Friday, 30 April 2010

Help on: Use of Caffeine for Wavelength Accuracy

MTS HELPDESK

Do you have any problems relating to analytical chemistry for pharmaceuticals or training? Send your questions to the MTS helpdesk using our contact form.

Question:
“Can you tell me why caffeine is used for the calibration of HPLC systems? I know it shows two maxima (205 nm & 272nm) & minima at245, apart from this property why is it used?”

Answer:
“The main reason that caffeine is used for the wavelength accuracy test is as you have already identified, it contains chromophores which absorb at the wavelengths you have quoted. Other reasons are that it is easily available and relatively safe to handle, this makes it an ideal choice for this test. In addition organisations which certify calibration standards, such as NIST in America, specify the use of caffeine for the test and thus the calibration can be performed in a NIST-traceable manner.”

Friday, 23 April 2010

MTS Recommends... Reduced Robustness Testing for Analytical Methods

Reduced method robustness testing of analytical methods driven by a risk-based approach’ by Phil Borman, Marion Chatfield, Patrick Jackson, Alice Laures, and George Okafo in Pharmaceutical Technology Europe, Volume 4, Issue 22

This article details an interesting approach to reducing the number of factors investigated during a robustness study. Basically the factors which are chosen to be studied in an experimental design are further reduced by performing a risk analysis of each factor and combining factors where possible. As we hear more and more about addressing method robustness earlier in the method development process as part of Quality by Design, more efficient approaches to performing these studies become desirable.

The thing that stands out for me about this article, and indeed all discussions of robustness, is that although the statistics and design of experiments is very important (and I think this article describes these quite well) the most important contribution to robustness testing comes from the experience of the analyst who understands the actual effects of the factors involved and can identify those which are most important. The risk assessment performed in the case study described in this article was performed by ‘GC experts’. Without this contribution the studies cannot produce meaningful results.

MTS Recommends... Using %RSD Correctly

%RSD: Friend or Foe? When to use percent relative standard deviation—and how to do so correctly.’ By Lynn D. Torbeck in Pharmaceutical Technology, January 2010, Volume 34, Issue 1, pp. 37-38

In most analytical laboratories percent relative standard deviation
(%RSD) is used extensively as a measure of variability. It is important to understand how to use, and how not to use, this useful statistic. This article from Lynn Torbeck provides a good guide to proper use.

Tuesday, 6 April 2010

HPLC Calculator for Mobile Phase Buffer Strength

PEAK SOLUTIONS
A resource for chromatographers

The HPLC calculator from MTS has been updated to include working out how much buffer salt to weigh out when preparing mobile phase.

Let us know your suggestions for HPLC calculations that you would like to be added to the calculator.