In this study, three organoarsenic compounds including dimethylarsinic acid, trimethylarsine oxide, and arsenic ethoxide were directly detected by coupling a direct sample insertion probe with a lithium ion attachment mass spectrometer. Previously only gaseous sample could be detected by this method; however, solid and liquid samples can also be detected directly with the use of a direct sample insertion probe. This method will be applicable for the direct analysis of various organometallic compounds in the latest metallomics studies.