Sample preparation using ISOLUTE PPT+ protein precipitation plates

Protein precipitation is a routinely used, high throughput sample preparation technique for removal of protein from biological fluid samples prior to analysis by LC-MS/MS.

Historically, protein precipitation has been carried out in vials or collection plates, followed by centrifugation; the supernatant is then transferred for analysis. Protein precipitation by filtration in the 96-well format has more recently been used as a high throughput, easy to automate alternative to the traditional centrifugation based technique. However, most filterplates require the plasma sample to be dispensed before the precipitating solvent is added (the ‘plasma first’ method), leading to leaking, cloudy filtrates and blocked wells.

ISOLUTE PPT+ protein precipitation plates have been designed to overcome the problems of the first generation 96-well filterplates. The functionalized bottom frit holds up organic solvents, in particular acetonitrile, allowing the precipitating solvent to be dispensed into each well prior to sample addition. This ‘solvent first’ methodology is optimal for both high efficiency protein precipitation and automation, since the solvent first approach negates the need for vortex mixing. The system has an optimized porosity distribution and acts as a depth filter, retaining the precipitated protein without well blockage.