Separation of analytes
Separation of analytes - contextAnalyte mixtures and separation - 1Analyte mixtures and separation - 2Analyte mixtures and separation - 3Introduction to chromatographyChromatographic columnsPrinciple setup of a chromatographic unitExample of separationChromatographic system - 1Chromatographic system - 2Standard gas chromatograph(Old) liquid chromatography unit(New) liquid chromatography unitHPLC columnsComparison GC and HPLC
Selftest
1) Purpose of chromatographic process Answer 2) Unsuitable compounds Answer 3) HPLC vs. GC Answer 4) Detectors Answer 5) Solvent properties Answer 6) Retention time Answer 7) Analyte identification Answer 8) Irreversible or reversible sorption process Answer 9) Short analysis time Answer 10) Retention factor Answer 11) Breakthrough-curve AnswerProblems
End of lesson6) Retention time
Question:
Which possibilities are there to estimate the retention time of an analyte on GC or HPLC with a given column and conditions?
Answer:
There are some software packages available but we (the authors) have no experience with them and cannot judge how good they are.
For some columns and conditions one may find predictive equations such as those shown in Table 20 in the script that one can use if the interaction descriptors of the analyte (Table 9 in the script) are known (see also Illustrative example 14 in the script) or can be estimated by using http://pharma-algorithms.com/webboxes/ (hit the ABSOV button). For temperature and solvent gradients such equations will only work if the gradients are steady and typically in this case one will have to calibrate an own individual equation for the specific chromatographic conditions that one has. In practice, the most realistic way is to use as much of the above information to estimate the retention behavior relative to other compounds with known retention times.
 |
 |