This Masterclass module condenses essential Pharmaceutical Analysis concepts for the UPSC Drug Inspector 2026 (CDSCO) exam. It covers analytical method validation, titrimetry, limit tests, spectroscopy, chromatography, bioassays, sterility testing, BET, dissolution, and critical pharmaceutical calculations. Emphasizing high-yield topics and application-based questions, it ensures zero loss of factual content, preparing candidates for both numerical and theoretical challenges.
🎯 Exam Strategy: This subject carries high numerical + factual weightage. CDSCO questions are application-based. Expect direct one-liners on limits, formula-based numericals in spectroscopy/calculations, and match-the-following on chromatography detectors/columns.
ANALYTICAL METHOD VALIDATION (ICH Q2 R1)
High-yield for Drug Inspector exams
| Parameter | Definition | How Assessed |
|---|---|---|
| Specificity | Ability to assess unequivocally the analyte in presence of impurities/degradants | Peak purity, resolution from nearest peak |
| Linearity | Ability to obtain test results proportional to analyte concentration | Correlation coefficient (r) ≥ 0.999 |
| Range | Interval between upper and lower concentration with acceptable precision, accuracy and linearity | Usually 80–120% of target |
| Accuracy | Closeness of agreement between true value and measured value | % Recovery (98–102%) |
| Precision | Closeness of agreement between independent test results | RSD (Relative Standard Deviation) |
| Repeatability | Precision under same conditions (same analyst, equipment, day) | Intra-day precision |
| Intermediate Precision | Precision within lab variations (different days/analysts/equipment) | Inter-day precision |
| Reproducibility | Precision between different labs | Collaborative studies |
| LOD (Limit of Detection) | Lowest amount detectable but not necessarily quantitated | 3.3 σ/S |
| LOQ (Limit of Quantitation) | Lowest amount quantitated with acceptable precision/accuracy | 10 σ/S |
| Robustness | Capacity to remain unaffected by small deliberate variations | Mobile phase pH, flow rate, column temp variations |
| Ruggedness | Degree of reproducibility under variety of conditions (different labs, analysts) | Similar to reproducibility |
System Suitability Tests (SST)
— Must before HPLC/GC runs:
- Tailing factor (T): 0.9 – 1.2 (ideally 1.0)
- Resolution (Rs): ≥ 2.0 between peaks
- Theoretical plates (N): ≥ 2000 (varies by method)
- RSD of replicate injections: ≤ 2.0%
TITRIMETRY (VOLUMETRIC ANALYSIS)
2.1 Fundamental Concepts
- Molarity (M): Moles of solute per litre of solution
- Normality (N): Gram equivalent weight per litre; N = M × n (where n = acidity/basicity/valence change)
- Equivalent weight (EW):
- Acid-base: EW = MW / Basicity
- Redox: EW = MW / n-factor (electrons transferred)
- Precipitation: EW = MW / valence of ion
Primary Standard: High purity, stable, non-hygroscopic, high EW (e.g., Oxalic acid, KHP, Na₂CO₃, K₂Cr₂O₇, As₂O₃)
Secondary Standard: Less stable, standardized against primary (e.g., NaOH, KMnO₄, Iodine, AgNO₃, EDTA)
2.2 Acid-Base Titrations
| Indicator | pH Range | Acid Colour | Base Colour | Uses |
|---|---|---|---|---|
| Methyl orange | 3.1 – 4.4 | Red | Orange-yellow | Strong acid vs strong base |
| Methyl red | 4.4 – 6.2 | Red | Yellow | Weak acid vs strong base |
| Phenolphthalein | 8.3 – 10.0 | Colourless | Pink | Strong acid vs weak base |
| Thymol blue | 8.0 – 9.6 | Yellow | Blue | Weak acid vs weak base |
Key Reactions:
- Standardization of NaOH: (COOH)₂ + 2NaOH → (COONa)₂ + 2H₂O
- Standardization of HCl: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
2.3 Redox Titrations
| Type | Titrant | Indicator | Medium | Key Application |
|---|---|---|---|---|
| Permanganometry | KMnO₄ (self-indicator) | Pink endpoint | Acidic (H₂SO₄) | Fe²⁺, oxalates, H₂O₂ |
| Dichrometry | K₂Cr₂O₇ | Diphenylamine (internal) / Potassium ferricyanide (external) | Acidic | Fe²⁺ |
| Iodimetry | Iodine (direct) | Starch (blue) | Neutral/weakly acidic | Ascorbic acid, sulfites |
| Iodometry | Na₂S₂O₃ (indirect, liberated I₂ titrated) | Starch (disappears) | Weakly acidic | KMnO₄, Cu²⁺, H₂O₂ |
| Cerimetry | Ceric ammonium sulfate (Ce⁴⁺) | Ferroin (red→pale blue) | Acidic (H₂SO₄/HClO₄) | Ferrous salts, hydroquinone |
| Bromatometry | KBrO₃ (+KBr) | Methyl orange / Starch-Iodide | Acidic | Phenol, aromatic amines |
Critical Memory Hook:
- Iodimetry = Iodine is the titrant (direct)
- Iodometry = Iodine is liberated and then titrated with thiosulfate (indirect)
2.4 Precipitation Titrations (Argentometry)
| Method | Indicator | pH/Condition | Endpoint Colour Change | Principle |
|---|---|---|---|---|
| Mohr’s | K₂CrO₄ | Neutral/weakly alkaline (pH 7–10) | Yellow → reddish-brown (Ag₂CrO₄) | Direct |
| Volhard’s | Ferric alum (FeNH₄(SO₄)₂) | Acidic (HNO₃) | Colourless → reddish-brown [FeSCN]²⁺ | Residual/back |
| Fajans’ | Adsorption indicator (Fluorescein/Dichlorofluorescein/Eosin) | pH 7–10 | Yellow-green → pink | Direct |
2.5 Complexometric Titrations
- Chelating agent: EDTA (Ethylenediaminetetraacetic acid) — hexadentate ligand, forms 1:1 stable complexes with metal ions
- pH dependence: EDTA fully ionized (Y⁴⁻) only at high pH; conditional stability constant (K') depends on pH
- Indicators:
- EBT (Eriochrome Black T): Wine red → pure blue (pH 10, for Ca²⁺, Mg²⁺, Zn²⁺)
- Murexide: Pink → violet (for Ca²⁺, pH 12)
- Xylenol Orange: Red → yellow (for Bi³⁺, Pb²⁺, Zn²⁺ at pH 5–6)
- Masking agents: KCN (masks Cu²⁺, Zn²⁺, Co²⁺, Ni²⁺), Triethanolamine (masks Fe³⁺, Al³⁺), Fluoride (masks Al³⁺, Mg²⁺)
2.6 Non-Aqueous Titrations
- Purpose: Titration of weak acids/bases with poor water solubility or very weak dissociation
- Solvents for weak bases (titrated with perchloric acid): Glacial acetic acid, dioxane (acidic solvents)
- Solvents for weak acids (titrated with sodium methoxide/tetrabutylammonium hydroxide): Dimethylformamide, pyridine, ethylenediamine (basic solvents)
- Indicator for weak bases: Crystal violet (acetic acid medium)
- Standardization of HClO₄: Potassium hydrogen phthalate (KHP) or dimethyl yellow
- Applications: Ephedrine, atropine, chlorpheniramine (weak bases); phenobarbital, sulfonamides (weak acids)
LIMIT TESTS (IP/BP Standards)
3.1 General Principle
Limit tests determine the maximum permissible quantity of impurities without exact quantification. Standard solution of impurity is prepared and turbidity/colour compared with sample.
3.2 Limit Test for Chlorides
- Reagent: AgNO₃ solution in presence of dilute HNO₃
- Principle: Cl⁻ + Ag⁺ → AgCl↓ (white opalescence)
- Standard: NaCl solution (10 µg Cl⁻/mL)
- Nitric acid prevents: Precipitation of Ag₂CO₃, Ag₃PO₄, Ag₂O
- Comparison: Sample opalescence ≤ Standard opalescence
3.3 Limit Test for Sulfates
- Reagent: BaCl₂ solution in presence of dilute acetic acid
- Principle: SO₄²⁻ + Ba²⁺ → BaSO₄↓ (white turbidity)
- Standard: K₂SO₄ solution
- Condition: Acetic acid medium prevents precipitation of BaCO₃, Ba₃(PO₄)₂
3.4 Limit Test for Iron
- Reagent: Thioglycollic acid in ammoniacal solution
- Principle: Fe³⁺ + Thioglycollic acid → Pink to purple-red complex
- Sensitivity: Detects very small amounts of iron
- Ammonia: Provides alkaline medium and prevents hydrolysis
3.5 Limit Test for Heavy Metals (as Lead)
- Method I (for substances soluble in water): pH 3.0–3.5 with acetate buffer, thioacetamide reagent (H₂S generator). Compare brown-black PbS colour with standard lead solution.
- Method II (for substances insoluble in water): Dissolve in organic solvent, extract with dilute acid, then proceed as Method I.
- Method III (sulfide method): Alkaline medium (NaOH), sodium sulfide. Compare dark brown colour.
- Method IV (special cases): Incineration method for substances where sulfur is present.
- Standard lead solution: 10 µg Pb/mL (usually prepared from lead nitrate)
- pH critical: Below pH 3, H₂S is not sufficiently ionized; above pH 3.5, metals may precipitate as hydroxides.
3.6 Limit Test for Arsenic (Gutzeit Test)
- Apparatus: Gutzeit apparatus (bottle, rubber bung with tube, lead acetate cotton, mercuric bromide paper)
- Reagents:
- Zn granules + HCl (generate H₂ gas)
- Lead acetate cotton (traps H₂S which interferes)
- Mercuric bromide paper (sensitized paper)
- Reaction: As³⁺/As⁵⁺ + Zn/HCl → AsH₃ (arsine gas)
- Detection: AsH₃ + HgBr₂ → Yellow to brown stain (HgBr₂·AsH₃ complex)
- Comparison: Stain from sample compared with stain from standard arsenic solution (As₂O₃)
- Sensitivity: Detects 1 µg arsenic
SPECTROSCOPY
4.1 UV-Visible Spectrophotometry
Beer-Lambert Law: A = ϵ · c · l = log₁₀(I₀/I)
- A = Absorbance (unitless)
- ϵ = Molar absorptivity (L mol⁻¹ cm⁻¹)
- c = Concentration (mol/L)
- l = Path length (cm)
Deviations from Beer-Lambert Law:
- Chemical: Association, dissociation, complex formation, reaction with solvent
- Instrumental: Stray light, polychromatic radiation, scattering, fluorescence
- Real: High concentration (>0.01M), refractive index changes
Electronic Transitions:
| Transition | Wavelength Region | Example |
|---|---|---|
| σ → σ* | < 150 nm (vacuum UV) | Alkanes |
| π → π* | 160–250 nm | Alkenes, carbonyls |
| n → σ* | 150–250 nm | Alcohols, ethers, amines |
| n → π* | 270–300 nm (weak) | Carbonyls, nitroso |
Terminology:
- Chromophore: Unsaturated group absorbing UV/visible light (C=C, C=O, NO₂, aromatic ring)
- Auxochrome: Saturated group attached to chromophore, shifts λmax and increases intensity (-OH, -NH₂, -Cl)
- Bathochromic shift (Red shift): Shift to longer λ (lower energy) due to solvent effect or auxochrome
- Hypsochromic shift (Blue shift): Shift to shorter λ
- Hyperchromic effect: Increase in absorption intensity
- Hypochromic effect: Decrease in absorption intensity
Instrumentation:
| Component | Type |
|---|---|
| Light Source | Deuterium lamp (UV, 160–375 nm), Tungsten-halogen lamp (Visible, 350–2500 nm) |
| Monochromator | Prism (quartz), Diffraction grating |
| Sample Cell | Quartz (UV), Glass (Visible), Plastic (Visible) |
| Detector | Photomultiplier tube (PMT), Photodiode, Photodiode Array (PDA) |
Woodward-Fieser Rules for Dienes: (Exam asks direct numericals)
Base values for Dienes:
- Base value for heteroannular diene: 214 nm
- Base value for homoannular diene: 253 nm
| Increment | Value |
|---|---|
| Each alkyl substituent/ring residue | +5 nm |
| Exocyclic double bond | +5 nm |
| Extended conjugation | +30 nm |
| Auxochrome: -OCOCH₃ | 0 nm |
| Auxochrome: -OR | +6 nm |
| Auxochrome: -SR | +30 nm |
| Auxochrome: -Cl, -Br | +5 nm |
| Auxochrome: -NR₂ | +60 nm |
Woodward-Fieser Rules for α,β-Unsaturated Carbonyl Compounds:
- Base value for 6-membered ring/acyclic enone: 215 nm
- Base value for 5-membered ring enone: 202 nm
- Base value for α,β-unsaturated aldehyde: 207 nm
| Increment | Value |
|---|---|
| Each alkyl substituent at α-position | +10 nm |
| Each alkyl substituent at β-position | +12 nm |
| Each alkyl substituent at γ or higher | +18 nm |
| Exocyclic double bond | +5 nm |
| Extended conjugation | +30 nm |
| Homoannular diene component | +39 nm |
| -OH at α-position | +35 nm |
| -OH at β-position | +30 nm |
| -OAc at α,β,δ | +6 nm |
| -OR at α-position | +35 nm |
| -OR at β-position | +30 nm |
| -Cl at α-position | +15 nm |
| -Cl at β-position | +12 nm |
Applications in Pharmacy:
- Assay of single-component drugs (single-point, double-point/base line)
- Simultaneous estimation of multi-component mixtures (Vierordt’s method)
- Dissolution testing
- Content uniformity
- Determination of pKa (from absorbance vs pH plot)
4.2 Infrared (IR) Spectroscopy
Principle:
Molecules absorb IR radiation (4000–400 cm⁻¹) causing molecular vibrations.
Types of Vibrations:
- Stretching: Symmetric and Asymmetric (change in bond length)
- Bending (Deformation): Scissoring, Rocking, Wagging, Twisting (change in bond angle)
Regions:
| Region | Wavenumber | Significance |
|---|---|---|
| Functional Group Region | 4000 – 1500 cm⁻¹ | Sharp, characteristic peaks for functional groups |
| Fingerprint Region | 1500 – 400 cm⁻¹ | Complex pattern, unique to molecule, used for identification |
Important Characteristic Frequencies (Must Memorize):
| Bond/Group | Frequency (cm⁻¹) | Intensity |
|---|---|---|
| O-H (alcohol, free) | 3650–3590 | Sharp, strong |
| O-H (alcohol, H-bonded) | 3550–3200 | Broad, strong |
| N-H (amines/amides) | 3500–3300 | Medium |
| C-H (alkane) | 3000–2850 | Strong |
| C-H (alkene, aromatic) | 3150–3000 | Medium |
| C-H (aldehyde) | 2900–2700 (twin peaks) | Weak |
| C≡N (nitrile) | 2260–2220 | Medium |
| C≡C | 2260–2100 | Weak |
| C=O (ketone) | 1725–1705 | Very strong |
| C=O (aldehyde) | 1740–1720 | Very strong |
| C=O (ester) | 1750–1735 | Very strong |
| C=O (carboxylic acid) | 1725–1700 | Very strong |
| C=O (amide) | 1690–1630 | Strong |
| C=C (alkene/aromatic) | 1680–1600 | Weak-medium |
| C-O (alcohol/ether/ester) | 1300–1000 | Strong |
| N-O (nitro) | 1560–1515 & 1380–1345 | Strong |
| C-F | 1400–1000 | Strong |
| C-Cl | 800–600 | Strong |
| S=O (sulfone/sulfoxide) | 1350–1300 & 1160–1120 | Strong |
Sample Handling Techniques:
- KBr Pellet: Most common, 1–2 mg sample + 200–400 mg dry KBr, pressed under vacuum
- Nujol Mull: For water-sensitive samples, mineral oil (Nujol) used
- Liquid Film: For liquids between NaCl plates
- ATR (Attenuated Total Reflectance): No sample prep needed, surface analysis
FTIR vs Dispersive IR:
- FTIR uses Michelson interferometer + Fourier transform
- Advantages: Faster (signal-to-noise ratio), higher sensitivity, better wavelength accuracy, no stray light, higher resolution
CHROMATOGRAPHY
5.1 General Principles
- Distribution coefficient (K): K = Cₛ/Cₘ (concentration in stationary phase / concentration in mobile phase)
- Retention factor (k): k = (tᵣ – t₀)/t₀
- Selectivity factor (α): α = k₂/k₁ (must be > 1.0)
- Resolution (Rs): Rs = 2(tᵣ₂ – tᵣ₁)/(W₁ + W₂); Rs ≥ 1.5 for baseline separation
- Theoretical plates (N): N = 16(tᵣ/W)² = 5.54(tᵣ/W½)²
- Plate height (H): H = L/N
Van Deemter Equation: H = A + B/u + Cu
- A: Eddy diffusion (multiple paths) → reduced by small, uniform particles
- B/u: Longitudinal molecular diffusion → reduced by high flow rate
- Cu: Resistance to mass transfer → reduced by low flow rate, thin stationary phase
5.2 Thin Layer Chromatography (TLC)
- Stationary phase: Silica gel G (with gypsum binder), Silica gel GF₂₅₄ (with fluorescent indicator), Aluminium oxide
- Mobile phase: Organic solvents (chloroform, methanol, hexane, ethyl acetate mixtures)
- Rf value: Rf = Distance travelled by solute / Distance travelled by solvent front
- Rf always between 0 and 1
- Higher polarity of solute → lower Rf in normal phase (polar stationary phase)
- Visualization: UV lamp (254 nm, 366 nm), Iodine chamber, Spray reagents (ninhydrin for amines, Dragendorff for alkaloids)
- Applications: Identification, purity testing, separation of mixtures, monitoring reaction progress
5.3 High Performance Liquid Chromatography (HPLC)
Modes:
| Mode | Stationary Phase | Mobile Phase | Application |
|---|---|---|---|
| Normal Phase | Polar (Silica, Alumina, Diol) | Non-polar (Hexane, CHCl₃) | Non-polar analytes |
| Reverse Phase (RP-HPLC) | Non-polar (C18, C8, Phenyl) | Polar (Water, Methanol, Acetonitrile) | Polar to moderately polar drugs (most common) |
| Ion Exchange | Cation/Anion exchanger | Aqueous buffer | Ionic compounds |
| Size Exclusion (SEC/GPC) | Porous gel | Aqueous/Organic | Molecular weight determination |
| Affinity | Ligand-bound support | Buffer | Proteins, antibodies |
Instrumentation:
- Solvent Reservoir: Degassed mobile phase
- Pump: Reciprocating pump (most common), syringe pump, diaphragm pump. Pressure: 6000–10000 psi
- Injector: Rheodyne injector valve (20 µL loop), autosampler
- Column: Stainless steel, 10–30 cm length, 3–5 µm particle size (C18 ODS most common)
- Detector:
- UV-Vis: Most common, selective
- PDA/DAD: Photodiode Array (records full spectrum)
- RI (Refractive Index): Universal but less sensitive, temperature sensitive
- Fluorescence: Highly sensitive for fluorescent compounds
- ELSD (Evaporative Light Scattering): Universal, for non-chromophoric compounds
- MS (Mass Spectrometry): LC-MS, structural elucidation
Isocratic vs Gradient Elution:
- Isocratic: Constant mobile phase composition (simple, reproducible)
- Gradient: Mobile phase composition changed during run (separates complex mixtures with wide polarity range)
HPLC Applications in Pharmacy:
- Assay of active pharmaceutical ingredients (API)
- Impurity profiling and related substances
- Dissolution testing
- Content uniformity
- Stability indicating methods
- Bioanalysis (plasma drug levels)
5.4 Gas Chromatography (GC)
Carrier Gases:
Helium (most common), Nitrogen, Hydrogen (high efficiency, dangerous)
Columns:
- Packed columns: 2–4 mm ID, 1–5 m length, packed with coated solid support
- Capillary columns: 0.1–0.5 mm ID, 10–100 m length, coated inner wall (WCOT, SCOT)
Detectors:
| Detector | Abbreviation | Selectivity | Sensitivity | Application |
|---|---|---|---|---|
| Flame Ionization | FID | Carbon-containing organics | High | Most organic compounds |
| Thermal Conductivity | TCD | Universal | Low | Inorganic gases, all compounds |
| Electron Capture | ECD | Electrophores (halogens, nitro) | Very high | Pesticides, halogenated drugs |
| Nitrogen-Phosphorus | NPD | N, P compounds | Very high | Alkaloids, amines |
| Mass Spectrometry | GC-MS | Universal/Structural | Very high | Identification, trace analysis |
Derivatization:
Non-volatile compounds (sugars, amino acids) converted to volatile derivatives (silylation, acylation, alkylation) for GC analysis.
Applications:
Residual solvents (USP <467>), fatty acid methyl esters (FAME), volatile oils, ethanol determination, blood alcohol analysis.
5.5 HPTLC (High Performance TLC)
- Smaller particle size (5–10 µm vs 10–20 µm in conventional TLC)
- Faster separation, higher resolution, better reproducibility
- Automated sample application, densitometric scanning for quantification
5.6 Other Chromatographic Methods
- Paper Chromatography: Ascending, Descending, Radial; used for sugars, amino acids
- Ion Exchange: Water softening, deionization, separation of ionic drugs
- Gel Filtration (Size Exclusion): Sephadex, Sepharose, Sephacryl; separates by molecular size
- Affinity Chromatography: Biospecific interactions (antigen-antibody, enzyme-substrate)
BIOASSAY
6.1 Principles
- Definition: Determination of potency of a drug by its effect on living tissue/animal
- Potency: Expressed in Units (IU) or micrograms per mg relative to standard
- Requirements:
- Standard preparation of known potency
- Suitable animal/tissue with consistent response
- Statistical validity
6.2 Types of Bioassays
| Type | Principle | Examples |
|---|---|---|
| Direct Endpoint | Dose required to produce specific biological endpoint | Digitalis (cardiac arrest in pigeon/cat), Histamine (guinea pig ileum contraction) |
| Interpolation | Response of unknown compared with standard at same dose level | Oxytocin (rat uterus), Vasopressin (rat blood pressure) |
| Bracketing / Matching | Standard dose bracketed around unknown response | Insulin (mouse convulsion method) |
| Multiple Point / Gravimetric | Multiple doses of standard and unknown; statistical analysis | Antibiotics (cylinder plate/turbidimetric assay), Digitalis (frog method) |
6.3 Specific Bioassays (CDSCO Favorites)
1. Digitalis Assay (One-Point / Cat Method)
- Animal: Cat (anaesthetized)
- Endpoint: Cardiac arrest (systolic standstill)
- Standard: International Standard Digitalis
- Calculation: Potency proportional to lethal dose
2. Insulin Assay (Mouse Convulsion Method)
- Animal: Mouse (20–26 g)
- Endpoint: Convulsions due to hypoglycemia
- Standard: International Standard Insulin
- Method: Bracketing technique
- Calculation based on percentage of mice showing convulsions
3. Oxytocin Assay
- Tissue: Isolated rat uterus (virgin rat, estrogen pretreated)
- Bath: Tyrode solution at 32°C
- Response: Uterine contraction measured
- Standard: International Standard Oxytocin
- Method: Interpolation or 2+2 dose assay
4. Antibiotic Microbial Assay
- Cylinder Plate Method (Cup Plate): Agar diffusion; zone of inhibition measured
- Turbidimetric Method: Growth inhibition measured by turbidity (absorbance)
- Organisms: Staphylococcus aureus (penicillin), Bacillus subtilis, Micrococcus luteus
- Calculation: 4-point or 6-point assay; potency from standard curve
6.4 Statistical Analysis in Bioassays
- 4-Point Assay: 2 doses of standard (S1, S2) and 2 doses of unknown (T1, T2)
- Potency ratio (R): R = antilog(M), where M = (T̄ – S̄) / b (slope)
- Fiducial limits: 95% confidence limits; potency should lie within 80–125% of claim
- LD₅₀ / ED₅₀:
- LD₅₀ = Lethal dose for 50% population
- ED₅₀ = Effective dose for 50% population
- Therapeutic Index = LD₅₀ / ED₅₀ (higher = safer)
- Methods for LD₅₀: Miller-Tainter (logarithmic), Litchfield-Wilcoxon, Karber method
STERILITY TESTING & BET
7.1 Sterility Testing (IP/BP/USP <71>)
Definition:
Complete absence of viable microorganisms.
Methods:
- Direct Inoculation: Sample directly added to culture media; suitable for small volumes, soluble items
- Membrane Filtration: Sample filtered through 0.45 µm membrane; filter transferred to media; suitable for antibiotics, oils, large volumes
Culture Media:
| Medium | Purpose | Incubation | Temperature |
|---|---|---|---|
| Fluid Thioglycollate Medium (FTGM) | Anaerobic + aerobic bacteria | 14 days | 30–35°C |
| Soybean Casein Digest Medium (SCDM) / Tryptic Soy Broth (TSB) | Aerobic bacteria + fungi | 14 days | 20–25°C |
Test Organisms for Validation (Growth Promotion):
- Clostridium sporogenes (anaerobe)
- Bacillus subtilis (aerobe)
- Pseudomonas aeruginosa (aerobe)
- Staphylococcus aureus (aerobe)
- Candida albicans (yeast)
- Aspergillus brasiliensis (mold)
Interpretation:
- Pass: No growth in test containers, growth in positive controls
- Fail: Growth in test containers → invalid batch
- Retest: If contamination suspected, retest with double quantity; if growth again → batch fails
7.2 Bacterial Endotoxin Test (BET) — USP <85>
Principle:
Based on amoebocyte lysate from horseshoe crab (Limulus polyphemus)
Methods:
| Method | Principle | Sensitivity | Application |
|---|---|---|---|
| Gel-Clot | Endotoxin causes gel formation in lysate | 0.03 – 0.5 EU/mL | Limit test, pass/fail |
| Turbidimetric (Kinetic) | Measures increase in turbidity over time | 0.001 – 50 EU/mL | Quantitative |
| Chromogenic | Free chromophore (p-nitroaniline) released, measured colorimetrically | 0.005 – 50 EU/mL | Quantitative |
Key Calculations:
- Endotoxin Limit (L): L = K / M
- K = Threshold pyrogenic dose per kg (5 EU/kg for parenterals, 0.2 EU/kg for intrathecal)
- M = Maximum recommended human dose per kg per hour
- Lambda (λ): Labeled sensitivity of LAL reagent (EU/mL)
- Maximum Valid Dilution (MVD): MVD = C × λ / L
- C = Concentration of drug in solution (mg/mL or Units/mL)
- Minimum Valid Concentration (MVC): MVC = λ × M / K
Controls Required:
- Negative Control (NC): LAL reagent + LAL Reagent Water (no endotoxin)
- Positive Control (PC): LAL reagent + Standard Endotoxin
- Positive Product Control (PPC): Sample + Standard Endotoxin (checks for inhibition/enhancement)
- Inhibition/Enhancement Test (IET): Must be performed before routine testing
DISSOLUTION TESTING (USP <711> / IP)
8.1 Apparatus Types
| Type | Name | Description | Use |
|---|---|---|---|
| I | Rotating Basket | 40-mesh stainless steel basket rotating in medium | Tablets, capsules, floating dosage forms |
| II | Paddle | Paddle stirring at 50–75 rpm | Most common for tablets |
| III | Reciprocating Cylinder | Cylinder moves up and down in medium | Extended-release, bead formulations |
| IV | Flow-Through Cell | Medium continuously flows through cell | Poorly soluble drugs, extended-release |
| V | Paddle Over Disk | Disk holds transdermal patch | Transdermal systems |
| VI | Cylinder | Cylinder stirrer for transdermal | Transdermal systems |
| VII | Reciprocating Holder | Sample holder dips reciprocally | Implants, special dosage forms |
8.2 Test Conditions
- Medium Volume: 500, 900, or 1000 mL (must provide sink conditions: volume ≥ 3× saturation solubility)
- Medium pH:
- pH 1.2 (Simulated Gastric Fluid, SGF)
- pH 4.5 (Acetate buffer)
- pH 6.8 (Simulated Intestinal Fluid, SIF)
- Water
- Surfactants: Sodium lauryl sulfate (SLS) added for poorly soluble drugs
- Temperature: 37°C ± 0.5°C
- Sampling: At specified intervals (e.g., 15, 30, 45, 60, 90, 120 min)
8.3 Acceptance Criteria (Q-Test)
| Stage | Number of Units | Acceptance Criteria |
|---|---|---|
| S1 | 6 | Each unit not less than Q + 5% |
| S2 | Additional 6 (Total 12) | Average of 12 units ≥ Q; no unit < Q – 15% |
| S3 | Additional 12 (Total 24) | Average of 24 units ≥ Q; not more than 2 units < Q – 15%; no unit < Q – 25% |
- Q value: Usually 75% or 80% dissolved at specified time (e.g., Q = 75% in 30 min)
- Profile Comparison: f₂ (similarity factor) for comparing dissolution profiles; f₂ between 50–100 indicates similarity
PHARMACEUTICAL CALCULATIONS
9.1 Concentration Expressions
- % w/v: g per 100 mL
- % w/w: g per 100 g
- % v/v: mL per 100 mL
- % v/w: mL per 100 g
- mg%: mg per 100 mL
- ppm / ppb: parts per million / billion (w/w or v/v)
- Ratio strength: 1:1000 = 0.1% w/v
9.2 Alligation
- Alligation Medial: To find the percentage strength of a mixture of two or more components of known quantities and strengths.
- Alligation Alternate: To find the proportion in which to mix two components to get a desired strength.
Higher strength | (Desired – Lower)
/
X
/
Lower strength | (Higher – Desired)
9.3 Proof Spirit
- Proof spirit: 57.1% v/v ethanol (49.3% w/w at 15.5°C)
- Overproof: % v/v stronger than proof spirit
- Underproof: % v/v weaker than proof spirit
- Formula: Proof = (% v/v ethanol × 1.753) – 100 (approximate)
9.4 Isotonicity Calculations
Method 1: Freezing Point Depression (ΔTf)
- Blood plasma ΔTf = 0.52°C
- Any solution with ΔTf = 0.52°C is isotonic
- ΔTf = Kf × m × i = 1.86 × (g/MW) × (1000/W) × i
- For 100 mL: ΔTf = 1.86 × (g/MW) × 10 × i
Method 2: Sodium Chloride Equivalent (E)
- E = 17 × (i / MW)
- i = number of ions/dissociation factor
- MW = molecular weight
- Amount of NaCl to add for isotonicity (per 100 mL):
- NaCl required = 0.9 – (E₁ × W₁ + E₂ × W₂ + ...)
- Where W = weight of substance in grams per 100 mL
Common E Values (Memorize):
| Substance | E Value |
|---|---|
| Boric acid | 0.52 |
| Atropine sulfate | 0.13 |
| Ephedrine HCl | 0.30 |
| Procaine HCl | 0.21 |
| Tetracaine HCl | 0.24 |
| Phenylephrine HCl | 0.32 |
| Sodium chloride | 1.00 |
| Dextrose | 0.18 |
| Mannitol | 0.18 |
9.5 Milliequivalents (mEq)
mEq = mg × Valence / Molecular Weight
9.6 Osmolarity
mOsm/L = g/L × i × 1000 / Molecular Weight
- Isotonic with blood: 300 mOsm/L
9.7 Dilution & Mixture
- C₁V₁ = C₂V₂ (for dilutions)
- Trituration: 1:10 or 1:100 dilution for potent drugs
- Alcohol dilution: Use weight/volume calculations; volumes are not additive for ethanol-water mixtures
9.8 pH and Buffer Calculations
- Henderson-Hasselbalch:
- Acidic buffer: pH = pKa + log([Salt]/[Acid])
- Basic buffer: pOH = pKb + log([Salt]/[Base])
- Buffer capacity (β): Amount of strong acid/base needed to change pH by 1 unit
QUICK REVISION TABLES
Table A: Comparison of Chromatographic Detectors
| Detector | Universal? | Sensitivity | Destructive? | Best For |
|---|---|---|---|---|
| UV-Vis (HPLC) | No | High | Non-destructive | Most drugs |
| PDA/DAD | No | High | Non-destructive | Peak purity, spectral ID |
| RI (HPLC) | Yes | Low | Non-destructive | Sugars, polymers |
| ELSD (HPLC) | Yes | Medium | Destructive | Lipids, surfactants |
| FID (GC) | No (organics only) | High | Destructive | Hydrocarbons, solvents |
| TCD (GC) | Yes | Low | Non-destructive | Permanent gases |
| ECD (GC) | No | Very High | Non-destructive | Halogenated compounds |
| MS (LC/GC) | Yes | Very High | Destructive | Identification, trace |
Table B: Standardization of Titrants
| Titrant | Primary Standard | Indicator | Medium |
|---|---|---|---|
| NaOH | Oxalic acid / KHP | Phenolphthalein | Aqueous |
| HCl | Na₂CO₃ | Methyl orange | Aqueous |
| KMnO₄ | Oxalic acid / As₂O₃ | Self-indicator | Acidic (H₂SO₄) |
| Iodine | Arsenious oxide / Na₂S₂O₃ | Starch | Weakly acidic |
| Na₂S₂O₃ | K₂Cr₂O₇ (liberates I₂) | Starch | Acidic + KI |
| AgNO₃ | NaCl | K₂CrO₄ (Mohr) | Neutral |
| EDTA | Zn metal / CaCO₃ | EBT / Murexide | pH 10 / pH 12 |
Table C: Essential Limits (IP)
| Test | Standard | Typical Limit |
|---|---|---|
| Chlorides | NaCl | 25–50 ppm (varies by monograph) |
| Sulfates | K₂SO₄ | 50–100 ppm |
| Iron | Thioglycollic acid | 10–20 ppm |
| Heavy metals (as Pb) | Lead nitrate | 10–20 ppm |
| Arsenic | As₂O₃ | 1–2 ppm |
📝 LAST-MINUTE EXAM CHECKLIST (Pharmaceutical Analysis)
- Beer-Lambert law, deviations, and Woodward-Fieser numericals
- All redox titration indicators and reactions (especially iodometry vs iodimetry)
- Mohr, Volhard, Fajans — conditions and indicators
- EDTA titration: pH dependence, EBT colour change, masking
- All limit tests: reagents, reactions, standards, apparatus (especially Gutzeit)
- IR frequencies: O-H, N-H, C=O, C-O regions
- HPLC: Reverse phase principle, C18 column, SST parameters
- GC detectors: FID, TCD, ECD — selectivity and sensitivity
- Bioassay types with one example each
- Sterility media: FTGM (30–35°C) and SCDM (20–25°C), 14 days
- BET: L = K/M, MVD formula, three methods
- Dissolution: Apparatus I–IV, Q-test stages S1/S2/S3
- Calculations: E-value formula, isotonicity, mEq, alligation
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