Photoacoustic spectrometry was applied to the determination of phosphorus as molybdenum blue species adsorbed on an anion-exchange resin (10 mg of uniform beads). The photoacoustic intensity of ten resin particles on a glass plate was measured at 760 nm. The calibration graph obtained was linear in the range of 0.05–0.5 μg of phosphorus. The relative standard deviation for ten determinations of 0.3 μg P was 5.0%. The detection limit was 2 ng P ml −1.