title: A microchip sensor for calcium determination.
abstract: A newly designed glass-PDMS microchip-based sensor for use in the determination of Ca(2+) ions has been developed, utilizing reflectance measurements from arsenazo III (1,8-dihydroxynaphthalene-3,6-disulfonic acid-2,7-bis[(azo-2)-phenyl arsenic acid]) immobilized on the surface of polymer beads. The beads, produced from cross-linked poly(p-chloromethylstyrene) (PCMS), were covalently modified with polyethylenimine (PEI) to which the Arsenazo III could be adsorbed. The maximum amount of Arsenazo III which could be immobilized onto the PEI-attached PCMS beads was found to be 373.71 mg g(-1) polymer at pH 1. Once fabricated, the beads were utilized at the detection point of the microfluidic sensor device with a fiber optic assembly for reflectance measurements. Samples were mobilized past the detection point in the sensor where they interact with the immobilized dye. The sensor could be regenerated and re-used by rinsing with HCl solution. The pH, voltage, linear range, and the effect of interfering ions were evaluated for Ca(2+) determination using this microchip sensor. At the optimum potential, 0.8 kV, and pH 9.0, the linear range of the microchip sensor was 3.57 x 10(-5) - 5.71 x 10(-4) M Ca(2+), with a limit of detection (LOD) of 2.68 x 10(-5) M. The microchip biosensor was then applied for clinical analysis of calcium ions in serum with good results.
authors.affiliation: Department of Chemistry, Hacettepe University, Beytepe 06532, Ankara, Turkey. percag@hacettepe.edu.tr
authors.forename: P
authors.initials: P
authors.lastname: Caglar
authors.forename: S A
authors.initials: SA
authors.lastname: Tuncel
authors.forename: N
authors.initials: N
authors.lastname: Malcik
authors.forename: J P
authors.initials: JP
authors.lastname: Landers
authors.forename: J P
authors.initials: JP
authors.lastname: Ferrance
mesh_terms: D001150:Arsenazo III / Q000737:chemistry; D002118:Calcium / Q000032:analysis*; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology; D005898:Glass; D006863:Hydrogen-Ion Concentration; D056656:Lab-On-A-Chip Devices; D046208:Microchip Analytical Procedures / Q000379:methods*; D055100:Optical Fibers; D010316:Particle Size; D011094:Polyethyleneimine / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D015203:Reproducibility of Results; D013499:Surface Properties; D013997:Time Factors
chemical_list: D004129:Dimethylpolysiloxanes; D011137:Polystyrenes; C426943:poly(p-chloromethylstyrene); D001150:Arsenazo III; D011094:Polyethyleneimine; D002118:Calcium