Table 1.

Potentiometric sensors for trace analysis realized to date

Analyte ion	LODDL1a, Mb	Membrane composition and comments	Reference
Na+	3 × 10−8	Filled monolithic column	[19]
K+	5 × 10−9	Polymeric; resin in inner solution	[20]
NH4+	2 × 10−8	Polymeric; resin in inner solution	[20]
Ca2+	ca. 10−10	Polymeric; microparticles in membrane	[21]
	3 × 10−9	Polymeric; EDTA in inner solution	[22]
	2 × 10−9	Polymeric; resin in inner solution	[20]
	ca. 10−11	Polymeric; EDTA in inner solution	[23]
	3 × 10−9	Filled monolithic column	[19]
Ag+	10−9	Polymeric; resin in inner solution	[13]
	2 × 10−9	Filled monolithic column	[19]
Pb2+	8 × 10−11	Polymeric; EDTA in inner solution	[22]
	10−9	Polymeric; NTA in inner solution; optimized for rugged response	[24,25]
	6 × 10−11	Polymeric; rotating electrode	[26]
	10−9	Polymeric; covalently attached ligand	[27]
	5 × 10−10	Polymeric (plasticizer-free); solid inner contact	[28]
	10−9	Polymeric; solid inner contact	[29]
Cd2+	10−10	Polymeric; NTA in inner solution	[30]
	10−10	Polymeric; Et4NNO3 in inner solution	[31]
Cu2+	10−9	Solid state; rotating electrode	[18]
	10−8	Polymeric	[32]
	2 × 10−9	Polymeric; hard membrane, Et4NNO3 in inner solution	[33]
Vitamin B1	10−8	Polymeric; very lipophilic ion exchanger	[34]
ClO4−	2 × 10−8	Polymeric; resin in inner solution	[35]
I−	2 × 10−9	Polymeric; resin in inner solution	[35]

^aLower LOD defined according to the convention for potentiometry [8], (DL1, see Fig. 2). For comparing with other methods, the numbers should be lowered by about 2 logarithmic units (DL2, see Fig. 2).

^bThe numbers refer to total sample concentrations.