Impactor Systems


Impactor Vision Inspection System (IVIS)

Overview

The Impactor Vision Inspection System (IVIS) has been specifically designed by Westech in conjunction with Specac Ltd, Uk, to measure with a high degree of certainty the significant parameters relating to the size and shape of the jets on each of the stages of Westech 8-stage Non-Viable Impactors or Andersen/Andersen-type impactors. It remains the only instrument designed solely for this application and has been optimised particularly for these measurements.

The purpose of the IVIS instrument is to dimensionally check the jets on Westech 8-stage Non-Viable Impactors or Andersen/Andersen-type impactor stages in a semi or fully automatic manner. There are two main applications:

1) In-house checking of stages during and after manufacture to ensure compliance with the drawing tolerances.

2) For periodic re-checking of impactors by customers’ during use.

The main advantage of the instrument is its ability to perform 100% validation of all impactor jets on any stage without requiring the continuous attention of an operator. It also offers the benefit of eliminating subjectivity in the measurement, and allowing straightforward traceable calibration of the measurements.

Detail specification

The IVIS consists of the following modules:
CCD Video Camera with Telecentric Lens
Impactor Stage Transport Module and jigs
PC system and software
UKAS/NIST certified calibration discs

The instrument has the following specifications:

  • Jet Diameter Range – 0.2mm to 5.5mm.
  • Measurement uncertainty – 0.005mm
  • Supply voltage – 240V, 110V +/-10%
  • Supply Frequency – 50Hz
  • Ambient Operating Temperature Range – 15 to 28C
  • Repeatability – 1 micron RMS – dependant on calibration frequency.
  • Temperature drift – laboratory conditions – 1 micron/day.
  • Overall performance – at 2-sigma (95%) confidence interval – approximately 4 microns for a single measurement.
  • System Resolution is 12 microns/pixel which limits linear measurements and related parameters to +/- 12 microns.

8 Stage Impactor for testing of DPIs

Overview

The aerodynamic particle size distribution of the drug leaving an inhaler device can define the manner in which an aerosol deposits in the respiratory tract during inhalation. This characteristic of the aerosol is often used in judging inhaler performance and is particularly relevant in the development of inhalation formulations during research, production, quality assurance and equivalency testing. The results of characterisations using cascade impaction techniques are additionally used for the determination of fine particle fraction or fine particle dose which may be correlated to the dose or fraction of the drug that penetrates to the lung during inhalation by a patient.

Dry Powder Inhaler (DPI) testing could require added options for preventing stage overloading and necessary to acheive the specified pressure drop through the device. Upper stage mass overloading can be prevented with the addition of a high capacity preseparator or pre-collector. The feature traps non-inhalable aerosols. To acheive the proper pressure drop of 4 kPa (40.8 cm water) in the inhaler, a higher vacuum flow rate at 60 or 90 L/minute may be needed. Higher flow rate application kits include additional stages for maintaining traditional cut point ranges with minimal setup effort. All DPI application options work together to acheive quality analytical results.

Westech 8-stage impactors are specifically designed to meet the highest criteria laid down in the various Pharmacopoeia (e.g. United States Pharmacopeia Chapter <601>; European Pharmacopoeia Chapter 29.9.18 for characterising aerosol clouds emitted by inhalers). By analysing the drug deposited on the individual stages and the final filter, the Fine Particle Fraction, the Fine Particle Dose, the Mass Median Aerodynamic Diameter (MMAD) and Geometric Standard Deviation (GSD) can all be calculated.

Apparatus D of the EP and Apparatus 1 of the USP clearly define the specifications of the Westech 8-stage impactor for use in the testing of inhalers. The standard device with the inclusion of the Induction Port, a compatible mouth-piece adaptor and a suitable pump calibrated to the required flowrate (28.3 lpm) with the impactor in place and shown to be leak tight can be used without modification to characterise the inhaler output.


8 Stage Impactor for testing of MDIs

Overview

The aerodynamic particle size distribution of the drug leaving an inhaler device can define the manner in which an aerosol deposits in the respiratory tract during inhalation. This characteristic of the aerosol is often used in judging inhaler performance and is particularly relevant in the development of inhalation formulations during research, production, quality assurance and equivalency testing. The results of characterisations using cascade impaction techniques are additionally used for the determination of fine particle fraction or fine particle dose which may be correlated to the dose or fraction of the drug that penetrates to the lung during inhalation by a patient.

Detailed specification

Westech 8-stage impactors are specifically designed to meet the highest criteria laid down in the various Pharmacopoeia (e.g. United States Pharmacopiea Chapter <601>; European Pharmacopoeia Chapter 29.9.18 for characterising aerosol clouds emitted by inhalers. By analysing the drug deposited on the individual stages and the final filter, the Fine Particle Fraction, the Fine Particle Dose, the Mass Median Aerodynamic Diameter (MMAD) and Geometric Standard Deviation (GSD) can all be calculated.

Apparatus D of the EP and Apparatus 1 of the USP clearly define the specifications of the Westech 8-stage impactor for use in the testing of Metered-Dose Inhalers. The standard device with the inclusion of the Induction Port, a compatible mouth-piece adaptor and a suitable pump calibrated to the required flowrate (28.3 lpm) with the impactor in place and shown to be leak tight can be used without modification to characterise the inhaler output.


Westech 8 Stage Impactors

Overview

Westech 8-stage non-viable cascade impactors are the result of many years experience in the design and manufacturing of similar devices. The team at Westech in collaboration with Dr Steve Nichols, then of Rhone Poulenc Rorer, were responsible for the design, configuration and validation of the 60 L/min and 90 L/min versions of the standard 28.3 L/min 8 stage impactor which has gained a significant reputation in the measurement of particle size distribution in the testing of pharmaceutical inhalers.

This experience has allowed Westech to produce extremely high quality impactors with ever improving specifications and tolerances to meet the increasingly stringent requirements of both the pharmaceutical industry and its legislators.

Detailed specification

Cascade impactors are multi-jet, multistage devices operating at constant flowrates that allow the characterisation of an aerosol in terms of its particle size distribution. (see Technical Focus – Impactors: How they work…)

Westech produces three main configurations of the 8-stage non-viable impactor – designed for flowrates of 28.3, 60 and 90 L/min – and all are available in a variety of materials including Aluminium, 316 Stainless Steel and Titanium. Conversion kits for 60 and 90 L/min allow the standard 28.3 lpm impactor to be upgraded to the higher flowrates. Recently trials have been undertaken on a Delrin version running at 15 L/min validating both the performance of an impactor constructed in Delrin and the cutpoints at the lower flowrate.

All these cutpoints have been independantly, traceably verified by a UKAS (United Kingdom Accreditation Service) certified laboratory including those of the peseparators used when testing Dry Powder Inhalers (see “8-stage Impactor for DPIs”).

All Westech 8-stage Non-Viable impactors are quality controlled to extremely high tolerances by the use of a vision inspection instrument – Impactor Vision Inspection System (IVIS). Developed by Westech personnel (in conjunction with Specac Ltd, UK) this unique instrument is specifically designed for the measurement of the area, diameter and shape of the jets of Westech impactors. Our history in the development of the 8-stage impactor gives us an unrivalled, intimate knowledge of the precision required to produce impactors with a guaranteed 100% of all jets being significantly within the required tolerances laid down in the various pharmacopiea.