Purchase of Used Laboratory Instruments

Nanjing Aikon Scientific Instruments offers a wide variety of second-hand analytical instruments, including liquid chromatographs, gas chromatographs, liquid chromatography-mass spectrometers, and gas chromatography-mass spectrometers. These instruments undergo rigorous screening and testing to ensure stable performance and accurate data, meeting users' needs across various application scenarios. Whether it's analytical instruments for research laboratories, or related instrument consumables, accessories, repairs, relocation, or leasing services, Nanjing Aikon can provide users with suitable solutions.

Chromatographic Peak Issues Caused by Chromatography Columns

1. Ghost Peaks or Carryover Contamination?

System contamination causes most ghost peaks or carryover contamination issues. If the additional ghost peaks have a similar peak width to the sample chromatographic peaks (with similar retention times), the contaminant may have entered the column simultaneously with the sample. Potential sources of additional components include the injector (e.g., contaminants) or the sample itself. Impurities in solvents, sample vials, vial caps, and syringes are also possible sources. Analyzing the sample and blank solvent separately can help identify the source of contamination. If the ghost peaks are much wider than the sample chromatographic peaks, the contaminant likely existed in the column before the sample entered. Residual components from a previous interrupted sample run remain in the column and elute later during the sample run, resulting in broader peaks. Sometimes, multiple injections can lead to overlapping ghost peaks or hump-shaped elution, accompanied by baseline drift.

Increasing the final temperature or extending the temperature programming time can reduce or eliminate ghost peaks. Additionally, performing a short column bake after each or several sample analyses can remove strongly retained compounds from the column, preventing adverse effects. Conducting a condensation test can determine whether contamination in the injector is causing carryover contamination or ghost peaks.

2. Why Do Sample Peaks Appear in Blank Runs?

This is related to sample preparation or system cleanliness. Replace the solvents used in sample preparation, blank preparation, and syringe washing vials. Use new syringes and septa. Remove and clean the split vent line. Run a blank temperature program without injection to observe whether the peaks are due to heating the column.

3. Is It Normal for Standard and Sample Peaks to Widen with Increasing Retention Time?

If the retention time does not change significantly but the peaks become wider and tailed, this indicates active sites in the system. If the widened peaks are symmetrical, it suggests normal column efficiency loss. If the peaks are fronting, it indicates column overload.

4. Excessive Baseline Noise?

5. Unstable or Erratic Baseline?

6. Tailing Chromatographic Peaks? 

Contamination in the injector or column, or an uneven column cut. Cool down the injector, turn off the gas flow, and replace or clean injector components, including the liner and gold-plated seals. Remove the column and trim a section from the column inlet to eliminate residual non-volatile components, septum material, and graphite ferrule debris. The length trimmed can range from 1 foot to 1 meter or more, as needed. Using the correct column cutting tool is crucial; uneven cuts can cause sample adsorption. Thoroughly clean the injector before reinstalling any components. Solvent cleaning of the split vent line is recommended.

When using splitless mode for analysis, excessively long splitless times can cause tailing. Commonly set times are 0.5 to 1 minute.

Volume can also cause tailing. Ensure the column is properly installed in the detector and injector.

If the same column length must be maintained, consider using an uncoated retention gap (a pre-column before the analytical column). The retention gap can be trimmed or replaced without losing column efficiency and can effectively extend the column's lifespan. When using a retention gap, ensure the connection between the retention gap and the analytical column is leak-free and does not adsorb samples.

7. Split Peaks?

8. Changes in Peak Size?

9. Retention Time Changes?

10. Loss of Resolution?

Nanjing Aikon Scientific Instruments Co., Ltd. is such a trustworthy partner. Whether it's selecting second-hand analytical instruments, laboratory equipment, daily maintenance, or technical support, Nanjing Aikon Instruments will be your choice.