Abstract: An analytical element for analyzing a specific component in a liquid sample, comprising a light-transmissive and liquid-impermeable support having thereon successively a first reagent layer and a second reagent layer, and a porous spreading layer provided above said second reagent layer, and containing an electron transport agent, a dye-forming precursor material, an oxidized type coenzyme, a buffering agent and at least one reagent capable of converting said oxidized type coenzyme to a reduced type coenzyme through a specific component in a liquid sample, wherein said oxidized type coenzyme is contained in said porous spreading layer, and a lactate dehydrogenase inhibitor is contained in at least one of said second reagent layer and said porous spreading layer.According to this invention, error originating from LDH and lactic acid present in a biological liquid sample can be eliminated and the accuracy of analysis can be improved.

Abstract: There is disclosed a dry analytical element for .alpha.-amylase in a fluid sample which comprises the analytical element including a starch capable of forming a complex with iodine, an iodine compound and an oxidizing agent, and the iodine compound and the oxidizing agent are disposed in the element so that iodine may be liberated therefrom when the fluid sample is brought into contact with the analytical element.The analytical element of this invention enables an easy, prompt and accurate dry quantitative analysis of a component in a fluid sample, especially a biological fluid sample by the use of visible light with the aid of a spectrophotometer.

Abstract: In a frequency discriminator for a first and a second input signal of a first and a second frequency, a phase detector produces first and second rectangular pulse sequences. When the first input signal leads the second by 0.degree. through 180.degree., the first pulse sequence takes a predetermined peak value with an instantaneous frequency corresponding to the phase difference while the second one continuously has the peak value. When the first input signal lags behind the second by 0.degree. through 180.degree., the second pulse sequence takes the peak value with the instantaneous frequency while the first one continuously has the peak value. A low-pass filter rejects components of the first pulse sequence which are higher than the first and second frequencies.