“…An Exceedingly Simple Mass Spectrometer Interface with Application to Reaction Monitoring and Environmental Analysis Sir: Mass spectrometry has proven valuable in the direct analysis of many complex samples, but it is not an established procedure for molecular analysis of aqueous solutions. Two ongoing developments address this problem, the well-known and various forms of liquid chromatography/mass spectrometry (1)(2)(3)(4)(5)(6)(7) and semipermeable membrane interfaces (8)(9)(10)(11)(12)(13)(14)(15). Several membrane interfaces previously developed to allow introduction of aqueous samples into a mass spectrometer give encouraging results with respect to sensitivity.…”