Buffer, Buffer, Toil and Trouble
Maybe Shakespeare's witches got it right! Buffers are common in many laboratories, serving a variety of important functions - to control mobile phase pH in HPLC, to control conditions for an extraction, or to aid a chemical reaction. But they can be double the trouble if not prepared and used correctly.
Why is pH control so important? We want to control the equilibrium in acid-base dissociation reaction:
The left side of the equation is the "neutral" form, while the right side is the "ionic" form for the acid (bases work the same way, except that the neutral form is on the left.
The neutral and ionic forms usually have different properties:
- The neutral form is more soluble in organic solvents.
- The neutral form is less soluble in water.
- The neutral form has longer retention in reversed phase HPLC.
- The neutral form may elute from a GC column, while the ionic form will not.
Buffers can also cause problems:
- They may be corrosive to stainless steel.
- Some are not very soluble in organic solvents.
- Buffers may precipitate from solution after preparation, This would be bad news if it happens inside an HPLC.
- They may contain particulates.
Preparation is equally important:
- Use the highest purity available (reagent grade or better).
- Calibrate your pH meter before use. Never assume it is calibrated.
- Never attempt to measure/adjust the pH of a solution that contains 10% or more organic solvent. Adjust the pH before you add the organic solvent.
- Filter the solution if it is to be used for HPLC.
- Protect from light and change often - microbes like to grow in buffers.
As we review methods or observe laboratory procedures, we see several common problems related to buffers. Learn to avoid these problems:
- Many methods do not even need a buffer.
- Microbial contamination will occur long before it is visible. Once you can see something growing, you have a big problem. We have seen entire HPLC systems contaminated. EVERY piece of equipment and glassware must be thoroughly cleaned, rinsed with organic solvent, and maybe even sterilized once you have this problem.
- Many procedures use buffers when they are not necessary, or prepare them at higher concentrations than are really needed.
- Choosing the best buffers for HPLC is important. Solubility and UV cutoff are far more important than concentration in some systems. In other separations, the concentration of buffer can actually change retention times.
Are you having problems choosing, preparing, or using buffers in your laboratory? Call us for a review and assistance. We have a long record of saving labs time and money on their procedures . . . but you have to contact us to see the benefit. |
We are pleased to report that the article "Investing to Save" by Dr. Merlin Bicking has been published in the December issue of Lab Manager Magazine.
This article discusses how laboratories can properly calculate the benefits of an investment in process improvements, technology changes, and even training. By learning to calculate Return on Investment (ROI), laboratory staff have more tools to sell their proposals to management.
The article is available on-line. Click here to view.
Would You Like to Learn More?
We would be happy to discuss this specific issue in more detail, but let's make it part of an overall discussion of how we can help you reduce the stress on your lab and lab staff. Click here to contact us.
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Expense Saving Solutions from
ACCTA, Inc.
With three decades of experience teaching labs about how to get the most from their chromatography systems, we are confident that we can make improvements to your methods and procedures, and save your laboratory both time and money. Click here for more details. |
Regards,
Merlin K. L. Bicking, Ph.D.
ACCTA, Inc. |
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| Concerned about the cost and benefits of the investments that we describe? Contact us for a personalized Cost-Benefit Analysis (CBA) that will show your management what a good investment this can be. Contact Robert Zarracina for details. |
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