Application of an ion pair reagent to biosensors

The biosensors based on the enzyme electrode in a flow injection analysis s uffer an interference from hemacyte, macromolecules and some lower molecula r weight species in whole blood, plasma, serum or urine, besides endogenous electroactive species such as ascorbate. This often results in an increasi ngly serious tailing phenomenon in the response current peak of substrates. A unique method used daily is to cover the outer enzyme membrane with a po rous ultrafilter film to isolate it from hemacyte and macromolecules but no t from some smaller molecules. In the present paper, we first introduce a t ailing inhibitor-ion pair reagent into the flowing buffer system for elimin ating the tailing phenomenon from the complex matrices on biosensors. When 0.25 or 0.5% tetrabutylammonium chloride (V/V) was added to 0.02 M phosphat e buffer, serious lags of whole blood, plasma, serum and urine on the two b iosensors for uric acid and glucose disappeared entirely so that their resp onse time was shortened to about 50 seconds; their base lines also became m ore smooth and stable. Thus, the resulting two biosensors were capable of d etecting over 60 biosamples per hour. The reported experiment shows that th e tailing inhibitor has effects on the response current and response time o f various biosamples and on the concentration of the dissolved oxygen in bu ffer, with no evident effect on the recoveries of glucose and mate in biosa mples with both sensors. The finding confirmed that some lower molecular we ight species with negative charge result in the serious tailing phenomenon in the response current peaks of various biosamples on the glucose and mate biosensors in a now injection system.