[Radioman]

Hi all,
I work in an FDG plant and we just switched over to using Kryptofix as the counter ion in the manufacturing process. This means we have developed a new method for our quality department to test for it. Under the EP we need to use a TLC plate soaked in iodoplantinate reagent to develop a spot to check if it is present. Below is the method we use for production of the reagent:
Equipment

TLC silica gel plates (R)
Development tank
5 mL volumetric flasks
10 mL volumetric flask
100mL measuring cylinder
Analytical grade water
Autopipette
Pipette tips
Small beakers or weigh boats
Balance
Drying tray

Reagents

Analytical grade water
Hexachloroplatinic Acid
Potassium Iodide
Kryptofix 2.2.2. (4, 7, 13, 16, 21, 24-hexaoxo-1, 10-diazabicyclo-[8.8.8]-hexacosane)

A.1 Preparation of Iodoplatinate solution stock

Method has been taken from European Pharmacopeia “Iodoplatinate reagent R1” (1172200)

Solution A

Accurately measure 0.5g ± 0.005g of Hexachloroplatinic acid into a suitable container.

Transfer to a 10mL volumetric flask using analytical grade water to wash out the container.

Make the volume up to 10mL using analytical grade water. Mix carefully until fully dissolved. This is a 50g/L solution of chloroplatinic acid.

Solution B

Accurately measure 5g ± 0.05g of Potassium iodide into a suitable container.

Transfer to a 50mL volumetric flask washing out with analytical grade water.

Make the volume up to 50mL using analytical grade water. Mix carefully until fully dissolved. This is a 100 g/L solution of potassium iodide.


A.2 Preparation of Iodoplatinate solution

Mix 2.5 mL of solution A with 22.5 mL of Solution B in a beaker.

Use a measuring cylinder to add 50mL of analytical grade water. Mix carefully.

Transfer the Iodoplatinate solution to a suitable container (beaker). This solution has an expiry of 1 day.

A.3 Preparation of silica plates

Method for preparation of plate has been taken from European Pharmacopeia “TLC silica plate for amino polyether test” (1172700). The plates have an expiry of 30 days after preparation.

Immerse a silica plate for 30 seconds in the iodoplatinate solution. Ensure the whole surface of the plate is covered.

Allow to dry at room temperature overnight (12 h) in the dark ideally in fume cupboard

We have tried two different types of plates both Merck Silica 60 plates and Mercah and Negal plates but both lose their colour after drying and don't work with the test.
Here are some photos of the completed plates



Does anyone have any suggestion what is causing these problems? Our sister company does not seem to have this problem at all and we cant seem to work out what is causing it