Patent GB-1419176-A (GB)
Title: Spectrum analysis
IPC: G01N21/72
Filed: 1973-10-24
Abstract: 1419176 Chemical analysis by spectroscopy AUSTRALIAN SELECTION (PTY) Ltd 24 Oct 1973 [27 Oct 1972] 49591/73 Heading G1A A chemical analysis method comprises: measuring the optical density of a solution containing a known quantity of a sample, to which solution a known quantity of dye is first added; comparing the sample optical density with that of a standard solution of dye and so determining the sample concentration in the sample solution; finding the concentration of a given element in the sample solution by spectral analysis; and thus determining the concentration of the element in the sample. Chemical analysis apparatus comprises: a light source; means for atomizing in the path thereof a dissolved sample; a spectrophotometer for measuring the concentration of a given element in the sample; means for measuring the transparency of the sample and for comparing it with that of a standard solution; and means for using the comparision to correct the measurement of element concentration. Alternative chemical analysis apparatus comprises: a flame emission spectrophotometer for atomizing a dissolved sample and detecting atoms of a particular element therein, to supply a value for the concentration of the element in the sample; means for measuring the transparency of the sample and for comparing it with that of a standard solution; and means for using the comparison to correct the measurement of element concentration. In an atomic absorption spectrophotometer an atomizer 2, usually a Venturi-type nebulizer with a flame, interposed in a collimating system between a lamp 8 and a mono-chromator 9, receives via a feed-line 4 a sample solution wherein accurately measured quantities of a sample substance and of a dye have been dissolved. The concentration of a given element in solution is determined by atomic absorption from a detector 10 connected to an electonic circuit 11. Alternative apparatus may use atomic fluorescence or flame emission. En route to the atomizer 2 the sample solution passes through a cell 3 interposed between a lamp 5 and a detector 6 which measures the transparency of the solution at a wavelength remote from and independent of that of the atomic spectrophotometer. Electronics 7 convert the transparency into sample concentration, either by comparison with appropriate pre-set data or by direct comparision with a similar standard-solution measurement, thus avoiding the need for accurate knowledge of the quantity of solvent in the sample solution. A multiplier 12, receiving both sample-concentration and element-concentration data, supplies signals representing the concentration of element in the sample via an integrator 13 and digital display 14 to a printer 15, a reset channel 17 being provided. The transparency apparatus may comprise a double-beam detector (16), Fig.2 (not shown) including an attenuator (18) and a chopper (19) connected by a drive (21) to a phase detector (23) in the photo-cell output (22). Log converters (24, 25) connected to a ratio amplifier (26) supply sample concentration data to the multiplier (12) of the atomic spectrophotometer. A further step in the method may comprise subjecting the standard solution, into which a known quantity of the given element has been introduced, to the atomic spectrophotometer so as to calibrate it. The two spectrophotometers 1, 16, Fig.1, may be combined in one apparatus.