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www.phenomenex.com/GC TROUBLESHOOTING GUIDE G C You asked for a better online e

www.phenomenex.com/GC TROUBLESHOOTING GUIDE G C You asked for a better online experience. One filled with technical resources, easy-to-find products, and useful tools to make your GC work easier. Good news… it’s here! • Troubleshooting resources and on-demand webinars • Get thousands of applications – save and access them anywhere! • Watch technical demonstrations and “how-to” videos • Create a virtual stockroom for your lab • Try tools that make selecting the right product easier than ever • Get FREE samples and special offers www.phenomenex.com/ResourcesGC Access GC Resources 24/7 Explore Online Tips & Tools 2 3 GC Troubleshooting Guide INDEX BEFORE YOU START 03 PEAK SHAPE PROBLEMS 12 COLUMN SELECTION PROBLEMS 24 PROBLEM PREVENTION 32 COLUMN CARE & USE 38 06 Baseline Problems 07 Bleed 07 Drift 08 Noise 09 Offset 09 Spiking 10 Wander 11 Waves 13 Reduced Size 14 Clipped/Flat 14 Fronting 15 Ghost Peaks 15 Irreproducibility 16 Negative Peaks 17 No Peaks 18 Peaks Added 19 Sensitivity Loss 19 Split Peaks 20 Tailing 21 Retention Time Shifts 22 Solvent Peak Broad 22 Resolution Loss 23 Performance Loss 25 Selectivity 26 Dimension Selection 28 Phase Selection Chart 30 Cross-Reference Chart 33 Injection Techniques 35 Maintenance Schedule 36 Inlet Maintenance 37 Detector Maintenance 39 Column Installation 41 Column Conditioning 42 System Conditioning © 2014 Phenomenex, Inc. All rights reserved. Phenomenex l WEB: www.phenomenex.com 4 BEFORE YOU START Goals & Approaches Troubleshooting Tools An important first step in troubleshooting is understanding the problem. This is best approached systematically; once you have a good understanding of what is causing the problem, it will be easier to implement a logical solution. Understanding the problem can also allow you to alter analysis or maintenance habits to avoid the problem in the future. Prevention is usually the most cost effective solution! Common Troubleshooting Approaches What To Have On Hand Have your instrument manual and these diagnostic tools at hand: • Flow meter with a range of 10 to 500 mL/minute • New syringes • Non-retained, detectable compound such as methane or propane • Septa, ferrules, inlet liners, and other consumables • Electronic leak detector • Reference sample • Reference column with known performance Problem Prevention Many GC problems can be prevented if the column and system are maintained routinely. Problem Prevention (see p. 32) outlines maintenance practices that will reduce the frequency of common issues. These suggestions should be modified to fit your GC column and instrument, and then made a regular part of your laboratory routine. Changing everything relating to the problem may allow a remedy, but won’t allow you to fully understand the solution. In the long run, this may be more costly than other approaches. Narrowing down or eliminating parts of the process may give a good starting point to determine the cause of the problem, but does not necessarily allow you to solve or prevent the problem in the future. A systematic approach includes checking the chromatographic system from one end to the other, isolating the problem, learning what went wrong, solving the problem, and then preventing it. This is the recommended approach! Change Everything Make An Educated Guess Eliminate Problems Systematically Phenomenex l WEB: www.phenomenex.com 5 BEFORE YOU START Tips For Effective Troubleshooting • When troubleshooting, remember to look at recent changes in the system, especially if the system was working previously. Was there something that changed and may be causing the problems now? Can you undo the changes and go back to the original performance? • Try to isolate the problem to one specific cause to minimize the changes that have to be made to the system that may result in other malfunctions. This will also make it easier to prevent the problem in the future and shorten troubleshooting times if a similar problem does occur in the future. • Remember to check every part of the process. Don’t overlook the obvious. If you are not getting peaks for example, the makeup flow to the detector may be off or the syringe may be clogged. Has the sample preparation method been altered? Verify your samples on another instrument if possible. • Keep good records of the troubleshooting process – closely observe and note operating parameters (temperatures, flow rates, columns used, etc.). Reliable system maintenance records (inlet liner changes, detector cleanings, etc.) are also important. For Additional Help • The operator’s and service manuals for the instrument should be consulted. These contain exploded diagrams, troubleshooting procedures for specific models, and part numbers to help you order replacement parts. • Other people in the lab may have had experience solving a problem that is giving you trouble; they can be a helpful resource. • The manufacturer of your instrument can help you. Most GC manufacturers offer free technical support to their customers. Phenomenex has experienced technical consultants who can assist you with almost any problem. We welcome your phone calls or emails! BASELINE PROBLEMS 6 Phenomenex l WEB: www.phenomenex.com 7 BASELINE PROBLEMS Bleed Symptom Possible Cause Suggested Remedy Improper column conditioning. Properly condition the column. See column installation. Contaminated column. There are several options: – Trim the column – Bake out the column – Solvent rinse the column – Replace the column Contaminated injector. Perform inlet maintenance – clean the injector, replace the inlet liner, replace glass wool. See inlet maintenance. Leak in system causing column oxidation. Check for leaks in the system. Tighten or replace connec- tions; replace seals and filters. If column is severely damaged, replace. See column installation. Septum is not conditioned. Condition septum prior to analysis or use pre-conditioned septum. Check septa tempera- ture rating – should be sufficient to run at method temperatures. Septum core is present in the flow path. Remove septum core from the inlet. Check septum nut and make sure it is not over tight- ened. Inspect injector syringe for bent or blunt tip and replace as necessary. Column Bleed Septum Bleed Drift Slow movement of the baseline in one direction (either up or down). Symptom Possible Cause Suggested Remedy Downward drift for a few min- utes is normal after installing a new column. Increase the oven temperature to the maximum continuous op- erating temperature for the col- umn. Maintain that temperature until a flat baseline is observed. If the detector signal continues to raise or does not drop in 10 minutes, immediately cool the column and check for leaks. See column installation. Unequilibrated detector or oven. Allow sufficient time for (tem- perature) equilibration of the detector or oven. Downward drift is frequently due to the “bakeout” of con- taminants from the detector or other parts of the GC. Clean out contamination. See detector maintenance. Excessive damage to the sta- tionary phase of the GC column. Determine the cause of the damage. It may be due to impurities in the carrier gas or to excessive temperatures. Replace column. See column installation. Drift in gas flow rates. Clean or replace flow or pressure regulator(s). Adjust pressure. See column installation. Upward Downward Phenomenex l WEB: www.phenomenex.com 8 BASELINE PROBLEMS Noise Rapid, random movement of the signal amplitude. Symptom Possible Cause Suggested Remedy The column may be inserted too far into the flame of an FID, NPD or FPD detector. Reinstall the column. Be sure to insert the column into the detector exactly the correct dis- tance specified in the instrument manual. See column installation. An air leak can result in noise in ECD and TCD detectors. Eliminate the leak. Incorrect combustion gases or flow rates can generate noise in FID, NPD, or FPD detectors. Be sure your gases are the prop- er grade, as well as clean and dry. Reset the flow rates of the gases to their proper values. Contaminated injector. Clean injector. Replace inlet liner. Replace glass wool. See injector maintenance. Contaminated column. Bake out the column.Cut off first 4 inches of column. Solvent rinse or replace column. See column installation. Drift in gas flow rates. Clean and/or replace parts as necessary. See detector maintenance. Defective detector board. Consult GC instrument manufacturer. Noise Phenomenex l WEB: www.phenomenex.com 9 BASELINE PROBLEMS Offset Sudden unexplained changes in baseline position. Spiking Peaks with no width, either positive or negative. Symptom Possible Cause Suggested Remedy Line voltage changes. Monitor line voltage for correla- tion with offset. If correlation is found, install voltage regulator. Poor electrical connections. Check electrical connections. Tighten any loose connections. Clean any dirty or corroded connections. Contaminated injector. Clean injector. Replace inlet liner. Replace glass wool. See injector maintenance. Contaminated column. Bake out the column. Cut off the first 4 inches of column. Solvent rinse or replace the column. See column installation. Column inserted too far into the flame of FID, NPD, or FPD detectors. Reinstall the column. Be sure to insert the column into the detector exactly the correct dis- tance specified in the instrument manual. See column installation. Contaminated detector. Clean the detector. See detector maintenance. Gas generator cycle. Baseline fluctuations can occur as the generator turns on and off. Add a tank with the appropriate volume after the generator to buffer uploads/Management/ gc-troubleshooting-guide.pdf