GC Trouble shooting

Gas Chromatography Gas Chromatograph Detector Injector Data Column Sample injection Chromatogram Detector Injector Carrier Gas Data System Column Gas Chromatograph 1 2

Injector Maintenance Capillary INJ Packed INJ

Injector Maintenance 1. Injector Leak Contamination - Septum, Glass insert & O-ring - Ferrule & Nut Contamination - Septum, Glass insert - Tubing

Injecting whole vaporized sample Packed Injector – Leak Injecting whole vaporized sample <Symptom> Decreased pressure compared to usual Reduced peak area with shifted RT <Remedy> Septum replacement Check the leak on column connection - Flow the gas without column and block the inlet port by a finger -> If column pressure increases, Check column connection ->If not, Check the leak on parts ahead of column - Welding, Sensor or Valve trouble -> Contact an engineer

Packed Injector – Contamination <Symptom> Irregular Ghost peak observed without sample injection <Remedy> 1) Contamination : Septum or Glass insert replacement 2) Check either injector or column contamination Check the ghost peak by injector temperature off, no sample injection, and oven program mode. => If Ghost peak area is reduced by injector temperature off, injector might be contaminated. Replace Glass insert with O-ring. => If Ghost peak area is not reduced by injector temperature off, Column might be contaminated. Condition the column.

Injecting a part of sample Capillary Injector – Leak <Symptom> - Column pressure is reduced - Split vent flow rate is increased as column flow rate is reduced - Reduced peak area with shifted RT <Remedy> Septum replacement Tighten Retainer Nut Check the leak on column connection - Flow the gas without column and block the inlet port by a finger -> If column pressure increases, Check column connection ->If not, Check the leak on parts ahead of column - Welding, Sensor or Valve trouble -> Contact an engineer Retainer Nut Injecting a part of sample

Capillary Injector – Contamination <Symptom> Irregular Ghost peak observed without sample injection <Remedy> 1) Contamination : Septum or Glass insert replacement 2) Check either injector or column contamination as same as packed injector. <Other trouble> Unstable flow rate – Perform Sensor zero, Valve Calibration and check APC parts. Peak area is increased higher 3times than usual. – Split vent Line is clogged. Split Vent line and Trap replacement Abnormal temperature and flow rate display - Check RTD sensor, APC board, Main board, AC power board

Column Oven Maintenance Oven temperature control problem - Temperature doesn`t increase : Check Heater coil resistance. (22ohm) - Abnormal temperature display : Check RTD sensor resistance. (110ohm) - Temperature fluctuation : Check Power supply. (220~240V) 2. Column Performance degradation & Contamination - Poor peak resolution, RT shifted, and Baseline increased <Column conditioning> - Connect the column to injector only and run oven program mode. If new column is connected to FID without conditioning, FID jet is frequently clogged. - Set proper column flow rate as per column ID. 100℃ 1hour 2-3 ℃ /min Column max temp.-30℃

Max temperature for typical columns

Detector Maintenance

Detector Maintenance <FID> <TCD> Ignition failure -Flow rate, Ignitor, Jet Abnormal signal - Collector contamination, FID B/D failure <TCD> Sensitivity trouble - Abnormal TCD cell -TCD B/D failure - Leak

FID – Ignition failure 1. Ignitor coil isn`t brighten after GC makes ‘Tic’ sound. => Coil is broken. Ignitor Replacement. 2. Flow rate check: Air 300, H2 30-40, Mkup 10-25(Cap). If Air or Mkup flow rate is too high, ignition is generally failed. If H2 flow rate is high, ignition sound is loud. 3. Jet or gas line is clogged. Check the Jet status under Room temp. Flow check Air H2

FID – Abnormal signal Normal signal is less than 50 1. Maximum signal display: 1,000,000 1) Moisture in FID => Bake FID out at 300 ℃ or clean the collector. 2) Shortage between spring and FID => Check FID whole assembly position. 3) FID B/D failure => Board replacement 2. High signal 1) Before ignition: Collector contamination (Clean it with Acetone) 2) After ignition: - Jet, or Gas line contamination - Injector or Column contamination (Plug FID port by a blank Nut and check the signal whether it is from FID, Injector, or Column.)

TCD – Sensitivity failure *Caution : Turn on Filament after all gas flows to TCD. Turn off Filament before turn off gas flow rate. * Check TCD cell resistance under room temperature. 1) Low sensitivity 2) Abnormal signal TCD Board and cell connection

TCD – Low sensitivity 1) Check Sam/Ref flow rate by a Flowmeter => Check the Leak in Cell Tubing. => Check the Leak on column connection. 2) Set proper Sense value? 6100GC : H2,He : 6, N2 and Ar : 3 or 4 6500GC : H2: 10, He : 8 or 9, N2 and Ar : 6 or 7 3) TCD Cell resistance measurement : Difference must be within 0.5Ω. 4) TCD B/D failure : Board replacement

TCD – Abnormal signal * Normal TCD signal under same Sam/Ref flow rate -Block Ref outlet by a finger for a second and signal changes to +3000. -Block Sam outlet as same as above and signal must change to -3000. (1:1 proportion change but polarity is opposite.) 1) Maximum signal display - Difference flow rate between Sam and Ref is too high and no flow rate either Sam or Ref. - Cell contamination =>Thermal conditioning (300 ℃) 2) Signal doesn`t change from Sen 0 to 9. TCD B/D failure =>Board replacement