Recently, Ade Kujore (Cecil Instruments), Tracie Brombos (GenTech Scientific) and I were asked by Angelo De Palma, a well-respected writer for Lab Manager magazine, to contribute to an article about maintaining and caring about your laboratory instruments.
Here are my tips/best practices for column and HPLC/UHPC/UPLC system maintenance.
Maintaining your LC columns
Proper storage of HPLC columns will increase longevity and performance. For long-term storage, it is best to follow manufacturer’s recommendations. Waters recommends storing used columns in 100% acetonitrile and avoiding long-term storage in buffered eluents. If the column was used with buffered mobile phase, it is recommended that the column be flushed with HPLC grade water followed by 100% acetonitrile.
Failure to flush with water may cause the mobile phase buffers to precipitate within the sorbent bed and potentially harm the column. Completely seal the column with the supplied end plugs to prevent drying of the chromatographic bed.
Maintaining your HPLC/UHPLC/UPLC systems
When working with any LC system, setting it up and storing it is very important. When preparing a system to run your method, it is always important to prime up the system to ensure you get fresh solvents in all of the required lines. The chemist should prime all the solvent lines on the system, not just the ones he/she plans to use. This not only replaces old solvent in all the lines, it ensures efficient performance of the degasser by evenly distributing the vacuum pressure across the entire manifold. By priming all solvent lines, the user also ensures that old solvent is not stagnant in the solvent lines to grow algae or bacteria that could affect system robustness.
Similarly, users should ensure that the pump seal wash is primed and running properly. This ensures that the pump seals get cleaned and protects the pump seals from getting damaged, thus maintaining the performance of the pump.
Users should also consider the mobile phase they are using when they select which solvent to use for the seal wash as well as the frequency at which to wash the pump seals. For customers using corrosive mobile phases or high concentration mobile phases, they should increase the frequency of the mobile phase to improve pump seal life.
Users should prime the needle wash and purge solvents in the autosampler as well. When selecting a solvent for the needle wash, users should use a solvent that is miscible with their sample to minimize the amount of carryover from injection to injection. These solvents should be primed at the same time that the mobile phase lines are primed to ensure fresh solvent is used throughout the system.
When setting up the detector, users should ensure proper warmup time for the unit (Waters recommends a minimum of 30 minutes) before starting any analysis to ensure a stable baseline for quantitation. Users should regularly check and know the lamp energy on the detector, as a precipitous drop of that energy can provide indication of possible issues with the lamp, flow cell or internal optics of the system, and they should call the field engineer to fix the problem.
When the chemist is done performing analyses, it is important to clean the system by flushing the unit out with water (for systems running reverse phase chromatography) and then storing the system in an organic water mobile solvent mixture to mitigate bacterial growth when the system is sitting idle.
The importance of high-quality autosampler consumables in modern HPLC and UHPLC analysis
The sensitivity of modern analytical instrumentation has advanced and samples become more precious. Autosampler consumables need to keep pace with these changes. Customers want to access most of their valuable sample and program autosamplers needles to go deep into the vial to access the limited sample volume. The needle could come in contact with the out-of-dimensional tolerance vial resulting in needle damage and system down time. Vials must be held to tight dimensional tolerances to avoid system damage.
Cleanliness of the vial and septa has also become critical with increasing sensitivity of HPLC and UHPLC systems. 10-15 years ago, customers started to see contaminants from vial and septa residues from the manufacturing process. The residues were always present, but peaks started to appear above the base line as systems became more sensitive. This requires suppliers to improve processing and handling capabilities.
As system sensitivity continues to improve, the chemistry limits of materials being used in autosampler consumables today are being challenged. Vendors will need to innovate processes or materials to ensure the consumables keep up with instrument advancement.
View the full Lab Manager article, “Down-proofing Your HPLC & UHPLC Systems“.
I have a written a blog on detectors and also a blog series on binary vs quaternary pumps for liquid chromatography. You are welcome to follow my blog!