Inter alia , an apparatus for selectively dispensing reagent into first and second vertical reagent dispense axes, for use in an automated analyzer to assay a test sample, the said analyzer having an event conveyor for conveying a plurality of cuvettes along an event path which includes a vertical sample dispense axis, the said first vertical reagent dispense axis which is spaced from and downstream of the said sample dispense axis and the said second vertical reagent dispense axis which is spaced from and downstream of the said first reagent axis, the said apparatus being characterised in that it comprises:

(a) a reagent transport and selection means for supporting a plurality of first reagent containers which contain labeled reagent and a plurality of second reagent containers which contain solid phase reagent, and for selectively positioning any one of the said first reagent containers at one of a first vertical reagent aspirating axis and a second vertical reagent aspirating axis, and for selectively positioning any one of the said second reagent containers at one of a third vertical reagent aspirating axis and a fourth vertical reagent aspirating axis;
(b) a first reagent probe transport means for supporting a first reagent aspirating and dispense probe for selective vertical movement between an upper position and a lower aspirating and dispense position and for selective horizontal movement between the said first reagent dispense axis and either of the said first and third reagent dispense axes;
(c) a second reagent probe transport means for supporting a second reagent aspirating and dispensing probe for selective vertical movement between an upper position and a lower aspirating and dispense position and for selective horizontal movement between the said second reagent dispense axis and either of the said second and fourth dispense axes;
and
(d) control means including a central processing unit operatively connected to the said reagent transport and selection means, the said first reagent probe transport means and the said second reagent transport means for selectively positioning a predetermined first reagent container at either of the said first and second reagent aspirating axes and a predetermined second reagent container at either of the said third and fourth reagent aspirating axes, for selectively positioning the said first reagent probe for aspirating reagent from a selected first reagent container at the said first reagent aspirating axis or a selected second reagent container at the said third reagent aspirating axis, or from both of the said selected first and second selected reagent containers and for dispensing aspirated reagent into a cuvette at the said first reagent dispense axis, and, for selectively positioning the said second reagent probe for aspirating reagent from a selected first reagent container at the said second reagent aspirating axis or a selected second reagent container at the said fourth reagent aspirating axis, or from both of the said selected first and second reagent containers and for dispensing aspirated reagent into a cuvette at the said second reagent dispense axis is disclosed.