Fluorescent pH detector system and related methods

1. A method for measuring the pH of a sample, comprising:

(a) irradiating a fluorescent species in communication with a sample with excitation light having a wavelength sufficient to effect fluorescent emission from the fluorescent species,

wherein the fluorescent species comprises a 2-halo seminaphthofluorescein and exhibits a first emission intensity at a first emission wavelength and a second emission intensity at a second emission wavelength, the ratio of the first and second emission intensities being dependent on pH; and

(b) measuring the first and second emission intensities to determined the pH of the sample.

2. The method of claim 1 , wherein the 2-halo seminaphthofluorescein is a 2-chloro seminaphthofluorescein.

3. The method of claim 1 , wherein the 2-halo seminaphthofluorescein is 2-(2-chloro-3-hydroxy-9-carboxyethyl-10-oxo-10H-benzo[c]xanthen-7-yl)benzoic acid.

4. The method of claim 1 , wherein the 2-halo seminaphthofluorescein is

5. The method of claim 1 , wherein the fluorescent species is a conjugate of a 2-halo seminaphthofluorescein and a macromolecule.

6. The method of claim 5 , wherein the macromolecule is an albumin.

7. The method of claim 5 , wherein the macromolecule is a human serum albumin.

8. The method of claim 5 , wherein the conjugate is a 2-(2-chloro-3-hydroxy-9-carboxyethyl-10-oxo-10H-benzo[c]xanthen-7-yl)benzoic acid/human serum albumin conjugate.

9. The method of claim 1 , wherein the sample comprises blood or a blood product.

10. A system for measuring pH, comprising:

(a) a light source for exciting a fluorescent species, wherein the fluorescent species comprises a 2-halo seminaphthofluorescein and has a first emission intensity at a first emission wavelength and a second emission intensity at a second emission wavelength;

(b) a first emission detector for measuring the first emission intensity;

(c) a second emission detector for measuring the second emission intensity;

(d) an excitation lightguide for transmitting excitation light from the light source to the fluorescent species, wherein the lightguide comprises a first terminus proximate to the light source and a second terminus distal to the light source;

(e) a first emission lightguide for transmitting emission from the fluorescent species to the first emission detector, wherein the lightguide comprises a first terminus proximate to the detector and a second terminus distal to the detector;

(f) a second emission lightguide for transmitting emission from the fluorescent species to the second emission detector, wherein the lightguide comprises a first terminus proximate to the detector and a second terminus distal to the detector;

(g) a probe housing the distal termini of the excitation lightguide, first emission lightguide, and second emission light guide; and

(h) an assembly for receiving the probe, the assembly comprising:

(i) a housing for receiving the probe, wherein the housing is adapted for receiving the probe at a first end and terminating with a window at the second end, the window being transparent to the excitation and the emission light,

(ii) a tip member reversibly connectable to the housing's second end, wherein the tip member is adapted to receive liquid from a sample to be measured, and

(iii) a fluorescent species immobilized on a substrate intermediate the tip member and the window, wherein the fluorescent species immobilized on the substrate is in liquid communication with the sample during the measurement.

11. The system of claim 10 , wherein the 2-halo seminaphthofluorescein is a 2-chloro seminaphthofluorescein.

12. The system of claim 10 , wherein the 2-halo seminaphthofluorescein is 2-(2-chloro-3-hydroxy-9-carboxyethyl-10-oxo-10H-benzo[c]xanthen-7-yl)benzoic acid.

13. The system of claim 10 , wherein the 2-halo seminaphthofluorescein is

14. The system of claim 10 , wherein the fluorescent species is a conjugate of a 2-halo seminaphthofluorescein and a macromolecule.

15. The system of claim 14 , wherein the macromolecule is an albumin.

16. The system of claim 14 , wherein the macromolecule is a human serum albumin.

17. The system of claim 14 , wherein the conjugate is a 2-(2-chloro-3-hydroxy-9-carboxyethyl-10-oxo-10H-benzo[c]xanthen-7-yl)benzoic acid/human serum albumin conjugate.

18. The system of claim 10 , wherein the light source is a light-emitting diode.

19. The system of claim 10 , wherein the first and second detectors are photodiodes.

20. The system of claim 10 , wherein the excitation lightguide, the first emission lightguide, and the second emission lightguide are optical fibers.

21. The system of claim 10 , wherein the probe comprises one or more optical fibers.

22. The system of claim 10 , wherein the sample comprises blood or a blood product.

23. The system of claim 10 , wherein the sample is contained within a sealed vessel.