A method for aspirating and dispensing a liquid sample in an automated analytical instrument, said method comprising using an apparatus comprising: (a) an aspiration probe, operably connected to a pump, and adapted to enter a sample container to aspirate a liquid sample within such container; (b) a transport system for selectively advancing the aspiration probe in mutually perpendicular planes so that said aspiration probe can aspirate or dispense liquid from or to different containers spaced apart; and (c) a liquid-sampling valve, operatively connected between said aspiration probe and pump, and comprising structure defining at least one aliquoting chamber (S1;S2) for temporarily storing a precise volume of liquid sample to be dispensed; the method comprising operating the pump selectively to either (i) draw a liquid sample through said aspiration probe and through the liquid-sampling valve to fill said aliquoting chamber (S1;S2), or (ii) to dispense an already aspirated liquid sample through said liquid-sampling valve and through said aspiration probe; said method further comprising operating the liquid-sampling valve selectively in either (i) a loading configuration in which the liquid sample aspirated by the aspiration probe under the influence of the pump will pass through the liquid-sampling valve while simultaneously filling said aliquoting chamber (S1;S2) thereof, or (ii) a segmenting/dispensing configuration in which the liquid sample within said aliquoting chamber (S1;S2) is positioned to be dispensed from said liquid-sampling valve to a reaction chamber (RC1, RC2) by a force external to the liquid sampling valve, while said pump operates in a suck-and-spit mode aspirating a liquid sample from a sample container and dispensing an already aspirated liquid sample to a reaction chamber (RC3, RC4) through said aspiration probe and through said liquid-sampling valve. (a) an aspiration probe, operably connected to a pump, and adapted to enter a sample container to aspirate a liquid sample within such container; (b) a transport system for selectively advancing the aspiration probe in mutually perpendicular planes so that said aspiration probe can aspirate or dispense liquid from or to different containers spaced apart; and (c) a liquid-sampling valve, operatively connected between said aspiration probe and pump, and comprising structure defining at least one aliquoting chamber (S1;S2) for temporarily storing a precise volume of liquid sample to be dispensed; the method comprising operating the pump selectively to either (i) draw a liquid sample through said aspiration probe and through the liquid-sampling valve to fill said aliquoting chamber (S1;S2), or (ii) to dispense an already aspirated liquid sample through said liquid-sampling valve and through said aspiration probe; said method further comprising operating the liquid-sampling valve selectively in either (i) a loading configuration in which the liquid sample aspirated by the aspiration probe under the influence of the pump will pass through the liquid-sampling valve while simultaneously filling said aliquoting chamber (S1;S2) thereof, or (ii) a segmenting/dispensing configuration in which the liquid sample within said aliquoting chamber (S1;S2) is positioned to be dispensed from said liquid-sampling valve to a reaction chamber (RC1, RC2) by a force external to the liquid sampling valve, while said pump operates in a suck-and-spit mode aspirating a liquid sample from a sample container and dispensing an already aspirated liquid sample to a reaction chamber (RC3, RC4) through said aspiration probe and through said liquid-sampling valve.