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: A method of analysis in which a first fluid is delivered to a sensing position at a controlled first rate of flow through a fluid junction. Fluid including this first fluid is pumped to the sensing position at a rate of flow greater than the first rate, whereby to aspirate further fluid into the first fluid at the fluid junction. A condition of the fluid is sensed at the sensing position. Associated analytic apparatus includes first and second pumps (1, 2). The first pump has a pair of ports and the second pump has at least one port. A conduit (4, 5) provides fluid flow communication from a first of the ports of the first pump (1) to the port of the second pump (2). A fluid junction (3) in the conduit (4, 5) is spaced from the second pump for admitting a further fluid to the conduit. A sensor (13) is associated with the conduit (5) to sense a condition of the fluid in the conduit at least at a sensing position between the fluid junction (3) and the second pump (2).

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.

Abstract: An electrode calibration apparatus which automatically calibrates a sensing electrode by providing a flow sensitive valve member which seals off flow of calibrating solution to the electrode during flow of a test solution past the electrode, but which permits calibrating solution to contact the electrode when the flow of test solution is interrupted.