Hindered Amine Light Stabilizers

The most common group of hindered amine light stabilizers (abbreviated to HALS) originates from 2,2,6,6-tetramethylpiperidine (6.1). The name HALS is generally accepted to be used for hindered piperidine analogues. However, HALS include a number of other structurally different hindered amines (Table 6.1). This group of stabilizers has been commercially developed by the Sankyo Co. Ltd (Japan) and Ciba-Geigy Ltd (Switzerland).
A sensitive fluorometric method for the determination of ctDNA (calf thymus DNA) is presented. It has good selectivity and sensitivity and uses nano-SiO2 particles as an effective dispersant and stabilizer for acridine orange (AO). Compared to resonance light scattering (RLS) and the conventional method that uses organic dyes as fluorescence probe, the new method is more tolerant towards coexisting foreign substances and also more stable. With 20 mg nano-SiO2 particles, 10 µmol L−1 AO, at pH 8.01 and an ionic strength of 0.02 mol L−1, the interaction of AO with nano-SiO2 and ctDNA results in fluorescent signal enhancement. The extent of enhancement was in good proportion to the concentration of ctDNA at excitation/emission wavelengths of 490/523 nm, respectively. The calibration curve was linear over 0.66–55.60 µg mL−1. The determination limit (3σ) was 15 ng mL−1. The method was applied to the determination of ctDNA in synthetic samples with satisfactory results.