Sodium monohydrogen phosphate

(-)-Epicatechin (EC), quercetin (Quer), ampicillin sodium salt, nistatine, agar, yeast extract, cholesterol, 5-fluoro-2′-deoxyuridine (FUdR), and bovine serum albumin were purchased from Sigma-Aldrich (Madrid, Spain). Sodium chloride, calcium chloride, 10% w/v sodium hypochlorite solution, hydrogen chloride, sodium hydroxide and dimethyl sulfoxide (DMSO) were obtained from Panreac (Barcelona, Spain). Potassium dihydrogen phosphate, potassium monohydrogen phosphate, sodium monohydrogen phosphate, acetic acid and magnesium sulfate were from Merck (Darmstadt, Germany). Petri plates Ø 35 and 60 mm were from Brand GMBH (Wertheim, Germany) and Petri plates Ø 90 mm from Francisco Soria Melguizo (Valdemoro, Madrid). MRS Broth was from Fisher Scientific (Madrid, Spain) and tryptone medium from Fluka Analytical (Madrid, Spain).

Glucidex 2^® (GLU2) was provided by Roquette Frères (Lestrem, France), while 1,4-diazabicyclo [2.2.2] octane (DABCO), 1,4 butanediol diglycidyl ether (BDE), trimethylolpropane triglycidyl ether (TTE), potassium nitrate, sodium sulfate, sodium orthophosphate, sodium mono-hydrogen phosphate, and sodium di-hydrogen phosphate were purchased from Sigma-Aldrich (Darmstadt, Germany). GLU2 was dried in an oven at 75 °C up to a constant weight before use.

The different field pea seeds (Pisum sativum L.) were kindly provided by Norddeutsche Pflanzenzucht Hans-Georg-Lembke KG (Holtsee, Germany) and are shown in Table 1. The Broad Range™ Unstained Standard, 4–20% Criterion™ TGX Stain-Free™ Precast Gels, and Coomassie blue R-250 were purchased from Bio-Rad Laboratories GmbH (Feldkirchen, Germany). Sodium dihydrogen phosphate, sodium dodecyl sulfate, and sodium monohydrogen phosphate were purchased from Sigma-Aldrich Chemie GmbH (Munich, Germany). All chemicals used in this study were of analytical grade.

Pea seeds (Pisum sativum L., cultivar Navarro) were provided by Norddeutsche Pflanzenzucht Hans-Georg-Lembke KG (Holtsee, Germany). Trypsin and Esperase^® 8.0 L were obtained from Sigma-Aldrich (Munich, Germany). Papain was from Carl Roth GmbH (Karlsruhe, Germany). L. plantarum (DSM 20174) was purchased from the German collection of microorganisms and cell cultures (Deutsche Sammlung von Mikroorganismen und Zellkulturen, Germany). Broad Range™ Unstained Protein Standard, 4–20% Criterion™ TGX stain-free™ precast polyacrylamide gels, Coomassie Brilliant Blue R-250 were from Bio-Rad Laboratories GmbH (Feldkirchen, Germany). Sodium dihydrogen phosphate, sodium dodecyl sulfate, sodium tetraborate decahydrate, o-phthaldialdehyde, and sodium monohydrogen phosphate were purchased from Sigma-Aldrich (Munich, Germany). All chemicals used in this study were of analytical grade unless otherwise indicated.

Tetraethylammonium hexafluorophosphate (TEAPF₆, puriss. electrochemical grade), p-benzoquinone (BQ), N-cyclohexyl-N’-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate (CMC), graphite oxide powder (GrO), sodium monohydrogen phosphate, potassium dihydrogen phosphate, 𝛽-D-glucose, glucose oxidase (GOx) from Aspergillus niger, saccharose, and ascorbic acid were from Sigma-Aldrich (Milan, Italy); CH₂Cl₂ (99.8%, packaged under nitrogen) was from Acros; 2,5-di(2-thienyl)thieno[3,2-b]thiophene (dTT-bT) was from TCI Chemicals (Zwijndrecht, Belgium); and the fructose and real samples (pear and apricot juices) were from a local food company. All the buffers were prepared according to generally known, obligatory standards.
A CHI-650 electrochemical station (CH Instruments, Austin, TX, USA) interfaced with a PC using its software was used in all the electrochemical tests. The experiments were performed in a three-electrode, single compartment cell equipped with a Ag/AgCl reference electrode, a graphite bar as an auxiliary electrode, and a Pt (diameter 2 mm), glassy carbon (GC, diameter 3 mm) or Au (diameter 2 mm) disk as a working electrode (WE). Working electrodes were polished with alumina powder (1 and 0.3 µm diameter), treated in an ultrasonic bath for 10 min, and rinsed with water and acetone before use in polymer film deposition.