Case Studies2021-07-01T12:54:07+00:00

Case Study 1 – Increase understanding of API crystallisation and improve consistency of PSD for a commercial product

Project Objective Increase understanding of API crystallisation and improve consistency of PSD for a commercial product: Approach

  • Identified success criteria for ideal API characteristics: D90 range, modality, crystal habit, filtration behaviour.
  • Assessment of process using JMP software determined complex crystallisation with multiple factors interacting with each other.
  • Fractional factorial design to generate parameter conditions for 9 experiments using JMP.
  • Key findings used to implement recommendations for manufacturing on scale.
  • Output measured using laser light scattering (Malvern), scanning electron microscopy, Morphologi G3 image analysis, leaf filtration.

Output Provide recommendations for on scale manufacturing

Case Study 2 – Determine proven acceptable range (PAR) for micronisation of a product to meet customer requirements

Project Objective Determine proven acceptable range (PAR) for micronisation of a product to meet customer requirements Approach

  • Central composite experimental design investigating mill pressure and product feed rate
  • Influence of input material assessed by performing confirmatory runs using different inputs at coarse and fine ends of PAR

Output

  • Established PAR and operating parameter set points
  • Determined input PSD has no impact on output

Case Study 3 – Crystallisation Optimisation for Improved Deliquoring Rates in a Filter Dryer

Problem Statement Variable bottleneck cycle times (97-161 hr, target is 91 hr) due to deliquoring rates during isolation of a commercial intermediate on a filter dryer. The process team requested that the crystallisation be investigated to determine if material with more suitable powder properties could be generated.

  • Fine hair-like needles observed post nucleation
  • Material blinding filter cloth → very long deliquoring times.
  • Limited development space for a filed commercial product.
  • Proposed the introduction of temperature cycles to the cooling step (Ostwald Ripening) to promote growth of material.
  • Proof of concept experiment completed to demonstrate benefits.
  • Consultation with process team and engineer followed by repeat experiment optimised for plant conditions.

Outcome

  • Filtration rates monitored in the lab using a pressurized leaf filter and analyzed using SEM and light microscopy.
  • Slurries were filtered at 1 bar gauge pressure with 10 mm filter cloth.
  • Filtration reduced from > 40 seconds to 2-5 seconds via introduction of temperature cycles.
  • Comparable material quality and losses to the mother liquor
  • As per the standard process the on plant filtration/isolation times ranged from 22 – 106 hours, after implementation of the revised process the on plant filtration/isolation times reduced by up to 83% and also reduced in variability (revised process times range from 8.6 to 18.4 hours).

Case Study 4 – Improved Consistency of Unmilled API PSD

Problem Statement

  • Variable PSD observed for unmilled API due to inconsistent nucleation and growth.
  • Potential for dendritic growth resulted in dryer attrition and bimodal PSD.
  • Modality and PSD observed using Morphologi-G3 and Malvern.

Attrition during extended crystallisation hold and agitated drying

Dendritic-columnar crystals

Presence of fines

  • An increase in variability had been observed over time, therefore a project was initiated to understand cause of variability and improve consistency.
  • A number of experiments performed using Radley’s AutoMATE reactor/RX10 with FBRM probe.

Factor investigated in the laboratory included:

  • Powder properties of seed
  • Temperature of solution on receipt to crystalliser
  • Seeding temperature
  • Anti-solvent addition time
  • Cooling profile/time

Crystallisation solution was determined to be highly supersaturated leading to variability in desupersaturation. Allowing more time for material to desupersaturate resulted in less dendritic growth. Recommendations included:

  • Target temperature to be maintained during transfer of batch to the crystalliser.
  • Adjustment of solvent matrix in seed slurry
  • Recommended RPM for agitation in the crystalliser (based on CFD study)

Batch Temperature before and after transfer to crystalliser

Case Study 5 – X-Ray Powder Diffraction (XRPD) Analysis

XRD is a powerful, non-destructive and rapid technique for analyzing a wide range of materials (1 µm to 100 mm), including metals, polymers, catalysts, plastics, pharmaceuticals etc.

Key Features

  • Vital method for investigation and characterization of crystalline materials in the QC and R&D Laboratories.
  • Best qualitative method for identification of a phase purity of unknown bulk composition.
  • Minimal sample preparation required.
  • The data interpretation is straightforward.
Figure 1: A photo of the Bruker D8 Advance diffractometer

Instrument Details

  • X-ray Tube: the main source of X Rays.
  • Incident-Beam Optics: condition the X-ray beam before it hits the sample.
  • Goniometer: a platform that holds and moves the sample, optics, and detector.
  • Sample Holder: Holds the sample in place and rotates it if required.
  • Air Scatter: controls the size of the viewed diffracting sample surface, so as to improve diffraction resolution and minimize cross-contamination.
  • Receiving-side Optics: condition the X-ray beam after it has encountered the sample.
  • Detector: count the number of X Rays scattered by the sample.

Operation of XRD

  • X-rays are generated in a cathode ray tube by heating a filament to produce electrons, accelerating the electrons toward a target by applying a voltage, and bombarding the target material (Cu, λ = 1.54 wavelength) with electrons.
  • The generated X-rays are directed towards the sample, and the diffracted rays are collected by the detector (See Figures 2 & 3).
  • A key component of all diffraction is the angle between the incident and diffracted rays (2θ). A typical powder patterns data is collected at 2θ from ~5° to 70°, angles that are present in the X-ray scan.
  • A detector records and processes this X-ray signal and converts the signal to a count rate which is then output to a device such as a printer or computer monitor.

Figure 2: A schematic illustration of operations of XRD main components.

Figure 3: A schematic diagram for coherent diffraction, satisfying Bragg’s Law.

Figure 3: A schematic diagram for coherent diffraction, satisfying Bragg’s Law.

Interpretation

  • The peak intensities in the diffractogram are determined by the distribution of atoms within the lattice. As a result, the X-ray diffraction pattern is the fingerprint of periodic atomic arrangements in a given sample.
  • Phases with the same chemical composition can have drastically different diffraction patterns.
  • The position and relative intensity of a series of peaks can be used to match experimental data to reference data in a database.

References

  • USP <941> : X-ray diffraction USP monograph, Current Edition

A – Identification of polymorphic forms

Problem statement:

  • After work up from the reaction mixture, it is possible to get different polymorphic forms of a material.

Impact:

  • Different polymorphs can effect the solubility, dissolution rate, bioavailability, and physical stability of the drug substance.

Identification Technique:

  • PXRD is the best technique to identify different polymorphic forms in the reaction mixture [USP <941>].

Results:

  • Comparison of sample diffractogram with the Ref Std diffractograms confirmed that the sample is present in Form D (For more details, see Figure 4).
  • The agreement in the 2θ-diffraction angles between the sample and the Ref Std is within 0.2°.
  • Peak relative intensities between sample and Ref Std may vary considerably due to preferred orientation effects.
Figure 4: Ref Std Form D (red line); Ref Std Form B (blue line): Sample (black line)

Figure 4:  Ref Std Form D (red line);  Ref Std Form B (blue line): Sample (black line)

B – In-Process Production Support

XRD analysis can be used for production support to confirm the correct Form is being produced Conversion from Form 2 to preferred Form 1 occurs during drying; XRD testing was performed as an “In-Process” test to confirm complete conversion to Form 1 Red arrow point out to undesired Form 2; present in the First Drying Sample and not present in Final Drying Sample