chromatography rules of thumb and how are they automated
ChromSmart®
is designed to automate HPLC data analysis and method control. The main
objective is either automated method development or sample analysis. The
key concept is the automatic analysis of equipment operating conditions
and chromatographic data. ChromSmart®
is unique in that it automates rules of thumb to analyze chromatographic
data, make recommendations, and execute those recommendations. Rules of
thumb can range from heuristics to the analysis of model predictions. A
good example of a rule of thumb for reversed phase chromatography is the
"Rule of 3"†: There is approximate a three-fold increase in k for a 10%
decrease in B (strong solvent). This rule would follow an analysis that
analyzes the current experimental results and determines that a decrease
in %B is required, i.e. the peaks are bunched left or an increase in
selectivity is required.
These rules of thumb are abundant in the field of chromatographic
analysis. Often chromatographers are implicitly making decisions based
upon these rules of thumb. To simplify matters, rules of thumb are
separated into two categories: in-method and post-method. In-method
refers to decisions made and actions taken during an actual experiment.
Such rules of thumb are concerned with equipment and method monitoring.
For example, automatic column equilibration consists of several in method
rules of thumb.
Consider a set of in-method rules to automatically determine if a
column is considered equilibrated. The information required to determine
if a column is equilibrated is UV signal source and the current method run
time. Rules that could apply include the following:
- Has the minimum method run time passed?
- Is the baseline stable? A baseline is considered stable if the
difference between the maximum and minimum absorbance over a specified
period of time does not exceed a given threshold.
- Has the baseline been stable for a minimum amount of time?
Many chromatographers may perform this analysis implicitly by simply
observing the chromatogram. Its possible to summarize such rules by
simply taking a step by step approach to the decision making process. The
first step is to summarize the information which is relevant. In this
case the UV signal level and the method run-time are important. The
second step is to summarize the relevant rules. A flow sheet is useful
tool to explore and diagram the information and rules.
Once the information and rules are summarized it is possible to execute
them within ChromSmart®. ChromSmart®
automatically executes rules in decision trees. A decision tree is
essentially an automated flow sheet. The figure below shows a portion of
the in-method, automatic equilibration decision tree.
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