Picture the scene. It's Monday morning, the laboratory lights flicker to life, analysts are slowly trickling into the lab, trying to switch themselves back on, after a relaxing week end, or in some cases a heavy weekend of partying. An analyst goes to the HPLC column drawer in the lab, rummages around for a few minutes before the familiar call breaks the silence and resounds across the lab "Anybody know if column 'XYZ ' is in good condition".  The not-too-convincing reply from the other side rebounds  " I might have used that one last week, it was OK then". The first analyst responds with relief "Great, I'll use this one then, any idea what's in it?"  It's a scenario witnessed at some point even in the best-run HPLC labs. However in a former capacity as Sales Director to a UK column manufacturer, while visiting labs the length and breadth of the UK, I was literally amazed at how I could witness this scenario every day in a different lab. 

Depending on your viewpoint HPLC Columns may be either an expensive consumable item, or the least expensive component of your HPLC system to replace, but regardless of the cost, they are the most critical component as far as the analysis goes. Changing the pump or detector for a different brand and still get the same result, but change the column material to a different brand of ODS and the analysis results can differ markedly. This, as experienced chromatographers know, is down to the surface chemistry of the silica packing material in the column. Different pore sizes, different surface areas, different carbon coverage, and different silanol activity, all contribute to make each brand of ODS column different. But that's not all that can affect the separation. Day after day water, solvents, buffers, samples and their matrix are pumped endlessly through the column, all the time affecting the column's surface chemistry. Water affects the silanol interaction, while organic solvents can re-solvate adsorbed impurity from previous samples. Components of the sample matrix can be retained or partially retained on the surface of the column packing and buffers can create various long-term effects on the chemistry of the packing and by precipitating in the column. Low pH can hydrolyse the bonded phase while high pH can dissolve the silica. Even when the column is not in use, if not stored in the correct concentrations, water and solvents can affect the surface chemistry of the material.

 Now lets return to the analyst we depicted above. He has his  XYZ' column ready to attach to the LC system now. What does the analyst know about the column? He knows the packing material and dimensions of the column. He doesn't know what solvents are currently in the column, he doesn't know if there are buffers in the column, he doesn't know what samples went through the column and he doesn't know if the column is contaminated. To be certain he must flush the column with various solvents and then equilibrate the column, before he can even test it.  How many times can HPLC chromatographers recall putting an HPLC column on a system to equilibrate and coming back fifteen minutes later€¦. thirty minutes later€¦ an hour later, only to replace the column with a different one and start again? To make maters worse, because the column failed to equilibrate and was never actually tested, nine times out of ten the analyst returns the column to the drawer, where it will lie till the next analyst repeats the process. Maybe it will work with a different equilibration for a different analysis, who knows, but one thing is for certain - one hour was wasted and at least another hour will go the same way at a later stage.   

HPLC Column Management is all about having solid information and knowledge to replace hopes and guesswork. Managing your HPLC columns produces large time-saving benefits by reducing or eliminating washes, equilibrations, unexpected lumps and bumps we get instead of a baseline when we attach an HPLC column with no history, to an HPLC system. To start with, HPLC columns need to be readily identifiable. The physical limitations of the column packing material should be highlighted to users ensuring that they are not exceeded, causing irreversible damaged to the column and costly re-analysis on a new column. To maximise effective analytical lifetime a column's proposed usage should be defined when new, and if necessary limited to a particular analysis, thus minimising spurious peaks often created by a contaminant from a different analysis. Their washing and storage conditions can also be defined, ensuring that columns are clean and require minimal equilibration prior to their next use. Lastly the columns analytical history should be recorded, thus ensuring that unexpected contaminants are avoided at a later date. The net result is complete audit trail on the HPLC column. A useful by-product of the exercise is that critical information on column performance and expected lifetime is generated. Premature failure can be identified. Such issues can be raised with your column manufacturer and defended by hard information. For the first time, meaningful comparisons can be made between different brands of column.

The first step in managing you HPLC columns is to take control of your column inventory. Columns are normally uniquely identified by their manufacturers serial number, but generally these numbers are inconsistent and far from easy to remember. Start by re-tagging all of your columns with a simple numbering system starting at '1'. Make sure you use permanent labels or tags and solvent resistant markings. Some column companies actually sell metal tags for this purpose. The second step is to create a logbook with at least a double page for each column. Alternatively a card file system or a relational database can be employed. Next decide which columns have to be set aside for specific analyses, and which columns are to be available for general analysis. Mark this clearly in the logging system. The next step is to define the physical limitations e.g. pH, temperature, pressure, %organic/aqueous, etc and again record this in the logbook clearly. Lastly define the washing and storage solvents for the column and record these in the log book. Each time a column is used it is signed out and when it is returned it is signed back in. The returning analyst should also note down the number of injections, the type of analysis and the solvents used. Lastly he notes the solvent left in the column after washing. In this way whenever a column is taken out of the drawer the analyst knows what the column may be used for, what solvents it contains and what condition its in.

 Building a relational database enhances the basic system, offering speed benefits when locating columns and when recording replicate details plus the added benefits automated reminders and warnings. This requires modest relational database skills to link, query, and automate data entry in related tables containing column details, usage, care, validation, history, performance. A database also offers ease of reporting and summarising, for stock and inventory control.

 If the logbook sounds a bit tedious and secretarial, but the software writing sounds a bit daunting then don't despair, there is help at hand in the form of a software program to take care of all these processes for you.