A portable sol-gel urea colorimetric method for the determination of urea in feedstuffs

A sol-gel urea colorimetric method was developed for the determination of urea in feedstuffs. The sol-gel platform contained p-dimethylaminobenzaldehyde (p-DMAB) as the reagent entrapped within polymer network. The urea analysis relied on the formation of Schiff base under acidic conditions. The colorimetric product was imaged with a Smartphone. Under optimized conditions, the calibration curve for urea was linear over the concentration range of 2.5–100 and 100–1000 mg L−1 with a good coefficient of determination (r2 > 0.99). The limit of detection (LOD) and limit of quantification (LOQ) were 0.1 and 0.5 mg L−1, respectively. The intra-day and inter-day precisions were 0.83–3.01%RSD and 2.20–5.47%RSD, respectively. Accuracy of urea analysis ranged from −1.15 to 2.76%. The proposed method was stable for at least 90 days. The amount of urea in feedstuff sample was determined. The developed method is easy to use with small samples and reagent consumption in field conditions for monitoring the quality of feedstuff.