Abstract: Apparatus and a regionless method of ascertaining the activity of each radionuclide in a dual-label sample. A set of correlation curves is generated utilizing quench standards for both a low energy radionuclide and a high energy radionuclide. A test sample was then counted and the quench-indicating parameters for the test sample are compared with the quench-indicating parameters of the correlation curves to determine the appropriate contribution of each radionuclide to the overall energy spectra of the test sample. From this comparison the overall count rate for the test sample may be allocated between a low energy radionuclide and a high energy radionuclide. By dividing the count rates by efficiencies determined from another set of correlation curves the actual disintegration per minute (DPM) rate for each radionuclide may be ascertained.

Abstract: A method for ascertaining radiochemical homogeneity in a liquid scintillation sample reliably identifies inaccurate geometries is disclosed so that meaningful activity counts can be determined. The novel method involves measuring the activity level of a set of homogeneous quench standard to obtain quench indicating parameter, or the Spectral Index of the External standard (SIE). The endpoint of each standard sample is computed allowing the formation of a table so that a calibration curve for each radionuclide of interest can be computed. The activity level of the unknown sample is then measured and the SIE determined so that an endpoint can be calculated. Finally, the theoretical endpoint obtained from a calibration curve is compared to the computed endpoint; if the computed endpoint of the sample deviates by more than 4% for tritium and 5% for higher energy radionuclides from the theoretical endpoint, the sample is considered to be nonhomogeneous or heterogeneous.

Abstract: A pipetting system for dispensing multiple liquids into a single receptacle includes a plurality of liquid reservoirs, a plurality of syringes for aspirating preselected quantities of liquids from the reservoirs, and a common dispensing head connected to all the syringes for simultaneously receiving the preselected quantities of liquids from a plurality of the syringes and simultaneously dispensing the liquids into the reservoir. The system also includes means for simultaneously aspirating the preselected quantities of liquids from the reservoirs into the syringes. In addition, the system includes aspirating means for withdrawing a liquid sample from a container into the dispensing head at an aspirating position, means for storing the aspirated sample while the dispensing head is moved from the aspirating position to a dispensing position, and means for dispensing the aspirated sample to the dispensing head simultaneously with the dispensing of the preselected quantities of other liquids.