The goal of the project is to support the measurement of formaldehyde on the NOAA research vessel deployed during CalNex 2010. Measurements of formaldehyde will assist in the elucidation of atmospheric processes relevant to both climate change and air quality issues. The CalNex ship-borne deployment represents an ideal opportunity to address outstanding questions in the marine boundary layer oxidation chemistry. This campaign also anticipates meteorologically modulated outflow of urban and continental air. Formaldehyde measurements will be key to understanding the chemical transformations taking place as this continental plume ages in the marine boundary layer. Because the analytical method proposed in this work is also rapid, (~1 sec.) near-field plume characterization of ship and near-shore emission sources can be conducted. Sensitive and selective measurements of the formaldehyde mixing ratio are essential to the interpretation of the dataset collected during CalNex 2010.