Methods and apparatus for measuring the concentration of a substance in a solution

1. A method for measuring the concentration of a substance in a solution, said substance having an absorption at 300 nm or less, said method comprising:

i) transmitting ultraviolet light of wavelength 300 nm or less from a light source which light source is a light emitting diode which emits light at a wavelength of 300 nm or less, through a band pass filter;

ii) passing said ultraviolet light emanating from said band pass filter through a beam-splitter;

iii) diverting a first portion of the light by the beam-splitter and quantifying the electromagnetic radiation of said first portion with a reference detector to obtain a reference value;

iv) irradiating a known path length of the solution with a second portion of the light passing through the beam splitter;

v) quantifying the electromagnetic radiation transmitted through the solution with a sample detector to obtain a sample value; and

vi) determining the absorbance (A) from said sample value and said reference value and using said absorbance to obtain a measuring value for the concentration by a dose-response curve; wherein said light source is a light emitting diode which emits light of wavelength of 300 nm or less;

further wherein said substance is separated from one or more compounds present in said solution by chromatography prior to step (i).

2. The method of claim 1 , wherein the solution is selected from the group consisting of cell extract, cell lysate and cell culture or mixtures thereof.

3. The method of claim 1 , wherein said reference detector and said sample detector is a UV sensitive photomultiplier or a UV sensitive photodiode.

4. The method of claim 1 , wherein said substance is a protein or a peptide.

5. The method of claim 1 , wherein said substance is a nucleic acid.

6. An apparatus for measuring the concentration of a substance in a solution, said substance having an absorption at 300 nm or less, comprising:

i) a cell of known path length for containing said solution, said cell being transparent to light of wavelength of 300 nm or less;

ii) a light source, wherein said light source is a light emitting diode which emits light of wavelength of 300 nm or less;

iii) a band pass filter;

iv) a beam splitter for dividing light into a first portion and a second portion;

v) a reference detector for detecting electromagnetic radiation diverted by said beam splitter;

vi) a sample detector for detecting the electro magnetic radiation transmitted through said solution; and

vii) a dose-response curve for determining the absorbance (A) from said sample value and a reference value and using said absorbance to obtain a measuring value for the concentration.

7. The apparatus of claim 6 , wherein said reference detector and said sample detector is a UV sensitive photodiode or a UV sensitive photomultiplier.

8. The apparatus of claim 6 , further comprising a collimating lens.

9. The apparatus of claim 6 , further comprising a focusing lens.