[Yerbol Abzhamiyev]

Hello people!
Have anybody experience with determination of Ca in Iodixanol? Iodixanol is a contrast agent, sold under the trade name Visipaque. Visipaque is commonly used as a contrast agent during coronary angiography. Full information is here http://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=2d964c13-88ad-43be-88d4-a3a7ea4d5b5e.
I work at pharm plant producing infusion solutions. One of them is Visipaque (Iodixanol).
We try to determine the content of calcium dichloride in this solution using Perkin Elmer's PinAAcle 900. Solution consist of the next compounds:
1)calcium chloride dihydrate   0.074 mg  in 1 mL
2)sodium chloride   1.87 mg  in 1 mL
3)tromethamine   1.2 mg  in 1 mL
4)edetate calcium disodium   0.1 mg  in 1 mL
5)hydrochloric acid   
6)sodium hydroxide

Making measurements on different wavelength don't provide repeatable results. We prepared solution of Visipaque (aka Iodixanol) containing 0.3 ppm of Ca, however AAS determined absolutely different amount of Ca. How could we find mistake in measurement and solve this problem?

[Yerbol Abzhamiyev]

Hello people!
Have anybody experience with determination of Ca in Iodixanol? Iodixanol is a contrast agent, sold under the trade name Visipaque. Visipaque is commonly used as a contrast agent during coronary angiography. Full information is here http://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=2d964c13-88ad-43be-88d4-a3a7ea4d5b5e.
I work at pharm plant producing infusion solutions. One of them is Visipaque (Iodixanol).
We try to determine the content of calcium dichloride in this solution using Perkin Elmer's PinAAcle 900. Solution consist of the next compounds:
1)calcium chloride dihydrate   0.074 mg  in 1 mL
2)sodium chloride   1.87 mg  in 1 mL
3)tromethamine   1.2 mg  in 1 mL
4)edetate calcium disodium   0.1 mg  in 1 mL
5)hydrochloric acid   
6)sodium hydroxide

Making measurements on different wavelength don't provide repeatable results. We prepared solution of Visipaque (aka Iodixanol) containing 0.3 ppm of Ca, however AAS determined absolutely different amount of Ca. How could we find mistake in measurement and solve this problem?

I also want to say that we did not  digest by microwave, and by electrical heating plates