Untreated and dried sample analysis by solid probe assisted nanoelectrospray ionization mass spectrometry†
The present paper describes the application of solid probe assisted nanoelectrospray ionization mass spectrometry (SPA-nanoESI-MS) for the direct analysis of samples in solid or dried form. The experimental procedure is simple and requires a metallic needle to touch the sample surface followed by inserting the needle into a solvent preloaded nano-capillary. A number of real-world samples in solid or dried form comprising proteins, drugs in tablets, illicit drugs in dried urine, and lipids in tissues were analyzed to evaluate the applicability of the technique in diverse fields. This technique can produce high quality mass spectra without clogging the capillary tip. The quantitative aspect of this technique was evaluated using morphine from dried urine. In addition, biofluids/biomolecules captured on the needle tip and stored for several days at room temperature produced almost similar spectra to those obtained for fresh samples of cancerous and noncancerous tissues. The high sensitivity, versatile applicability and capability of dried sample analysis extend the scope of SPA-nanoESI to new ventures like bioanalytical and forensic analysis as well as clinical diagnosis.