Določanje acesulfama K v prehranskih dodatkih

Matoh, Jan (author), Kralj Cigić, Irena (mentor)

V diplomskem delu sem optimiziral HPLC metodo za določitev pogosto uporabljanega umetnega sladila acesulfama K v različnih vzorcih prehranskih dodatkov za športnike. Najprej sem v literaturi poiskal podatke za določanje sladil s HPLC metodami. Na osnovi literaturnih podatkov sem uporabil reverznofazno C18 kolono in izbral acetonitril ter 0,5 % fosforjevo(V) kislino v prečiščeni vodi kot komponenti mobilne faze v gradientnem načinu s konstantnim pretokom 0,7 mL/min. Volumen injiciranja je bil 15 µL, valovno dolžino detektorja sem nastavil na 226 nm. Z injiciranjem standardnih raztopin sladila v različnih koncentracijah sem izrisal umeritveno premico za ta analit in ugotovil linearnost v širokem koncentracijskem območju (0,040 mg/L – 10 mg/L). Določil sem še mejo zaznave (0,025 mg/L) in mejo določitve (0,040 mg/L). Nato sem analit kvantitativno določil v izbranih trinajstih vzorcih prehranskih dodatkov, med katerimi je bila v treh vzorcih (energijski gel in dve pijači v prahu) presežena maksimalna dovoljena dnevna doza. Pri prav tako treh vzorcih, tokrat iz skupine energijskih gelov, je bila ponovljivost med paralelkami posameznih vzorcev najslabša, kar sem pripisal nehomogenosti gelov in neuporabi centrifugiranja tekom priprave vzorcev za analizo. Pri ostalih vzorcih je bila ponovljivost zadovoljiva in vsebnost v dovoljenih mejah, tako da sem zaključil, da metoda omogoča uspešno določitev acesulfama K v realnih vzorcih. V enem izmed vzorcev pa sem namesto acesulfama K, ki je bil naveden kot sladilo, potrdil prisotnost drugega umetnega sladila aspartama. Za kvantitativno določitev dodatnega sladila v izbranih vzorcih sem pripravil umeritveno premico za aspartam, ki pa je izkazala bistveno slabšo linearnost kot tista za acesulfam K. Prav tako je bila podpovprečna tudi ponovljivost, kar sem pripisal razgradnji aspartama pri sobnih pogojih, zaradi česar sem to metodo ovrednotil kot neprimerno za kvantitativno določitev aspartama v vzorcih.

• Language: Slovenian
• Keywords: acesulfam K, HPLC, optimizacija metode, prehranski dodatki, aspartam
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2023
• PID: 20.500.12556/RUL-147551
• COBISS.SI-ID: 160309251
• Publication date in RUL: 07.07.2023

Secondary language

• Language: English
• Title: Determination of acesulfame K in nutritional supplements

Abstract

In my bachelor’s thesis, I have optimised the HPLC method for the determination of a common high-intensity artificial sweetener acesulfame potassium (acesulfame K) in various samples of sports nutritional supplements. Firstly, I have sought for HPLC methods for determination of artificial sweeteners in the literature. Based on the parameters of those methods, I have used a C18 reverse phase column and chose the mixture of acetonitrile with 0.5 % phosphoric(V) acid as components of the mobile phase. I have opted for gradient elution of the mobile phase at a constant flow rate of 0.7 mL/min. The injection volume was 15 µL and the wavelength on the detector was set to 226 nm. Multiple standard solutions of the sweetener were injected, based on which the calibration line was drawn. The latter exhibited good linearity across a broad range of concentrations (0.040 mg/L – 10 mg/L). Furthermore, I have determined the limits of detection (0.025 mg/L) and quantification (0.040 mg/L). Then followed the quantification of the analyte in thirteen samples of nutritional supplements. I have found out that in three (one energy gel and two instant drinks) of the thirteen chosen samples the maximum accepted daily intake values were exceeded. Moreover, three other samples (all energy gels) showed the worst repeatability between duplicates, which I found an explanation for in the fact that the samples were not homogenous enough. This could have perhaps been avoided with the usage of centrifugation for the sample preparation. Among all other samples the repeatability was satisfactory, and the quantities determined were within the allowed limits according to the regulations. According to aforementioned facts I have concluded that the method allows for a successful determination of acesulfame K, which I have found in all but one of the chosen samples. In the one where this sweetener was not present, even though the manufacturer claimed the product to contain it, I have confirmed that it instead contains aspartame. In order to quantify this additional analyte in my range of samples I have prepared solutions of aspartame for construction of the calibration line, which exhibited extremely poor linearity in comparison to that of acesulfame K. What is more, the repeatability was also below par, which I have connected to the fact that aspartame is very prone to degradation even at room conditions. For this reason, I have labelled this method as inappropriate for quantitative determination of aspartame in the samples.

• Keywords: acesulfame K, HPLC, optimisation of the method, nutritional supplements, aspartame