Optimizacija metode priprave vzorca z mikrovalovnim razkrojem za določitev večelementne sestave v vzorcih insektov z ICP-MS

Štrukelj Kučan, Fedja (author), Kralj Cigić, Irena (mentor)

V okviru diplomskega dela je bila optimizirana metoda priprave vzorcev insektov z mikrovalovnim razkrojem za določitev večelementne sestave z ICP-MS. Uporabljena sta bila dva vzorca insektov in sicer ličinke mokarja (Tenebrio molitor) in hišni čriček (Acheta domesticus), ter trije standardni referenčni materiali: SRM Oyster Tissue-1566b (tkivo ostrige), SRM Typical Diet-1548a (mešanica živil) in SRM Mussel Tissue 2976 (tkivo klapavice), vendar slednji ni bil upoštevan pri analizi podatkov. Optimizacija priprave vzorca je bila izvedena na podlagi spreminjanja mas vzorcev in SRM-jev, ter spreminjanja volumnov različnih reagentov za razkroj. Preverjene so bile tri različne mase materiala: 0,1 g; 0,2 g; 0,4 g. Volumni reagentov so se spreminjali sledeče: HNO3 (67 %-69 %): 1 mL; 2 mL; 4 mL, H2O2 (30 %): 0 mL; 0,25 mL; 0,5 mL; 1 mL in HF (40 %): 0 µL; 10 µL; 20 µL; 30 µL. S kombinacijami navedenih parametrov je bilo nato sestavljenih devet različnih metod priprave vzorca, ki je bil vsakič razkrojen z mikrovalovnim sistemom z nastavljenim programom: 20 min naraščanje temperature do 240 °C, razkroj 15 min pri 240 °C in 100 barov in 30 min ohlajanja in nižanja tlaka. Razkrojenim raztopinam so bile nato z ICP-MS tehniko pomerjene koncentracije sledečih elementov: natrij, kalcij, kalij, magnezij, železo, cink, aluminij, vanadij, krom, mangan, nikelj, baker, kobalt, arzen, selen, srebro, kadmij in svinec. Umeritvene krivulje so bile pripravljene s standardnimi raztopinami teh elementov v sledečih koncentracijskih območjih: 0; 0,05; 0,100; 0,500; 1,00; 5,00; 10,0; 50,0 in 100 ng/mL za prvih sedem navedenih elementov, oziroma: 0; 1,00; 5,00; 10,00; 50,0; 100; 500; 1000 in 2000 ng/mL za ostale elemente. Rezultati so bili potem statistično obdelani. Izračunani in zbrani v preglednici so bili povprečni izkoristki za oba standardna referenčna materiala, narejene so bile kontrolne karte za določene elemente in izračunani so bili relativni standardni odmiki, ter njihovo povprečje masnih deležev elementov v vzorcih. Na podlagi najboljših izkoristkov in najmanjših relativnih standardnih odmikov je bila nato določena najoptimalnejša od devetih metod mikrovalovnega razkroja vzorca. To je bila metoda, pri kateri smo uporabili 0,1 g vzorca ali referenčnega materiala, 1 mL HNO3 in 0,25 mL H2O2.

• Language: Slovenian
• Keywords: insekti, mikrovalovni razkroj, elementi, optimizacija metode
• 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-149154
• COBISS.SI-ID: 167137795
• Publication date in RUL: 04.09.2023

Secondary language

• Language: English
• Title: Optimization of sample preparation using microwave digestion for the determination of multi-elemental composition in insect samples with ICP-MS

Abstract

In the making of the thesis, the method of preparation of insect samples with microwave digestion was optimized for the determination of multi-elemental composition with ICP-MS. Two insect samples were used, i.e., the mealworm larvae (Tenebrio molitor) and the house cricket (Acheta domesticus). Besides that, three standard reference materials were used: SRM Oyster Tissue-1566b, SRM Typical Diet-1548a and SRM Mussel Tissue 2976, however tha latter was not included in the data processing. Optimization of the sample preparation was caried out on the basis of changing the masses of samples and standard referance materials and volumes of different reagents for decomposition. Three different masses of material were tested: 0,1 g; 0,2 g; 0,4 g. The volumes of the reagents varied as follows: HNO3 (67 %-69 %): 1 mL; 2 mL; 4 mL, H2O2 (30 %): 0 mL; 0,25 mL; 0,5 mL; 1 mL and HF (40 %): 0 µL; 10 µL; 20 µL; 30 µL. Using a combination of these parameters, nine different methods of sample preparation were than constructed. Each time samples were digested using a microwave digestion system with a set program: 20 min temperature rise to 240 °C, digestion for 15 min at 240 °C and 100 bar and 30 min cooling and pressure reduction. The concentrations of the following elements were then measured in the digested solutions using ICP-MS technique: sodium, calcium, potassium, magnesium, iron, zinc, aluminum, vanadium, chromium, manganese, nickel, copper, cobalt, arsenic, selenium, silver, cadmium and lead. Calibration curves were prepared with standard solutions of these elements in the following concentration ranges: 0; 0,05; 0,100; 0,500; 1,00; 5,00; 10,0; 50,0 in 100 ng/mL for the first seven listed elements and: 0; 1,00; 5,00; 10,00; 50,0; 100; 500; 1000 in 2000 ng/mL for other elements. The results were than statisticly processed. Average recoveries for the two standard referance materials were than calculated and control charts for selected elements were created. Furthermore, relative standard deviations and their averages were calculated for concentrations of elements in both samples. Based on the best recoveries and smallest relative standard deviations, the most optimal of the nine methods of sample preparation for microwave digestion was then determined. That was a method that used 0,1 g of sample or standard referance material, 1 mL of HNO3 and 0,25 mL of H2O2.

• Keywords: insects, microwave digestion, elements, optimisation