ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Exploring alternative measurement methods and greenness metrics for nitrate levels in coconut water: android application and mid-infrared spectroscopy approaches

V. Arunachalam, Ashwini D. Toraskar, Krutika R. Mardolkar, and Bappa Das

Horticulture Section, ICAR-CCARI (Indian Council of Agricultural Research-Central Coastal Agricultural Research Institute) Ela, Old Goa, India

E-mail: v.arunachalam@icar.gov.in

Received: 13 April 2024  Accepted: 8 August 2024

Abstract:

The nitrate content of coconut water may be dangerous if it exceeds the prescribed limits. The present study compares the ease of analysis and environmental chemistry of nitrate estimation in coconut water via four different methods (UV‒visible spectroscopy, tristimulus colorimetry (Hunter laboratory), infrared spectroscopy, and Color Grab, an android application) using 80 samples of coconut water. Positive correlations were found between the absorbance at 410 nm and the b and chroma values measured by the Color Grab app lab (r = 0.97, 0.89) and Hunter lab (r = 0.98, 0.99) instruments. The Color Grab app b value also showed a good detection limit of 44.5 ppm and a low signal-to-noise ratio of 15.6. According to the Fourier transform infrared spectroscopy data from 399 to 4000 cm⁻¹, wavenumbers from 1351 to 1341 cm⁻¹, especially 1346 and 1345 cm⁻¹, after the cubit and partial least squares analyses are important for predicting the nitrate content of coconut water. The results are discussed concerning the FTIR peak shifts of mixtures of compounds of varying molecular masses. The predicted results based on the infrared spectrum are similar to those obtained by a UV–visible spectrophotometer. The analytical green method is used to estimate the environmental and occupational hazards of the four methods based on 12 criteria of the agents and processes used for sampling and assessment. The infrared spectroscopy method showed the highest analytical greenness metric value of 0.91 out of 1.0. The tristimulus colorimeter and Color Grab app methods had lower scores of 0.31 each, while the conventional UV‒Vis spectrophotometer had a medium score of 0.36.

Graphical abstract

Keywords: Environmental Chemistry; Android app; Coconut water; Colorimeter; Green analytical chemistry; Mid-infrared spectroscopy; Nitrate

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-024-03653-6

Chemical Papers 78 (14) 8031–8044 (2024)