The conjugates were then quenched for thirty minutes using ethanolamine, again on the orbital shaker. Next, 6% casein was added to the mixture to a final concentration of 1% casein. The conjugates were blocked overnight at room temperature on the orbital shaker. The following day, conjugates were washed and stored in 50 mM borate with 1% casein (from the 6% latex block stock) as described under the latex bead casein block preparation. Concentrations for the completed conjugates were determined by measuring the absorbance at 560 nm for red and 660 nm for blue. Final stocks were stored at 4⁰C until use.