Have you ever picked up your mobile phone and stopped to wonder at how far communication technologies have advanced since you were at school? I must admit I rarely give it any thought at all. I’m also pretty certain that most people carrying out routine analysis focus on looking at or using the results, rather than stopping to think about the methods and technology that deliver the data. This is, of course, as it should be. In fact, how it must be if a method is to become one that is used day in, day out, rather than when there is no other choice.
The recent publication of an article by my colleague, Dr. Anne Virden; “Method development for laser diffraction particle size analysis” (Pharmaceutical Technology, Nov 10) is a good reminder that an easy to use method relies on effective developmental work. To get to the point where users of an analytical technique can simply push a button and then gather the data, someone, at some point, must define how the sample for analysis is going to be obtained and what the instrument is going to do with the sample.
Guidance for method development
In Anne’s article, she describes the process of method development for laser diffraction, with reference to ISO13320 (2009) and other guidance documents. The latest edition of ISO13320 is a useful reference for those of you engaged in making laser diffraction measurements, due to the considerable amount of information it provides regarding method development. It reflects a decade of substantial progress in the application of the technique, and is a good resource if you want to learn more. It even provides a description of the fundamentals of how the technique works, for those of you who are mathematically inclined!
Alongside ISO13320, I also think USP<429>, the USP’s general chapter on laser diffraction particle size analysis, is also worth a mention, especially if you are working in the pharmaceutical industry. Again, it provides some useful pointers as to how methods can be developed, reminding users that laser diffraction involves the measurement of ‘a representative sample, dispersed at an adequate concentration in a suitable liquid or gas.’ This is the challenge of method development.
Successful method development depends on rigorous and systematic examination of all the factors known to influence results, including sampling, dispersion/sample prep and measurement conditions. Anne’s article considers each of these issues in turn, helping you to answer questions such as:
‘Should I measure my sample wet or dry?’
‘What dispersant should I use?’
‘Are my dispersion conditions breaking the particles I want to measure?’
‘How do I know if the method I’ve developed is a good one?’
The article takes you step-by-step through all these issues, summarising the important points and directing the way towards a successful conclusion. With the input of years of historical data, shared knowledge and carefully evolved strategies arrived at by industry experts, users can confidently develop robust methods that deliver reliable, automated analysis.
Benefit from the science behind the convenience
Just as I simply pick up my mobile phone and make a call, good method development can allow users to simply walk up to a Malvern Mastersizer , load their sample, take the measurement and obtain a good result. While this convenience is a huge advantage, there are still times when stopping to reflect on the science behind it is equally illuminating. So, why not check out Anne’s article? We’re also interested in your feedback regarding your own method development secrets!