Method for Determining the Identity, Absence and Concentration of a Chemical Compound in a Medium

• US 20090006004A1
• Filed: 12/27/2006
• Published: 01/01/2009
• Est. Priority Date: 12/29/2005
• Status: Abandoned Application

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF SE
• Inventors: Thiel, Erwin, Sens, Rudiger, Ahlers, Wolfgang, Vamvakaris, Christos
• Application Number:
  US12/159,005
• Publication Number:
  US 20090006004A1
• Time in Patent Office: Days
• US Class Current: 702/23
• CPC Class Codes: G01J 2001/4242 Modulated light, e.g. for synchronizing source and detector circuit
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0232 using shutters
• CPC Class Codes: G01J 3/4406 Fluorescence spectrometry
• CPC Class Codes: G01J 3/457 Correlation spectrometry, e.g. of the intensity G01J3/453 takes precedence
• CPC Class Codes: G01N 2021/6491 Measuring fluorescence and transmission; Correcting inner filter effect
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence
• CPC Class Codes: G01N 21/643 non-biological material
• CPC Class Codes: G01N 21/645 Specially adapted constructive features of fluorimeters
• CPC Class Codes: G01N 2201/129 Using chemometrical methods

Abstract

A method is proposed for detecting at least one chemical compound V contained in a medium (312). The method comprises a verification step (420) which is used to determine whether V is contained in the medium (312). The method furthermore comprises an analysis step (424) in which a concentration c of the at least one chemical compound V is determined.

The verification step comprises the following substeps:

• (a1) the medium (312) is exposed to a first analysis radiation (316) of a variable wavelength λ, the wavelength λ assuming at least two different values;
• (a2) at least one spectral response function A(λ) is generated with the aid of the radiation (324) absorbed and/or emitted and/or reflected and/or scattered by the medium (312) in response to the first analysis radiation (316);
• (a3) at least one spectral correlation function K(δλ) is formed by spectral comparison of the at least one spectral response function A(λ) with at least one pattern function R(λ+δλ), the at least one pattern function R(λ) representing a spectral measurement function of a medium (312) containing the chemical compound V and δλ being a coordinate shift;
• (a4) the at least one spectral correlation function K(δλ) is examined in a pattern recognition step (418), and a conclusion is made as to whether the at least one chemical compound V is contained in the medium (312);

The analysis step (424) comprises the following substeps:

• (b1) the medium (312) is exposed to at least one second analysis radiation (318) having at least one excitation wavelength λ_EX;
• (b2) at least one spectral analysis function B(λ_EX,λ_RES) is generated with the aid of the radiation (326) of the response wavelength λ_RES absorbed and/or emitted and/or reflected and/or scattered by the medium (312) in response to the second analysis radiation (318) of the wavelength λ_EX and the concentration c is deduced therefrom.

Claims

1. :

A method for detecting at least one chemical compound V comprised in a medium, comprising a verification step which is used to determine whether V is comprised in the medium, and furthermore comprising an analysis step in which a concentration c of the at least one chemical compound V is determined,

the verification step comprising the following substeps;

(a1) the medium is exposed to a first analysis radiation of a variable wavelength λ

, the wavelength λ

assuming at least two different values;

(a2) at least one spectral response function A(λ

) is generated with the aid of the radiation absorbed and/or emitted and/or reflected and/or scattered by the medium in response to the first analysis radiation;

(a3) at least one spectral correlation function K(δ

λ

) is formed by spectral comparison of the at least one spectral response function A(λ

) with at least one pattern function R(λ

+δ

λ

), the at least one pattern function R(λ

) representing a spectral measurement function of a medium comprising the chemical compound V and δ

λ

, being a coordinate shift;

(a4) the at least one spectral correlation function K(δ

λ

) is examined in a pattern recognition step, and a conclusion is made as to whether the at least one chemical compound V is comprised in the medium;

the analysis step comprising the following substeps;

(b1) the medium is exposed to at least one second analysis radiation having at least one excitation wavelength λ

_EX;

(b2) at least one spectral analysis function B(λ

_EX, λ

_RES) is generated with the aid of the radiation of the response wavelength λ

_RES absorbed and/or emitted and/or reflected and/or scattered by the medium in response to the second analysis radiation of the wavelength λ

_RES and the concentration c is deduced therefrom,

wherein the verification step and the analysis step are carried out separately and in that the analysis step is carried out only if the verification step has established that the compound V is comprised in the medium.

2. :

The method as claimed in claim 1, wherein the spectral correlation function K(δ

λ

) is formed from the at least one spectral response function A(λ

) and the at least one pattern function R(λ

) according to one or more of the following Equations (1) to (4);

$\begin{array}{cc}K<br><br>\left(\mathrm{\delta <br><br>\lambda <br><br>}\right)=\frac{1}{N}·<br><br>{\int <br><br>}_{\mathrm{\lambda <br><br>}}<br><br>A<br><br>\left(\mathrm{\lambda <br><br>}\right)·<br><br>R<br><br>\left(\mathrm{\lambda <br><br>}+\mathrm{\delta <br><br>\lambda <br><br>}\right)·<br><br><br><br><br><br>\mathrm{\lambda <br><br>},& \left(1\right)\end{array}$

where N is a normalization factor,

$\begin{array}{cc}N={\int <br><br>}_{\mathrm{\lambda <br><br>}}<br><br>A<br><br>\left(\mathrm{\lambda <br><br>}\right)·<br><br>R<br><br>\left(\mathrm{\lambda <br><br>}\right)·<br><br><br><br><br><br>\mathrm{\lambda <br><br>}& \left(2\right)\end{array}$

or according to a corresponding Riemann sum

$\begin{array}{cc}K<br><br>\left(\mathrm{\delta <br><br>\lambda <br><br>}\right)=\frac{1}{N^{*}}·<br><br>\underset{i}{\sum <br><br>}<br><br>A_i<br><br>\left({\mathrm{\lambda <br><br>}}_i\right)·<br><br>R_i<br><br>\left({\mathrm{\lambda <br><br>}}_i+\mathrm{\delta <br><br>\lambda <br><br>}\right)·<br><br>{\mathrm{\Delta <br><br>\lambda <br><br>}}_i& \left(3\right)\end{array}$

where summation is carried out over a number of support points i, Δ

λ

_i being an interval length of the respective support point i and N* being a normalization factor,

$\begin{array}{cc}{N}^{*}=\underset{i}{\sum <br><br>}<br><br>A_i<br><br>\left({\mathrm{\lambda <br><br>}}_i\right)·<br><br>R_i<br><br>\left({\mathrm{\lambda <br><br>}}_i\right)·<br><br>{\mathrm{\Delta <br><br>\lambda <br><br>}}_i.& \left(4\right)\end{array}$

3. :

The method as claimed in claim 1, wherein more than one spectral response function A(λ

) is generated in the substep (a2).

4. :

The method as claimed in claim 1, wherein at least one raw response function A′

(N) is firstly recorded in substep (a2) and the at least one raw response function is subsequently transformed as follows into the at least one spectral response function A(λ

);

A(λ

)=A′

(λ

′

)−

H(λ

′

) 

 

(5)

where λ

is a shift-corrected wavelength with

λ

=λ

′

=Δ

λ

_S(6)

where Δ

λ

_S as is a predetermined wavelength shift and where H(λ

′

) is a predetermined background function.

5. :

The method as claimed in claim 4, wherein the wavelength shift Δ

λ

_S is empirically determined by at least one of the following methods;

a spectral response function of a medium comprising the compound V is compared with a spectral response function of a reference medium comprising the compound V and/or with a reference response function, and the wavelength shift Δ

λ

_S is determined from a spectral shift according to Equation (6);

a spectral correlation function K(δ

λ

) is formed according to substep (a3) by comparing a spectral response function of the compound V in the medium with a spectral response function of the compound V in another medium and/or with a standard response function.

6. :

The method as claimed in claim 4, wherein the spectral background function H(λ

′

) is empirically determined by at least one of the following methods;

a spectral response function of the medium comprising the compound V is compared with a spectral response function of the medium not comprising the compound V and/or with a reference response function, and the spectral background function H(λ

′

) is determined from a deviation;

the spectral background function H(λ

′

) is determined by fitting a first spectral correlation function K(δ

λ

), formed by spectral comparison of the at least one spectral response function A(λ

) with the at least one pattern function R(λ

) according to substep (a3), to a second spectral correlation function K_Auto(δ

λ

) formed by spectral comparison of the at least one pattern function R(λ

) with itself according to substep (a3).

7. :

The method as claimed in claim 4, wherein at least one spectral background function H(λ

′

) and/or at least one wavelength shift Δ

λ

_S is taken from a database.

8. :

The method as claimed in claim 1, wherein the excitation wavelength λ

_EX of the second analysis radiation assumes at least two different values.

9. :

The method as claimed in claim 1, wherein the at least one spectral analysis function B(λ

_EX, λ

_RES) comprises a fluorescence function.

10. :

The method as claimed in claim 1, wherein the at least one spectral analysis function B(λ

_EX, λ

_RES) is recorded integrally over a wavelength range of the response wavelength λ

_RES.

11. :

The method as claimed in claim 1, wherein a lock-in method is used in the analysis step, at least one second analysis radiation of the excitation wavelength λ

_EX modulated periodically with a frequency f being used.

12. :

The method as claimed in claim 11, wherein the at least one spectral analysis function is recorded with time resolution as B(λ

_EX, λ

_RES, t).

13. :

The method as claimed in claim 12, wherein the concentration c of the compound V is determined according to c=f(B), where f is a known, empirically determined or analytically derived function of the spectral analysis function B,

$\begin{array}{cc}c=K_1·<br><br>B<br><br>\left(\mathrm{\tau <br><br>},{\mathrm{\lambda <br><br>}}_{\mathrm{EX}},{\mathrm{\lambda <br><br>}}_{\mathrm{RES}}\right)<br><br><br><br>\mathrm{or}& \left(7\right)\\ c=K_2·<br><br>\log <br><br><br><br>B<br><br>\left(\mathrm{\tau <br><br>},{\mathrm{\lambda <br><br>}}_{\mathrm{EX}},{\mathrm{\lambda <br><br>}}_{\mathrm{RES}}\right)<br><br><br><br>\mathrm{with}& \left(8\right)\\ B<br><br>\left(\mathrm{\tau <br><br>},{\mathrm{\lambda <br><br>}}_{\mathrm{EX}},{\mathrm{\lambda <br><br>}}_{\mathrm{RES}}\right)={\int <br><br>}_0^{\mathrm{\tau <br><br>}}<br><br>B<br><br>\left({\mathrm{\lambda <br><br>}}_{\mathrm{EX}},{\mathrm{\lambda <br><br>}}_{\mathrm{RES}},t\right)·<br><br>\cos <br><br>\left(2<br><br>\mathrm{\pi <br><br>}·<br><br>f·<br><br>t\right)<br><br><br><br><br><br>t& \left(9\right)\end{array}$

where τ

is a time constant, and where K₁ and K₂ are predetermined proportionality constants.

14. :

The method as claimed in claim 1, wherein the detection of the at least one chemical compound is carried out in order to identify a mineral oil and/or in order to check the authenticity of goods.

15. :

A device for carrying out the method as claimed in claim 1, comprising

at least one sample holder for holding the medium;

at least one first beam source for generating the first analysis radiation;

at least one first detector for detecting the radiation absorbed and/or emitted and/or reflected and/or scattered by the medium in response to the first analysis radiation;

at least one set of correlation electronics having correlation means for forming the spectral correlation function K(δ

λ

) and having pattern recognition means for carrying out the pattern recognition step;

at least one second beam source for generating the second analysis radiation;

at least one second detector for detecting the radiation absorbed and/or emitted and/or reflected and/or scattered by the medium in response to the second analysis radiation,

characterized by

an evaluation device for determining the concentration c of the at least one chemical compound V comprised in the medium and by a decision logic for starting the analysis step as a function of the result of the pattern recognition step.

16. :

The device as claimed in claim 15,

further comprising at least one modulator for periodically modulating the second analysis radiation, and at least one lock-in amplifier.

17. :

The device as claimed in claim 15, wherein the at least one first beam source comprises a multiplicity of individual radiation sources with predetermined spectral properties, and the at least one first beam source is switchable between the individual radiation sources.

18. :

The method as claimed in claim 3, wherein the more than one spectral response function A(λ

) is a transmission function T(λ

) and an emission function E(λ

), and the emission function E(λ

) comprises a fluorescence function.

19. :

The method as claimed in claim 12, wherein the at least one spectral analysis function is recorded, with time resolution as B(λ

_EX, λ

_RES, t), integrally over a wavelength range of the response wavelength λ

_RES as B(λ

_EX, t).

20. :

The device as claimed in claim 15, wherein the at least one second beam source is identical to the at least one first beam source, and the at least one second detector is different from the at least one first detector.