Gas chromatographic negative ion mass spectrometric assay of 2‐dicyclopropylmethylamino‐2‐oxazoline (S‐3341), a new antihypertensive drug

The quantification in plasma and urine of 2‐dicyclopropylmethylamino‐2‐oxazoline (S‐3341), a new antihypertensive drug is described using a sensitive gas chromatographic negative ion mass spectrometric method with ammonia as moderating gas. After a two‐step extraction, derivatization is carried out with 3,5‐bis(trifluoromethyl)benzoyl chloride and the abundance of the molecular ion ( m / z 420) obtained is compared with that of the tetradeuterated standard ( m / z 424). The low background due to the high mass and negative ion detection provides a detection limit of about 1 pg per injection. Oral administration of 1 or 2 mg S‐3341 to patients gives a maximum concentration of 3.3±0.7 ng ml −1 and 7.6±2.0 ng ml −1 at 1.8±0.6 h and 1.4±0.7 h and an average elimination half‐life of 6.7 h.