Minimization of carry-over for LC/MS analysis by autosampler with unique rinse function

With the increasing sensitivity of LC/MS in recent years, the number of cases in which extremely low concentration compounds are analyzed has increased. So-called carry-over and adsorption, in which the sample remains in the system, are more likely to become apparent in such sensitive analyses. The rinse mechanism used in many autosamplers is rinsing by immersing the sampling needle in a rinse solution, and only the surface of the sampling needle can be rinsed. However, carry-over may also occur at locations other than the surface of the sampling needle, such as sample loops and injection ports. It is difficult to take countermeasures with a normal rinse mode when it occurs in these parts. It is also important to select a rinse solution. However, due to the many limitations of the solutions that can be handled by LC/MS, it may be difficult to use rinses that match the characteristics of the compounds. Therefore, this study evaluated carry-over reduction using an autosampler with a unique rinse mechanism. The feature of this functions, called the internal rinse mode is that it is possible to rinse of the needle inner surface and injection port, etc., with multiple rinsing solutions. We also evaluated the reduction of the carry-over by using UHPLC system offering non-metal of the sample flow path.