Low cost in situ digital image method, based on spot testing and smartphone images, for determination of ascorbic acid in Brazilian Amazon native and exotic fruits.

In this work, we propose a method that employed a smartphone to capture images obtained from a colorimetric spot test to determine ascorbic acid (AA) in Brazilian Amazon native and exotic fruits. The spot test reaction was based on reduction of Fe(III) by AA and further complexation with 1,10-phenanthroline. After optimization, the limit of detection was 8.5 × 10-7 mol L-1. Brazilian Amazon native fruits such as bacuri, cupuaçu, muruci, yellow mombin, as well as others as cashew, mango, orange and passion fruit, were analyzed. In order to determine the accuracy of this method, iodometric titration was used; results were in close agreement with a confidence level of 95% (paired t-test). Moreover, recoveries ranged from 87.1 to 116%. The method is economic, environmentally friendly, and portable, and might useful for small producers and family agriculture businesses unable to afford specialized laboratory analysis in the north region of Brazilian Amazon.

Detection of coffee adulteration with soybean and corn by capillary electrophoresis-tandem mass spectrometry.

The detection of coffee adulteration with soybean and corn by capillary electrophoresis-tandem mass spectrometry was accomplished by evaluating the monosaccharides profile obtained after acid hydrolysis of the samples. The acid hydrolysis, using H2SO4 as a catalyst, increases the ionic strength of the sample impairing the electrophoretic separation. Therefore, Ba(OH)2 was used to both neutralize the medium and reduce the content of sulfate by precipitation of BaSO4. The best separation of nine determined monosaccharides (fucose, galactose, arabinose, glucose, rhamnose, xylose, mannose, fructose and ribose) plus inositol as internal standard was obtained in 500 mmol·L-1 triethylamine, pH 12.3. The monosaccharides are separated as anionic species at this pH. The proposed method is simple, fast (<12.0 min), present linear calibration curves (r2 = 0.995), and relative standard deviation for replicate injections lower than 5%. The LOQ for all monosaccharides was lower than 0.01 mmol·L-1, which is in accordance with the tolerable limits for coffee. Principal component analysis (PCA) was used to evaluate interrelationships between the monosaccharide profile and the coffee adulteration with different proportions of soybean and corn. Fucose, galactose, arabinose, glucose, sucrose, rhamnose, xylose, mannose, fructose, and ribose were quantified in packed roast-and-ground commercial coffee samples, and differences between adulterated and unadulterated coffees could be detected.