Dimethylglyoxime reagent for cobalt analyses
Dissolve 0.2232 g of EDTA into 600 mL of Milli - Q for a final concentration of 10 - 3 mol L - 1 EDTA .
Weigh out approximately 1.2 g of DMG ( dimethylglyoxime ) onto a weigh boat , and combine it into the EDTA solution .
Weigh what is left on the weigh boat ( DMG is very sticky so not all of it will pour into the EDTA solution ) and record the final weight that was placed into the EDTA solution .
Heat this solution in a microwave at 50 % power until the DMG is fully dissolved , stirring it carefully in between microwaving , and trying to prevent it from boiling .
This takes up to 30 minutes , so be patient and heat it slowly and carefully .
Put the solution on ice and let it recrystallize overnight in a refrigerator .
After it has recrystallized , pour off ( or slowly pipette off ) the supernatant until there is as little liquid as possible .
Then pour the remaining crystals into a clean , dry weigh boat ( that you have weighed and noted the weight for later use ) and let the remaining liquid evaporate overnight inside a laminar flow hood .
After all the liquid has evaporated , measure the weight boat again to get an approximate measurement of the amount of DMG you have recrystallized .
Calculate how much methanol is needed to add to the DMG in order to get a final concentration of 0.1 mol L - 1 DMG , and obtain a trace metal clean bottle of the appropriate size .
Weigh the clean bottle , and then carefully transfer the recrystallized DMG into this clean bottle and re - weigh ( not all the DMG is easily transferred into the clean bottle , so the re - weigh is necessary ) .
Now recalculate the amount of optima methanol needed to get the desired concentration of 0.1 mol L - 1 , and add that amount of optima methanol .
Make sure to test the reagent before use .
