engleski

Optimization of FTIR-ATR spectroscopy for beeswax adulteration detection

Beeswax adulteration represents a growing problem worldwide as supported by frequent reports on adulterated beeswax (comb foundations, wax blocks) being present on the international market. This implies an urgent need for the implementation of mandatory regulations defining the beeswax quality criteria, as well as standardized analytical methods for beeswax authenticity testing. Among numerous analytical methods used for this purpose, Fourier transform infrared spectroscopy (FTIR) coupled with Attenuated Total Reflectance (ATR) accessory was the most recently developed analytical tool utilized for beeswax adulteration detection. FTIR-ATR technique has many advantages compared to classical physico-chemical analyses (such as determination of melting point, acid, saponification and ester value), as well as gas chromatography - based techniques (commonly used for detection of beeswax adulteration with hydrocarbons of alien origin, such as paraffin). Mentioned advantages are primarily reflected in general characteristics of FTIR-ATR spectroscopy ; it is a rapid, easy-to-use, non-destructive, reagent-free, and reliable method. The aim of this study was to optimize preliminary established FTIR-ATR analytical procedures (2013, 2015) in terms of both accuracy and efficiency for routine beeswax authenticity testing (qualitative and quantitative). The calibration procedure was carried our based on the acquisition of the IR spectra of in-house reference standards (samples of genuine beeswax, adulterants, beeswax-adulterant mixtures containing 0-100% of adulterants) exhibiting spectral features characteristic for authentic beeswax and for particular level of adulteration. This procedure was performed on four types of beeswax adulterants of different origin: paraffin wax (petroleum-derived), tallow (animal), carnauba wax (plant), and stearic acid (synthetic). The results have revealed good accuracy, repeatability, and reproducibility of IR measurement results for all investigated types of adulterants, which was successfully validated on a set of samples of unknown chemical background (comb foundations from the market). FTIR-ATR spectroscopy is also useful for studies of other aspects of beeswax research (e.g. overall chemical characterization based on IR fingerprinting, effects of temperature treatments, beeswax variations depending on geographical origin). In addition, it is suitable for analysing various types of beeswax specimens (including wax scales) due to the small amount of a sample required for FTIR-ATR measurements (< 0.5 g).

Beeswax adulteration detection ; FTIR-ATR spectroscopy ; optimization ; routine beeswax authenticity testing

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