"Reducing Lab Stress With
Analytical Solutions To Analytical Problems"

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Vol. 3, No. 2.  February, 2014

 In this issue...
Writing the Perfect Method
Part 2 - Reagents, Solutions, Supplies

Writing the Perfect Method!

Your goal should always be to write a perfect method, even if you aren't always successful!  Can you answer "yes" to the following questions?

• Can anyone use this method as written?
• Do you know what samples can and cannot be analyzed, and what kind of information will be produced?
• Do users know all the procedures needed needed for success?

Last month we started with the "Scope" section of your method.  This month we move on to the next section.

Part 1: Reagents, Solutions, and Supplies:
 
It is important to list everything needed to perform the analysis.  Nothing is more frustrating than having to stop in the middle of the procedure to find something that wasn't on the list. 

The same idea applies to any solutions that must be prepared, especially calibration standards.  If they should be prepared in a certain order, or the order of reagent addition is important, that must me in the method.

Step back from your own experience and ask yourself - "have I included everything that I would do if I were in the lab following the method for the first time?"

Do:

• List all reagents in their proper chemical form (hydrate, anhydrous, etc.) as they would be purchased and used.
• List the required purity or grade if it is important.  In important analytical methods, it almost always is critical. 
• Provide suggested suppliers (e.g., USP), only if that is important to method success.
• Indicate what grade of glassware should be used.  Most analytical methods require Class A volumetric containers.  TC or TD should also be specified.
• Carefully describe preparation of pre-mixed mobile phases.  Adding two volumes together or adding one solution and diluting to volume will not produce the same concentration in the two mixtures!  Describe which procedure must be used.

Do Not:

• Specify a single supplier unless you are certain that only one source is acceptable.
• Specify part/product numbers in the method, unless necessary.  These numbers can change (as can suppliers) and then you must change the method.
• Allow choices or options for critical processes and components.  If it is important to success, it must be performed a certain way.
• Assume that a future reader will understand what you are thinking or doing.  You may not have control over who is assigned to follow this method, or how much experience that they have. 

Some labs will have a separate section, appendix, or document with "Notes" for the procedure.  These notes are the little tricks and suggestions that make the method easier, or faster, or more reliable.  Every good lab scientist knows the "secrets" to success.  Your method is an opportunity to help train future scientists.


Would you like us to evaluate your methods, or comment about this topic?  Contact us.

Quote for the Day

"In any science, then, one must present at the very outset evidence of repeatability, replication, reproducibility, accuracy, and precision ... repeatability or precision of analysis done in one laboratory by a single individual on a single day with one particular piece of equipment does not constitute science; that is a combination of science and art ... when we make a single observation without then proceeding to ensure it can be demonstrated again and again is when we start to fall off the cliff of reality and enter the twilight zone of irreproducible results. Those are results that should not and must not be published ..."

– Professor Ira S. Krull,
"Guest Editorial — Reproducibility, Reproducibility, and Reproducibility,"
American Laboratory: Nov 2000, pp 7-8.