EP0396291B1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Apparatus and methods for optical emission spectroscopy
Assignee: Fisons Ltd
•
Filing: 1990-04-23
•
Granted: 1994-11-30
•
Expires: 2010-04-23
Abstract
Abstract A spark generator suitable for use in an optical emission spectrometer, and capable of generating a spark in a spark gap formed between an electrode and a sample to be analysed, comprises means for generating a current of programmable amplitude in the spark gap in each of a series of discrete time intervals. The spark generator according to the invention is advantageous when compared with conventional spark generators in that it enables a higher degree of choice and control in the form of the spark. In particular, it enables the amplitudes of various portions of the spark to be independently varied, thus permitting the shape of the spark to be tailored to the particular analysis being performed. Also described are methods of optical emission spectroscopy which make use of the advantageous properties of the spark generator.
Inventors
- 👤 Francis Pilloud
- 👤 Wilfried Vogel
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 08:21
CPC Classifications
H; H03; H03K; H03K4/00; H03K4/02; G; G01; G01N; G01N21/00; G01N21/62; G01N21/66; G01N21/67; H03K3/00; H03K3/02; H03K3/53; H03K3/57
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
124 words
An optical emission spectrometer comprising: a) a spark generator (2) for generating in a spark gap formed between an electrode (3) and a sample (4) to be analyzed a spark which extends over a series of discrete time intervals and which results in a flow of current; b) an optical system (8) to disperse light emitted by said sample;and c) light detection means (9) for measuring the intensity of the light dispersed by said optical system; said spectrometer characterized by:- i) means (10) for measuring said current during at least one of said discrete time intervals; ii) means (1) for comparing said measured current with a reference current; and iii) means for adjusting said current to a predetermined value dependent on said reference current.
Claim 2
Dependent Claim
46 words
An optical emission spectrometer as claimed in claim 1 further comprising:- a) first circuit means (A) for generating in said spark an initial current pulse of relatively high amplitude; and b) second circuit means (B) for generating in said spark a current of relatively low amplitude.
Claim 3
Dependent Claim
27 words
An optical emission spectrometer as claimed in any previous claim wherein said discrete time intervals during which said current is measured are between 5 and 20 µs.
Claim 4
Dependent Claim
27 words
An optical emission spectrometer as claimed in any previous claim wherein the value of said reference current is stored in the memory of a computer unit (1).
Claim 5
Dependent Claim
26 words
An optical emission spectrometer as claimed in any previous claim wherein said means for adjusting the current comprises a comparator (26) and a transistor switch (22).
Claim 6
Dependent Claim
23 words
An optical emission spectrometer as claimed in any pervious claim further comprising programming means for defining the form of a desired spark discharge.
Claim 7
Dependent Claim
28 words
An optical emission spectrometer as claimed in any previous claim wherein the comparison of said current with said reference current is made at a frequency of 50-200 kHz.
Claim 8
Dependent Claim
36 words
An optical emission spectrometer as claimed in any previous claim further comprising a transformer (33) connected in series with said spark gap for initiating said spark by application of a high voltage across said spark gap.
Claim 9
Dependent Claim
69 words
An optical emission spectrometer as claimed in any previous claim further comprising means (2) for generating a series of sparks and a feedback system which measures the intensity of light emitted by said sample following a first spark and adjusts the amplitude of the initial portions of subsequent sparks comprised in said series so as to match the intensity of light emitted during those sparks with a standard value.
Claim 10
Independent Claim
115 words
A method of optical emission spectroscopy comprising the steps of:- a) generating a spark in a spark gap formed between an electrode (3) and a sample (4) to be analyzed, the duration of said spark extending over a series of discrete time intervals and resulting in a flow of current; b) optically dispersing the light emitted by said sample during said spark; c) measuring the intensity of the light so dispersed; said method characterized by the further steps of:- i) measuring said current during at least one of said discrete time intervals; ii) comparing said measured current with a reference current; and iii) adjusting said current to a predetermined value dependent on said reference current.
Claim 11
Dependent Claim
41 words
A method of optical emission spectroscopy as claimed in claim 10 wherein said spark comprises an initial portion during which flows a current pulse of relatively high amplitude and a second portion during which flows a current of relatively low amplitude.
Claim 12
Dependent Claim
107 words
A method of optical emission spectroscopy as claimed in claim 11 further comprising the steps of:- a) generating a first spark having an initial portion during which flows a current of sufficient amplitude to vaporize said sample and a second portion during which flows a current of relatively low amplitude; b) measuring a first intensity of light emitted during a time window located in the second portion of said first spark; c) generating a second spark during the entirety of which the current is insufficient to vaporize said sample; and d) measuring a second intensity of light emitted during the same time window in said second spark.
Claim 13
Dependent Claim
55 words
A method of optical emission spectroscopy as claimed in claim 12 wherein a series of sparks is generated and the light emitted during a large number of the discrete time windows contained in each of said sparks is integrated, said integrated value for each spark in said series of sparks being separately stored and evaluated.
Claim 14
Independent Claim
88 words
A method of optical emission spectroscopy as claimed in either of claims 11 or 12 further comprising the steps of:- a) measuring a first intensity of light emitted during a portion of a spark in which the light comprises substantially only background; b) measuring a second intensity of light emitted during a portion of a spark in which the light comprises both background and spectral light emitted by the sample; and c) correcting said second intensity for the contribution of background on the basis of said first intensity.
Claim 15
Dependent Claim
52 words
A method of optical emission spectroscopy as claimed in claim 14 wherein the measurement of said first intensity is made during the first 30 microseconds of a critically damped exciting spark and the measurement of said second intensity is made during the period of 30-200 microseconds from the beginning of a spark.
Claim 16
Dependent Claim
32 words
A method of optical emission spectroscopy as claimed in claim 15 wherein the measurements of said first and said second intensities, respectively, are made on alternate sparks in a series of sparks.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.