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BONFIGLIOLI PHARMA MACHINERY LAUNCH NEW VACUUM TESTER FOR LYOPHILISED VIALS09 July 2004 10:47BONFIGLIOLI PHARMA MACHINERY LAUNCH NEW VACUUM TESTER FOR LYOPHILISED VIALS A standard method for checking the vacuum in sealed vials containing freeze-dried (lyophilised) product has been the spark test. In this method the vials are exposed to a high voltage. A resulting glow discharge in the headspace of the vial indicates the presence of some level of vacuum. Drawbacks to this method include a limited measuring range (0 – 250 mbar) and the possibility that protein-based biological product can be damaged by the high voltage. A revolutionary method has now been developed to quantitatively measure the headspace pressure inside a vial using laser absorption spectroscopy. Light from a near-infrared semiconductor laser is tuned to match the internal vibrational frequency of a target molecule. The light is passed through the headspace region of a sealed container and some of the laser energy is absorbed by the target molecules. The laser is scanned in frequency and a photodetector records an absorption profile. The laser absorption signal contains information about the headspace gas concentration and the total headspace pressure. The measurement method also incorporates a high sensitivity detection technique known as frequency modulation spectroscopy (FMS). This results in a measurement sensitivity that is 104 greater than traditional direct absorption spectroscopy. Developed by Lighthouse Instruments LLC, this laser absorption technique solves the drawbacks of the spark test method. Headspace pressure measurements can be made over the full range (0 – 1 atm). Since the laser light simply passes through the headspace of the vial, there is no affect on the product. Bonfiglioli Pharma Machinery has incorporated the Lighthouse Instruments optical platform to launch a new rapid and non-destructive vacuum tester. MEASUREMENT OF HEADSPACE PRESSURE USING MOISTURE ABSORPTION Absolute pressure or vacuum level in a pharmaceutical container can be determined by measuring the pressure broadening of a water vapor (moisture) absorption line. Light from a tunable semiconductor laser is directed through the headspace region of a container. The laser light is tuned in frequency to match the internal absorption frequency of moisture molecules at 1382 nm. The width of the resulting moisture absorption signal is directly proportional to total headspace pressure. This means that a direct quantitative measurement of the vacuum level in the container can be made using this method. Note that moisture is always present in the headspace due to water molecules in the cake that evaporate and remain in equilibrium in the headspace as residual water vapor. Figure 1 shows the moisture absorption signal broadening as the nitrogen pressure in the headspace of a 10cc vial increases from 0.04 atm to 1.0 atm (40 mbar to 1 bar). Figure 1. Moisture absorption signals for vials with different headspace pressures. Each vial was prepared with constant moisture content (6% relative humidity) and a balance of nitrogen to the stated pressure. Note the signal width varies with pressure. The signal amplitudes are all normalized. MEASUREMENT OF HEADSPACE PRESSURE USING OXYGEN ABSORPTION To measure oxygen concentrations the laser light is tuned in frequency to match the internal absorption frequency of oxygen molecules at 760 nm. The vacuum level in the container can be inferred from the measured headspace oxygen levels. Figure 2 shows the laser absorption signals for various amounts of oxygen in the headspace of 10cc vials. Figure 2. Laser absorption signals from varying amounts of oxygen in a 10cc vial. The absorption signal is proportional to oxygen concentration (noted to the right of each scan). The compact LVA machine as seen in the photo is fully computerised utilising a SCADA platform. Both Moisture or Oxygen Absorption is available for vacuum testing. The software is easy to operate and includes utilities such as a products database, Statistical reports etc. A printer is also installed for printing test results and parameters. The output may easily reach 400 cpm. Vials may range up to 150ml and may be both amber or transparent. Laboratory semi-automatic models are also available. For more information on this company: Bonfiglioli Pharma Machinery - Controlled Micro-Leak Detection In Packaging and Pharmaceutical Machinery |
