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tips & techniques moisture analysis ...Continued from p. 37 moisture balance to a new location or altering the method, such as using rubber gloves to avoid transferring sweat or grease onto the sample or sample pan. The detection limits should be low enough that you can accurately measure to the specifcation levels of your materials. If the amount you're trying to measure is below your LOQ that means that the value of the instrument reading is highly variable and more unreliable at that level. That ultimately translates to more variability in the measured moisture of the material that is being processed. The samples should be confrmed to be giving off only water in the moisture balance. If you can't adjust the method to make sure that only water is being released. then a moisture balance is not an appropriate instrument to determine the percent moisture of your material. When these four steps are completed you can be certain whether you are getting accurate results from your moisture balances. You will be able to confrm whether your current procedures for testing for moisture are appropriate to the materials. You also will be able to identify potential problems with the testing process, if there are any, and if no problems exist, your production personnel will have confdence that they have reliable values on which to base their decisions. All of this translates into less variation in the results, which ultimately means less variation in processing, which reduces processing problems and saves time and money. about the authors Joel Lischefski is laboratory manager at teel analytical laboratories, div. of teel Plastics, inc., baraboo, Wis. his specialty is analytical chemistry and he has spent time developing methods, performing research, and analyzing samples in the fields of polymer materials and environmental science. Alison Maicke is a chemist at teel analytical laboratories, specializing in chromatographic separations, method validation, and quality control. she has worked in thermal analysis and identification of active ingredients in polymers and pharmaceuticals. contact: (608) 355-4520; email: jlischefski @teel.com; website: teelplastics.com HITECH TM Fully Automatic, Continuous Screen Changers ✓ ❑ Fully Automatic - uniform melt pressure and temperature maintained indefinitely ✓ ❑ Improve Quality - steady head pressure results in closer tolerances, tighter gauge control ✓ ❑ Reduce Labor & Downtime - 120' of screen lasts for months. Eliminates handling breaker plates & dirty screen packs. ✓ ❑ No Leaks - no moving parts, no hydraulics High-Technology Corp. Leaders in Continuous Melt Filtration Since 1969 144 South Street • Hackensack, NJ 07601 Tel: 201- 488-0010 • Fax: 201-488-4318 www.screenchanger.com Plastics technology february 2013 47