Determination of chemical or physical properties of sample or component of a sample

• US 8,010,299 B2
• Filed: 11/16/2006
• Issued: 08/30/2011
• Est. Priority Date: 11/16/2005
• Status: Active Grant

• Current Assignee: ChemoMetec A/S
• Original Assignee: ChemoMetec A/S
• Inventors: Arnvidarson, Börkur
• Primary Examiner(s): Bui; Bryan
• Application Number:
  US12/094,006
• Publication Number:
  US 20090024360A1
• Time in Patent Office: 1,748 Days
• Field of Search: 702/22, 702/189, 356/451, 356/452, 600/301, 600/407
• US Class Current: 702/22
• CPC Class Codes: G01J 3/45 Interferometric spectrometry

Abstract

The present invention offers an alternative strategy for the correlation of interference information to chemical and/or physical properties of a sample. This strategy can be implemented in a method and a system, which offer substantial technical and commercial advantages over state of the art techniques based on interference spectroscopy. The method comprises the steps of: a. obtaining an interferogram and/or at least one interferogram element corresponding to a modulation of electromagnetic signal emitted from, transmitted onto or through, or having interacted with at least a part of the sample, b. performing i. at least one transformation of the interferogram and/or a segment of the interferogram and/or an interferogram element with at least one function, ii. optionally repeating i) for another segment of the interferogram and/or interferogram element, wherein the transformation does not comprise a Fourier Transformation if i) is conducted only once, thereby obtaining at least one score, c. correlating said at least one score to the at least one chemical or physical property.

Claims

1. A method for the determination of chemical or physical property of a sample or a component of a sample comprising the steps of:

a. obtaining an interferogram and/or at least one interferogram element corresponding to a modulation of electromagnetic signal emitted from, transmitted onto or through, or having interacted with at least a part of the sample,

b. performing

i. at least one transformation of the interferogram and/or a segment of the interferogram and/or an interferogram element with at least one function, wherein said function is capable of transforming an interferogram, an interferogram segment or element to a score, wherein a score is defined by

2. The method according to claim 1, where the interferogram comprises two or more interferogram elements representing substantially different status of modulation, preferably where the interferogram comprises three or more interferogram elements representing status of modulation at equal representation spacing of time, frequency, position or distance.

3. The method according to claim 2, where one or more interferogram elements represent status of modulation at time, frequency, position or distance not equally spaced relative to at least two different interferogram elements, preferably where the relative spacing has the purpose of improving representation of a feature in the interferogram.

4. The method according to claim 3, where spacing between interferogram elements is shorter in one section of the interferogram than in another section of the interferogram, preferably where the size of the section of shorter spacing corresponds to time, frequency, position or distance of at least one, preferably two or more, cycle(s) of the electromagnetic signal of highest frequency being considered, preferably where the section of shorter spacing is at or around the centre burst of an interferogram.

5. The method according to claim 1, where the modulated electromagnetic signals are in the frequency range of between 10,000 and 200 cm⁻

1, and modulating means are an interferometer modulating the light by means of combining light having travelled different distance (Optical Path Difference, OPD), the maximum OPD is preferably less than 1.0 cm, preferably where it is shorter than 0.8, 0.6, 0.5, 0.4, 0.3, 0.2 or even shorter than 0.1 cm, such as shorter than 0.08 cm, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02 or shorter than 0.01 cm.

6. The method according to claim 1, where interference of modulated electromagnetic radiation is symmetric or substantially symmetric around a point in the interferogram domain, where the extent of representation of interferogram domain is equal or substantially equal in both directions relative to a symmetry point.

7. The method according to claim 1, where interference of modulated electromagnetic radiation is symmetric or substantially symmetric around a point in the interferogram domain, where the extent of representation of interferogram domain is unequal in the two directions relative to a symmetry point.

8. The method according to claim 7, where the point of symmetry in the interferogram domain is located at position in the interferogram of between 5% and 45% of the representation of the interferogram domain, relative to either extremes of the represented interferogram domain, preferably between 20% and 30% of the representation of the interferogram domain.

9. The method according to claim 7, where the point of symmetry in the interferogram domain is located at position in the interferogram at or closer than 20% of the representation of the interferogram domain from either extremes of the represented interferogram domain, preferably at or closer than 10% from either extremes of the represented interferogram domain.

10. The method according to claim 1, where the interferogram is transformed into frequency intensities using the method of fast fourier transformation, preferably where the property of the sample or a component of the sample is a determination of absorption, transmission or emission spectrum.

11. The method according to claim 1, where spectral property is the result of an inner product of the interferogram and a loading function, i.e. score value.

12. The method according to claim 11, where the loading function is determined through calibration, preferably where the purpose of the calibration is to substantially optimise the determination of chemical or physical property of a sample or a component of a sample.

13. The method according to claim 11, where the loading function is a periodic function, preferably where the periodic function has 2 or more periods represented in the interferogram, such as 4 or more periods represented in the interferogram, such as 8 or more periods represented in the interferogram, such as 16 or more periods represented in the interferogram, preferably where the periodic functions are cosine or sine functions.

14. The method according to claim 11, where the loading function is symmetrical, preferably where sum of the loading function is substantially equal to zero.

15. The method according to claim 11, where scores are used to determine absorption, transmission or emission properties of sample or component of a sample.

16. The method according to claim 1, where interferogram and/or loadings and/or scores are scaled prior to transformation to spectral property, preferably where purpose of scaling is to obtain substantially improved stability and/or reliability in correlation of spectral property to chemical or physical property, preferably were scaling partially or substantially compensates for variations affecting the correlation.

17. The method according to claim 16, where scaling is determined on bases of information reflecting the status of the measuring system, preferably where scaling is determined on bases of properties reflected in the interferogram.

18. The method according to claim 16, where the scaling has the purpose of relating interferogram and/or loading and/or score to corresponding properties obtained through measurement of reference material or reference conditions of the measuring system, preferably where the reference material represents sample substantially without chemical or physical component, e.g. a sample blind.

19. The method according to claim 1, where interferogram and/or loading and/or score are subjected to predetermined numerical function, preferably where the numerical function transforms information in such a manner that it corresponds better to a chemical or physical property, more preferably were the numerical function transforms information in such a manner that it is corresponds substantially linear to chemical or physical property.

20. The method according to claim 1, where a measured interferogram is subjected to transformation, preferably where the purpose of the transformation is to represent the observations in the interferogram as measured on a first instrument as if it was obtained on a second instrument, preferably where the purpose is to improve statistical quality of a determination using a determination model developed using the second instrument.

21. The method according to claim 20, where the property of the transformation is determined on status of the first instrument relative to a status of the second instrument.

22. The method according to claim 20, where the property of the transformation or status of the first instrument is determined on the bases of the measured interferogram, preferably where it is determined on the bases of one or several previously measured interferogram(s).

23. The method according to claim 1, where a loading, a part of a model for determination based on measurements on a first instrument, is subjected to transformation, preferably where the purpose of the transformation is to represent the determination derived from measurement on a second instrument as if it was obtained on a first instrument, preferably where the purpose is to improve statistical quality of a determination using a determination model developed using the first instrument.

24. The method according to claim 23, where the property of the transformation is determined by status of the first instrument relative to a status of the second instrument.

25. The method according to claim 23, where the property of the transformation or status of the second instrument is determined on the bases of the measured interferogram, preferably where it is determined on the bases of one or several previously measured interferogram(s).

26. The method according to claim 1, where a model for determination is developed on a first instrument, preferably by calibration including known properties of samples relating to chemical or physical property of the sample or a component of the sample and one, preferably several measurement these samples, preferably where the properties of the model allow it to be applied to measurements on a second instrument, substantially without any a priori knowledge of the status of the second instrument, more preferably by including a priori knowledge of the status of the second instrument.

27. The method according to claim 1, where determination of chemical or physical property is preformed by applying predetermined prediction model to interferogram and/or spectral property, preferably where the prediction model is determined through calibration, preferably where the calibration is a multivariate calibration, such as PLS, PCA, LS, ANN, PARAFAC, Tucker3.

28. The method according to claim 1, wherein the sample is a sample representing one of the following:

Aqueous sample, such as environmental sample, drinking water, bathing water, process water, cooling water;

Biological sample, such as tissue sample, blood sample, urine sample, feces sample, cell culture sample, bacteria culture, yeast culture;

Industrial sample such as oil sample, petroleum sample, grease sample, pharmaceutical sample;

Food sample such as milk sample, dairy product sample, meat sample, fish sample, fruit sample, vegetable sample;

Gaseous sample such as exhaust gas, fermentation gas, combustible gas.

29. The method according to claim 1, wherein the chemical or physical property being assessed is one of the following:

spectral property, temperature, turbidity, total organic material, dry material, dissolved material, chlorophyll, fibres, amino acids, proteins, fat, fatty acids, lipids, glyserids, cholesterol, enzymes, sugars, glucose, alcohols, ethanol, methanol, acids, citric acid, acidic acid, aliphats, aromats, ketones, aldehydes, pH, density, salinity, colour.

30. The method according to claim 1 where electromagnetic signal is in one or several of the following spectral rage(s) X-Ray, UV/Vis, Near-IR, Mid-IR, Far-IR, microwave, radio frequency.

31. The method according to claim 1 where the interferogram is obtained in connection with one or several of the following spectroscopic methods, absorption, transmission, reflection, emission.

32. The method according to claim 31 where the interferogram reflects detection of one or several phenomena, photons, heat, pressure.

33. The method according to claim 1 where the property which is determined is a chemical or physical property of a food or feed sample, preferably where the food or feed sample is one or several of the following, fruit juice, milk, milk product, grain, cereals.

34. The method according to claim 1 where the property which is determined is a chemical or physical property of a beverages sample, preferably where the beverages sample is one or several of the following, juice, soft drink, beer, wine, spirits.

35. The method according to claim 1 where the property which is determined is a chemical or physical property of a pharmaceutical sample, preferably where the pharmaceutical sample is one or several of the following, raw material used in the production of pharmaceutical product, intermediate product in the production of pharmaceutical product, pharmaceutical product.

36. The method according to claim 1 where the property which is determined is a chemical or physical property of a biological sample, preferably where the biological sample is one or several of the following, tissue sample, blood sample, urine sample, feces sample, preferably where the sample is of human or veterinary origin.

37. The method according to claim 1 where the property which is determined is a chemical or physical property of an environmental sample, preferably where the n environmental sample is one or several of the following, soil, aqueous liquid, gas.

38. The method according to claim 1 where the property which is determined is a state or a property of a location, preferably where the state or property of a location is one or several of the following, pre-stages to a fire, fire, chemical spillage, water spillage, preferably where the interferogram is obtained as a result of passive remote sensing.

39. The method of claim 1, wherein said at least one function is at least one loading function.

40. The method of claim 1, wherein said at least one function is a sine or cosine at frequency between two Fourier transform frequencies set by the length of the interferogram.

41. The method of claim 1, wherein said at least one function comprises at least three cosine or sine functions unevenly spaced in frequency.

42. The method of claim 1, wherein said transformation comprises calculating the inner product between the said interferogram and the respective function.

43. The method of claim 1, wherein said at least one function is substantially balanced.

44. The method of claim 1, wherein said at least one function is apodized.

45. The method of claim 1, wherein said at least one function is at least one segment of a periodic function such as a cosine and zero for other values.

46. The method of claim 1, wherein said at least one function is a Dirac or Kronecker delta function.

47. The method claim 1, wherein said at least one function is an analytically defined function.

48. The method of claim 1, wherein said at least one function comprises a discrete data set.

49. The method of claim 48, wherein said at least one function is a loading function found by multivariate calibration.

50. The method of claim 1, wherein said at least one function is different from as sine or cosine.

51. The method of claim 1, wherein the interferogram or interferogram segment is sampled with varying density and/or unevenly distribution.

52. The method of claim 1, further comprising a step of estimating each data points forming the interferogram, segment of the interferogram or interferogram element based on at least one proximal data point.

53. The method of claim 48, wherein the said discrete data set is found by estimating each data point from proximal data points in the interferogram domain to match the position in the modulation domain of the data points obtained in the said interferogram, segment of the interferogram or interferogram element.

54. A system for the determination of chemical or physical property of a sample or a component of a sample comprising

an interferometer for obtaining an interferogram and/or at least one interferogram element corresponding to a modulation of electromagnetic signal emitted from, transmitted onto or through, or having interacted with at least a part of the sample,

a. processor for performing

i. at least one transformation of the interferogram and/or a segment of the interferogram and/or an interferogram element with at least one function, wherein said function is defined as in claim 1,

ii. optionally repeating i) for another segment of the interferogram and/or interferogram element,

wherein the transformation does not comprise a Fourier Transformation if i) is conducted only once,

said processor including means for obtaining at least one score as defined in claim 1, and

b. means for correlating said at least one score to the at least one chemical or physical property.

55. The system according to claim 54, further comprising means for performing one or more interferogram elements representing substantially different status of modulation.