Browsing by Author "Zaharieva Z."

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    DETERMINATION OF SOME PROHIBITED SUBSTANCES IN FOOD SUPPLEMENTS USING HPLC WITH MS OR UV DETECTION - VIEW ON CURRENT DEVELOPMENT
    (2021-01-01) Zaharieva Z.; Foteva T.; Karadjova V.; Danalev D.
    Nowadays bioanalytical techniques including liquid and gas chromatography combined with different types of detectors are largely introduced in a practice. They are largely used for detection and control of substances and for monitoring of the whole production process. The type of detector depends on necessary levels of detection, but also on the matrix where aimed compounds have to be determined. Herein are summarized data from the last ten years related to determination of six main prohibited substances sildenafil, tadalafil, vardenafil, dapoxetine, yohimbine and sibutramine as well as their derivatives in food supplements using high performance liquid chromatography combined with mass spectrometric or UV detection. All these compounds are in a large interest because they are introduced often in products freely distributed in the internet market.
  • No Thumbnail Available
    Item
    Development and validation of HPLC-DAD methodology for simultaneous qualitative and quantitative determination of thirteen substances with a steroid structure
    (2023-01-01) Zaharieva Z.; Atanasova S.; Danalev D.; Jaber S.; Foteva T.; Nemska V.; Tanev D.; Georgieva N.
    Using supplements in different sports is a common practice for many athletes. Unfortunately, the growth of this market has entailed some speculations, such as the addition of excessive doses of potentially toxic ingredients. Sometimes the doses listed on the package do not correspond to the real content. Some nutritional supplements on sale may contain undeclared ingredients. Some of those supplements are prohibited substances according to different regulations. Herein, a simple HPLC/DAD procedure that is easy to apply in conventional laboratory practice was developed for the simultaneous determination of 13 substances with steroid structure in nutritional supplements for sport: testosterone, testosterone propionate, testosterone enanthate, methyltestosterone, nandrolone, nandrolone propionate, nandrolone decanoate, methandienone, androstenedione, trenbolone, trenbolone acetate, trenbolone enanthate and boldenone undecylenate. The methodology includes gradient elution with mobile phase A: MeOH:ddH2O (55:45) and mobile phase B: 100% MeOH in a standard HPLC system containing a Halo 90 Å, C18 (150 x 4.6 mm, 2.7 µm) column, flow rate 0.6 mL/min, UV wavelength of 254 nm, temperature of 40 °C and 20 μL injection volume. The developed methodology was validated according to the corresponding official documents. The key parameters used for the selection of the optimal HPLC conditions were the ability of the mobile phase and solvents to be used with both an HPLC/MS and a GC/MS chromatographic system. The obtained total run time, the reproducibility of the retention times, the separation of all peaks and peak characteristics meet all requirements.
  • No Thumbnail Available
    Item
    Development and Validation of HPLC/DAD Method for Simultaneously Determination of Six Prohibited Substances in Model Matrices
    (2020-12-01) Zaharieva Z.; Tanev D.; Danalev D.
    The authorities have identified an emerging trend where over-the-counter products, represented as dietary supplements, contain hidden active ingredients that could be harmful. Consumers may unknowingly take products laced with varying quantities of approved prescription drug ingredients, controlled substances, and untested and unstudied pharmaceutically active ingredients. Hidden ingredients are increasingly becoming a problem in products promoted for sexual enhancement, weight loss, or bodybuilding. The tests have revealed the presence of some undesired substances like sildenafil, tadalafil, vardenafil, and their analogues in tainted sexual enhancement products. The content of these substances is usually around the daily curative dose. A simple high-performance liquid chromatography (HPLC) method for simultaneously determination of sildenafil, vardenafil, tadalafil, dapoxetine, yohimbine, and sibutramine was developed and validated. InfinityLab Poroshell 120 EC-C18 (150 '4.6 mm '4 μm particles) was used, as well as a diode-array detector (DAD) at 230 nm, and a gradient flow with 0.030 Eœ ammonium acetate buffer and acetonitrile. The method is linear in the following range: 2.5-37.5 μg/mL for yohimbine, 2.06-30.9 μg/mL for vardenafil, 2.0-30.0 μg/mL for sildenafil, 3.1-46.5 μg/mL for tadalafil, 1.98-29.7 μg/mL for dapoxetine, and 2.2-66.0 μg/mL for sibutramine. The linearity coefficient is R2 = 1 for all substances. Model matrices were spiked, and the analytical recoveries for all substances are in the range 97.5%-99.5%. The method exhibited an upper hand compared with previously reported methods in terms of speed and simplicity. Additionally, the mobile phase (also used as extracting, column washing, and diluting solvent) was composed of only buffer and acetonitrile, which rendered the method much cheaper than others.