Fault Diagnosis and Solution of Gas Chromatograph
A. Possible reasons for all component peaks becoming smaller 1. Suggested measures 1. Defective injection needle use new needle or non-defective needle 2. Judge the night leakage after sample injection, repair 3. Night MAE is too large: the split ratio is too large to adjust Gas flow rate and split ratio 4. The molecular weight of the analyzed substance is too large, and the INJ is increased when the sample is evaporated. OVEN (the highest temperature of the main column makes the vaporization temperature of the sample too low, or the column temperature is low)
5 NPD is covered with contaminants (silica) to replace the rubidium beads 6. NPD temperature is too high (use or ambient temperature), gas is not pure Replace the rubidium beads: avoid high temperature use 7. Splitless injection, the split valve is closed quickly: initial OVEN Wen Gao
8 The detector does not match the sample
9. Volatilization of the sample Adjust the concentration of the sample or choose a suitable solvent
B. Peak tongue extension The peak tongue extension is mostly caused by the overload of the chromatographic column. Reduce the injection volume (may need to increase the sensitivty of the instrument)
Use large capacity column: increase OVEN, INJ temperature:
Increase gas flow rate
C. The peak area is not repeated 1. The injection is not repeated, the deviation is large. The automatic sampler: strengthen the manual injection practice 2. The peak dislocation caused by other peak shape changes, interference 3. The baseline interference instrument system parameter setting changes Parameter standardization
D. Negative peak 1 Detector has data processing system with signal polarity reversed and signal connection inverted 2 In TCD, the thermal conductivity of the sample is greater than the thermal conductivity of the carrier gas Select "Negative Peak Processing" in data processing
3 The ECD is contaminated. The positive peak may be followed by the negative peak. Clean the ECD and replace it (if necessary)
E. Decreased detection sensitivity of the sample 1. The chromatographic column and liner are contaminated, making the active material less sensitive. Cleaning the liner: cleaning the column with solvent (superior pure methanol): replace it (if necessary)
2. Leakage of the sample during injection (more so for volatile substances) Find the leak point 3 In the splite vaporization injection, the initial temperature of OVEN is too high to be lower than the initial temperature of the sample solvent; this causes the diffusion of the sample after vaporization to increase Tearing boiling point samples with reduced sensitivity using high boiling point solvents
F. Peak bifurcation 1 The injection is too aggressive and unstable, forming a second injection exercise. Manual injection: using an autosampler 2. Failure to install the chromatographic column. Reinstallation 3. Spliteless or on-column injection. The sample solvent is mixed using the same Solvent 4. Column temperature fluctuation repair stability control system 5 spliteless injection, large volume and long time. It is hoped that the "solvent is installed at the front end of the capillary column for 5 meters of de-effect". When the band is concentrated, the solvent's stationary phase is poorly wetted, and the capillary solvent that is not covered with the fixing solution will form a solvent with a length of several meters in the column and varying thickness The band disrupts normal concentration and widens the peak
G 〠Peak tailing 1. The liner and the chromatographic column are contaminated; there are active spots to clean and replace (if necessary)
2. The liner and the chromatographic column are not installed, and there is dead volume injection of methane. If the peak is tailed, reinstall it. 3. The column head is not flat and cut with emery to make it flat. 4. The polarity index of the stationary phase is not analyzed with the sample. Match and change the matching column 5 There is a cold well in the sample circulation route to eliminate the low temperature zone in the route 6. There is accumulated cutting debris in the liner or chromatographic column. Clean and replace the liner; remove the column head 10cm
7 The injection time is too long, shorten it 8. The split ratio is low Increase the split ratio (at least greater than 20/1)
9. The injection volume is too high. Reduce the injection volume or dilute the sample. 10 Alcohol amines, primary amines, tertiary amines, and carboxylic acids are easy to tail. Use a polar column; sample derivation treatment
A. Possible reasons for all component peaks becoming smaller 1. Suggested measures 1. Defective injection needle use new needle or non-defective needle 2. Judge the night leakage after sample injection, repair 3. Night MAE is too large: the split ratio is too large to adjust Gas flow rate and split ratio 4. The molecular weight of the analyzed substance is too large, and the INJ is increased when the sample is evaporated. OVEN (the highest temperature of the main column makes the vaporization temperature of the sample too low, or the column temperature is low)
5 NPD is covered with contaminants (silica) to replace the rubidium beads 6. NPD temperature is too high (use or ambient temperature), gas is not pure Replace the rubidium beads: avoid high temperature use 7. Splitless injection, the split valve is closed quickly: initial OVEN Wen Gao
8 The detector does not match the sample
9. Volatilization of the sample Adjust the concentration of the sample or choose a suitable solvent
B. Peak tongue extension The peak tongue extension is mostly caused by the overload of the chromatographic column. Reduce the injection volume (may need to increase the sensitivty of the instrument)
Use large capacity column: increase OVEN, INJ temperature:
Increase gas flow rate
C. The peak area is not repeated 1. The injection is not repeated, the deviation is large. The automatic sampler: strengthen the manual injection practice 2. The peak dislocation caused by other peak shape changes, interference 3. The baseline interference instrument system parameter setting changes Parameter standardization
D. Negative peak 1 Detector has data processing system with signal polarity reversed and signal connection inverted 2 In TCD, the thermal conductivity of the sample is greater than the thermal conductivity of the carrier gas Select "Negative Peak Processing" in data processing
3 The ECD is contaminated. The positive peak may be followed by the negative peak. Clean the ECD and replace it (if necessary)
E. Decreased detection sensitivity of the sample 1. The chromatographic column and liner are contaminated, making the active material less sensitive. Cleaning the liner: cleaning the column with solvent (superior pure methanol): replace it (if necessary)
2. Leakage of the sample during injection (more so for volatile substances) Find the leak point 3 In the splite vaporization injection, the initial temperature of OVEN is too high to be lower than the initial temperature of the sample solvent; this causes the diffusion of the sample after vaporization to increase Tearing boiling point samples with reduced sensitivity using high boiling point solvents
F. Peak bifurcation 1 The injection is too aggressive and unstable, forming a second injection exercise. Manual injection: using an autosampler 2. Failure to install the chromatographic column. Reinstallation 3. Spliteless or on-column injection. The sample solvent is mixed using the same Solvent 4. Column temperature fluctuation repair stability control system 5 spliteless injection, large volume and long time. It is hoped that the "solvent is installed at the front end of the capillary column for 5 meters of de-effect". When the band is concentrated, the solvent's stationary phase is poorly wetted, and the capillary solvent that is not covered with the fixing solution will form a solvent with a length of several meters in the column and varying thickness The band disrupts normal concentration and widens the peak
G 〠Peak tailing 1. The liner and the chromatographic column are contaminated; there are active spots to clean and replace (if necessary)
2. The liner and the chromatographic column are not installed, and there is dead volume injection of methane. If the peak is tailed, reinstall it. 3. The column head is not flat and cut with emery to make it flat. 4. The polarity index of the stationary phase is not analyzed with the sample. Match and change the matching column 5 There is a cold well in the sample circulation route to eliminate the low temperature zone in the route 6. There is accumulated cutting debris in the liner or chromatographic column. Clean and replace the liner; remove the column head 10cm
7 The injection time is too long, shorten it 8. The split ratio is low Increase the split ratio (at least greater than 20/1)
9. The injection volume is too high. Reduce the injection volume or dilute the sample. 10 Alcohol amines, primary amines, tertiary amines, and carboxylic acids are easy to tail. Use a polar column; sample derivation treatment
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