title: Sequential injection titration with spectrophotometric detection for the assay of acidity in fruit juices.
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.
authors.affiliation: Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand. scijjkmn@chiangmai.ac.th
authors.forename: Jaroon
authors.initials: J
authors.lastname: Jakmunee
authors.forename: Thitima
authors.initials: T
authors.lastname: Rujiralai
authors.forename: Kate
authors.initials: K
authors.lastname: Grudpan
mesh_terms: D001628:Beverages / Q000032:analysis*; D002138:Calibration; D019343:Citric Acid / Q000032:analysis*; D017022:Flow Injection Analysis / Q000295:instrumentation / Q000379:methods; D005504:Food Analysis / Q000295:instrumentation / Q000379:methods; D005638:Fruit / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D020113:Phenolphthalein / Q000737:chemistry; D012680:Sensitivity and Specificity; D012972:Sodium Hydroxide / Q000737:chemistry; D013053:Spectrophotometry / Q000295:instrumentation / Q000379:methods; D013997:Time Factors; D017186:Titrimetry / Q000295:instrumentation / Q000379:methods
chemical_list: D007202:Indicators and Reagents; D019343:Citric Acid; D012972:Sodium Hydroxide; D020113:Phenolphthalein