The electrode array detector also gives improved apparent chromatographic resolution in a similar way to that of the diode array detector. Two peaks that have not been chromatographically resolved and are eluted together can still be shown as two peaks that are resolved electrochemically and can be quantitatively estimated. Another advantage is that high oxidation potentials can be used without the high background currents and noise that usually accompany such operating conditions. The electrodes that are operating at high voltages are "buffered" by the previous electrodes operating at lower voltages which results in reduced background currents and noise.
Another example of the application of the detector to the separation of a number of neuroactive substances (54)is shown in figure 63. It is seen that for certain applications the electrochemical array detector can be extremely useful.
Mobile Phase 1% Methanol to 40% Methanol in a Phosphate (0.1 mol l-1 buffer with ion pairing (pH 3.4)
|1. Dihydroxyphenylacetic acid||16. Metenephrine|
|2. Dihydroxyphenylethylene glycol||17. Methoxyhydroxyphenyl glycol|
|3. L-Dopa||18. Methoxytyramine|
|4. Dopamine||19. N-methylserotonin|
|5. Epinephrine||20. Norepinephrim|
|6. Guanine||21. Normetenephrine|
|7. Guanosine||22. Salsolinol|
|8. Homovanallic acid||23. Octopamine|
|9. Hydroxybenzoic acid||24. Seratomin|
|10. Hydroxyindoleacetic acid||25. Tryptophan|
|11. Hydroxyphenylacetic acid||26. Tyrosine|
|12. Hydroxyphenyllactic acid||27. Uric Acid|
|13. Hydroxytryptophan||28. Vanillic acid|
|14. Kynurenine||29. Vanylmandelic acid|
|15. Melatonin||30. Xanthine|
Courtesy of the Analyst.
Figure 11 The Separation of 30 Neuroactive Substances Monitored by an Electrochemical Array
Nevertheless, in order to use the detector, the solutes must be amenable to electrochemical reaction and capable of being separated using a mobile phase that will conduct an ion current