This work deals with the preparation of model biological microsamples for Substrate Assisted Laser Desorption Inductively Coupled Plasma Mass Spectrometry (SALD ICP MS). This technique provides direct and fast analysis of liquid samples deposited onto polyethylene terephthalate (PET) plate (substrate) in the form of dried droplets with minimal sample preparation and submicrolitre sample volume requirements. Furthermore, SALD allows direct analysis of samples in organic solvents, which cannot be directly nebulised to ICP MS. These benefits are, however, balanced out by low repeatability of the assay, typically about 30 %. One of the approaches to increasing the repeatability is a modification of the substrate surface by Diffuse Coplanar Surface Barrier Discharge (DCSBD) with an addition of an internal standard to the sample. Using this approach, a relative standard deviation under 10 % for model biological samples can be achieved. The only limitation of this technique is the occurrence of the so-called “aging effect”, i.e., the gradual return of the modified physicochemical surface properties to the original state.