Novel analytical method to measure formaldehyde release from heated hair straightening cosmetic products: Impact on risk assessment.

Hair straightening cosmetic products may contain formaldehyde (FA). In Europe, FA is permitted for use in personal care products at concentrations ⩽ 0.2g/100g.

Indirect optical analysis of a dynamic chemical system.

Hide and seek: The composition of a dynamic covalent equilibrium reaction is determined by measuring the 'left-over' concentration of a reference compound (blue object, see picture). Reaction of the reference compound with a scavenger generates a characteristic UV/Vis signal that is independent of the molecular structure of the target.