OMD Time Resolution

ALEXYS On-line Microdialysis Time Resolution

• Triple cell control (TCC)
• Parallel analysis for time resolution

The ALEXYS OMD TR is used when time resolution is an issue, the system has a triple loop 14 port valve to analyse 3 sequential fractions simultaneously. If high throughput is a requirement, the system can be used to analyse 3 microdialysis stations in parallel. Microdialysis systems are optimised for analysis of small sample volumes at picomolar detection limits.

Conventional sampling of once every 20 minutes is not enough to accurately describe fast neurochemical responses. To improve time resolution, a 14-port valve with 3 loops connected in series is used to directly collect the microdialysate. The content of these loops is then simultaneously injected on 3 HPLC flow paths that run the same analysis. During analysis the loops are filled with the following set of three samples. A DECADE II Triple Cell Control (TCC) detector acquires all signals. In this way, the time resolution can be improved to 3 minutes.

Figure 1A: On-line microdialysis sampling for improved time resolution. Collection of sample in three sample loops. Figure 1B: Simultaneous injection of sample in three parallel 50 x 1 mm ID LC columns for fast analysis of neurotransmitters.

Fig. 2.Chromatograms of two subsequent analyses with three columns in parallel. The first traces (top left) show the start, without peaks. After 9 minutes the first peaks appear.

System configuration

For the analysis of microdialysates we selected the VT03 electrochemical cell. This cell not only has an excellent reproducibility but also the best possible detection sensitivity. A triple loop 14-port valve is used for sampling.

The ALEXYS system comprises the following parts:

• LC 110S HPLC pump
• OR 110 organiser rack
• Clarity data acquisition software
• DECADE II electrochemical detector, TCC (triple channel)
• VT cells with GC WE
• Valco external valve(s)

No autosampler is required in an on-line setup.

Notes

• 213_025_03 - Monoamines analysis in microdialysates

Posters

• 221_011_05 - Time resolution in online microdialysis
• 221_025_01 - Recent Developments in Neurotransmitter Analysis