A method for identifying a liquid-liquid interface (FI) between a first liquid (F1) and a second liquid (F2) in a conduit through which at least the first liquid (F1) and the second liquid (F2) are configured to pass, the conduit having an ultrasonic flow meter coupled thereto, the method comprising: transmitting, via the ultrasonic flow meter , an acoustic signal into the conduit ; receiving, via the ultrasonic flow meter , a reflected acoustic signal; determining, via a controller , an amplitude of the reflected acoustic signal; characterized by calculating a standard deviation of the amplitude of the reflected acoustic signal measured at various time points; determining if the standard deviation of the amplitude of the reflected acoustic signal exceeds a predetermined threshold of the amplitude of the reflected acoustic signal; identifying the liquid-liquid interface in the conduit when the standard deviation of the amplitude of the reflected acoustic signal exceeds the predetermined threshold of the amplitude of the reflected acoustic signal, wherein the liquid -liquid interface (FI) is identified independent of the temperature; determining, via the controller , a speed of sound of the reflected acoustic signal based on transit time of the reflected acoustic signal; calculating a standard deviation of the speed of sound of the reflected acoustic signal; determining if the standard deviation of the speed of sound of the reflected acoustic signal exceeds a predetermined threshold of the speed of sound of the reflected acoustic signal; and identifying the liquid-liquid interface in the conduit when the standard deviation of the speed of sound of the reflected acoustic signal exceeds the predetermined threshold of the speed of sound of the reflected acoustic signal. transmitting, via the ultrasonic flow meter , an acoustic signal into the conduit ; receiving, via the ultrasonic flow meter , a reflected acoustic signal; determining, via a controller , an amplitude of the reflected acoustic signal; characterized by calculating a standard deviation of the amplitude of the reflected acoustic signal measured at various time points; determining if the standard deviation of the amplitude of the reflected acoustic signal exceeds a predetermined threshold of the amplitude of the reflected acoustic signal; identifying the liquid-liquid interface in the conduit when the standard deviation of the amplitude of the reflected acoustic signal exceeds the predetermined threshold of the amplitude of the reflected acoustic signal, wherein the liquid -liquid interface (FI) is identified independent of the temperature; determining, via the controller , a speed of sound of the reflected acoustic signal based on transit time of the reflected acoustic signal; calculating a standard deviation of the speed of sound of the reflected acoustic signal; determining if the standard deviation of the speed of sound of the reflected acoustic signal exceeds a predetermined threshold of the speed of sound of the reflected acoustic signal; and identifying the liquid-liquid interface in the conduit when the standard deviation of the speed of sound of the reflected acoustic signal exceeds the predetermined threshold of the speed of sound of the reflected acoustic signal. <EOS>