Which action could lead to analytical error in a sweat chloride collection?

Leaving the preweighed gauze exposed to air could lead to an analytical error in a sweat chloride collection because exposure can result in evaporation of the sweat sample. This evaporation would decrease the amount of sweat on the gauze and lead to inaccurate measurements of chloride concentration. The collection process relies on maintaining the integrity of the sample, and any factor that alters the quantity of sweat collected directly impacts the resulting analytical results.

In contrast, options such as using unweighed gauze, collecting an excessive amount of sweat, and rinsing the collected sweat are associated with specific procedural considerations, but they do not inherently compromise the integrity of the sample in the same way that exposure to air does. Therefore, maintaining proper handling and minimizing exposure to external factors is crucial for obtaining valid results in sweat chloride tests.