Characteristics of picoliter droplet dried residues as standards for direct analysis techniques.

The characteristics of dried residues of picodroplets of single-, two-, and three-element aqueous solutions, which qualify these as reference materials in the direct analysis of single particles, single cells, and other microscopic objects using, e.g., laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) and micro-X-ray fluorescence (MXRF), were evaluated.