Abstract: Apparatus are provided which automatically add diluent/quench reagent in such a manner as to enable adequate mixing as well as a short period for further mixing in automated immunoassay techniques. The probes for adding the diluent/quench reagents are offset from the optics module probe so that reagents are being added to a second row while the optics probe aspirates solutions from a first row.

Abstract: Methods and apparatus useful in automated performance of immunoassays, in some preferred embodiments, relying upon the sandwich immunoassay technique, are described. Each rack of reaction tubes is uniquely identified by an optical identifier disc which is read by the automatic controller. The assays are performed at two stations which configuration thereby permits arrays to be run on a second rack of reaction tubes while the first rack is in process. The cooperation of the identifier disc and the automatic controller minimizes operator error and helps improve the reliability of the data obtained.

Abstract: Apparatus and method for adding liquid to, aspirating liquid from, a rack of reaction tubes wherein a rack and carriage-dependent probes are made to move relative each other in the horizontal and vertical planes. The method calls for performing the first half of a wash sequence on tube located at x row, y column, then completing the sequence on tube at (x-1) row, y column, and returning to the tube at x row, (y+1) column to initiate the first half of the sequence. This "backtracking" of probes permits an incubation-soak period without cumulatively extending the total rack processing time.

Abstract: Means for reducing intersample contamination in an automatic chemical testing apparatus, in which liquid from a sample is aspirated from a sample source into a reservoir, and aliquots of the sample are each dispensed into individual reaction containers for analysis by well-known means. A cylindrical reservoir is utilized with a piston therein shaped for pushing out virtually all of the remaining sample from the cylinder after dispensing the sample liquid through a hollow needle, communicating with the cylinder. A solid pin coaxially mounted within the piston is projected through the needle and has minimum clearance therewith, for pushing remaining sample out of the needle. The portion of the pin projecting through the needle is retracted into the piston prior to aspiration of liquid from a next sample.