Near UV absorption spectrometer and method for using the same

• US 20070138401A1
• Filed: 12/20/2005
• Published: 06/21/2007
• Est. Priority Date: 12/20/2005
• Status: Active Grant

• Current Assignee: Ecolab USA Incorporated (Ecolab, Inc.)
• Original Assignee: Ecolab, Inc.
• Inventors: Tokhtuev, Eugene, Owen, Christopher, Pilipchenko, Anna, Schilling, Paul, Kraus, Paul, Sanville, Katherine
• Granted Patent: US 7,372,039 B2
• Time in Patent Office: Days
• US Class Current: 250/373
• CPC Class Codes: G01J 2003/1226 Interference filters
• CPC Class Codes: G01J 3/021 using plane or convex mirrors, parallel phase plates, or particular reflectors
• CPC Class Codes: G01J 3/0264 Electrical interface; User interface
• CPC Class Codes: G01J 3/0272 Handheld
• CPC Class Codes: G01J 3/0283 using a charging unit
• CPC Class Codes: G01J 3/12 Generating the spectrum; Monochromators
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01J 3/4412 Scattering spectrometry particle sizing by light scattering G01N15/0205; optical velocimetry of particles G01P5/20, G01P5/26
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/532 with measurement of scattering and transmission
• CPC Class Codes: G01N 21/5907 Densitometers
• CPC Class Codes: G01N 21/8507 Probe photometers, i.e. with optical measuring part dipped into fluid sample
• CPC Class Codes: G01N 2201/0221 Portable; cableless; compact; hand-held

Abstract

A UV absorption spectrometer includes a housing, a controller, and a sensor unit including an ultraviolet light source, an analytical area in an analytical cell or in running water or gaseous medium, and an UV wavelength separator including a UV detector. An ultraviolet light in a wavelength range of 200-320 nm emits from the light source through the analytical area to the wavelength separator, and the controller transforms output signals from the UV detector into absorbance values or optical densities for two or more wavelengths in the wavelength range, calculates differences of said absorbance values or optical densities, determines a concentration of a chemical in the solution with calibration constants found for a known concentration of the chemical and said differences of said absorbance values or optical densities.

Claims

1. A UV absorption spectrometer comprising:

a housing, a controller, and a sensor unit including an ultraviolet light source, an analytical area in an analytical cell or in running water or gaseous medium, and an UV wavelength separator including a UV detector, wherein

an ultraviolet light in a wavelength range of 200-320 nm emits from the light source through the analytical area to the wavelength separator, and

the controller transforms output signals from the UV detector into absorbance values or optical densities for two or more wavelengths in the wavelength range, calculates differences of said absorbance values or optical densities, determines a concentration of a chemical in the solution with calibration constants found for a known concentration of the chemical and said differences of said absorbance values or optical densities.

2. The UV absorption spectrometer according to claim 1, wherein the chemical is a biocide.

3. The UV absorption spectrometer according to claim 1, wherein the solution is a sanitizing solution, and the chemical is quat.

4. The UV absorption spectrometer according to claim 1, wherein the ultraviolet light source is a gas discharge lamp, a mercury lamp, a deuterium lamp, a metal vapor lamp, a light emission diode, or a plurality of light emission diodes.

5. The UV absorption spectrometer according to claim 1, wherein the ultraviolet light source is a mercury low pressure lamp with main line at about 254 nm, or a Krypton gas discharge lamp

6. The UV absorption spectrometer according to claim 1, further comprising another ultraviolet detector for monitoring an intensity of the ultraviolet light source.

7. The UV absorption spectrometer according to claim 1, wherein the analytical cell is a sample cell, a flow cell, or an open path cell.

8. The UV absorption spectrometer according to claim 1, wherein the housing includes a first cylinder which accommendates the UV light source and a first optical means for directing and focusing the light emitted by the UV light source towards the analytical area, a second cylinder which accommendates the UV director and a second optical means for directing and focusing the light passing via the analytical area towards the UV detector, axes of the first and second cylinders are arranged in parallel while perpetual to a light traveling path in the analytical area.

9. The UV absorption spectrometer according to claim 8, wherein the first optical means include a first prismatic mirror, and the second optical means include a second prismatic mirror, two lenses, and two spacers.

10. The UV absorption spectrometer according to claim 8, further comprising another UV detector for measuring turbidity which is positioned inside of the housing, between the first cylinder and the second cylinder, and right on top of the analytical area thereby receiving scattered radiation from the analytical area.

11. The UV absorption spectrometer according to claim 8, wherein the UV wavelength separator further includes a ruled or holographic diffractional grating, or a variable UV wavelength linear interference filter, or a plurality of UV interference filters.

12. The UV absorption spectrometer according to claim 11, wherein the UV wavelength separator includes an input slit, a spherical mirror, and the ruled diffractional grating.

13. The UV absorption spectrometer according to claim 12, wherein the input slit is symmetrically aligned with the axis of the second cylinder,

a receiving surface of the UV detector is positioned perpendicular to the axis of the second cylinder,

a center of the spherical mirror is aligned with the axis of the second cylinder, while a bottom of the spherical mirror is positioned at a 20 degree angle from the axis of the second cylinder, and

a center of the diffraction gratings corresponds to the center of the spherical mirror such that the diffraction gratings reflects UV lights of different wavelengths under different angles to produce a linear spectrum on the UV detector.

14. The UV absorption spectrometer according to claim 1, wherein the controller is included in a controller unit which includes a power supply, a memory, a display, and a keypad.

15. The UV absorption spectrometer according to claim 11, wherein the UV director is a linear detector array, and the UV wavelength separator includes a flat mirror, an astigmatic/toroidal mirror, the variable wavelength optical UV filter, a pair of UV filter mounts, and an input diaphragm.

16. The UV absorption spectrometer according to claim 15, wherein the input diaphragm is symmetrically aligned with the axis of the second cylinder,

a receiving surface of the linear detector array is positioned perpendicular to the axis of the second cylinder,

a center of the flat mirror is aligned with the axis of the second cylinder, while a bottom of the flat mirror is positioned at a 20-degree angle from the axis of the second cylinder, and

a center of the astigmatic/toroidal mirror corresponds to the center of the flat mirror such that the flat mirror directs UV light from the input diaphragm to the astigmatic/toroidal mirror 75 which transforms light from a circular input diaphragm into the line on the sensitive surface of the linear detector array.

17. The UV absorption spectrometer according to claim 8, wherein the UV wavelength separator includes optically opaque walls, a positive lens, four optical filters, and four additional UV detectors.

18. The UV absorption spectrometer according to claim 17, wherein the four optical filters include a first optical filter with a maximum transmission at 288 nm for a 45 degree angle, a second optical filter with a maximum transmission at 296 nm for a 45 degree angle, a third optical filter with a maximum transmission at 312.5 nm for a 45 degree angle, and a forth optical filter with a maximum transmission at 365 nm for a 45 degree angle, and

wherein the five UV detectors include a first UV detector for measuring UV intensity at 288 nm, a second UV detector for measuring UV intensity at 296 nm, a third UV detector for measuring UV intensity at 312.5 nm, a forth UV detector for measuring UV intensity at 365 nm, and a fifth UV detector for measuring UV intensity at 254 nm.

19. The UV absorption spectrometer according to claim 17, wherein each of the optical filter is an interference filter which has a thin transparent spacer placed between two semi-reflective coatings so as to use multiple reflections and interference to select a narrow frequency band.

20. The UV absorption spectrometer according to claim 18, wherein a center of the first optical filter is aligned with the axis of the second cylinder, while a body of the first optical filter is positioned at a 45-degree angle from the axis of the second cylinder,

the second optical filter is positioned parallel with the first optical filter and with a center thereof corresponding to the center of the first optical filter,

a body of the positive lens is arranged perpendicular to the axis of the second cylinder with a center thereof corresponding to the center of second optical filter,

the third optical filter is positioned perpendicular to the second optical filter and with a center thereof corresponding to the center of the second optical filter as well as the center of the positive lens,

the fourth optical filter is positioned parallel with the third optical filter and with a center thereof corresponding to the center of the third optical filter, and

each of the five UV detectors are positioned at a 45-degree angle from a respective optical filter, and with the center thereof corresponding to the center of the respective optical filter.

21. The UV absorption spectrometer according to claim 8, wherein the first and second optical means include off-axis parabolic mirrors.

22. The UV absorption spectrometer according to claim 1, further comprising a sensor connector, wherein the controller is included in a wall-mounted controller unit, the sensor unit is a dip sensor unit for dipping into a sanitizing chamber, and the sensor connector connects between the controller unit and the sensor unit.

23. The UV absorption spectrometer according to claim 22, further comprising assemblies of quartz sleeves with UV lamps positioned on walls of the sanitizing chamber for UV sanitization.

24. The UV absorption spectrometer according to claim 1, wherein the UV director is a UV array detector which includes UV photodiodes, UV photomultipliers, a CCD array, or a photodiode array.

25. A method for measuring a chemical concentration in a solution or running water or gaseous medium, comprising:

providing a near UV spectrometer with a sample chamber, the ultraviolet spectrometer comprising an ultraviolet light source emitting light in a wavelength range of 200-320 nm, an UV wavelength separator including a UV detector, a controller;

providing a liquid or gaseous medium into the sample chamber;

using the ultraviolet spectrometer to measure values or optical densities for two or more wavelengths in the wavelength range;

programming the controller to calculate differences of said absorbance values or optical densities, and to determine a concentration of the chemical in the sample chamber with calibration constants found for a known concentration of the chemical and said differences of said absorbance values or optical densities.

26. The method according to claim 25, wherein the solution is a sanitizing solution, the chemical if a detergent, and the controller calculates and determines based upon equations:

$y=178.16·<br><br>x-14.608·<br><br>x^2+0.5726·<br><br>x^3-0.0081·<br><br>x^4<br><br>\text{\hspace{1em}<br><br>}$ $\mathrm{where}<br><br>\text{\hspace{1em}<br><br>}<br><br>y=\frac{\mathrm{Concentration}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{detergent},\text{\hspace{1em}<br><br>}<br><br>\mathrm{ppm}}{\mathrm{Concentration}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{sanitizer},\text{\hspace{1em}<br><br>}<br><br>\mathrm{ppm}}$ $x=\left(\mathrm{Position}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{minimum},\text{\hspace{1em}<br><br>}<br><br>\mathrm{nm}-230<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{nm}\right)$

the % is a ratio of the detergent to a sanitizer contained in the sanitizing solution.

27. The method according to claim 25, wherein the UV light source is a mercury lamp, and the controller calculates and determines based upon equations:

C_quat=2852·

Z(s)·

(1−

0.042·

Z(s)²)
Z(s)=(D₂₅₄(s)−

2.62·

D₂₈₀(s)+1.62·

D₂₉₆(s)) $D_{254}<br><br>\left(s\right)=\log <br><br>\left(\frac{U_{254}<br><br>\left(0\right)}{U_{254}<br><br>\left(s\right)}\right)$

is an optical density at the wavelength 254 nm

$D_{280}<br><br>\left(s\right)=\log <br><br>\left(\frac{U_{280}<br><br>\left(0\right)}{U_{280}<br><br>\left(s\right)}\right)$

is an optical density at the wavelength 280 nm

$D_{296}<br><br>\left(s\right)=\log <br><br>\left(\frac{U_{296}<br><br>\left(0\right)}{U_{296}<br><br>\left(S\right)}\right)$

is an optical density at the wavelength 296 nm

wherein U₂₅₄ (0), U₂₈₀ (0) and U₂₉₆ (0) are intensities of ultraviolet signals at wavelengths of 254 nm, 280 nm and 296 nm during zeroing, and U₂₅₄((s), U₂₈₀(s) and U₂₉₆(s) are intensities of ultraviolet signals at wavelengths 254 nm, 280 nm and 296 nm during measuring.

28. The method according to claim 25, wherein the UV light source is a krypton lamp or a deuterium lamp, and the controller calculates and determines based upon equations:

C_quat=2450·

(D₂₅₉(s)−

D₂₇₅(s))

where C_quat is an actual concentration of chemicals,

$D_{259}<br><br>\left(S\right)=\log <br><br>\left(\frac{U_{259}<br><br>\left(0\right)}{U_{259}<br><br>\left(s\right)}\right)$

is an optical density at the wavelength 259 nm

$D_{275}<br><br>\left(S\right)=\log <br><br>\left(\frac{U_{275}<br><br>\left(0\right)}{U_{275}<br><br>\left(s\right)}\right)$

is an optical density at the wavelength 275 nm,

U₂₅₉ (0) and U₂₇₅ (0) is an intensity of ultraviolet signals at wavelengths 259 nm and 275 nm during zeroing, and

U₂₅₉ (0) and U₂₇₅(0)—

is an intensity of ultraviolet signals at wavelengths 259 nm and 275 nm during measuring.

29. The method according to claim 25, further comprising:

measuring turbidity of the liquid or gaseous medium, and compensating for turbidity influence on the determined chemical concentration.

30. The method according to claim 29, wherein the controller calculates a compensated concentration value Ccomp based upon equations:

C_comp=C_meas−

K_t·

U_t(s)

C_meas is a not-compensated output concentration value.

U_t(s) is an output of a turbidity channel

$K_t=\frac{C_{\mathrm{meas}}<br><br>\left(T_{\mathrm{st}}\right)}{U_t<br><br>\left(T_{\mathrm{st}}\right)}$

is a compensation coefficient, where C_meas(T_st) is a not-compensated output concentration value, and U_t(T_st) is an output of a turbidity channel during calibration when calibration solution has a known turbidity T_st and zero concentration of sanitizer.

31. The method according to claim 25, further comprising:

sanitizing the sample chamber with UV light.

32. The method according to claim 25, further comprising:

monitoring an intensity of the ultraviolet light source.