Extraction and quantification of vitamins A & D in fluid samples
The invention discloses monoclonal antibodies for vitamins A (retinol palmitate) and D3 (cholecalciferol); a method for using monoclonal antibodies, and the monoclonal antibodies disclosed herein, in particular, to quantitate these vitamins in fluids such as dairy products, and blood, and also raw or processed agri-food and beverage products. The method involves contacting the sample with a mixture of polar and non-polar organic solvents in combination with inorganic salts to remove fat molecules into an organic fraction, and assaying the organic fraction by immunoassay involving the monoclonal antibodies. The presence of a mixture of non-polar and polar organic solvents increases the separation of vitamins from fat molecules and enables the test samples to be quantified by immunoassay without any further treatment.
1. A method of quantifying vitamin A or D3, or vitamins A and D3, in an aqueous dairy sample within a few hours, comprising the steps of:
(a) extracting the aqueous dairy sample with an alkaline metal salt and an extraction solvent comprising a mixture of a non-polar organic solvent and a polar organic solvent, to isolate vitamin A or D3, or vitamins A and D3 from the aqueous dairy sample into an organic fraction; and
(b) determining the amount of vitamin D3 or vitamin A, or both vitamin D3 and vitamin A, in the organic fraction,
wherein the vitamin is quantified with a monoclonal antibody which specifically binds to the vitamin, and wherein the non-polar organic solvent comprises an aliphatic hydrocarbon having from 4 to 10 carbon atoms, or a mixture thereof, and the polar organic solvent comprises a chloroalkane or ethyl acetate.
2. The method of claim 1 wherein the inorganic alkaline metal salt is added to the sample in an alcoholic solution.
3. The method of claim 2 wherein the alcoholic solution comprises greater than about 50% and less than about 75% ethanol in water (v:v).
4. The method of claim 1 , wherein the alkaline metal salt is selected from potassium hydroxide, potassium chloride, sodium hydroxide, sodium bicarbonate or sodium ascorbate.
5. The method of claim 1 wherein the non-polar organic solvent comprises a mixture of hexane and petroleum ether and the polar organic solvent comprises methylene chloride.
6. The method of claim 1 wherein the vitamin D3 or vitamin A, or vitamins D3 and vitamin A, is detected by an immunosorbent assay.
7. The method of claim 1 wherein the vitamin is quantified by direct measurement.
8. The method of claim 4 wherein the alkaline metal salt comprises potassium hydroxide.
9. The method of claim 1 , wherein the non-polar organic solvent is selected from butane, pentane, hexane, heptane, octane, or a mixture thereof.
10. The method of claim 1 , wherein the chloroalkane is methylene chloride.