Gas Chromatography Troubleshooting and Reference Guide

1 Gas ChromatographyTroubleshooting and Reference GuideVersion , August 2005 Copyright 2005 MSP KofelGC Troubleshooting and Reference GuideTroubleshootingTroubleshooting 1 Eight Problem 1 Baseline 2 Drift (Upward/Downward) .. 2 Irregular Peak Shapes or 2 Reduced Peak Sizes .. 3 Tailing 4 Rounded or Flat-Topped Peaks .. 4 Split 4 Negative 4 Retention Time 4 Loss of Separation or 4 Quantitation 5 Rapid Column 5 Ghost 5 Broad Solvent Front .. 5 Troubleshooting 6 ReferenceWhat Is a Capillary Column?

2 7 Stationary Phase 8 Bonded and Cross-LinkedStationary 8 Column 9 Column 9 Film 10 Phase Ratio ( ) .. 11 Temperature 12 Column 12 Chemical 13 Column 13 Selecting Capillary 14 Column Installation Tips .. 15 Carrier 16 Makeup 17 Capillary GC 18 Injection 19 Split 19 Splitless 20On-Column 21 Megabore Direct 21 Injector 22 Split Injector 22 Splitless Injector 22 Megabore Injector 24 Guard Columns/Retention 24 Unions, Glass 25 Column 26 Performance 26 Column Test 28245 Troubleshooting GCThe gas chromatograph and capillary column function as a complete system and not as two individual parts.

3 A problem or defi ciency in any part of the system usually will result in some type of chromatographic difficulty. The same problem can be caused by a number of different system deficiencies. A logical and controlled roubleshooting procedure will quickly and accu rately identify the source of the prob lem. This will result in the fastest, easiest and most complete solution to the problem. Troubleshooting is a skill that be comes easier with practice. Someone equipped with the right tools and a rudimentary understanding of cap illary column gas Chromatography , can identify, locate and correct prob lems with minimal amount of effort.

4 Troubleshooting Tools Flowmeter A digital or manual model with a range of 10 to 500 mL/min is suitable. New Syringe A working syringe that has not been used for samples should be avail able. Some problems may actually be syringe or autosampler related. Methane or Another Nonretained Compound A non-retained compound is used to set and verify carrier gas flow and to check out injector operation and setup. New Septa, Ferrules and Injector Liners These are used to replace parts that eventually become defective, worn out or dirty.

5 Leak Detector Electronic models are recommended. Liquid leak detection fluids are satisfactory, but care has to be exercised to avoid possible contami nation problems. Column Test Mixture or Reference Sample These are used to diagnose select system and column problems. They are useful to compare current system performance to past performance. Checkout Column This is a column that is not used for samples. The performance and quality is known so that evaluation of the system can be made. It helps to verify or eliminate the previous column as the source of a problem.

6 Instrument Manuals These are not a last resort. The manuals are a good source of Troubleshooting information special to a particular model of gas chro matograph. Performance specifica tions are often contained in the manuals. Eight Problem Categories Most performance problems can be placed within one of eight areas. These are baseline distur bances, irregular peak shapes or sizes, retention time shifts, loss of separation or resolution,quan-titation difficulties, rapid column deterioration, ghost peaks and broad solvent fronts.

7 It is not uncommon to have more than one of these prob lems occurring at the same time. Sometimes, it is difficult to deter mine the actual nature of the prob lem. This makes a logical and systematic approach to problem solving very important. It is important to realize that the following comments and recom mendations are generalizations and simplifications. Every possible problem or correction cannot be covered, nor can every detail be mentioned. The page where addi tional information can be found is shown in parentheses following each solution.

8 Baseline Disturbances (Figure 1) see page 2 for figure Spiking: matter passing through the detector. Solution: Clean the detector per the instruction manual. connections on cables or circuit boards (usually random spiking). Solution: Clean and repair the electrical connections as needed. Noise: injector and/or column. Solution: Clean the injector. Solvent rinse the column (pg 26). column is inserted into the flame of an FID, NPD or FPD. Solution: Reinstall the column. leak when using an ECD or TCD. Solution: Find and repair the leak.

9 Combustion gases or flow rates when using an FID, NPD or FPD. Solution: Check and reset the gases at their proper values. defect in the detector. Solution: Clean or replace parts as necessary. detector board. Solution: Consult the instruc tion manual or contact the GC manufacturer. Phone 031 972 3152 2005 MSP163,.,1*12,6(2))6(7:$1'(5'5,)7' :$1'(52))6(7'5,)7 GCTroubleshooting Baseline Disturbances (Continued) Wander: carrier gas if using isothermal conditions. Solution: Change the carrier gas or use (change) carrier gas impu rity traps (pg 25).

10 Gas chromatograph. Solution: Clean the injector and/or gas lines. Solvent rinse the column (pg 26). control of the carrier gas or detector gas flows. Solution: Clean, repair or change the flow controller. thermal control of the detector. Solution: Consult the instruction manual or contact the GC manufacturer. Drift (Upward): or column contamination. Solution: Clean the injector. Solvent rinse the column (pg 26). stationary phase. Solution: Replace the column. Determine the cause of the dam age (oxygen, thermal or chemical) to prevent future problems (pg 15).