Interactive variable pathlength device
This disclosure relates generally to a sampling device, and more particularly, a sampling device that facilitates spectroscopic measurements with a variable path length and the necessary software controlled algorithms and methods for such a device.
1. A method of determining the concentration of a sample flowing through a flow cell comprising:
(a) flowing the sample through the flow cell;
(b) placing a probe within sample;
(c) taking an absorbance reading;
(d) moving the probe relative to the flow cell by a predetermined increment taking an absorbance reading at a predetermined wavelength;
(e) repeating step (d) one or more times;
(f) generating a regression line from the absorbance values such that a slope of the regression line is obtained; and
(g) determining the concentration of the sample by dividing the slope of the regression line by the extinction coefficient of the sample.
2. The method of claim 1 wherein the predetermine increment is the same for each iteration.
3. The method of claim 1 wherein the predetermined increment is from about 0.005 mm to about 50 mm.
4. The method of claim 1 wherein the predetermined increment is from about 0.0002 mm to about 10 mm.
5. The method of claim 1 wherein the regression line has an measure of goodness-of-fit for the linear regression R 2 value of from around 0.99950 to about 0.99999.
6. The method of claim 1 wherein the regression line has an measure of goodness-of-fit for the linear regression R 2 value of from around 0.99990 to about 0.99999.
7. A method of determining the extinction coefficient of a sample flowing through a flow cell at a wavelength where the extinction coefficient is not known comprising:
(a) flowing the sample through the flow cell;
(b) placing a probe within the sample;
(c) taking an absorbance reading at a first predetermined wavelength where the extinction coefficient is known and a second predetermined wavelength where the extinction coefficient is not known;
(d) repeating step (c) one or more times to determine the ratio of the absorbance to the path length at the first wavelength and the second wavelength;
(e) calculate the extinction coefficient at the second wavelength from the ratios of the absorbance to path length at both wavelengths and the extinction coefficient for the first wavelength.
8. The method of claim 1 wherein the flow cell comprises:
a) a flow cell bodythrough which a sample solution moves;
b) an inlet port through which the solution enters the flow cell body;
c) an outlet port through which the solution exits the flow cell body;
d) at least one transparent window where a detector is placed adjacent to the window; and
e) a port comprising a seal disposed opposite to the window such that light passes from the probe through the sample solution and through the window wherein the probe may pass through the seal and move relative to the window without the sample solution leaking from the port.