there is provided the reagent layer composition that can substantially reduce the measurement bias arising from hematocrits . the addition of fatty acid and quaternary ammonium salt to a commonly used reagent layer composition composed of an enzyme , an electron transfer mediator , and several water soluble polymers not only reduce the hematocrit level - dependent bias but also provide very stable performance for an extended period of time . disclosed are also various types of sub microliter sample volume electrochemical biosensors that are suitable to use with the reagent layer composition of present invention .