Light stabilization methods

The UV method performs well in the absence of interferences of other additives or pigments but is liable to be in error owing to interference by highly absorbing impurities that may be present in the sample or in the solvent [56,57]. Commercial erucamides with variable light stability have been analysed by means of SEC-UV (254nm)/RI and UV absorption in MeOH [58]. 

In addition, a great need exists for improved test procedures to predict end-use performance. The correlations between accelerated exposure devices and normal fluorescent lamps, described in this report, represent only a preliminary effort to refine and establish meaningful laboratory methods for evaluating light stabilizers. Exposure data from a greater number of samples, containing a greater variety of formulations, are needed for more accurate correlations. 

Bartholomew, B.P., Ogden, L.V. 1990. Effect of emulsifiers and fortification methods on light stability of vitamin A in milk. J. Dairy Sci. 73, 1485-1488. 

The real merit of our work stems from the light it sheds on the parallelisms /47,91-94/ between the complex scaling and the stabilization method /17,93,126/ for the treatment of resonances. A notable feature of the stabilization method is that at the point of optimal stabilization of the resonant root there is an avoided crossing with another nearly degenerate root which descends from above and replaces the stabilized root when further changes in the stabilization parameter (no. of configurations as in ref. 22 or scale parameter a as in ref. 87-92) is affected. 

There are various accelerated light stability test methods available and/or exposure in harsher climates (Florida, Arizona) to test the weathering performance. The prediction of photoageing stability based on accelerated laboratory testing is very difficult, but some attempts have been made for PVC-P (445). The most relevant point is to use as reference a formulation known to have good outdoor weathering performance. 

Matsuo was the principal compiler of information for the Research and Technology Committees for Drug Standards, the Osaka Pharmaceutical Manufacturers Association and the Pharmaceutical Manufacturers Association of Tokyo s Basic Study on Establishing a Light Stability Testing Method both basic study and draft Light Stability Test. This information was published by Yatani et al. (288). 

A reference to the use of "Quinine actinometry as a method for calibrating ultraviolet radiation intensity in light stability testing of pharmaceuticals was added."... 

Oxidation and Photolysis. In Chemical Stability of Pharmaceuticals A Handbook for Pharmacists. Kenneth A, Connors, GL Amidon, VJ Stella, eds. NY Wiley, 1986 113. Yoshioka S, Ishihara Y, Terazono T, et al. Quinine actinometry as a method for calibrating ultraviolet radiation intensity in light stability testing of pharmaceuticals. Drug Dev Ind Pharm 1994 20(13) 2049-2062. 

Recently,with respect to the importance of particle size distribution in terms of particle characterization and product physical stability testing, there has been interest in newer light-scattering methods for particle detection called photon correlation spectroscopy (PCS). PCS methods can be applied to both micro-and nanosuspensions. 

While the inherent thermal decomposition of some additives such as light stabilizers has initiated the development of less destructive techniques like supercritical fluid extraction (SFE), it does not preclude the use of thermal desorption methods. Actually, the thermal decomposition products of the additives can be used to assign an identity to a particular compound. 

Triphenylphosphate, igranox, diglycol phosphate, trimethyl borate [265], benzotriazole [266] are used as light stabilizers. Fibres modified by such substances exceed goods from compositions produced by traditional method to a far greater extent as to their resistance to ultra-violet irradiation. 

G.E. Krichevskiy, Mechanism of ageing of dyed textile materials and ways of their light stabilization//All-Union conference "Modern chemical and physico-chemical methods of textile materials finishing, Dushanbe (1980) (in Russian). 

B. Garware, Shashikant Method of polyesters light-stabilization. Patent of the USA No 4399265 (1983) (in Russian). 

Elimination of the yellowing introduced by the stable nitroxyl radicals was essential for commercial development of these excellent stabilizers. Since phenolic antioxidants are necessary for the thermal stabilization of polymers during processing, we turned our attention to ways in which unfavorable interactions between the hindered phenols and the stabilizing nitroxyl radicals could be avoided. In this section we describe the discovery of the light-stabilizing activity of hindered amine compounds, an improved synthetic method for these compounds, the synthesis of a number of derivatives, and the evaluation of their stabilizing activity. 

The light-stabilization activity of several esters was tested by an improved test method (25). This method was carried out as follows (i) Preparation of the test specimen. A mixture of 100 parts... 

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