Table 4.

Method III: droplet deposition on confined, circular, and hydrophilic areas

Sample Matrix	Droplet volume	Size of dried residue	Sample loading	Surface material	LOD	Reproducibility	Additional information	Ref.
Photo-resistant used in photolithography	64.7 pL	150 μm	4 × 10−6 μL μm−2	PDMS-columns (micro-machined)	2.33, 15.4, 5.72 ng mL−1 (Al, Cu, Pb)	17.1–46.9 % RSD (due to extremely low sample volume)	No matrix added, photo resist	[164]
Human urine from supposedly healthy patients	300 μL	16 mm	10−6 μL μm−2	Filter paper (precut saturated filter disks)	0.1–13 μg L−1	2–5 % RSD	No additive	[160]
Cu isotopes in urine of Wilson’s disease patients, treated patients and one control patient	300 μL	16 mm	10−6 μL μm−2	Filter paper (precut saturated filter disks)	–	200–500 ppm RSD intra-spot, and 540  ppm RSD inter-spot	No additive, corona ablation with 10 kHz	[18]
Phosphorus in fermentation media	10 μL	5 mm	5 × 10−7 μL μm−2	Filter paper (precut saturated filter disks)	10 μg mL−1 (ICP-OES detection)	10 % RSD	Analysis via laser ablation ICP-OES	[165]

^aSample volume / area of dried residue (assuming a circular spot)