grab sampling

https://doi.org/10.1351/goldbook.G02668
The taking of a sample (often in an evacuated bulb) in a very short time; preferred terms are spot sampling or spot sampling.
Source:
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2212 (https://doi.org/10.1351/pac199062112167)