary standard serves the purpose of external quality control for laboratories. So it is essential that the secondary standard must first be standardized against the primary standard.

For preparation of secondary standard solution, aqueous solution must be of high grade purity. It must be deionized, if water is used as aqueous solvent.

A secondary standard is a chemical or reagent which has certain properties such as

(a)   The purity of secondary standard is less than primary standard

(b)   Secondary standard  is less stable and more reactive than primary standard

(c)   The secondary standard solution remains stable for a long time

(d)   Secondary standard is titrated against primary standard

Example – 1. Anhydrous sodium hydroxide (NaOH). It is extremely hygroscopic. As  soon  as  the  bottle  is  opened,  NaOH  absorbs moisture from atmosphere and it becomes moist. Lets do it practically, take an analytical balance and place a Petridish and make its weight as zero (Tare). Now open the NaOH bottle and place little NaOH crystal on the petridish and note the weight. Now keep the glass windows of the analytical balance open for few minutes and notice the gradual increase in its weight. This is because the NaOH crystals absorb water molecule from air.

  1. Potassium permanganate (KMnO4) very often used as secondary standard. It is a good oxidizing agent, that’s why reactive and hence less stable. Its own oxidized product manganese oxide (MnO2) contaminates the content. Hence it is unsuitable for being a primary standard.

–  Secondary standard is used as a calibrator by smaller laboratories involved in actual analysis of unknown samples.

Calibration – Calibration means to check whether an instrument is working properly or not i.e. the instrument is giving correct measurement or not. Calibration and standardization are synonyms of each other but in case of solution we use the word standardization and in case of instruments  we use the calibration . This is the process by which we compare the measurements by a standard or an instrument (primary) with another standard or an instrument (secondary). By doing so, we try to eliminate any variation or difference in measurement by the secondary standard or an instrument.

–  Calibration using titration:

Example – Estimation of vitamin C in lemon. For this estimation, ascorbic acid is used as standard. For estimation first of all, take ascorbic acid and prepare a standard solution of known concentration (for example 40mg/dl). Now prepare a diluted solution of indicator called 2 Di -chloro indophenol (2- DCIP) and add ascorbic acid drop by drop till it is completely decolourized e.g. 20 ml.

100 ml ascorbic acid standard solution has 40 mg of ascorbic acid in it

1 ml of standard solution has = 40/100 = 0.4 mg ascorbic acid

Now 20 ml of standard solution has = 0.4 ×20 = 8 mg ascorbic acid

This says that our 2- DCIP requires 8 mg of pure ascorbic acid for its complete neutralization or titration.

Next let us use our lemon. Weigh the lemon. Let us say it weighs 4 g. add lemon juice drop by drop. Let us say it took several drops of lemon juice for complete neutralization of 2- DCIP. Now weigh lemon and now it weighs 2 g. So it proves that 2g of lemon juice present in 4 g of lemon has 8 mg of ascorbic acid. Why 8 mg of ascorbic acid? Simple. This is so because; 8 mg of ascorbic acid is required to completely neutralization 2 DCIP. So from this we came to know that 4 g of lemon has 8 mg of ascorbic acid

So 100 g of lemon would contain = 50 mg of ascorbic acid

So concentration of ascorbic acid in our variety of lemon is 50 mg/100 g that is equal to 50 mg%.

–  The secondary standard is used for calibration of control materials in a lab using a reference method and it is 0closer to the true value of the substance. So it is used for external quality control programme.

–  Whereas in a clinical laboratory unknown samples are analyzed against control materials using a routine/ field method

POINTS TO REMEMBER

  • There are two types of standard.
  • A primary standard should be >99.8% pure.
  • Secondary standard is more reactive, on comparing primary and secondary standards.
  • Secondary standard or an instrument can be calibrated using primary standard.
  • By titration using primary standard, secondary standard can be prepared.
  • A standard also called a calibrator is a material containing a known substance with known concentration.
  • Standard is of two types primary standard and secondary standard.
  • If we compare primary and secondary standard, then it is found that Primary standard is purer, more stable, less reactive, anhydrous and less hygroscopic compared to secondary standard.
  • Secondary standard is titrated or calibrated against primary standard and used as a reference material in laboratories for the purpose of analysis.
  • To get quality solution, pure and de-ionized aqueous solvent should be used to prepare standard solution.
  • In laboratory, primary standard acts as primary reference material.
  • Secondary standard is used as an external quality control for calibration of internal quality control in laboratories.

SIGNIFICANT FIGURES & RULES

SIGNIFICANT FIGURES

The significant figures of a number are digits that carry meaning contributing to its measurement resolution.

There are certain rules to find out the significant figures of a given number-

Rules 1 – All non-zero digits are significant.

Example –

  1. 91 – In 91, there are two significant figures 9 & 1.
  2. 123.45 – Here, there are five significant figures 1,2,3,4 & 5.

Rule 2 – Zeros between non-zero digits are significant.

Example- 101.1203 – As per the rule, there are seven significant figures in 101.1203, these are 1,0,1,,1,2,0 & 3.

Rule 3 – Leading zeros are never significant.

Example – 0.00052 – There are only two significant figures 5 & 2.

Rule 4 – In a number with a decimal point, trailing zero those to the right of the last non-zero digit are significant.

Example – 12.2300 – Here, there are six significant figures 1,2,2,3,0,& 0.

Rule 5 – In a number without a decimal point, trailing zeros may or may not be significant.

Example  – 1300 – In 1300, there are four significant figures 1,3,0 & 0.

 

PHARMACEUTICAL ANALYSIS, QUALITATIVE & QUANTITATIVE ANALYSIS, METHODS OF ANALYSIS

PHARMACEUTICAL ANALYSIS

Pharma means drug and analysis means determination or estimation. So pharmaceutical analysis means determination or estimation of drug in a simple way. But in the language of science, pharmaceutical analysis is defined as it is the branch of science which deals with the study of separation, identification and quantification of drugs (analyte). The person who is involved in analysis, is known as analyst.

Example – i. A mixture when analyzed gives compounds and when a compound is analyzed gives elements. Element is the basic unit of any substance.

  1. separation of protein into its individual components (amino acids), its identification and then quantification.

QUALITATIVE & QUANTITATIVE ANALYSIS

Qualitative Analysis – The word qualitative is made from quality. In qualitative analysis tests are performed on the sample to know its composition i.e. constituents present in the sample. Simply we can say qualitative analysis is the identification of the analyte.

Example – Suppose a sample (Z) is to be analyzed.

When Z is analyzed, the analyst found 5 constituents A, B, C, D & E in that sample. So determination of constituents only not its amount is called qualitative analysis.

Quantitative analysis – the word quantitative is made from quantity. In quantitative analysis tests are performed on the sample to know its composition along with its quantity/amount  i.e. in how much quantity, constituents are present in the sample. Simply we can say the quantitative analysis is determination of amount or concentration of analyte.

Methods of Analysis

  1. Chemical method – It is also called wet analysis, which is based on titrations i.e. reactions between titrant and titrand. Lot of titrations are their which have their own working principles e.g. acid ase titration, redox titration, precipitation titration, complexometric titration etc.
  2. Instrumental method – it includes spectroscopic and chromatographic methodsI. i. Spectroscopic method – in this method specific instruments are employed which works on the principle of absorption and emission of electromagnetic radiations g. Ultraviolet-Visible spectroscopy (UV/Vis), Infrared spectroscopy (IR), Nuclear magnetic resonance spectroscopy (NMR). ii. Chromatographic method – Here we use affinity or partition coefficient differences between drugs e.g. Thin layer chromatography (TLC), High performance liquid chromatography (HPLC), Gas chromatography (GC).

ACCURACY, PRECISION & ERRORS -STATISTICAL TOOLS OF MEASUREMENT

STATISTICS INVOLVED IN PHARMACEUTICAL ANALYSIS

Statistics is of great importance in calculating the result from the analytical data obtained. These are accuracy, precision, errors and significant figures. To understand accuracy, precision and error some terms should be very clear in mind i.e. observed value & standard value.

Observed value – These are the values which an analyst obtains after analysis of sample e.g. an analyst after analysis of a sample says that the sample is 80% pure. This 80% is observed value.

Standard value – Sometimes it is also called as true value. This is the value which the sample claims e.g. a tablet sample claims paracetamol 100 mg. This 100 mg is standard value.

Accuracy, Precision & Errors

These can be easily explained by an example. Two analysts (Analyst 1 & analyst 2) are analyzing a sample five times using same method and instruments (sample claims it is 100% pure i.e. standard value is 100%). The results  of the of the tests performed by the two analysts are given in the table below-

TEST NUMBER ANALYST 1 ANALYST 2
1 99.10 % 98.95 %
2 99.30 % 98.91 %
3 99.80 % 98.96 %
4 99.50 % 98.92 %
5 100.00 % 98.93 %

Now, if we calculate the average/mean value of the results obtained by analyst 1, we get

99.10 + 99.30 + 99.80 + 99.50 + 100.00

Mean = —————————————————————— = 497.7 / 5 = 99.54 %

5

Error = 100 – 99.54 = 0.46 %

Now, if we calculate the average/mean value of the results obtained by analyst 2, we get

98.95 + 98.91 + 98.96 + 98.92 + 98.93

Mean = —————————————————————— = 494.67 / 5 = 98.934 %

5

Error = 100 – 98.934 = 1.066 %

Accuracy – Accuracy means how near the observed value is to the standard value.

Precision – Precision means nearness between several measurements of the same quantity.

If we compare the results of the two analysts, error of analyst 1 is 0.46% and of analyst 2 is 1.066%, following things can be concluded-

  1. Results of analyst 1 is more accurate than the results of analyst 2 because comparably, error of analyst 1 (0.46%)is much less than the error of analyst 2 (1.066%)
  2. Results of analyst 2 is much more précised than the results of analyst 1 because there is very less difference in each other.

Now we will discuss about error, its types and methods of minimizing error.

ERROR

Error – The difference between the observed value and the standard value. Larger the difference, more be the error. If two analysts performs a analysis using the same instrument and for measurement, its not essential that both will get the same results. There may be difference in their measurements. This difference is called as error.

Types of error

Broadly we can divide error into three types namely personal error, systematic error and random error.

  1. Personal error – it arises due to the use of faulty procedure. For example
  2. two persons if taking reading of thermometer, there readings may differ.
  3. two persons if pipetting some chemicals, quantity may differ because some use lower meniscus and some upper meniscus while pipetting.
  • during titration, if the end point is pink color, a person can do mistake because of the confusion in colors like light pink or dark pink.
  1. Systematic error or determinate error – it arises due to instrumental fault i.e. use of uncalibrated (calibration means to check the machine whether it working properly or not, if not it will be corrected) instruments.

Example – if a person is using a digital weighing machine to weigh a sample and the machine is giving weight 50 mg. he takes the weight of the sample as 50 mg. This reading may be wrong because may e the machine is uncalibrated, may be the correct result is 48 mg or 52 mg. This type of error comes under systematic error.

  1. Random error or indeterminate error – These errors are beyond our control and arises due to sudden change in environmental conditions like
  2. Sudden change in temperature, humidity
  3. Voltage fluctuation

Sources of error

Human error and equipment error are the sources of error.

  1. Human error – Examples of human error are-
  2. Incorrect measurement
  3. Use of contaminating glasswares e.g. a person uses a pipette to pipette 5 ml nitric acid and without washing he uses it for pipetting hydrochloric acid. Here the hydrochloric acid gets contaminated.
  • Dirty working place, glasswares, instruments
  1. Equipment error – taking measurement without checking, its giving correct reading or not.

Methods for minimizing errors –     

  1. Correct measurements
  2. Working place and instruments should be clean
  3. Glasswares should be washed, cleaned and dried.
  4. Calibrated instruments should be always used
  5. Use of correct procedure
  6. Running a blank determination
  7. Use of two methods and results are compared