Effect of conditioning time on a novel PVC-based membrane for chemFET sensitive to histamine

Histamine is produced by the decarboxylation of histidine in fish muscle tissue. When histamine is ingested in excessive amount, Scombroid poisoning occurs. Scombroid poisoning is a type of allergy with symptom such as headache, nausea, vomiting, diarrhea, facial swelling and low blood pressure. Existing methods to detect histamine include HPLC and TLC. However, they are expensive; in need of well trained technician and are laborious and time consuming. In contrast, ISFET is robust, cheap, miniaturization enabling and simple. This is the first attempt to apply ISFET technology on detection of histamine. Our previous work has shown histamine can be detected by depositing a PVC-based liquid membrane, plasticized with DOP added with ionophore Mn(TPP)Cl and polyHEMA layer on the insulator gate of ISFET. In order to increase the sensitivity of ISFET towards histamine, the effect from duration to condition the ISFET in 0.05 molar of histamine, is examined here. It is found that ISFET A and C, which show good sensitivity near Nernstian response towards pH, are showing good sensitivity towards histamine also. It is also observed that the longer the conditioning time, the lower the sensitivity. ISFET A is found to display a more stable and repeatable performance, at a sensitivity of about 7mV/dec. The sensitivity is found higher with 1 hour conditioning in 0.05 molar of histamine.