Experimental Procedure A dry, empty freezing-point tube and its cork were weighed together. Carefully, 15-20g of pre-cooled cyclohexane was poured into the freezing-point tube, the tube recorked, and the whole thing was reweighed, to find the exact mass of the cyclohexane. The dry thermistor and stirrer were inserted into the FP tube, ensuring they were immersed in the liquid. A large beaker was filled with ice and water, which the FP tube was placed into. The cooling curve was determined by recording the temperature at regular time intervals (every fifteen seconds) as the cyclohexane cooled, until the temperature became constant.
6) Next, prepare a 50 cm3 beaker, and pour both reactants into it. Wait for at least 1 minute to allow the reaction to reach completion. Procedure—Post-dilution 1) Use a pipette to fill 3/4 of each cuvette with the new solution from the beaker. Repeat until you have 4 cuvettes with the same solution. 2) Put a lid on each cuvette in order to prevent
Add deionized water to the volumetric flask to the 250ml mark on the volumetric flask. 13. Read the volume from the bottom of the meniscus. 14. Swirl the solution to ensure that the oxalic acid crystals are properly dissolved in the deionised water.
In the round-bottom flask (100 mL), we placed p-aminobenzoic acid (1.2 g) and ethanol (12 mL). We swirled the mixture until the solid dissolved completely. We used Pasteur pipet to add concentrated sulfuric acid (1.0 mL) to the flask. We added boiling stone and assembled the reflux. Then, we did reflux for 75 minutes.
After we got the different masses, we added them up until we got a final total and we put that mass into a table. Next, we poured the Hydrochloric acid into the flask and we will quickly put the rubber stopper on the flask. After the reaction settled down, we placed the flask with the new substance, the rubber stopper, and the graduated cylinder onto a scale and we got the total mass and we wrote that down on the data table. Finally, we subtracted the beginning weight with the final weight to see the comparison of the mass of the products verses the
4- Set up reflux system using a clean and dry condenser . 5- Place the flask on the hot plate and heat the reaction for 45 minutes - 1 hour . 6- When the reflux is over , remove magnetic stirrer and allow the reaction to cool to room temperature . 7- Add 20 ml of ice water to a separating funnel
Then, the test media is then incubated at 37 ° C, for 18-24 hours. Rinsing reusable instruments The samples were rinsed with 40 ml of pyrogen-free water using a glass beaker that is free from pyrogens. Endotoxin testing using STV A total of 0,2mL from the water obtained from the rinsing was placed in the STV containing LAL reagent and was shaken for 20 to 30 seconds. Then STV was placed in an incubator at 37 ° C for 60 ± 2 minutes. STV was then observed by reversing the reaction tube in one smooth motion.
3) Centrifuged at 2500 rpm for 12 mins. Upper hexane layer (supernatant) was transferred carefully into another test tube. 4) Evaporated the hexane under a stream of grade 1 nitrogen gas and added 100 µl of methanol to the residue left and vortexed for 1 min. 5) Injected 100 µl of extract in HPLC vials and closed properly. Standard curves and calculations- Retinol was quantified from standard curves peak area for each vitamin.
Shake c) Drain the lower aqueous layer through the stopcock into the same 250 ml beaker in which the solution had been prepared in steps above. d) Pour the upper solvent layer through the neck of the funnel into a clean 125 ml Erlenmeyer flask. Return the aqueous solution from the 250 ml beaker to the separatory funnel. Add another fresh 20 ml of solvent to the funnel and again extract the aqueous solution as you did in b)
Membranes were prepared by solvent casting for which 600 mg of the dispersions (table 1) were deposited on PVDF cylindrical plates and dryed at 60ºC from 12 hours under vacuum. The membranes formed are carefully retired from the PVDF plates, analysed for fractures and deformations and their thickness were measures using a digital micrometer (Mitutoyo). Al samples shows a mean thickness between 100-200 µm. Membranes are stored on plastic bags at ambient temperature. Membrane characterization: Water vapour permeability determination: Circular portions of the membranes of 1.1 cm of radius were punched out by means of a metal die of 2 cm of diameter.