Q: What is the difference between Quality Control (QC) and Quality Assurance (QA)?
QA = Prevents defects (Process assurance)
QC = Detects defects (Product inspection)
Quality Assurance (QA):
Focus:
Process-oriented — ensures correct methods are followed to produce quality products.
Purpose:
Prevents defects by improving systems and procedures.
Activity Type:
Proactive (before production).
Responsibility:
Handled by process and system teams.
Example:
Preparing SOPs, conducting audits, training staff, process validation.
Quality Control (QC):
Focus:
Product-oriented — checks the final product for quality compliance.
Purpose:
Detects defects in finished goods.
Activity Type:
Reactive (after production).
Responsibility:
Handled by inspection and testing teams.
Example:
Sampling, testing raw materials, in-process checks, final product inspection.
Q. What is Organic and Inorganic Chemistry?
Organic = Carbon-based chemistry
Inorganic = All other elements’ chemistry.
Organic Chemistry:
Deals with carbon-containing compounds (except simple salts like CO₂, CO, carbonates).
Focuses on structure, properties, synthesis, and reactions of hydrocarbons and their derivatives.
Examples: Alcohols, acids, polymers, drugs, petrochemicals.
Widely used in pharmaceuticals, agrochemicals, and polymer industries.
Inorganic Chemistry:
Deals with non-carbon-based compounds such as metals, minerals, and salts.
Focuses on structure, bonding, and reactivity of elements across the periodic table.
Examples: Oxides, sulfates, chlorides, and coordination compounds.
Commonly applied in catalysts, metallurgy, ceramics, and materials science.
Q. List the instruments used in a QC (Quality Control) Laboratory.
A Quality Control Laboratory ensures the purity, potency, and quality of raw materials and finished products.
It uses various analytical instruments for qualitative and quantitative testing.
1. Chromatographic Instruments
HPLC (High-Performance Liquid Chromatography): For separation and quantification of drug substances.
GC (Gas Chromatography): For analysis of volatile and semi-volatile compounds.
TLC Apparatus (Thin Layer Chromatography): For quick qualitative identification.
2. Spectroscopic Instruments
UV–Visible Spectrophotometer: For concentration and purity determination (Beer–Lambert Law).
IR Spectrophotometer (FTIR): For identification of functional groups.
NMR Spectrometer: For structural elucidation of compounds.
Fluorimeter: For fluorescent compound analysis.
3. Physico-Chemical Testing Instruments
pH Meter: For acidity or alkalinity measurement.
Conductivity Meter: For ionic concentration in solutions.
Melting Point Apparatus: For checking compound purity.
Polarimeter: For optical rotation and chirality studies.
Refractometer: For refractive index measurement.
4. Titration and Wet Chemistry Instruments
Auto Titrator / Karl Fischer Apparatus: For water content estimation.
Analytical Balance: For accurate weighing of samples.
Hot Air Oven / Muffle Furnace: For drying and residue testing.
5. Microbiological & Stability Instruments
Laminar Air Flow & Incubator: For microbial limit testing.
Stability Chamber: For shelf-life and degradation studies.
Q. What are the types of titration used in a QC (Quality Control) Laboratory?
In a QC Lab, titration is a fundamental analytical technique used for quantitative chemical analysis to determine concentration or purity of a substance.
The main types of titration used are:
1. Acid-Base Titration
Based on neutralization reaction between acid and base.
Indicators like phenolphthalein or methyl orange are used.
Example:
Assay of NaOH or HCl solution.
2. Redox Titration (Oxidation–Reduction)
Involves transfer of electrons between analyte and titrant.
Common reagents: KMnO₄ (permanganate), K₂Cr₂O₇ (dichromate), Iodine.
Example:
Determination of iron (Fe²⁺) or hydrogen peroxide.
3. Complexometric Titration
Based on complex formation between metal ions and a chelating agent.
Common reagent: EDTA (Ethylenediaminetetraacetic acid).
Example:
Determination of hardness of water or metal content like Ca²⁺, Mg²⁺, Zn²⁺.
4. Precipitation Titration
Involves formation of an insoluble precipitate during titration.
Example:
Mohr’s method or Volhard’s method for chloride or silver determination.
5. Non-Aqueous Titration
Performed in non-water solvents for poorly water-soluble substances.
Common in pharmaceutical QC for assay of weak acids or bases.
Example:
Titration of benzoic acid or weakly basic drugs using perchloric acid in glacial acetic acid.
Q. Name the reagents used in titration.
Common titrants: NaOH, HCl, KMnO₄, K₂Cr₂O₇, EDTA, AgNO₃, Na₂S₂O₃, HClO₄
Each selected based on reaction type and analyte nature.
The reagent used in titration is called a titrant — a solution of known concentration used to determine the unknown concentration of another solution.
The choice of reagent depends on the type of titration being performed.
1. Acid–Base Titration
Titrant:
Acid: Hydrochloric acid (HCl), Sulfuric acid (H₂SO₄)
Base: Sodium hydroxide (NaOH), Potassium hydroxide (KOH)
Indicator: Phenolphthalein, Methyl orange
2. Redox Titration
Titrant:
Oxidizing Agents: Potassium permanganate (KMnO₄), Potassium dichromate (K₂Cr₂O₇), Iodine (I₂)
Reducing Agents: Sodium thiosulfate (Na₂S₂O₃), Oxalic acid (H₂C₂O₄)
Indicator: Starch (for iodine), Ferroin, Diphenylamine
3. Complexometric Titration
Titrant: Ethylenediaminetetraacetic acid (EDTA)
Indicator: Eriochrome Black T (EBT), Murexide
Used for metal ion determination (Ca²⁺, Mg²⁺, Zn²⁺).
4. Precipitation Titration
Titrant: Silver nitrate (AgNO₃)
Indicator: Potassium chromate (K₂CrO₄) or Ferric alum (in Volhard’s method)
Commonly used for chloride or halide estimation.
5. Non-Aqueous Titration
Titrant: Perchloric acid (HClO₄) in glacial acetic acid
Indicator: Crystal violet, Methyl red
Used for weakly basic or acidic drug substances.
Q.Do you know what is GLP?
GLP means Good Laboratory Practice. It is a framework or pattern under which research work are planned, performed, monitored, recorded, reported and archived.
Q. What is Polymorphism?
Polymorphism means a compound can have different crystalline forms with same chemical structure but different physical and pharmaceutical properties — critical for drug quality and performance.
Definition:
Polymorphism is the ability of a substance to exist in more than one crystalline form with the same chemical composition but different molecular arrangement in the solid state.
The different forms are called polymorphs.
Each polymorph has distinct physical properties such as:
Melting point
Solubility
Density
Stability
Dissolution rate
Polymorphism is common in pharmaceuticals, affecting:
Bioavailability
Stability
Processing behavior
Patentability
Example:
Ritonavir and Carbamazepine show polymorphism, leading to changes in solubility and drug performance.
2.Do you know what is Calibration Curve?
Calibration curve is the relationship between the various concentration of analyte in a suitable solvent or matrix and the signal response of the instrument.
3.Do you know what is co-chromatography?
Co-chromatography is the procedure used to detect an unknown substance by comparing the chromatic comparison with a known substance.
4.Tell me what do you know about MSDS?
Material Safety Data Sheets are used to handle chemical use in a laboratory. They are issued with every chemical that any lab uses or stocks.
5. Do you know what is blank?
Blank term is used to refer the sample tube which does not contain the analyte.
6. Do you know why GLP is followed in the lab?
Following GLP standard, minimizes the chance of error occurs due to humans.
It supports for product registration, also assures the suitability of data to the regulatory authorities.
It helps to reduce the cost of industry and governments by avoiding duplicative testing.
It helps to re create a study from the recorded data and information.
7. Tell me what are the factors on which the gas sterilization depends on?
Gas sterilization depends on factors like:
Concentration of the gas
- Humidity
- Time of exposure
- Temperature
- Nature of the load
8.Do you know what does a quality control chemist do?
Quality Control:
Testing samples of raw materials or products either in mid stage or close to final stage to make sure that they are of high enough quality, reaching the standards and qualifications, before the product can be mass produced.
9. What Is Titration?
Titration is a process of determining molarity of a base or an acid.
10. Explain the term Aliquot and Diluent?
Aliquot: It is a measured sub volume of the original sample
Diluent: Material with which sample is diluted
11. What is Molality?
Molality is the number of solutes that are present in 1 kg of a solvent.
12. What is Titration?
Titration is a process to determine the molarity of a base or an acid. In this process, a reaction is carried out between the known volumes of a solution with a known concentration, against the known volume of a solution with an unknown concentration.
13. Mention the formula to calculate pH of a solution?
In order to calculate the pH of a solution you have to use the formula
17. How will you calculate how many moles of glucose present in 320 mL of 5.0 M of glucose solution?
First step:
Convert the volume from milli litres to litres
320 X (1 litre/ 1000 mL) = 0.320 L solution
Second step:
use the formula = MV = 5 moles glucose/ litre solution X 0.320 L solution = 1.6 moles of glucose present in 320 mL of solution.
18.What is the difference between Molarity and Normality?
Both techniques are used to the amount of chemical present in the solution. However, they are almost similar but differs in:
Molarity is used to know the total amount of molecules in a 1 liter solution, It is expressed as moles of a compound per liter of solution
Normality is used to know the total number of reactive units in 1 liter of solution, It is expressed in equivalent per liter
19.What is Valency?
Valency is a property of groups or atoms, equal to the number of atoms of hydrogen that the group or atom could combine with or displace it in forming compounds.
20.What is Avogadro s law?
According to Avogadro law, at the same temperature and pressure, an equal volume of gases contains the same number or molecules.
41.What is the acid anhydride of H2CO3?
61.What wavelengths can the human eye see?
- Cyclic base line
- Synchorinise noise
- Asynchorinise noise
- Base line drift
- Spikes
- Negative peaks
- No peaks
Principle of UV Spectrophotometer:
-
Based on Beer–Lambert’s Law: Absorbance is directly proportional to concentration and path length.
-
When UV light (200–400 nm) passes through a sample, molecules with conjugated double bonds or aromatic groups absorb specific wavelengths.
-
The instrument measures the intensity of light absorbed compared to a reference, giving quantitative (concentration) and qualitative (structural) information.
-
Widely used for analyzing purity, concentration, and identification of compounds.
79: What is Split Ratio in Gas Chromatography (GC)?
The split ratio controls sample load, ensuring accurate, sharp, and reproducible chromatographic peaks.
Definition: Split ratio is the ratio of the amount of sample vapor vented out through the split vent to the amount that actually enters the GC column.
Purpose: It is used to control the sample amount injected into the column, preventing column overloading and improving peak shape and resolution.
Working Principle: In split injection mode, only a small portion of the vaporized sample enters the column while the rest is vented.
Formula:
Significance:
Helps in analyzing high-concentration samples.
Improves peak resolution and reduces tailing.
Protects the column from sample overload.