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FLEXO Magazine : October 2009
58 FLEXO OCTOBER 2009 www.flexography.org Attention to routine maintenance can eliminate most GC problems. Use an electronic leak detector to check for helium and hydrogen leaks in the gas supply lines to the GC. The column is the heart of the gas chromatograph. If a problem appears it could be a result of the last change on the GC. FLEXIBLE PACKAGING The gas chromatograph (GC) is one of the most com- monly used instruments in quality control laboratories around the world. For the flexible packaging printer and convertor, its primary use is to test for residual solvents that remain in printed flexible packaging materials. This test is important for production start-up and optimization and is specified by many food and candy manufacturers. This article will review and discuss the aspects of GC main- tenance and troubleshooting for achieving good long-term performance and to eliminate some common GC problems. A GC must operate as a gas-tight system. Carrier gas leaks can develop as a result of normal use and if not corrected the data for your unknowns samples will be incorrect. Attention to routine maintenance can eliminate most GC problems. Important GC hardware that requires routine maintenance includes: 1. Gas supplies and filters. 2. Injector. 3. Column. 4. Detector. 5. Data system. GAS SUPPLY MAINTENANCE Let's review some of the important items of gas supply maintenance. Use an electronic leak detector to check for helium and hydrogen leaks in the gas supply lines to the GC. These leak detectors are available from your GC supply house and are very easy to use. Check all fittings and connections in the gas supply line from the gas cylinder to the end of the column in- side the GC oven. Preventing carrier gas leaks will eliminate many of the problems that may develop over time in your GC. Routinely monitor your gas supply cylinders. Monitor and record the cylinder pressure on a regular basis so that you can replace the cylinders when they reach 200-300 psi. Allow- ing the gas cylinders to go empty can contaminate the entire GC gas flow path and require extensive cleanup or replace- ment of the GC's pneumatic components. Install and maintain indicating filter-driers that remove trace-level contaminates from the gas supplies, e.g. hydrocar- bons, moisture and oxygen. Always replace these filter-driers when they become exhausted. INJECTION PORT There are three key things that must be checked as part of injector maintenance. Gas Chromatograph Maintenance and Troubleshooting Routine Preventive Maintenance of Your GC is Essential for Good Quality Residual Solvent Results By Burton S. Todd Major components of a gas chromatograph system. Excessive peak tailing (left) will negatively affect the reported results of your analysis. Example of a good peak can be seen on the right. TECHNOLOGIES & TECHNIQUES
Sustainable Fall 2009