1385541 Analysing substances using photoelectric apparatus; dispensing device for automatic analysis ABBOTT LABORATORIES 12 April 1972 [12 April 1971] 16981/72 Headings G1A and G1B A specimen or specimens of a chemical substance or substances is (are) analysed by passing an analyzing beam of radiant energy intermittently through the same specimen or successively through different specimens, converting the beam emerging from the or each specimen into an analysis signal having a value proportional to a property of the specimen at the time the beam is passed therethrough converting each analysis signal into a digital signal representing a digital number, storing at least one digital number constituting a reference or created by at least one of the analysis signals in a memory, and comparing the at least one stored digital number with a digital number subsequently produced by the passing of the beam through the same or a different specimen. As described, a plurality of specimens are dispensed into individual cuvettes of a cuvette assembly 30 and the specimens are subsequently analvzed. Cuvette Assembly 30, Figs. 2-4 (not shown) This consists of a plurality of compartments, such as 67, 83 shown in Fig.5, arranged in a circle and mounted for rotation. The assembly is formed integrally of acrylic plastics, which transmits ultraviolet light, the compartments being defined by spacers. Light is transmitted through plane parallel laver walls of each compartment. The assembly dips into a water bath 124 which is maintained at a constant temperature. Associated with each compartment is a test tube 138 which each contain a specimen, the test tube assembly being mounted for rotation with the cuvette assembly each test tube and corresponding cuvette being identified by means of binary coded holes (152) in skirt 132, the holes being illuminated by light transmitted by light pipe 156. Dispensing Apparatus 200, Figs. 8-17 (not shown) The cuvette assembly and test tube assembly are intermittently rotated by an arrangement, Fig. 7 (not shown). The dispenser consists of a microsyringe (280), a micro-syringe (290) a container (272) holding reagent and a valve (300). Each time the assemblies stop the dispensing assembly operates so that a probe 212 (260) dips into a test tube and the valve is operated and a carriage mounting the plungers of the syringes is lowered so that the specimen in the test tube is sucked into the micro-syringe and reagent is sucked into the micro-syringe. Thereafter, the probe (260) is positioned in the corresponding cuvette and the valve is operated and the carriage is raised so that the reagent and specimen contained in the syringes are dispensed into the cuvette, the reagent from the micro-syringe passing via the valve through a hollow bore in the plunger of the micro-syringe Fig. 13 (not shown) to the cuvette. The probe (260) is then returned to its original position ready for the next test tube. When the assemblies are rotated to the next position, the cuvette containing the dispensed reagent and specimen is positioned adjacent the analyzing apparatus. Analyzing Apparatus, Figs. 5, 20 and 23. This consists of a filament light source 402 which emits visible and ultraviolet light, lenses 406, 407, mirror 408, a rotating disc 410, Fig. 20, containing filters, lens 456, mirror 457, mirror 458, lens 460, photo-multiplier tube 462, and analyzing circuitry, Fig. 23, connected to the output of the photo-multiplier 462. Disc 410, which is rotated continuously consists of windows containing filters 414, 416 centered on a wavelength L1, filters 418, 420 centered on a wavelength L2, and filters 420, 422 centered on a wavelength L3, and slits 432-442 for synchronizing purposes. Thus, each cuvette in the analyzing position has three beams at different wavelengths passed therethrough, the beams, after passing through the cuvette, passing through the corresponding filters displaced by 180 degrees on disc 410. The photomultiplier thus provides three output pulses for each specimen. These three pulses, after amplification, are synchronized through three filters 490, 491, 492 by signals from phototransistors 443a, 443b, 443c which receive light through the slits 432-442. After passing through the filters 490-492, the pulses are passed to a logarithmic ratiometer which provides an analysis signal corresponding to log. (JP 2 +KP 3 /LP 1 )where J, K and L are constants, and P 1 , P 2 and P 3 are the pulses corresponding to light at the wavelengths L 1 , L 2 , and L 3 respectively. The analysis signal is then digitised and applied to a counter 536. Operation During the first cycle of the assemblies the apparatus is calibrated. Up-dating and adjustments are made. As described three different types of analysis may be made using the apparatus. A. Slow rate determination During the first cycle of operation, the cuvettes are supplied with the specimens as previously described. During the second cycle, the value of each analysis signal applied to the counter 536 is written into the memory 562 together with an identity code for each cuvette supplied by phototransistors 716-720 associated with coded holes in the cuvette assembly. During the third cycle each analysis signal is compared in the counter with the corresponding stored value and the remainder is displayed on a display 563 and recorded on a printer 564. Each analysis signal obtained during the third cycle is stored in memory 562. Further cycles may then be provided and analysis continues as described above. B. Rapid rate determination During the first cycle, the cuvettes are supplied with specimens as previously described. During the second cycle, each specimen is analyzed at short intervals e.g. every 15 seconds. Thus for each specimen a set of time-spaced analysis signals are sequentially stored in memory 562 and the value of each succeeding analysis signal is compared with a previous analysis signal stored in the memory. After one specimen has been analyzed in this manner, the next specimen is supplied for analysis. C. End-point determination One of the specimens comprises a known concentration of a substance, and other specimens contain unknown concentrations of the substance. The value corresponding to the known concentration is stored in the memory and other value corresponding to the unknown concentrations are compared with the value stored in the memory. Details of the circuitry of Fig.23 are described with reference to Figs.24-38 (not shown).