Porous mesh spectrometry methods and apparatus
Described herein are methods and apparatus for spectroscopic analysis of samples. In many embodiments, an apparatus for providing spectroscopic analysis of a sample comprises a sample holder. For example, the sample holder may comprise a consumable single use sample holder that can be readily coupled to and removed from a measurement apparatus such as a spectrometer. The sample holder may comprise a measurement surface configured to receive the sample during measurement, wherein the measurement surface may comprise a porous mesh. The porous mesh can receive the sample to optimally configure the sample for spectroscopic measurement, as described in further detail herein.
1. An apparatus to measure spectra of a sample, the apparatus comprising:
an optical waveguide comprising a measurement surface, the optical waveguide configured to transmit measurement light within the optical waveguide via total internal reflection to generate an evanescent wave at the measurement surface; and
a porous mesh disposed over the measurement surface, the porous mesh comprising a plurality of pores configured to receive a portion of the sample therein, such that the portion of the sample contacts the measurement surface, and the porous mesh comprises an internal standard impregnated therein such that the sample deposited over the porous mesh solvates the impregnated internal standard to a known concentration in the sample,
wherein the evanescent wave at least partially penetrates the portion of the sample in contact with the measurement surface to measure the spectra of the portion of the sample.
2. An apparatus as in claim 1 , wherein the porous mesh comprises a material that imparts no aberrant spectral signal in a spectral region of interest for the sample.
3. An apparatus as in claim 2 , wherein the porous mesh comprises a material that imparts no aberrant spectral signal in a mid-infrared spectral range of about 2 μm to about 20 μm.
4. An apparatus as in claim 1 , wherein the porous mesh comprises one or more of silver, polyethylene, and polytetrafluoroethylene.
5. An apparatus as in claim 1 , wherein the porous mesh comprises a hydrophilic material.
6. An apparatus as in claim 1 , wherein each of the plurality of pores is configured to receive a substantially fixed volume of the sample to provide a substantially fixed pathlength of travel of the measurement light.
7. An apparatus as in claim 1 , wherein each of the plurality of pores has a diameter of about 0.1 μm to about 20 μm.
8. An apparatus as in claim 7 , wherein each of the plurality of pores has a diameter of at least about 10 μm.
9. An apparatus as in claim 7 , wherein each of the plurality of pores has a diameter of at least about 5 μm.
10. An apparatus as in claim 7 , wherein each of the plurality of pores has a diameter of at least about 1 μm.
11. An apparatus as in claim 1 , wherein each of the plurality of pores is sized and shaped to selectively receive a first portion of the sample and selectively exclude a second portion of the sample.
12. An apparatus as in claim 1 , wherein the sample comprises whole blood, and wherein the portion of the sample comprises one or more components of the whole blood.
13. An apparatus as in claim 12 , wherein the portion of the sample comprises plasma, and does not include cellular components.
14. An apparatus as in claim 12 , wherein the portion of the sample comprises plasma and red blood cells, and does not include white blood cells.
15. An apparatus as in claim 12 , wherein the portion of the sample comprises plasma, red blood cells, and white blood cells.
16. An apparatus as in claim 12 , wherein the portion of the sample comprises red blood cells having cell membranes with rigidity below a predetermined threshold value.
17. An apparatus as in claim 1 , wherein the sample is at least partially dehydrated before measurement with the evanescent wave.
18. An apparatus as in claim 1 , wherein the sample comprises the internal standard at the known concentration, the internal standard having a distinct spectral signal in a spectral region of interest for the sample.
19. An apparatus as in claim 18 , further comprising a sample collection device having the internal standard impregnated therein, and wherein the sample collected in the sample collection device solvates the impregnated internal standard to the known concentration in the sample.
20. An apparatus as in claim 18 , wherein the distinct spectral signal is in a mid-infrared spectral region.
21. An apparatus as in claim 1 , further comprising one or more absorbent members in contact with the porous mesh to absorb excess sample.
22. An apparatus as in claim 21 , wherein the one or more absorbent members comprise one or more blotting papers.
23. An apparatus as in claim 21 , wherein the one or more absorbent members are disposed underneath the porous mesh.
24. An apparatus as in claim 23 , wherein the porous mesh comprises a first end disposed laterally with respect to the optical waveguide and a second end opposite the first end, and wherein a first absorbent member is disposed underneath the porous mesh near the first end, and a second absorbent member is disposed underneath the porous mesh near the second end.