A method of detection of a target nucleic acid is provided. The method includes fractionating a sample into a plurality of sample volumes wherein more than 50% of the fractions contain no more than 1 target nucleic acid molecule per sample volumes, and subjecting the plurality of sample volumes to conditions for amplification. The method further includes detecting a change in ion concentration in a sample volume wherein a target nucleic acid is present, counting the number of fractions with an amplified target nucleic acid, and determining the quantity of target nucleic acid in the sample.