Pharmaceutical Analysis
Pharmaceutical Analysis in NIPER JEE covers titrimetry, UV–Visible spectrophotometry, HPLC/GC, hyphenated techniques, and ICH validation.
Core rules and concepts
- Beer–Lambert law: A = εbc, where A is absorbance, ε molar absorptivity, b path length (cm), c concentration (mol/L). Absorbance is linear only over a validated range.
- Titrations: acid–base, redox (iodometry), complexometric (EDTA), and nonaqueous for weak bases in glacial acetic acid.
- HPLC reversed-phase uses C18; retention increases with hydrophobicity. System suitability checks resolution, tailing factor, theoretical plates, and RSD.
- ICH Q2(R1) validation parameters: accuracy, precision, specificity, linearity, range, LOD/LOQ, robustness. LOD = 3.3σ/S and LOQ = 10σ/S, where σ is SD of response and S is slope.
- GC suits volatile and thermostable analytes; derivatization can improve volatility.
Worked example
A solution has absorbance 0.45 at 1 cm path length and ε = 1.5 × 10^4 L mol⁻¹ cm⁻¹. c = A/(εb) = 0.45/(1.5 × 10^4 × 1) = 3.0 × 10⁻⁵ mol/L = 30 µM. For a compound of MW 300, that is 3.0 × 10⁻⁵ × 300 = 9.0 × 10⁻³ g/L = 9.0 mg/L.
Traps that cost marks
- Using percent transmittance as absorbance; A = log10(100/%T).
- Calling LOD the same as LOQ; LOQ is the lowest quantifiable level.
- Treating system suitability as method validation; it is a run-time check.
- Reporting precision from one injection; precision requires replicate preparations.