The withdrawal of 2 ml of the external medium from the system was done at predetermined time interval, replaced by an equal volume of fresh medium, and filtered through a 0.45-μm membrane.
At predetermined time interval, samples (3 ml) were withdrawn, replaced with same volume of fresh media, filtered, and assayed for drug content at 231 nm against blank using UV visible spectrophotometer.
At the end of predetermined time interval, the content was filtered and the supernatant was analyzed for residual concentration of phenol spectrophotometrically (APHA et al. 1995) using UV visible spectrophotometer (Systronics, Vis double beem Spectro 1203).
At predetermined time intervals, a 4-mL buffer solution outside the dialysis bag was extracted and it was replaced by an equal volume of fresh media to keep the sink condition.
At predetermined time intervals, an appropriate amount of medium was removed and replaced with fresh medium.
The general method used is described as follows: the specified doses of adsorbent were mixed with 50 mL of 100 ppm Cr VI) solution in the 250 mL conical flasks and kept for predetermined time intervals on a mechanical shaker at 30 °C.
Cell morphologies were observed under a phase contrast microscope (Nikon Eclipse TS100, Tokyo, Japan) at predetermined time intervals.
The samples were collected from the flasks through filtration by Whatman filter paper (Cat No 1001 125) (Remi Instruments Ltd., Mumbai, India) after fixed contact time for thermodynamic studies as well as at predetermined time intervals for kinetic studies, and a part of filtrate was diluted with HNO3 solution (10%, v/v).
A sample volume of 300 μl was collected at predetermined time intervals and was assayed by the analytical methods described above.
