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

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Classification: Food -> olive oil

Citations 3

"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 Spectrophotometry Flow reversal Multichannel Method comparison

"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 Spectrophotometry Heated reaction Multichannel

"Enzymic Determination Of Peroxides In Non-aqueous Media"
Analyst 1997 Volume 122, Issue 12 Pages 1543-1547
Gerardo Piñeiro Avila, Amparo Salvador and Miguel de la Guardia

Abstract: A fast enzymatic flow injection procedure was developed for the determination of peroxides in non-aqueous samples. The biochemical reaction is effected in a flow injection system using a non-covalently immobilized horseradish peroxidase reactor, followed by spectrophotometric monitoring of p-anisidine. The method provides a limit detection of 0.9 M for hydrogen peroxide, 2.6 M for tert-butyl hydroperoxide and 2.0 M for benzoyl peroxide with a maximum sampling frequency of 60 h-1. The enzyme reactor exhibits enhanced stability in water-saturated toluene, being stable for more than 4 months, and during this period an average number of 250 reactions can be performed with 1 mg of enzyme (220 purpurogallin units). The method permits the determination of peroxide in olive oil and margarine samples without any chemical pre-treatment or extraction of the sample. An average recovery of 98% was found for the determination of hydrogen peroxide in 12 different types of olive oil samples spiked with known amounts of H2O2, indicating the applicability of the procedure to real sample analysis. The procedure was also applied to the determination of H2O2 in four olive oils and a margarine sample and the results were comparable to those obtained by the reference method.
Peroxide ion Spectrophotometry Enzyme