Ultrapure water purification system

LC-MS-grade acetonitrile and ammonium acetate, as well as NH₃, were obtained from VWR (Vienna, Austria). Analytical-grade acarbose, arabinose, erythritol, fructose, galactose, glucose, inositol, lactitol, lactose, maltitol, raffinose, rhamnose, ribose, sucrose, xylitol, potassium chloride, ammonium iodide and potassium bromide were purchased from Sigma Aldrich (Schnelldorf, Germany). Erythrose, isomaltulose, lyxose, maltose, maltotriose, mannitol, mannose, sorbitol, sorbose, xylose, sodium nitrate and sodium sulfate were purchased from VWR (Vienna, Austria). LC-MS-grade water (< 0.055 µS cm⁻¹) from an ultrapure water purification system (Sartorius, Göttingen, Germany) was used for both elution and sample preparation. Food samples produced by various companies were obtained from local supermarkets. Sample matrices have been selected over a wide range of beverages and food to investigate the impact on sample preparation and robustness of the analytical method. Food and beverages were stored at the recommended temperature until analysis.

A Varian Cary 50 UV-vis spectrophotometer was used for absorption measurement of the microbial intracellular enzymatic reaction in the solution with the ruthenium complex optical pH probe. Reflectance measurement of the optosensing biomaterial was performed by using a fibre optic reflectance spectrophotometer (Ocean Optic SD2000) with a DH-2000-BAL UV-Vis-NIR light source within the wavelength range of 200–1099 nm. Ultrapure water with a conductivity of 0.055 µS cm⁻¹ (18.2 MΩ·cm) obtained from the Sartorius Ultrapure Water Purification System, model arium^® pro DI (Sartorius, Göttingen, Germany), was used to prepare all the chemical and biological solutions. The size and morphology of the microbial biomimetic nanosilica were determined using a field emission scanning electron microscope (FESEM, brand Zeiss, model Merlin) at an accelerating voltage of 3 kV (STEM mode) and magnification of 50 k×.

Standards of acrylamide (≥99.5%), D3-acrylamide (500 mg L⁻¹ in acetonitrile), and asparagine (99%), as well as both GC-grade derivatization reagents xanthydrol (≥99%) and N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) (≥99%) with 1% tert-butyldimethylsilyl chloride (TBDMSCI), were obtained from Sigma Aldrich (Schnelldorf, Germany). For pH adjustments, Na₂CO₃ and acetic acid (80%) were purchased for VWR (Vienna, Austria).
Analytical-Grade fructose, glucose, maltose, and sucrose were purchased from Sigma Aldrich. LC-MS-grade acetonitrile and ammonium acetate, as well as ammonia (25%), were obtained from VWR. GC-MS grade ethylacetate, hexane, HCl (37% p.A.) and Carrez I and Carrez II solutions were purchased from VWR. Sample cleanup was performed using J.T. Baker BAKERBOND spe C18 polarplus 1 mL SPE (solid phase extraction) columns (Schwerte, DE). LC-MS-grade water (<0.055 μS cm⁻¹) from a Sartorius ultrapure water purification system (Göttingen, Germany) was used for sample preparation.
The grain and rye varieties (Secale cereale) used were obtained from Arnreiter Mühle GmbH (Wallern a der Trattnach, Austria), Plohberger Malz GmbH (Grieskirchen, Austria), and Saatgut Erntegut GmBH (Linz, Austria). Asparaginase (EC 3.5.1.1, hydrolase) was purchased as PreventAse (product #23156) from DSM (Heerlen, Netherlands), and CaCl₂ was purchased from Solvay (Brussels, Belgium).