Melatonin (Mt) is the primary secretory product of the pineal gland and is commonly used in supplements for sleep regulation. However, concerns about dosage accuracy and product quality highlight the need for simple detection methods. Here, a paper-based colorimetric kit is proposed for the determination of Mt. The kit includes the reaction cartridge, graduated sampling vessel, sample prep-holder, measuring box, and a colorimetric chart for Mt quantification; all components are paper-based and custom-molded using benchtop technologies (such as an office printer, wax printer, or CO2 laser plotter) to make the kit user-friendly and ready for use. The reaction cartridge contains the colorimetric assay, which is based on Mt reaction with 4- dimethylaminobenzaldehyde (Dm), producing a measurable violet color within 15 min, monitored through a smartphone camera. The assay requires only diluting the sample in a graduated sampling vessel, loading it into the reaction cartridge, and then directly comparing the resulting color with the colorimetric chart (Figure 1). The calibration chart has been carefully developed to match the experimental trials (r= 0.999) and allows rapid on-site quantitative analysis of Dm without specialized equipment, enabling the determination of Mt in the range of 1-50 ppm (R2 = 0.993) with a LOD of 0.90 ppm and acceptable inter-batch reproducibility (RSD ≤ 4%, n = 3). The method's selectivity was thoroughly evaluated against 17 potential interfering compounds, including tryptophan and other structural analogs. The kit’s reliability in real-world applications was demonstrated by measuring Mt in 7 ‘drugs,’ providing accurate (recovery: 81-117%) and reproducible data (RSD ≤ 16%, n = 3), with a relative error ranging from -7.4% to +13.5% when comparing the Mt concentration to the amounts claimed on the drugs’ labels. The proposed paper-based melatonin kit comprises all the necessary components for in situ analysis, resulting in a low-cost and user-friendly tool, making it a promising tool for routine quality control of pharmaceutical and nutraceutical products, offering a straightforward alternative to conventional, cumbersome laboratory methods.
Colorimetric paper-based kit for the selective determination of melatonin.
Dounia El Fadil;Paolo Di Battista;Annalisa Scroccarello;Flavio Della Pelle;Dario Compagnone
2025-01-01
Abstract
Melatonin (Mt) is the primary secretory product of the pineal gland and is commonly used in supplements for sleep regulation. However, concerns about dosage accuracy and product quality highlight the need for simple detection methods. Here, a paper-based colorimetric kit is proposed for the determination of Mt. The kit includes the reaction cartridge, graduated sampling vessel, sample prep-holder, measuring box, and a colorimetric chart for Mt quantification; all components are paper-based and custom-molded using benchtop technologies (such as an office printer, wax printer, or CO2 laser plotter) to make the kit user-friendly and ready for use. The reaction cartridge contains the colorimetric assay, which is based on Mt reaction with 4- dimethylaminobenzaldehyde (Dm), producing a measurable violet color within 15 min, monitored through a smartphone camera. The assay requires only diluting the sample in a graduated sampling vessel, loading it into the reaction cartridge, and then directly comparing the resulting color with the colorimetric chart (Figure 1). The calibration chart has been carefully developed to match the experimental trials (r= 0.999) and allows rapid on-site quantitative analysis of Dm without specialized equipment, enabling the determination of Mt in the range of 1-50 ppm (R2 = 0.993) with a LOD of 0.90 ppm and acceptable inter-batch reproducibility (RSD ≤ 4%, n = 3). The method's selectivity was thoroughly evaluated against 17 potential interfering compounds, including tryptophan and other structural analogs. The kit’s reliability in real-world applications was demonstrated by measuring Mt in 7 ‘drugs,’ providing accurate (recovery: 81-117%) and reproducible data (RSD ≤ 16%, n = 3), with a relative error ranging from -7.4% to +13.5% when comparing the Mt concentration to the amounts claimed on the drugs’ labels. The proposed paper-based melatonin kit comprises all the necessary components for in situ analysis, resulting in a low-cost and user-friendly tool, making it a promising tool for routine quality control of pharmaceutical and nutraceutical products, offering a straightforward alternative to conventional, cumbersome laboratory methods.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
