GB1369146A - Chemical analyzer - Google Patents

Abstract

1369146 Photo-metric chemical analysis; sampling for analysis ROHE SCIENTIFIC CORP 23 June 1972 [24 June 1971] 29541/72 Headings G1A and G1B Apparatus for the chemical analysis of liquid samples presented in rows of containers at a readout station comprises means for lowering probes into the row of containers, an aspirator and a distributor for withdrawing samples sequentially from the containers through the probes, and readout means for analysing the successive samples presented by the distributor. A bulk sample is fractioned into a row of test tubes and mixed with appropriate reagents by the apparatus shown in Fig. 1d. The sample is placed in container 27 and the probes 39 lowered into reagent containers 43. Peristaltic pump 31 is operated to pass predetermined quantities of sample and reagent into each one of a row of test tubes 32 mounted in a rack (not shown). The probes 39 are then lifted and the remainder of the sample is ejected by pump 33. A quantity of buffer solution is inserted into container 27 and the pump 31 again operated to transfer a predetermined quantity to each of the test tubes 32. The excess buffer is ejected by pump 33, the test tube rack is advanced to present the next row of tubes and the next sample is placed in the container 27. The test tube rack is then passed to a readout station Fig. 1c which detects the first row of tubes; stops the conveyor and lowers a row of probes 36 into the test tubes. The samples are sequentially removed from the row of tubes by means of an aspirator and a distributor 48 which has a rotor arranged to connect each of a number of peripheral tubes connected to the probes lowered into the test tubes with a central tube connected to the aspirator and the readout head. The conveyor comprises a slideway for the test tube rack and a chain drive 16 having angle members (24) arranged at spaced intervals which engage the rear of the test tube rack and push it along the slideway. As shown, Fig. 8, the reading head may comprise a cuvette 108 through which the sample flows, a light beam from lamp 110, collimating lens 114 and filter 116 passing through the cuvette and its intensity being measured by a detector 112. Part of the light is split off by a curved mirror 118 and is received by a reference detector 122 the output of which is subtracted from that of the measuring detector 112 to produce an output which is applied to a voltmeter and a print out device. The reference detector 122 is provided with a slit 124 the width of which can be adjusted to zero set the system and an opaque plate 124a is provided which can be used to block the measuring beam during the adjustment of the full scale value of the measurement. The light source may be a W filament lamp or a Hg, H or Xe lamp. The detectors may be Se or Si cells, photo-tubes or photo-multipliers. A logarithmically scaled voltmeter may be used to provide a readout of the concentration. In a modification, Fig. 8a (not shown) the curved mirror (118) is replaced by a plane stainless steel plate having parallel rulings which reflects a circular beam to a line focus. As shown, Fig. 9, the reading head may also comprise a plasma jet photo-meter comprising a spray aspirator 126 in which the sample is converted into a fine mist in an Ar flow which is then ionised by two electrodes 138a, b, the resulting jet 139 emitting radiation which is detected by an optical system using a filter 202 which selects the radiation emitted by a particular chemical element. A plurality of detectors may be arranged round the flame to take measurements at different wavelengths and one of these may be used as a reference for the others e.g. if the water used as a diluent contains a known concentration of Li, a detector with a Li filter may be used as a reference for the other detectors which measure the concentrations of the elements Na, K, Ca, Mg and Cl. Conventional photo-meters may also be used. In another system, Fig. 10 (not shown), an adjustable monochromator comprises a broad spectrum Hg-Xe source which emits from the UV to the near IR wavelengths, the light from which is collimated and then passed through a prism or a diffraction grating to produce a spectrum which is reflected by a mirror onto a plate having a narrow slit which passes a monochromatic beam for transmission through a cuvette to a detector. Alteration of the angle of the mirror moves the spectrum across the slit so that different wavelengths can be selected. The mirror is provided with an adjusting mechanism which operates in synchronism with the distributor so that successive samples in a row are illuminated with monochromatic light of different wavelengths. In a modification the different wavelengths are selected by interference filters mounted in apertures in a disc which can be rotated to position them in turn in the light path. In a specific blood serum test described, the measuring head is used to detect the fluorescence of a certain compound when illuminated by light of a specific wavelength, decrease of the fluorescence being due to reduction of the compound by the reaction of the reagents and serum components.