Calculation of the expected amount of each oxygen labeled phosphate (OLP) species formed with completely random assortment of the oxygen atoms and comparison to the actual results from OLP synthesized with fresh POCl3 in December 2008.

†Number of different ways this combination of oxygen-16 and oxygen-18 atoms can be arranged around the phosphorus atom.‡Probability was calculated by taking the amount of each oxygen atom (62.2 and 37.8% for oxygen-18 and oxygen-16, respectively) to the power of the number of that atom contained in the OLP species (e.g., the probability for m/z 99 is 0.3783 * 0.6221 = 0.033594).§Calculated by multiplying the number of combinations by the probability.