Simple Colorimetric and Fluorometric Assay Based on 2,3-Naphthalenedialdehyde for Melatonin in Human Saliva

Abstract

In this paper, 2,3-naphthalenedialdehyde (2,3-Nda) was selected as color reagent with colorimetric and fluorometric assay for detecting melatonin in human saliva. 2,3-naphthalenedialdehyde reacted with melatonin under the catalysis of hydrochloric acid and Fe 3+ , which the color change was observed sensitively from colorless to yellow with the naked eye. On the other hand, the product of the reaction had a large conjugate structure with strong fluorescence for the fluorometric analysis. Under optimized experimental conditions, a concentration range of melatonin was 2.5-37.5 µM (R 2 = 0.998) by colorimetry with the limit of detection for 1.288 µM (S/N = 3), and 0.01-0.1 µM (R 2 = 0.997) by fluorometry with the limit of detection for 0.004 µM (S/N = 3). The two assays were successfully applied to the determination of melatonin in human saliva, which average recoveries were 97.80% and 95.96%, respectively, which has the potential in fast clinical examination of melatonin in human saliva.

Recent Advances in Electrochemical and Optical Sensors for Detecting Tryptophan and Melatonin

“…Another colorimetric/fluorometric sensor was developed for the detection of melatonin in saliva, using 2.3naphthalenedialdehyde (2,3-Nda) as a chromogenic reagent. 167 Under acidic conditions, 2.3-Nda reacted with melatonin in the presence of iron (III) chloride catalyst; the color of the solution changed from colorless to yellow in a concentration-dependent manner. Furthermore, applying different concentrations of the reactants generated fluorescence due to the large conjugated system of the reaction product.…”

Dispersive Solid Phase Extraction of Melatonin with Graphene/Clay Mixtures and Fluorescence Analysis in Surfactant Aqueous Solutions

“…Also, melatonin shows native fluorescence due to the presence of the indole group in its chemical structure, which makes it suitable for direct analysis by fluorescence. This technique has been widely used owing to its high sensitivity and selectivity, easiness, speediness, and low solvent consumption, and has been applied to different types of samples, such as pharmaceutical preparations and urine [ 14 ], biological [ 15 ], and food/beverage samples [ 16 ]. In the presence of cyclodextrins, the fluorescence of melatonin is enhanced [ 17 ], while reagents such as 2,3-naphthalenedialdehyde provide a fluorescent product of the reaction with melatonin, which is measured by absorbance and fluorescence [ 15 ].…”

“…This technique has been widely used owing to its high sensitivity and selectivity, easiness, speediness, and low solvent consumption, and has been applied to different types of samples, such as pharmaceutical preparations and urine [ 14 ], biological [ 15 ], and food/beverage samples [ 16 ]. In the presence of cyclodextrins, the fluorescence of melatonin is enhanced [ 17 ], while reagents such as 2,3-naphthalenedialdehyde provide a fluorescent product of the reaction with melatonin, which is measured by absorbance and fluorescence [ 15 ]. Other systems, such as metal–organic frameworks (MOFs) encapsulated into molecularly imprinted polymers (MIPs) (MOF@MIP), have been utilized for developing a sensor with luminescence detection [ 16 ].…”