Principles of DIOS

Due to the hydrophobicity of the silicon surface, samples are typically dissolved in water or mixtures of water and methanol. While samples dissolved in pure non-polar solvents tend to spread over the whole surface, aqueous/organic mixtures form droplets that stay localized to a small surface area. Additionally, mixtures also guarantee that the sample penetrates sufficiently deep into the silicon. Spotted volumes are typically in the low microliter to submicroliter range. Traditionally, sample spotting in DIOS-MS is carried out using pipettes, which mostly suffers from an inhomogeneous analyte distribution. This can be overcome by 

Although DIOS-MS is mainly a tool for qualitative analysis, many examples have shown that quantitative analysis is possible when internal standards are used. These may either be isotope-labelled - mostly deuterated - compounds or structurally related analogues. For example, subsequent to electrospray deposition, amino acids such as phenylalanine and tyrosine have been successfully quantified by means of DIOS-MS using their deuterated analogues as internal standards. 

---