Mohammed Esa, SF; Lee, KY; Jarmin, R
Histidine, a type of amino acid in fish muscle tissue, is capable of causing scombroid poisoning. This happens when the toxin produced by the fish due to mishandling of storage, histamine, reacts with the decarboxilased enzymes. Ingesting of histamine exceeding the FDA safety limit of 100ppm brings on symptoms of scombroid poisoning such as facial swelling, headache, vomiting, diarrhea and low blood pressure. Existing techniques for detecting histamine such as HPLC and TLC are expensive in terms of cost, labour and time, as well as in need of seasoned physicians. On the contrary, recent advances in semiconductor IC technology based manufacturing enables production of robust, simple, cost effective and miniaturized ISFETs. Literature review found majority previous works on ISFETs for detection of H+-ions. However, ISFETs can be adapted to detect other ion types. Our previous work, being the first attempt, has shown that ISFET can be adapted for detecting histamine with the use of a novel polyvinylchloride (PVC)-based membrane, plasticized with dioctyl phthalate (DOP), dissolved in tetrahydrofuran (THF), enhanced with ionophore manganese tetraphenylporphyrin chloride (Mn(TPP)Cl) and polyHEMA layer on its insulator gate.This paper intends to determine the membrane deposition volume and conditioning time for membrane to achieve high Nernstian slope of sensitivity. It is found that ISFETs that are sensitive to H+-ions also are sensitive to histamine ions. In examining the effect of deposition volume, it can be deduced that a deposition volume of 20μL is optimal for sensitivity of adapted ISFETs to histamine ions. In examining the effect of conditioning time, it is observed that adapted ISFETs with membrane conditioned for 1 hour are found with higher sensitivity than those for 3 hours, over the full range of histamine solution concentration, in 0.05 molar of histamine conditioning solution and at a constant 20uL of membrane cocktail.