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Article: Save Solvent, Save Time, Save Money
Published
in "What's New in Scientific and Laboratory Technology Magazine"
Date:
October / November Edition 1998, Pages 28 And 29.
The highly competitive nature of today’s business world means that every aspect of business must be cost-effective and customer responsive. All laboratories whether QA/QC, R&D or public analytical, must meet the challenge of tighter legislative controls, (e.g. NATA, ISO 9000, TGA, FDA), tighter timetables and tighter budgets.
In a manufacturing industry, the customers might be internal (manufacturing and product release) or external (end-user) but their requirements are no different to those of any private analytical firm-the correct result, in a convenient time, at the lowest possible cost.
Recent surveys of HPLC users have indicated that many are wasting thousands of dollars because they are not making use of all available cost minimizing technology.
There are a number of money saving products on the market, but perhaps the most affordable and easiest to use is a Mobile Phase Recycler or Solvent Saver. New generation devices are superior to earlier analogue models in that they are microprocessor-controlled instruments of extreme versatility, low cost and numerous benefits.
How They Work:
The “firmware” (built in software) in a solvent saver uses the HPLC’s detector signal as a “trigger” to operate a recycle valve and send mobile phase (MP) to waste if a peak is present or, if there is no absorbance, recycle the mobile phase back to the reservoir for re-use. Simple Interactive programming allows the user to select the exact mode of operation required, including a Rejection Limit in absorbance or millivolt terms, a recycle Delay Time to ensure tubing is rinsed and a Rate Mode to compensate for long term detector drift. A Manual Mode is available to manually switch the valve during set up.
Features:
- Rate Mode: Compensates for long term detector drift, allowing instruments to continue running at operational flow rates when not in use (highly desirable in a situation requiring immediate results at long intervals e.g. production support, drug trials, clinical “stat” tests). This feature also ensures optimal recycling for long injection times and in situations where an incorrect initial baseline “zero” has been established.
- Injection Detection: If no injection has occurred for a specific period of time, the system recycles continuously.
- Wash Trigger: A HPLC event trigger can be used to set a solvent saver to wash the column and then send a “pump off” trigger.
- Pump Off Control: Most current HPLC pumps will accept a "Pump Off" trigger, which the solvent saver can send after the HPLC run has been completed, and the column has been rinsed with a wash solution.
- Reboot Operation: This ensures that if a laboratory suffers a power interruption, the recycler will re-start. Without this feature HPLC systems could run dry after their pumps have re-started, or the mobile phase might be contaminated if the recycler rebooted into an “idle mode’ which recycles continuously.
- Validation Output: In a highly regulated environment all instruments must be validated as performing their required functions correctly. This is easily done with any recycler with a “validation output”.
A chart recorder may be attached to a Solvent Saver via this output. This will show both a trace of the analogue detector output (signal), and when the mobile phase is rejected (one tick) or recycled (two ticks). Critical parameters of the MP (e.g. pH, conductivity and peak retention time) are measured at the start of the run, the recycler is attached and the run completed. The rejection of contaminated mobile phase is confirmed on the chart, critical parameters are confirmed as within specification and documented results stored for audit purposes.
Primary Benefits of Solvent Savers:
The cost of a mobile phase for a routine, standard, reverse phase HPLC run (24 hours or less) is over $35. This includes preparation time, materials cost and waste disposal costs. Other indirect costs, which should be considered are:
If the analysis is not correct- time spent in repeating the analysis, lost instrument time, delayed results, lower customer satisfaction.
If the system has run dry- time spent in checking pistons, changing pump seals and de-bubbling the HPLC system.
It is not unusual for two litres of MP to be prepared for an overnight run, all of which ends up as solvent waste. Solvent savers can cut usage of MP down to less than 200ml and so cut run costs to under $10 per run.
Given that some companies are running a large number of HPLCs and that this can lead to solvent saver purchases for as little as $1000 it is easy to see that such an accessory would not only pay for itself in a very short time, but also significantly reduce overall laboratory running costs.
Secondary Benefits:
Many regulatory bodies, such as TGA, require that all anomalous results, whether outside of specified limits or simply out of trend against past results, should be investigated and a probable cause assigned. In any such investigation the more variables are changed, the harder it is to draw a conclusion and the longer it takes to do so.
Solvent Savers mean that there is inevitably adequate MP left to launch an investigation. It is much easier then to simply re-inject standards and failed test solutions to confirm results.
Without the solvent saver either a very large excess of MP must be made up for every run, or MP must be freshly prepared, the system suitability re-established, and finally the investigation started. In both cases both time and money are wasted.
Whenever a HPLC system running a MP containing both organic solvents and salts runs dry, pump piston and seal wear results.
Checking and replacing seals and pistons takes time and the components can be expensive. If seals and pistons are not checked and replaced, erratic performance can result, leading to further time spent investigating poor results and repetition of work.
Environmentally, of course, the benefits of reduced toxic waste disposal are self-evident and something we should all be working towards. Even methanol is now considered toxic and a possible carcinogen, so decreasing the amount discharged is a positive step.
Conclusion:
No matter how simple or how complex the requirement, there is probably an instrument available to meet it. The basic aim, however, remains the same: Save Solvent, Save Time, Save Money.
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