I am having problems with commercial probes (Without mentioning company name). The probes fail after about 4-6 hours in the brain. The collection volume drops. The probes are not broken. They appear to curl at the tip blocking the return solution. About 60% of the probes fail this way. When taken out of the brain and straightened they work again.
Questions: 1) what is the failure rate that is acceptable?
2) Where is the dialysis solution going? Is the dialysis solution going through the membrane under pressure?
3) any suggestions to improve the collection volumes?

They should not fail after 4-6 hours in the brain. I have probes that last through 10-20 sessions of microdialysis and sometimes longer then that. If there is nothing coming out of the outlet side of the probe then your dialysate is leaking out of the probe. I have recently started using a new type of probe that is suppose to be more durable and does not need to be kept cold. The probe is the CMA Elite. Also what is your profusion rate? If the rate is too high this may be putting too much pressure on the probe. I hope this helps.

I am using a flow rate 0.5 microliters per minute. The probes appear to be curling. The curled membrane obstructs the return solution for the dialysate. I looked more carefully and found that the dialysis perfusion solution can't get out. The increased the pressure, usually dripping out of one of the connectors or breaks the seal on the syringe. The membrane is not broken it doesnt drip from the tip of the probe.
I will take a look at the Elite probes.
How long are your 10-20 sessions?
Thank you it did help.