Method of normalizing surface tension of a sample fluid
View Patent ↗A method of normalizing surface tension of a sample fluid on a clinical analyzer is disclosed. The method comprises aspirating a portion of a sample fluid into a metering tip, the metering tip having a lower end through which the sample fluid is aspirated and an upper end; sealing the lower end of the metering tip, forming a cuvette for the portion of the sample fluid; pre-treating a micro-tip with a surface tension-normalizing agent, and then dispensing the surface tension-normalizing agent into the sample fluid in the cuvette; mixing the surface tension-normalizing agent and the sample fluid in the cuvette using the micro-tip to create a mixture of the sample fluid and the surface tension-normalizing agent, the mixture having a normalized surface tension; and using the mixture for testing on the clinical analyzer.
1. A method of normalizing surface tension of a sample fluid on a clinical analyzer, the method comprising:
first aspirating a portion of a sample fluid into a metering tip, the metering tip having a lower end through which the sample fluid is aspirated and an upper end, and the sample fluid being free of surface-tension normalizing agent;
then sealing the lower end of the metering tip, forming a cuvette for the portion of the sample fluid;
then pre-treating a micro-tip with a surface tension-normalizing agent by aspirating a volume of a surface-tension normalizing agent into the micro-tip, then dispensing out a portion of the volume of the surface-tension normalizing agent and retaining in the micro-tip a remaining portion of the volume of the surface-tension normalizing agent;
then dispensing the remaining portion of the volume of the surface tension-normalizing agent into the sample fluid in the cuvette;
then mixing the remaining portion of the volume of the surface tension-normalizing agent and the sample fluid in the cuvette using the micro-tip to create a mixture of the sample fluid and the surface tension-normalizing agent, wherein the mixing comprises repeatedly aspirating and dispensing a volume of the mixture, the volume of the mixture being less than or equal to the volume of the surface-tension normalizing agent used to pre-treat the micro-tip, the mixture having a normalized surface tension; and
using the mixture for testing on the clinical analyzer.
2. The method of claim 1 wherein portions of the mixture for testing are aspirated from the cuvette to a reaction vessel using a second micro-tip and wherein the surface tension-normalizing agent blocks adhesion of analytes present in the mixture to the second micro-tip.
3. The method of claim 1 wherein normalizing surface tension also improves metering performance of the clinical analyzer.
4. The method of claim 1 wherein the surface tension-normalizing agent is a surfactant.
5. The method of claim 4 wherein the surfactant is a non-ionic surfactant.
6. The method of claim 5 wherein the non-ionic surfactant is a poly(oxyalkylene) block copolymer of the formula (PO) Y (EO) X (PO) Y , wherein PO is polypropylene oxide, EO is polyethylene oxide, and X<Y.
7. The method of claim 6 wherein the poly(oxyalkylene) block copolymer is Pluronic 25R2®, wherein X is 14 and Y is 22.
8. The method of claim 5 wherein the non-ionic surfactant is a polyalkoxylated alkanol.
9. The method of claim 8 wherein the polyalkoxylated alkanol is ceteareth 55 (Plurafac A39®).
10. The method of claim 1 wherein the surface tension-normalizing agent agent is a mixture of Pluronic 25R2® and Plurafac A39®.
11. The method of claim 1 wherein the surface tension-normalizing agent is polyethylene glycol P-1,1,3,3-tetramethylbutylphenyl ether (TX-100®).
12. The method of claim 1 wherein the sample is urine.
13. The method of claim 1 wherein the sample fluid is being analyzed for a hydrophobic molecule.
14. The method of claim 13 wherein the hydrophobic molecule is a tetrahydrocannabinoid or a tetrahydrocannabinoid metabolite.
15. The method of claim 13 wherein the hydrophobic molecule is methadone.