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Updated: Aug 5, 2026

Fruit Volatile Analysis Using an Electronic Nose
Published on: March 30, 2012
Sequential injection titration with spectrophotometric detection for the assay of acidity in fruit juices
Jaroon Jakmunee1, Thitima Rujiralai, Kate Grudpan
1Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand. scijjkmn@chiangmai.ac.th
Abstract:
A simple sequential injection analysis (SIA) with spectrophotometric detection for an assay of acidity in fruit juice was investigated. An alkaline reagent (sodium hydroxide), a sample and an indicator (phenolphthalein) were first aspirated and stacked as adjacent zones in a holding coil. With flow reversal through a reaction coil to the detector, zone penetration occurred, leading to a neutralization reaction that caused a decrease in the color intensity of the indicator being monitored for absorbance at 552 nm. The effects of various parameters were studied. Linear calibration graphs for acidities of 0.2 - 1.0 and 0.5 - 2.5% w/v citric acid as a standard, with a relative standard deviation of 1% (acidity of 0.3 - 0.6% w/v as citric acid, n=11) and a sample throughput of 30 samples h(-1), were achieved. The developed method was validated by a standard titrimetric method for assaying the acidity of fruit juice samples.
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