Chromatography and Microbiological Control in Pharmaceutical Manufacturing

Posted on Aug 2, 2024 in Biology

1. Chromatography

Chromatography is a separation method that exploits differences in the partitioning behavior between a mobile phase and a stationary phase to separate the components of a mixture.

Key Concepts:

  • Column: Maintains the stationary phase.
  • Mobile Phase: Transports the sample.

Sample components that partition more with the stationary phase will spend more time inside the column. As components elute, they can be quantified by a detector and collected for further analysis.

Chromatographic Methods:

  • Gas Chromatography
  • Thin Layer Chromatography
  • Immobilized Liquid Chromatography
  • Gel-Filtration Chromatography
  • Ion Exchange Chromatography
  • Hydroxyapatite Chromatography
  • Hydrophobic Affinity Chromatography
  • HPLC (High-Performance Liquid Chromatography)

Limitations of Low-Pressure Chromatography:

  • Physically unable to increase flow rate
  • Compressible resins
  • Long run times (many hours)
  • Large sample volumes

Advancements Leading to HPLC:

  • Synthesis of incompressible resins
  • New column packing techniques
  • Microparticulate resins
  • Advances in spectrophotometry technology

Types of HPLC:

  • Molecular Exclusion
  • Ion Exchange
  • Hydrophobic Interaction
  • Affinity
  • Reverse Phase

HPLC Instrumentation:

  • Pumping System: Chemically resistant, low variability, pressures from 30 to 400 atm, constant flow (pulse-free), capable of mixing solvents, good reproducibility in gradient formation.
  • Types of Pumps: Syringe pumps, reciprocating piston pumps, constant pressure diaphragm pumps.
  • Detectors: UV-Vis detectors (can read at 2 or more wavelengths simultaneously), diode array detectors (spectrum from 200 to 600 nm in less than 1 second).
  • Other Components: Column thermostat, micropore cell, analytical cell, preparative cell, solvent manager, sample manager.

2. Microbiological Control in Pharmaceutical Manufacturing

Microbiological control is an essential part of Good Manufacturing Practices (GMP) to ensure products are free from harmful levels of bacteria, fungi, and other microorganisms.

Objective:

Detect and control the presence of pyrogens, fungi, bacteria, yeast, microbial toxins, and filaments.

Purpose:

Assess and quantify microbial contamination in raw materials, the manufacturing process, and finished products.

Levels of Action:

  • Environment: Air, water, personnel
  • Pharmaceutical Form: Raw materials, intermediates, finished products

Microbiological Control of the Working Environment:

  • Air Monitoring: Controlled contamination areas classified as M1 (100 particles/m3), M2 (10,000 particles/m3), and M3 (100,000 particles/m3).
  • Surface Monitoring: Swabbing, contact plates, rinsing.
  • Water Monitoring: Ion exchange resins to remove impurities. Pseudomonas is a common and potentially dangerous water contaminant.

Microbiological Control of Water:

  • Classification: Drinking water, purified water, water for injection.
  • Analysis for Microbiological Limits: Total coliforms, fecal streptococci, Clostridium, sulfite-reducing bacteria (all must be absent).

Personal Control:

  • Monitoring before, during, and after work.
  • Regular medical examinations.
  • Proper training in health and hygiene measures.

Note: The human body sheds millions of particles daily (skin: 100-1,000/cm2, scalp: 1,000,000/cm2, armpits: 1,100,000/cm2).

3. Antibacterial Potential Assessment

Effectiveness of Antibacterial Therapy:

Evaluates the inhibitory effect of an antibacterial agent on the growth of microorganisms. The antimicrobial activity can be compared to a standard reference.

Determination of Antibacterial Potency:

  • Cylinder Plate (Diffusion) Method: Measures the zone of inhibition around an antibiotic-impregnated disk.
  • Turbidimetric Method: Measures the turbidity (light intensity) of a bacterial suspension in the presence of varying concentrations of the antibacterial agent.

Sterility Testing:

Applied to finished products to ensure sterility. Non-selective sampling is used. For solutions or large containers (over 50 ml), membrane filtration is employed.

Good Manufacturing Practices (GMP) and FDA Regulations:

  • Avoiding cross-contamination is crucial, especially for highly sensitizing materials like beta-lactams and cephalosporins.
  • The FDA sets strict limits for penicillin contamination (0.05 IU for injectables, 0.5 IU for oral drugs).

4. Drug Formulation and Physical Stability

Physical Stability:

Refers to the ability of a pharmaceutical product to maintain its physical characteristics over time. Changes in physical stability can affect solubility, dissolution rate, emulsion stability, and ultimately, therapeutic effectiveness.

Measurable Physical Properties:

  • Particle size and distribution
  • Viscosity
  • pH
  • Color
  • Clarity
  • Melting point

Factors Affecting Physical Stability:

  • Time
  • Temperature
  • Light
  • Humidity
  • Packaging

Examples of Physical Stability Issues:

  • Emulsions: Phase separation due to changes in surface tension and interfacial tension.
  • Suspensions: Sedimentation, caking, particle aggregation.
  • Tablets: Hardness changes, disintegration time, dissolution rate.
  • Solutions: Precipitation, color change, microbial growth.
  • Creams, Ointments, Suppositories: Changes in viscosity, homogeneity, and drug release.

Packaging Considerations:

  • Migration of packaging components into the product.
  • Moisture penetration.
  • Changes in packaging appearance.

Note: Vitamin A is susceptible to degradation by ultraviolet and infrared light. Antioxidants like BHT and quinine can be added to improve stability.