Document Detail

Amperometric microsensor for direct probing of ascorbic acid in human gastric juice.
MedLine Citation:
PMID:  20888449     Owner:  NLM     Status:  MEDLINE    
This article reports on a novel microsensor for amperometric measurement of ascorbic acid (AA) under acidic conditions (pH 2) based on a carbon fiber microelectrode (CFME) modified with nickel oxide and ruthenium hexacyanoferrate (NiO-RuHCF). This sensing layer was deposited electrochemically in a two-step procedure involving an initial galvanostatic NiO deposition followed by a potentiodynamic RuHCF deposition from solutions containing the precursor salts. Several important parameters were examined to characterize and optimize the NiO-RuHCF sensing layer with respect to its current response to AA by using cyclic voltammetry, and scanning electron microscopy-energy dispersive X-ray spectroscopy methods. With the NiO-RuHCF coated CFME, the AA oxidation potential under acidic conditions was shifted to a less positive value for about 0.2 V (E(p) of ca. 0.23 V vs. Ag/AgCl) as compared to a bare CFME, which greatly improves the electrochemical selectivity. Using the hydrodynamic amperometry mode, the current vs. AA concentration in 0.01 M HCl, at a selected operating potential of 0.30 V, was found to be linear over a wide range of 10-1610 μM (n=22, r=0.999) with a calculated limit of detection of 1.0 μM. The measurement repeatability was satisfactory with a relative standard deviation (r.s.d.) ranging from 4% to 5% (n=6), depending on the AA concentration, and with a sensor-to-sensor reproducibility (r.s.d.) of 6.9% at 100 μM AA. The long-term reproducibility, using the same microsensor for 112 consecutive measurements of 20 μM AA over 11 h of periodic probing sets over 4 days, was 16.1% r.s.d., thus showing very good stability at low AA levels and suitability for use over a prolonged period of time. Moreover, using the proposed microsensor, additionally coated with a protective cellulose acetate membrane, the calibration plot obtained in the extremely complex matrix of real undiluted gastric juice was linear from 10 to 520 μM (n=14, r=0.998). These results demonstrated the unique featuring of the proposed NiO-RuHCF microsensor under acidic conditions with enhanced sensitivity and stability and proved its promising potentiality for direct amperometric probing of AA at physiological levels in real gastric juice environments.
Emily A Hutton; Rasa Pauliukaitė; Samo B Hocevar; Božidar Ogorevc; Malcolm R Smyth
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Publication Detail:
Type:  Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-09-18
Journal Detail:
Title:  Analytica chimica acta     Volume:  678     ISSN:  1873-4324     ISO Abbreviation:  Anal. Chim. Acta     Publication Date:  2010 Sep 
Date Detail:
Created Date:  2010-10-04     Completed Date:  2011-01-13     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370534     Medline TA:  Anal Chim Acta     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  176-82     Citation Subset:  IM    
Copyright Information:
Copyright © 2010 Elsevier B.V. All rights reserved.
Analytical Chemistry Laboratory, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
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MeSH Terms
Ascorbic Acid / analysis*,  chemistry
Biosensing Techniques / instrumentation,  methods*
Carbon / chemistry
Cellulose / analogs & derivatives,  chemistry
Electrochemical Techniques / instrumentation,  methods*
Ferrocyanides / chemistry
Gastric Juice / chemistry,  metabolism*
Hydrogen-Ion Concentration
Limit of Detection
Microscopy, Electron, Scanning
Nickel / chemistry
Reproducibility of Results
Ruthenium Compounds / chemistry
X-Ray Absorption Spectroscopy
Reg. No./Substance:
0/Ferrocyanides; 0/Ruthenium Compounds; 0/carbon fiber; 1313-99-1/nickel monoxide; 50-81-7/Ascorbic Acid; 7440-02-0/Nickel; 7440-44-0/Carbon; 9004-34-6/Cellulose; 9004-35-7/acetylcellulose

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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