University of North Florida
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Contact Info

Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Constantinos A. Georgiou

Abbrev:
Georgiou, C.A.
Other Names:
Address:
Chemistry Laboratory, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Greece
Phone:
+301-52-94-248
Fax:
+301-52-94-264
Email:
cag@aua.gr

Citations 6

"Edible Oil Analysis By Flow Injection"
Lab. Autom. Inf. Manage. 1999 Volume 34, Issue 2 Pages 101-114
Nikolaos S. Thomaidis and Constantinos A. Georgiou

Abstract: Flow injection methods developed for the analysis of edible oils are critically reviewed. Oil quality control can be automated using flow injection methods for the determination of acidity, peroxide value, iodine value, 2-thiobarbituric acid reacting substances, antioxidants, sterols, pesticide residues, aniline and heavy metals. Applications range from mere sample transportation to the detector to hyphenated flow injection-chromatographic techniques.

"Flow Injection Analysis System For L-Lysine Estimation In Foodstuffs Using A Biosensor Based On Lysine Oxidase Immobilization On A Gold-Poly(m-Phenylenediamine) Electrode"
Anal. Lett. 2003 Volume 36, Issue 9 Pages 1939-1963
Maria H. Divritsioti, Ioannis D. Karalemas, Constantinos A. Georgiou, Demetrius S. Papastathopoulos

Abstract: The development and the evaluation of an amperometric FIA biosensing system for l-lysine determination in foodstuffs is described. The system employs a home-made flow-cell with an amperometric biosensor, prepared by immobilization of lysine oxidase on a gold-poly(m-phenylenediamine) electrode. A peristaltic pump is connected to the flow-cell via a 2-position 6-port sample injector/switching valve for the on-line transfer of the samples. The analytical procedure is based on the oxidation of l-lysine by l-lysine α-oxidase. The produced H2O2 is monitored amperometrically at 650 mV in FIA set-up. The lysine biosensor construction procedure comprises: a) the electropolymerization of m-phenylenediamine on a Si-gold strip electrode and b) the immobilization of l-lysine α-oxidase on the poly(m-phenylenediamine) membrane with glutaraldehyde in the presence of bovine serum albumin. Parameters, such as, flow rate, enzyme amount, monomer concentration, matrix effect, effect of interference's, etc., were studied. The flow-cell biosensor system provides a linear response from 1 x 10-3 to 5 x 10-5 M of lysine, with excellent characteristics of reproducibility, stability, and life-time. The system was further applied and evaluated for the estimation of lysine in various hydrolysate food samples (e.g., pasta, milk, wheat flour, etc.) without any pretreatment with an average recovery of 97.3%.

"Direct Olive Oil Anisidine Value Determination By Flow Injection"
Anal. Chim. Acta 2001 Volume 448, Issue 1-2 Pages 201-206
Eleni P. Labrinea, Nikolaos S. Thomaidis and Constantinos A. Georgiou

Abstract: A flow injection (FI) spectrophotometric method for the determination of olive oil anisidine value (AV) is presented. A 40-1 aliquot of 10% (w/v) olive oil samples in 2-propanol are injected in a p-anisidine in 2-propanot/acetic acid stream. The reagents are premixed in the FI system using a two-line manifold. Detection is achieved by monitoring absorbance continuously at 350 urn. The proposed FI method achieves a high analysis rate (110 samples/h), minimizes solvent consumption (2 mL 2-propanol and 0.4 mL acetic acid per analysis) and compares well with the manual spectrophotometric method (relative difference 0.5-6.8% for the analysis of 25 olive oil samples). Precision was found to be better than 1% relative standard deviation (RSD; n = 7). The linear range was 6-85 AV and is suitable for analysis of abused olive oils.

"Determination Of Olive Oil 2-thiobarbituric Acid Reactive Substances By Parallel Flow Injection"
Anal. Chim. Acta 2000 Volume 417, Issue 1 Pages 119-124
Panayotis G. Nouros, Constantinos A. Georgiou and Moschos G. Polissiou

Abstract: A flow injection system incorporating multiple incubation coils is used for the automated determination of olive oil 2-thiobarbituric acid reactive substances (TBARS). The use of a laboratory-made parallel flow injection (PA-FI) analyzer. allows the simultaneous incubation of 10 samples. Olive oil samples are injected in a 2.0 x 10^-2 M 2-thiobarbituric acid (TBA) stream in n-propanol and then acidified by merging with a 0.10 M trichloroacetic acid stream in n-propanol. The resulting reaction mixture is diverted to an incubation coil through a stream selection valve. All incubation coils, that are immersed in a water bath at 95±1°C, are loaded in 5 min and then the flow stops for 25 min. After sample incubation, the reaction mixture is cooled by passing through an ice bath and the reaction products are measured at 532 nm. The proposed PA-FI method achieves olive oil analysis without pretreatment and minimizes solvent consumption (1.9 mL of n-propanol, 2.7 mg of TEA and 16 mg of trichloroacetic acid per analysis). Precision was found to be better than 4.6% RSD (n=10). The linear range was (0.4-10) x 10^-4 M (calculated as malondialdehyde (MDA)) and was suitable for olive oil analysis. The proposed method compares well with a manual method (relative difference 0-6.2% for the analysis of 30 olive oil samples). The analysis rate is 20 samples hr-1, while individual samples are incubated for 30 min. The PA-FI analyzer. developed allows automation of methods that require long incubation times without loss of sampling rate, overcoming the one sample at a time disadvantage of Fl.
Thiobarbituric acid Food Spectrophotometry Heated reaction Multichannel

"Direct Parallel Flow Injection Multichannel Spectrophotometric Determination Of Olive Oil Iodine Value"
Anal. Chim. Acta 2000 Volume 405, Issue 1-2 Pages 239-245
Nikolaos S. Thomaidis and Constantinos A. Georgiou

Abstract: An automated parallel flow injection (PA-FI) spectrophotometric method for the determination of olive oil iodine value (IV, g I-2/100 g of oil) is presented. A home made PA-FI analyzer, incorporating 10 incubation coils and using flow reversals, achieves a sampling rate of 60 samples per hour, while each sample is incubated for 10 min. Olive oil samples are diluted 1 : 50 in n-propanol and a 60 µl aliquot is injected into a 6.0 x 10^-3 M IBr carrier solution prepared in acetic acid. The injected sample is mixed with the reagent while flowing through the detector and then diverted to the incubation coil, where it is incubated for 10 min. The sample is then aspirated for measurement by flow reversal. The IBr absorbance in the carrier stream is monitored continuously at 392 nm. Injected samples consume IBr, resulting in negative absorbance peaks. The linear range was 9-125 IV, that is suitable for the analysis of edible oils. The method was applied to the determination of TV of 25 olive oil samples. Results obtained by the proposed method compare well (0.1-1.7% relative difference, mean 0.7%) with those obtained by the official AOAC method, which is time consuming and uses large amounts of organic solvents. The relative standard deviation ranged from 0.4 to 1.1% (n = 6). The new PA-FI technique minimizes reagent and solvent consumption (3.1 mi of acetic acid per sample) and allows automation of methods that require long incubation times without loss of sampling rate. The method is environmental friendly since it eliminates the use of chlorinated solvents.
Iodine Food Spectrophotometry Flow reversal Multichannel Method comparison

"Direct Parallel Flow Injection Multichannel Spectrophotometric Determination Of Olive Oil Peroxide Value"
Anal. Chim. Acta 1999 Volume 389, Issue 1-3 Pages 239-245
Panayotis G. Nouros, Constantinos A. Georgiou and Moschos G. Polissiou

Abstract: An automated parallel flow injection (PA-FI) spectrophotometric method for the determination of peroxide value (PV, meg O-2 kg-1 oil) in olive oil is described. A home-made PA-FI analyzer. incorporating 10 incubation coils and using flow reversals achieves a sampling rate of 83 samples h-1 while each sample is incubated for 5 min. Detection is achieved by monitoring iodine liberated from NaI by lipid peroxides at 360 nm. The new PA-FI method allows olive oil analysis without pretreatment or dilution and minimizes solvent consumption (2.0 mi of acetic acid and 3.4 mi of n-propanol per analysis). Precision was found to be better than 2.0% relative standard deviation (n=10). The linear range was 2.5-80 PV, rendering the method useful for the analysis of edible olive oils. Results obtained by the proposed method compare well (0-5.6% relative difference, mean 1.0%) with those obtained by an official method that is time-consuming and uses large amounts of organic solvents. The PA-FI analyzer. developed allows automation of methods that require long incubation times without loss of sampling rate. Up to 60 samples h-1 can be analyzed when 10 min incubation time is required. The detector is inserted in the flow path before the incubation coils and incubated samples are aspirated back to the detector by flow reversal. This overcomes construction difficulties and allows the measurement of the sample blank value.
Flow reversal