WO2008150780A1

WO2008150780A1 - Apparatus and methods for photo-degradation analysis

Info

Publication number: WO2008150780A1
Application number: PCT/US2008/064941
Authority: WO
Inventors: Michael Swartz
Original assignee: Waters Investments Limited
Priority date: 2007-05-29
Filing date: 2008-05-28
Publication date: 2008-12-11

Abstract

Embodiments of the present invention are directed to apparatus and methods for photo- degradation analysis. In one embodiment, the present invention is an apparatus for the analysis of compounds in a solution comprising a photon source, a sample carrier means and a separator. The photon source may emit photons of a selected wavelength or wavelengths. The sample carrier means has an inlet aperture and an outlet aperture. The inlet aperture is for receiving a solution having one or more compounds and the outlet aperture is for discharging the solution and the one or more compounds. The sample carrier means has at least one section translucent to photons of a selected wavelength or wavelengths. This section is in optical communication with the photon source to subject the one or more compounds in the solution to the photons and potentially form one or more photoreaction products. The separator is in fluid communication with the outlet aperture and is for receiving the solution, the one or more compounds and the one or more photoreaction products. The separator resolves or separates the compounds and photoreaction products for detection.

Description

APPARATUS AND METHODS FOR PHOTO-DEGRADATION ANALYSIS

CROSS REFERENCE RELATED APPLICATION INFORMATION

This application claims priority from United States Provisional Patent

Application No. 60/940,464, filed May 29, 2007. The contents of this application is incorporated herein by reference.

STATEMENT ON FEDERALLY SPONSORED RESEARCH N/A

BACKGROUND OF THE INVENTION

Embodiments of the present invention are directed to the analysis of photo- degradation of chemical compounds.

In many industries, it is desirable to understand the susceptibility of particular chemical compounds to degradation when exposed to particular kinds of radiation. Degradation is of special relevance in the pharmaceutical field, where new drugs must be tested for both their rate of degradation under UV light, as well as the potential toxicity of any degradation products.

Photo-degradation is traditionally analysed in a forced degradation study. The compound of interest, usually in its solid or salt form, is exposed to UV radiation of an appropriate wavelength. The radiation is usually provided at a higher intensity than naturally occurring radiation, such that the rate of degradation is increased. After the compound has been exposed to the radiation for a given time, it is loaded onto a liquid chromatograph for separation of the resultant degradation products. This process may then be repeated, varying the residence time of the sample in the exposure of the radiation and the intensity of the radiation. This method, being entirely manual, is time consuming, expensive, and open to human error. The present invention describes an apparatus and method for online photo-degradation analysis.

The term "photon source" as used herein, refers to a source of photons of electromagnetic radiation of any wavelength.

The term "photoreaction" as used herein refers to any chemical reaction, involving one or more chemical compounds, involving the absorption, by one or more chemical compounds, of a photon of electromagnetic radiation.

The term "photoreaction product" as used herein refers to a product compound resulting from a photoreaction.

The term "photostability" as used herein refers to the stability of compounds when exposed to electromagnetic radiation, including ultra-violet radiation, visible radiation, infra-red radiation, X-ray radiation or gamma-ray radiation.

The term "sample solution" as used herein refers to any fluid sample, including a single analyte, or a simple or complex mixture of analytes, dissolved in a solvent. The term "sample solution" as used herein may also refer to any pure fluid anaiyte or any fluid anaiyte with further compounds dissolved within.

SUMMARY OF INVENTION

Embodiments of the present invention are directed to apparatus and methods for photo-degradation analysis. In one embodiment, the present invention is an apparatus for the analysis of compounds in a solution comprising a photon source, a sample carrier means and a separator.

The photon source may emit photons of a selected wavelength or wavelengths. The sample carrier means has an inlet aperture and an outlet aperture. The inlet aperture is for receiving a solution having one or more compounds and the outlet aperture is for discharging the solution and the one or more compounds. The sample carrier means has at least one section translucent to photons of a selected wavelength or wavelengths. This section is in optical communication with the photon source to subject the one or more compounds in the solution to the photons and potentially form one or more photoreaction products.

The separator is in fluid communication with the outlet aperture and is for receiving the solution, the one or more compounds and the one or more photoreaction products. The separator resolves or separates the compounds and photoreaction products for detection.

Preferably, the apparatus further comprises an injector, in fluid communication with said sample carrier means, for injecting a sample through the inlet aperture. The apparatus preferably comprises a controller for controlling said injector, enabling the user to control the flow of the solution through the sample carrying means.

A preferred separator is a chromatograph, in particular a liquid chromatograph.

Preferably, the sample carrier means may be a tube, conduit, capillary, pipe or other vessel capable of conveying a fluid. A preferred sample carrier has a translucent section arranged as a knitted coil to maximise the exposure of the solution to the photons. Another preferred translucent section is a flow cell.

The photon source is any means for emitting electromagnetic radiation, for example a lamp. Such a lamp may emit photons from a broad range of the electromagnetic spectrum, or from a narrower range, for example only ultra-violet, visible or infra-red light. In some embodiments, the lamp may emit photons of a single wavelength, or photons of several particular wavelengths. Further, the photon source may be a gamma-ray emitter, or an X-ray emitter. Preferably, the apparatus further comprises a detector in fluid communication with said separator. The detector produces a signal indicative of the photostability of one or more of the compounds in solution. The detector may detect the presence of a photoreaction product by exhibiting changes in a physico- chemical property of the solution carrying the compounds, for example, light absorbance. The detector may be a mass spectrometer. The detector may also be an ultra-violet/visual spectroscope, fourier transform ultra violet/visual spectroscope, infra-red spectroscope, fourier transform infra red spectroscope, nuclear magnetic resonance spectroscope, fourier transform nuclear magnetic resonance spectroscope, raman spectroscope fluorescence detector, electrochemical detector, chemiluminescence detector, refractive index detector, conductivity detector, photodiode array detector or evaporative light scattering detector.

In another aspect of the invention, a method for analysing compounds in solution is described. This method comprises the step of providing a photon source, a sample carrier means, an injector and a separator. The photon source may emit photons of a selected wavelength or wavelengths. The sample carrier means has an inlet aperture and an outlet aperture. The inlet aperture is for receiving a solution having one or more compounds and the outlet aperture is for discharging the solution and the one or more compounds. The sample carrier means has at least one section translucent to photons of a selected wavelength or wavelengths. This section is in optical communication with the photon source to subject the one or more compounds in the solution to the photons and potentially form one or more photoreaction products. The injector is in fluid communication with said sample carrier means and is for injecting a sample through the inlet aperture. The separator is in fluid communication with the outlet aperture and is for receiving the solution, the one or more compounds and the one or more photoreaction products. The separator resolves or separates the compounds and photoreaction products for detection.

In preferred embodiments, the method further comprises the step of operating the photon source to irradiate at least part of the sample carrier with photons at a first intensity and of a first selected wavelength or first selection of wavelengths.

Preferably, the method further comprises the step of operating the injector to inject a first aliquot of a sample through the sample carrier at a first rate.

Preferably, the method further comprises the step of operating the separator to separate the sample into one or more components.

In preferred embodiments, the method according to the invention further comprises the steps of operating the photon source to irradiate at least part of said sample carrier with photons at a second intensity and at the first selected wavelength or first selection of wavelengths, operating the injector to inject a second aliquot of sample through the sample carrier at a first rate, and operating the separator to separate the sample into one or more components.

In preferred embodiments, the method according to the invention further comprises the steps of operating the photon source to irradiate at least part of the sample carrier with photons at the first intensity and at the first selected wavelength or first selection of wavelengths, operating the injector to inject a second aliquot of sample through the sample carrier at a second different rate, and operating the separator to separate the sample into one or more components.

In preferred embodiments, the method according to the invention further comprises the steps of operating the photon source to irradiate at least part of the sample carrier with photons at the first intensity but at a second different selected wavelength or second different selection of wavelengths, operating the injector to inject a second aliquot of sample through the sample carrier at the first rate, and operating said separator to separate the sample into one or more components.

In certain embodiments, the method may further comprise the step of detecting one or more components after separation. This detection step may be performed by mass spectrometry. In other embodiments, this detection step may be performed by ultra-violet/visual spectroscopy, fourier transform ultra violet/visual spectroscopy, infra-red spectroscopy, fourier transform infra red spectroscopy, nuclear magnetic resonance spectroscopy, fourier transform nuclear magnetic resonance spectroscopy, raman spectroscopy, fluorescence detection, electrochemical detection, chemiluminescence detection, refractive index detection, conductivity detection, photodiode array detection or evaporative light scattering detection.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an improved apparatus and method for investigating the photostability of chemical compounds by enabling on-line photostability analysis.

Figure 1 displays a preferred embodiment of photoreaction analyser 110. Injector 122 is in fluid communication with inlet aperture 116 of sample carrier means 118. At least one section of sample carrier means 118 is translucent to photons of a wavelength or wavelengths and this section is in optical communication with photon source 117. Sample carrier means 118 has an outlet aperture 119, which in turn is in fluid communication with a separator 120. Separator 120 is in further fluid communication with detector 121.

Injector 122 may be a pump or a syringe or a sampling system, or any such means for injecting a fluid sample into an analytical device. A standard HPLC pump, such as an ALLIANCE® pump, as supplied by Waters Corporation, Milford, MA, or in particular an ACQUITY® pump, as supplied by Waters Corporation, Milford, MA is ideal for use as an injector according to the invention.

Sample carrier means 118 may be any hollow member having an inlet and an outlet and at least one section translucent to photons of a certain wavelength or wavelengths. Sample carrier means may, for example, be a flow cell or a tube constructed from an inorganic or organic glass, or a flexible tube constructed from polymers such as polytetrafluoroethylene.

Photon source 117 may be a lamp capable of emitting photons of a particular wavelength or wavelength, such as UV lamp. Photon source 117 may be an emitter of electromagnetic radiation of any wavelengths. A preferred photon source 117 can be set to emit photons at different intensities. A preferred photon source 117 can be set to emit photons of different wavelength or wavelengths.

Separator 120 is a device capable of separating a number of analytes in solution, such that individual analytes may be resolved. Preferably, separator 120 is a chromatographic column. Any chromatography columns may be used, including liquid, gas or supercritical fluid, but for ease of use, liquid chromatography columns are preferred.

Detector 121 is capable of detecting analytes in solution after separation. Detector 121 may indicate the presence of an analyte, the presence of an analyte of a particular type, or give more detailed information about the structure of an analyte. Detector 121 is preferably a mass spectrometer. Detector 121 may also be selected from the group comprising an ultra-violet/visual spectroscope, fourier transform ultra violet/visual spectroscope, infra-red spectroscope, fourier transform infra red spectroscope, nuclear magnetic resonance spectroscope, fourier transform nuclear magnetic resonance spectroscope, raman spectroscope, fluorescence detector, electrochemical detector, chemiluminescence detector, refractive index detector, conductivity detector, photodiode array detector or evaporative light scattering detector. Any chromatographic detector may be used in the device, either alone or in combination with another. In a preferred embodiment, for example, a Waters 2996 PDA detector, as supplied by Waters Corporation, Milford MA₁ is used in conjunction with a Waters ACQUITY® SQD mass spectrometer, as supplied by Waters Corporation, Milford MA. In another preferred embodiment, a Waters 2996 PDA detector is used in conjunction with a Waters ACQUITY® TQD mass spectrometer, as supplied by Waters Corporation, Milford MA. In a preferred embodiment, control means 111 controls injector 122, to affect the input and flow rate of a sample solution, and photon source 117, to affect the intensity and wavelength of radiation incident upon sample carrier means 118. Control means 111 may be a computer or, for instance, a manual user interface.

In use, the apparatus is used for the analysis of photostability of compounds in solution. Photon source 117 is operated to irradiate at least part of sample carrier means 118 with photons at a first intensity and of a first selected wavelength or wavelengths. Injector 122 is operated to inject a first aliquot of a sample solution through sample carrier means 118 at a first flow rate. Residence time of the sample solution in the exposure of the radiation from photon source 117 is a function of the flow rate and the length translucent section of sample carrier means 118 that is exposed to incident radiation from the photon source. The compounds in solution may degrade to form degradation products upon exposure to the incident radiation. Separator 120 is operated to separate any degradation products and original compounds in solution after the solution has passed through sample carrier means 118. Suitable separation solvents, or solvent gradients, may be pumped through the system by injector 122. Separated photoreaction products and original compounds in solution may then be detected by detector 121.

According to further embodiment of the invention, photon source 117 is operated to irradiate at least part of sample carrier means 118 with photons at a first intensity and of a first selected wavelength or wavelengths. Injector 122 is operated to inject a second aliquot of a sample solution through sample carrier means 118 at a second flow rate, to affect a second different residence time. The compounds in solution may degrade to form degradation products upon exposure to the incident radiation. Separator 120 is operated to separate any degradation products and original compounds in solution after the solution has passed through sample carrier means 118. Separated photoreaction products and original compounds in solution may then be detected by detector 121. According to further embodiment of the invention, photon source 117 is operated to irradiate at least part of sample carrier means 118 with photons at a second intensity and of the first selected wavelength or wavelengths. Injector 122 is operated to inject a second aliquot of a sample solution through sample carrier means 118 at the first flow rate. The compounds in solution may degrade to form degradation products upon exposure to the incident radiation. Separator 120 is operated to separate any degradation products and original compounds in solution after the solution has passed through sample carrier means 118. Separated photoreaction products and original compounds in solution may then be detected by detector 121.

According to further embodiment of the invention, photon source 117 is operated to irradiate at least part of sample carrier means 118 with photons at the first intensity and of a second selected wavelength or wavelengths. Injector 122 is operated to inject a second aliquot of a sample solution through sample carrier means 118 at the first flow rate. The compounds in solution may degrade to form degradation products upon exposure to the incident radiation. Separator 120 is operated to separate any degradation products and original compounds in solution after the solution has passed through sample carrier means 118. Separated photoreaction products and original compounds in solution may then be detected by detector 121.

In a further feature of the invention, the changing values of flow rate, photon intensity and photon wavelength or wavelengths may be controlled by control means 111.

In one embodiment, the present invention is an apparatus as shown in Figure 1. Sampling system 122 consists of multiport valve 115 which has six ports A to F, having a sample loop 114 between ports A and D, a syringe 112 at port B, a sampling needle 113 at port C, and a binary gradient pump 110 at port F. Port E is in fluid communication with inlet aperture 116 of sample carrier means 118. Outlet aperture 119 of sample carrier means 118 is in fluid communication with separator 120. Separator 120 is in turn in fluid communication with detector 121. Separator 120 is a liquid chromatography column selected from the group comprising reverse-phase, cation exchange, anion exchange, gel permeation. Detector 121 is a mass spectrometer.

Sample carrier means 118 takes the form of a transparent tube and is wrapped around photon source 117. Photon source 117 may be elongated, and may also be a source of ultra-violet photons. In certain embodiments, sample carrier means 118 may take the form of a transparent tube and may be wrapped around photon source 117. In further embodiments, sample carrier means 118 may take the form of a transparent tube and may be wrapped around photon source 117 as a knitted coil. The knitted coil arrangement extends the length of the sample carrier means 118 that is exposed to incident radiation, thereby increasing residence time, without increasing band-broadening in the system.

Control means 122 controls the sampling system 122, to affect the input and flow rate of a sample solution, and the photon source 117, to affect the wavelength and intensity of radiation incident on the sample carrier means 118.

In use, sampling system 122 is set such that multiport valve 115 connects ports A and B, ports C and D and ports E and F. Syringe 112 is operated so as to draw an aliquot of a sample solution, containing at least one analyte, through sampling needle 113 into sample loop 114. Sampling system 121 may then be adjusted such that multiport valve 115 connects ports B and C, ports D and E and ports F and A. Photon source 117 is operated to expose sample carrier means 118 to incident radiation. Pump 110 may then be operated to urge the sample solution from the sample loop, through inlet aperture 116 to sample carrier means 118. Residence time in the incident radiation emitted by photon source 117 is a function of the flow rate of the sample solution through sample carrier means 118 and the length of sample carrier means 118 that is exposed to incident radiation from photon source 117.

When the sample solution is be urged through outlet aperture 119, the at least one analyte in the sample solution may have been subject to photodegradation, producing one or more photoreaction products. The sample solution is loaded onto separator 120. Pump 110 may be operated to urge an appropriate solvent or solvent gradient through the plumbing of the apparatus, to elute the at least one analyte or photoreaction products. In certain embodiments, a reverse-phase solvent or solvent gradient is used. Individual analytes and photoreaction products may hence be resolved from each other and may be fed into detector 121. The detector may be a mass spectrometer, enabling the user to ascertain some structural information.

The method may be repeated to analyse further aliquots of the same sample solution under different experimental conditions. For example, the residence time in exposure to incident radiation, or the intensity or wavelength or wavelengths of the photons, may be changed. Such parameters may be changed by control means 122. Control means 122 may be a computer or, for instance, a manual user interface.

Thus while preferred embodiments of the invention have been described, those skilled in the art will recognize that the present invention is subject to modification and alteration. Therefore, the invention should not be limited the precise details in the detailed description and the Figures, but should include such subject matter encompassed by the following claims and their equivalents.

Claims

What is claimed:

1. An apparatus for analysing the photoreaction products of compounds in a solution comprising: a photon source for emitting photons of a selected wavelength or wavelengths, a sample carrier means having an inlet aperture and an outlet aperture, said inlet aperture for receiving a solution having one or more compounds and said outlet aperture for discharging said solution and said one or more compounds, said sample carrier means having at least one section translucent to photons of a selected wavelength or wavelengths in optical communication with photon source to subject said one or more compounds in said solution to said photons and potentially forming one or more photoreaction products; a separator in fluid communication with said outlet aperture, for receiving said solution, said one or more compounds and said one or more photoreaction products; wherein said compounds are separated from said photoreaction products for detection.

2. The apparatus of claim 1 further comprising an injector, in fluid communication with said sample carrier means, for injecting a sample through said inlet aperture.

3. The apparatus of claim 1 where said separator is a chromatograph.

4. The apparatus of claim 1 where said separator is a liquid chromatograph.

5. The apparatus of claim 1 where said sample carrier means is a tube.

6. The apparatus of claim 5 where said sample carrier means is arranged as a knitted coil.

7. The apparatus of claim 1 where said sample carrier means is a flow cell.

8. The apparatus of claim 1 where said photon source is a lamp.

9. The apparatus of claim 1 further comprising a detector in fluid communication with said separator.

10. The apparatus of claim 9 wherein said detector produces a signal indicative of the photostability of one or more of said compounds.

11. The apparatus of claim 9 where said detector is a mass spectrometer.

12. The apparatus of claim 9 where said detector is an ultra-violet/visual spectroscope, fourier transform ultra violet/visual spectroscope, infra-red spectroscope, fourier transform infra red spectroscope, nuclear magnetic resonance spectroscope, fourier transform nuclear magnetic resonance spectroscope, raman spectroscope fluorescence detector, electrochemical detector, chemiluminescence detector, refractive index detector, conductivity detector, photodiode array detector or evaporative light scattering detector.

13. The apparatus of claim 2 further comprising a controller for controlling said injector.

14. A method of analysing photoreaction products of compounds in solution comprising the steps of. providing a photon source for emitting photons of a selected wavelength or wavelengths, a sample carrier means having an inlet aperture and an outlet aperture, said inlet aperture for receiving a solution having one or more compounds and said outlet aperture for discharging said solution and said one or more compounds, said sample carrier means having at least one section translucent to photons of a selected wavelength or wavelengths in optical communication with photon source to subject said one or more compounds in said solution to said photons and potentially forming one or more photoreaction products, a separator in fluid communication with said outlet aperture, for receiving said solution, said one or more compounds and said one or more photoreaction products, and an injector, in fluid communication with said sample carrier means, for injecting a sample through said inlet aperture; operating said photon source to irradiate at least part of said sample carrier with photons at a first intensity and of a first selected wavelength or first selection of wavelengths, operating said injector to inject a first aliquot of a sample through said sample carrier at a first rate, operating said separator to separate the sample into one or more components.

15. The method of claim 14 further comprising the step of detecting one or more components after separation.

16. The method of claim 15 where said step of detecting one or more components after separation is performed by mass spectrometry.

17. The method of claim 15 where said step of detecting one or more components after separation is performed by ultra-violet/visual spectroscopy, fourier transform ultra violet/visual spectroscopy, infra-red spectroscopy, fourier transform infra red spectroscopy, nuclear magnetic resonance spectroscopy, fourier transform nuclear magnetic resonance spectroscopy, raman spectroscopy, fluorescence detection, electrochemical detection, chemiluminescence detection, refractive index detection, conductivity detection, photodiode array detection or evaporative light scattering detection.

18. The method of claim 14 further comprising the steps of, operating said photon source to irradiate at least part of said sample carrier with photons at a second different intensity and of said first selected wavelength or first selection of wavelengths, operating said injector to inject a second aliquot of said sample through said sample carrier at a first rate, operating said separator to separate the sample into one or more components.

19. The method of claim 1δ further comprising the step of detecting one or more components after separation.

20. The method of claim 19 where said step of detecting one or more components after separation is performed by mass spectrometry.

21.The method of claim 19 where said step of detecting one or more components after separation is performed by ultra-violet/visual spectroscopy, fourier transform ultra violet/visual spectroscopy, infra-red spectroscopy, fourier transform infra red spectroscopy, nuclear magnetic resonance spectroscopy, fourier transform nuclear magnetic resonance spectroscopy, raman spectroscopy, fluorescence detection, electrochemical detection, chemiluminescence detection, refractive index detection, conductivity detection, photodiode array detection or evaporative light scattering detection.

22. The method of claim 14 further comprising the steps of, operating said photon source to irradiate at least part of said sample carrier with photons at a first intensity and of said first selected wavelength or first selection of wavelengths, operating said injector to inject a second aliquot of said sample through said sample carrier at a second different rate, operating said separator to separate the sample into one or more components.

23. The method of claim 22 further comprising the step of detecting one or more components after separation.

24. The method of claim 23 where said step of detecting one or more components after separation is performed by mass spectrometry.

25. The method of claim 23 where said step of detecting one or more components after separation is performed by ultra-violet/visual spectroscopy, fourier transform ultra violet/visual spectroscopy, infra-red spectroscopy, fourier transform infra red spectroscopy, nuclear magnetic resonance spectroscopy, fourier transform nuclear magnetic resonance spectroscopy, raman spectroscopy, fluorescence detection, electrochemical detection, chemiluminescence detection, refractive index detection, conductivity detection, photodiode array detection or evaporative light scattering detection.

26. The method of claim 14 further comprising the steps of, operating said photon source to irradiate at least part of said sample carrier with photons at said first intensity but of a second different selected wavelength or second different selection of wavelengths, operating said injector to inject a second aliquot of said sample through said sample carrier at said first rate, operating said separator to separate the sample into one or more components.

27. The method of claim 26 further comprising the step of detecting one or more components after separation.

28. The method of claim 27 where said step of detecting one or more components after separation is performed by mass spectrometry.

29. The method of claim 27 where said step of detecting one or more components after separation is performed by ultra-violet/visual spectroscopy, fourier transform ultra violet/visual spectroscopy, infra-red spectroscopy, fourier transform infra red spectroscopy, nuclear magnetic resonance spectroscopy, fourier transform nuclear magnetic resonance spectroscopy, raman spectroscopy, fluorescence detection, electrochemical detection, chemiluminescence detection, refractive index detection, conductivity detection, photodiode array detection or evaporative light scattering detection.