Method for determining concentrations by means of atomic emission spectroscopy

• US 5,218,553 A
• Filed: 08/20/1990
• Issued: 06/08/1993
• Est. Priority Date: 08/23/1989
• Status: Expired due to Fees

• Current Assignee: Perkinelmer Incorporated
• Original Assignee: Perkinelmer Incorporated
• Inventors: van Veen, E. H., de Loos-Vollebregt, M. T. C.
• Primary Examiner(s): Cosimano, Edward R.
• Application Number:
  US07/569,888
• Time in Patent Office: 1,023 Days
• Field of Search: 356/305, 356/319, 356/326, 356/328, 364/497, 364/498
• US Class Current: 702/23
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01N 21/62 Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light

Abstract

A method for determining concentrations by means of atomic emission spectroscopy which contains the method steps: (a) generating an atomic emission with a known concentration of a looked-for element, (b) scanning the obtained emission spectrum by means of a spectral photometer with a spectral slit width in a wavelength range which contains a spectral line of the looked-for element, (c) generating an atomic emission with an unknown sample which contains the looked-for element with the concentration of the looked-for element in the unknown sample to be determined, (d) scanning the obtained emission spectrum by means of the spectral photometer with the same spectral slit width and in the same wavelength range in which the scanning of the emission spectrum with the known concentration was made, (e) processing the spectral-representing signal, which is provided by the spectral photometer independent of the wavelength by means of a recursive Kalman filter, in order to generate an estimate for the concentration of the looked-for element.

Claims

1. Method for determining concentrations by means of atomic emission spectroscopy from an atomic emission spectrophotometer having a spectral photometer, a detector receptive of spectra from the spectral photometer and a data processor receptive of spectra data from the detector, the method comprising the steps of:

(a) operating the atomic emission spectrophotometer so as to generate an atomic emission spectrum with a known concentration of a looked-for element,

(b) scanning the obtained emission spectrum by means of the spectral photometer with a spectral slit width in a wavelength range which contains a spectral line of the looked-for element to obtain a first set of spectral data,

(c) operating the atomic emission spectrophotometer so as to generate an atomic emission spectrum with an unknown sample which contains the looked-for element in the unknown sample to be determined,

(d) scanning the obtained emission spectrum by means of the spectral photometer with the same spectral slit width and in the same wavelength range in which the scanning of the emission spectrum with the known concentration was made to obtain a second set of spectral data,

(e) processing in said data processor the spectral data, which is provided by the spectral photometer dependent of the wavelength by means of a recursive Kalman filter to generate an estimate of the concentration of the looked-for element in the sample,

(f) consecutively detecting with said recursive Kalman filter the signals of the spectral photometer with recursion steps in wavelength steps,

(g) forming with said recursive Kalman filter the difference of each measured signal from a predicted signal which results from the estimate of the concentration obtained in the preceding recursion step, and

(h) correcting with said recursive Kalman filter the estimate of the concentration by said difference multiplied by a filter amplification for generating a new estimate for the next recursion step.

2. The method as set forth in claim 1 wherein the wavelength values associated with the signals obtained with the scanning of the emission spectrum of the known concentration, and the wavelength values associated with the signals obtained with the emission spectrum of the sample are varied relative to each other until the difference becomes independent of the wavelength and an associated difference number, which is determined by iteration, assumes a minimum value.

3. Method for determining concentrations by means of atomic emission spectroscopy from an atomic emission spectrophotometer having a spectral photometer, a detector receptive of spectra from the spectral photometer and a data processor receptive of spectra data from the detector, the method comprising the steps of:

(a) operating the spectrophotometer so as to generate atomic emission spectra of a plurality of elements with known concentrations of the looked-for elements,

(b) scanning the obtained emission spectra by means of the spectral photometer with a spectral slit width in a wavelength range which contains spectral lines of the looked-for elements and normalizing said spectra with respect to concentration,

(c) operating the atomic emission spectrophotometer so as to generate an atomic emission spectrum with an unknown sample which contains the looked-for elements with the concentrations of the looked-for element in the unknown sample to be determined.

(d) scanning the obtained emission spectrum by means of the spectral photometer with the same spectral slit width and in the same wavelength range in which the scanning of the emission spectrum with the known concentration were made to obtain a second set of spectral data,

(e) forming a model of the sample emission spectrum and normalizing said last named spectrum with respect to concentration,

(f) determining the relative wavelength positions of model vectors in the emission spectrum model by varying relative to each other known emission wavelength values of the individual elements and the measured emission wavelength values until the difference becomes independent of the wavelength and the associated difference number which is determined by iteration approaches a minimum value, and

(g) processing in said data processor the spectral data which is provided dependent of the wavelength by means of a recursive Kalman filter to form concentration estimates according to the model emission spectrum.

4. The method as set forth in claim 3, wherein the emission lines of the looked-for elements overlap within the scanned wavelength range.