title: Fiber-optic microsensor array based on fluorescent bulk optode microspheres for the trace analysis of silver ions.
abstract: An optical microsensor array is described for the rapid analysis of silver ions at low parts per trillion levels. Because the ionophore o-xylylenebis(N,N-diisobutyldithiocarbamate) (Cu-I) was reevaluated and shown to exhibit excellent selectivity for silver ions, ion-selective electrode (ISE) membranes were optimized and found to exhibit the lowest reported detection limit so far (3 x 10(-10) M). A corresponding Ag+-selective fluorescent optical microsensor array for the rapid sensing of trace level Ag+ was then developed. It was fabricated using plasticized PVC-based micrometer-scale fluorescent microspheres that were produced via a sonic particle casting device. They contained 156 mmol/kg Cu-I, 10 mmol/kg 9-(diethylamino)-5-[4-(15-butyl-1,13-dioxo-2,14-dioxanodecyl) phenylimino]benzo[a]phenoxazine (chromoionophore VII, ETH 5418), 2.3 mmol/kg 1,1' '-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (internal reference dye), and 14 mmol/kg sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate and were deposited onto the etched distal end of a 3200-microm-diameter optical fiber bundle. The microarray was characterized by fluorescence spectroscopy in samples containing 10(-12)-10(-8) M AgNO3 at pH 7.4, with selectivity characteristics comparable to the corresponding ISEs. The response time of the microsensor array was found to be less than 15 min for 10(-9) M AgNO3, which is drastically shorter than earlier data on optode films (8 h) and corresponding ISEs (30 min). A detection limit of 4 x 10(-11) M for Ag+ was observed, lower than any previously reported optode or silver-selective ISE. The microsensor array was applied for measurement of free silver levels in buffered pond water samples.
authors.affiliation: Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Wygladacz
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Radu
authors.forename: Chao
authors.initials: C
authors.lastname: Xu
authors.forename: Yu
authors.initials: Y
authors.lastname: Qin
authors.forename: Eric
authors.initials: E
authors.lastname: Bakker
mesh_terms: D002138:Calibration; D002412:Cations / Q000737:chemistry; D004566:Electrodes; D005336:Fiber Optic Technology / Q000379:methods*; D046228:Microarray Analysis / Q000379:methods*; D008863:Microspheres; D055100:Optical Fibers; D012834:Silver / Q000032:analysis* / Q000737:chemistry*; D012996:Solutions; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013997:Time Factors
chemical_list: D002412:Cations; D012996:Solutions; D012834:Silver