“…The Kjeldahl method is the official method for determining urea in cosmetics and dermatological formulations, which suffers mainly from poor selectivity and long pre-treatment and procedure times [ 6 ]. A number of alternative methods have been published for quality control purposes in the dermatological and cosmetic industry, including spectrophotometry [ 7 , 8 ], electrochemistry [ 9 ], column chromatography with ultraviolet detection [ 10 , 11 ], HPTLC combined with densitometry [ 7 ], urea online derivatisation via the Ehrlich reaction in a rotor of centrifugal partition chromatography [ 12 ], or spot test coupled with diffuse reflectance spectroscopy [ 13 ]. The above alternative methods rely either on urea extraction prior to analysis and/or on the use of organic solvents, while they all employ instrumental analysis.…”