Abstract: A method and apparatus for recalibrating analytical instruments such as atomic absorption and inductively coupled plasma spectrophotometers comprises the use of coupled piston pumps and valves in a fluid conduit system to obtain a sample value (h) during one half of a pump cycle and standard gradients (S1-S6) during the other half cycle. The piston pumps are actuated by cams of selected profiles to obtain a predetermined flow rate from each pump, the flow from each pump being selectively combined to construct standard gradients from two or more standard solutions and to effect autoranging of the standards in response to a previously determined sample value.

Abstract: Fluid mixing apparatus includes a non-magnetic conduit (4) and a magnetically susceptible rod (5) which is contained in and extends longitudinally of the conduit. The rod is substantially not permanently magnetized. A least two electromagnets (6, 7) are positioned externally of the conduit so that each may, when activated, individually cause movement of the rod across the conduit. The electromagnets may be activated in turn and one at a time to induce an effective vibratory mixing motion of the rod within the conduit.