A calix[4]arene based calcium-selective optode membrane: measuring the absorbance maximum wavelength shift.
An absorbance based calcium ion sensor is presented which applies a new immobilized chromogenic calix[4]arene. The membrane consists of a hydrogel/1,3-pentanedial mixture and the 1,3-bis(indoaniline)-derived 2,4-bis-[(ethylcarbonyl)methoxyl-calix[4]arene as calcium receptor. The indicator entrapped within the gel was not rapidly washed out. Upon calcium complexation a bathochromic shift up to 70 nm was observed along with an increase of the absorption coefficient. The dynamic range of calcium measurements is from 3 to 10 mM with a point of inflection of the calibration curve at a calcium concentration of about 7 mM. The concentration of calcium ions can be calculated from either absorbance at a distinct wavelength or--preferably when indicator leaching occurs--from the wavelength shift of the absorbance occurring when calcium levels are increased.
University of Regensburg, Institute of Analytical Chemistry, Chemo- and Biosensors, Germany.
J M
JM
Kürner
T
T
Werner
D002118:Calcium / Q000737:chemistry*; D002138:Calibration; D047250:Calixarenes; D002614:Chelating Agents / Q000737:chemistry*; D004396:Coloring Agents; D020100:Hydrogels; D007476:Ionophores; D008567:Membranes, Artificial; D010636:Phenols / Q000737:chemistry*; D011140:Polyurethanes; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
D002614:Chelating Agents; D004396:Coloring Agents; D020100:Hydrogels; D007476:Ionophores; D008567:Membranes, Artificial; D010636:Phenols; D011140:Polyurethanes; C121325:calix(4)arene; D047250:Calixarenes; D002118:Calcium