How good repeatability can be ensured for Tetracycline (TC) degradation study in UV-visible spectrophotometer?

08 January 2021 2 4K Report

Hai all,

I am using 50 ppm Tetracycline hydrochloride for the degradation study ( Fenton process). After each interval sample taken, filtering through 0.22 micrometer syringe filter, then analysed in UV spectrophotometer.

1. When I am analysing 50 ppm TC in Spectrophotometer, absorbance values are significantly varying on repetitions ( for example, at 60 min, absorbance found to be 0.9, then after some time on repeating the same , the value may become 0.5). I am taking my samples after filtration, without adding quenchers. How can I overcome this issue?

2. Can I keep TC stock solution at 4 degrees for a few weeks? 2. I read that washing glasswares with 10% HNO3 can lower the TC sorption on glasswares. Is it advisable to use glass vials for sample storage? Please help me resolve these problems.

Thank you, Jaimy Scaria

Bojidarka B. Ivanova

Mrs/Miss Scaria,

Tetracycline is a unsuitable analyte for analysis by UV-VIS spectroscopy, due to (i) the saturated molecular structure, excluding from the substitute benzene fragment; and (ii) the presence of a large number of same type of chromophores. Furthermore, (iii) there are a large number of tautomeric forms, which complicate further the experimental assignment of the UV-VIS bands of the analyte itself and its degradation products.

Of course, if there is used complementary experimental UV-VIS spectroscopy with theoretical quantum chemical analysis of the electronic structure and the electronic transitions of the analyte and its degradation products, then there would be obtained a reliable assignment of the experimental data.

The method of choice for such study, like yours is the mass spectrometry; however, within the framework of our (mine and my co-author's) innovative stochastic dynamic theory and model formulas.

Please, consider more detail on reference [1] and the corersponding reference section cited, therein.

[1] Steroids, 164 (2020) 108750

Stochastic dynamic mass spectrometric quantification of steroids in mixture — Part II; Bojidarka Ivanova, Michael Spiteller

Jaimy Scaria

Thank you Bojidarka B. Ivanova for the constructive suggestions.

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