It was rinsed with tap water and later soaked in 10% HNO3 for 24 hours and further rinsed with deionized water before use.
The samples were stored in a refrigerator at 4ºC prior to analysis to inactivate bacteria and prevent any change in volume
that may be caused due to evaporation. 1432 Olafisoye O. B., et al. Fig. 1.