A flow conduit system (100,200a,200b) suitable for biochemical sensing, the flow conduit system comprising, a first flow cell conduit comprising one or more sensing areas for biochemical sensing; a first selector valve; a second selector valve; a first inlet/outlet conduit which fluidly connects the first flow cell conduit to the first selector valve; a first injection conduit having a first end and a second end; a second injection conduit having a first end and a second end; a fluid injecting means fluidly connected to the second ends of each of the first and second injection conduits (6, 7) so that the fluid injecting means can selectively inject fluids into the first and/or second injection conduits (6,7); a control unit for controlling the fluid injection means and the first and second selector valves (4,5); wherein the first injection conduit is fluidly connected, at its first end, to the first inlet/outlet conduit by a valveless junction, and the second injection conduits is fluidly connected, at its first end, to the first inlet/outlet conduit by a valveless junction; wherein the control unit is configured to consecutively, (i) open the first selector valve and close the second selector valve, and to then initiate the injecting means to inject a sample fluid which contains molecules to be sensed into the first injection conduit, so that the sample fluid flows through the first injection conduit and to the first selector valve; and, (ii) close the first selector valve and open the second selector valve, and to then initiate the injecting means to inject a sample fluid, which contains molecules to be sensed, into the first injection conduit, so that the sample fluid flows through the first injection conduit and through the first flow cell conduit to the second selector valve. a first flow cell conduit comprising one or more sensing areas for biochemical sensing; a first selector valve; a second selector valve; a first inlet/outlet conduit which fluidly connects the first flow cell conduit to the first selector valve; a first injection conduit having a first end and a second end; a second injection conduit having a first end and a second end; a fluid injecting means fluidly connected to the second ends of each of the first and second injection conduits (6, 7) so that the fluid injecting means can selectively inject fluids into the first and/or second injection conduits (6,7); a control unit for controlling the fluid injection means and the first and second selector valves (4,5); wherein the first injection conduit is fluidly connected, at its first end, to the first inlet/outlet conduit by a valveless junction, and the second injection conduits is fluidly connected, at its first end, to the first inlet/outlet conduit by a valveless junction; wherein the control unit is configured to consecutively, (i) open the first selector valve and close the second selector valve, and to then initiate the injecting means to inject a sample fluid which contains molecules to be sensed into the first injection conduit, so that the sample fluid flows through the first injection conduit and to the first selector valve; and, (ii) close the first selector valve and open the second selector valve, and to then initiate the injecting means to inject a sample fluid, which contains molecules to be sensed, into the first injection conduit, so that the sample fluid flows through the first injection conduit and through the first flow cell conduit to the second selector valve. (i) open the first selector valve and close the second selector valve, and to then initiate the injecting means to inject a sample fluid which contains molecules to be sensed into the first injection conduit, so that the sample fluid flows through the first injection conduit and to the first selector valve; and, (ii) close the first selector valve and open the second selector valve, and to then initiate the injecting means to inject a sample fluid, which contains molecules to be sensed, into the first injection conduit, so that the sample fluid flows through the first injection conduit and through the first flow cell conduit to the second selector valve.