Whatman no. 1 lab filters

Ingredients

Whatman no. 1 paper, cotton linters, potassium meta-periodate (KIO4), Carbotrace 680 dye, deionized water, 2,3,5-triphenyltetrazolium chloride (TTC), KOH, HCl, ethanol

Preparation Steps

Original Recipe Text

Paper oxidation was performed through the Malaprade reaction. A paper filter of ~0.5 g (Whatman no. 1) was soaked in 50 mL of 15 mM potassium meta-periodate (KIO4, 99.8 %) aqueous solution at various time intervals (p. 3, Section 2.1). Then, the paper filter was rinsed with deionized water and dried overnight in the dark at room temperature (p. 3). For characterization, paper samples (5 mg) were stained by soaking in 100 ΙL of 4 Ιg/mL Carbotrace 680 aqueous solution for 2 h (p. 3, Section 2.4). Carbonyl content was determined via TTC assay: 30 mg paper pieces were treated with 0.5 mL KOH (0.2 M) and 0.5 mL TTC (0.2% w/v), heated to 70 °C for 10 min, then cooled in an ice bath and treated with 0.2 mL HCl (1 M). The resulting red precipitate (triphenylformazane) was solubilized in ethanol to a final volume of 10 mL and measured by UV-Vis absorption spectroscopy at 485 nm (p. 3, Section 2.2).

Evidence

"The pure cellulose paper samples used for the experiments were Whatman no. 1 lab filters. This type of paper is obtained from cotton linters and is constituted of pure cellulose."

Remarks

The study investigates the oxidation of cellulose, the main component of paper, as a primary mechanism of ageing (p. 1). Oxidation results in loss of paper strength and yellowing due to carbonyl group formation and conjugated double bonds, while hydrolysis induces cellulose chains depolymerization (p. 1). A two-step oxidation mechanism was observed: first, the oxidation and depolymerization of amorphous portions (leading to an initial increase in crystallinity), followed by the oxidative attack on packed crystalline regions (p. 2, p. 5). pH measurements recorded a decrease from 6.3 to 5.3 over 600 minutes (p. 4). Fluorescence spectra of Carbotrace 680 on oxidized paper showed a blue-shift from 655 nm to 635 nm and band narrowing, suggesting a more rigid, less polar environment (p. 6). Phasor-FLIM mapping revealed that oxidation is non-uniform, starting at the outer portions of the fibers before affecting the inner core within 24 hours (p. 8, p. 9). This approach provides sub-micrometric spatial information on the oxidation process (p. 1, Abstract).