The Computrac® Vapor Pro® series (Standard & Rx) have proven their worth as reliable and accurate moisture-specific instruments used in a variety of different industries. The Vapor Pro® interface is very easy to use and program with only a handful of testing parameters required to accurately analyze your sample for moisture content. Testing parameters include test temperature, ending criteria, start weight input method, and a bottle purge option (in seconds); but what does a bottle purge do? If you have asked yourself this question, you are not alone. This adjustable option may not be intuitive, but imagine an empty sample vial sitting on your bench top. If you were to cap that empty vial and run it as a mock sample with a ‘0 sec’ bottle purge you might expect 0 µg of water to come from an empty vial right? The answer might surprise you since the vial is not actually empty!
Although the vial may look dry and void of condensation, there are actually microscopic droplets of water adhered to the sides of the vial. Moreover, as you cap the empty vial, you are actually trapping the relative humidity from the environment within the vial. If this humidity is not accounted for, you could be inadvertently adding moisture to your sample during testing. So how much moisture is in an empty vial? This may depend on your local and seasonal humidity, however normal levels range from 200-400 µg of water! The function of the bottle purge is to rid the vial of this moisture prior to analyzing your sample’s true moisture. The empirical data below presents several empty vials run with varying bottle purges with their corresponding moisture levels. Arizona Instrument typically recommends a bottle purge from 30-45 seconds (although exceptions may be made depending on sample type). If you are unsure of what bottle purge to use for your sample, feel free to contact your Account Representative at AZI for more information. Your Account Representative can arrange for samples to be sent to the Sales Test Lab for testing to give you an optimized set of parameters including a recommend bottle purge time.