I have SiO2 standard stock solution of 1000 ppm where SiO2 in 2M Na2CO3.
I want to prepare working standards of 0.3, 0.5. and 1 ppm solutions to be used in ICP-AES. The matrix of samples for ICPAES is usually HNO3. Should I dilute appropriate volumes of SiO2 with HNO3 or is there any other way?
(All other stock standards are either in 0.1 or 1 M HNO3, thus no complication)
Thanks in advance
Prepare a 2 M Na2CO3 solution (it is alkaline) and dilute your stock solution with that solution to the appropriate concentrations you need. F-containing acid solutions can work, but they are dangerous. It is safer with Na2CO3 - and according to my colleagues' lab experience it gives a better recovery and higher sensitivity compared with HF-solutions. As Michael Päch wrote, dilution in 0.1 M Nitric Acid will result in precipitation of the Si and hence no, or low, signal.
If you need to analyze multiple elements, you should make separate analyses of those metals which are soluble in acids (nearly all) from those which are not (e.g. Si, Mo, W). The samples need also to be adjusted to an alkaline pH if you want to detect Si (not only the standards). If you want to go for acidic, F-containing, solutions, you need to add flourides/HF in the samples as well.
Remember that you might have lost the analyte (Si) in your samples at the bottom or on the walls of the vessels, if you have acidified them.
As Michael Päch wrote, don't use glass vessels at all if you have F-containing solution. But also don't use it in any case for your samples or standards (or the dilution solution), since you might get background concentration from Si dissolved out of the glass (this happens at neutral or alkaline pH).
You can dilute your standards in 0.1M Nitric Acid.
By the way Tharanga, I will be in Sri Lanka on the 7th September for two weeks. I would like to visit your university. Could it be possible?. Please send me your and the university contact information, to get more information for a visit. Thanks
Prepare a 2 M Na2CO3 solution (it is alkaline) and dilute your stock solution with that solution to the appropriate concentrations you need. F-containing acid solutions can work, but they are dangerous. It is safer with Na2CO3 - and according to my colleagues' lab experience it gives a better recovery and higher sensitivity compared with HF-solutions. As Michael Päch wrote, dilution in 0.1 M Nitric Acid will result in precipitation of the Si and hence no, or low, signal.
If you need to analyze multiple elements, you should make separate analyses of those metals which are soluble in acids (nearly all) from those which are not (e.g. Si, Mo, W). The samples need also to be adjusted to an alkaline pH if you want to detect Si (not only the standards). If you want to go for acidic, F-containing, solutions, you need to add flourides/HF in the samples as well.
Remember that you might have lost the analyte (Si) in your samples at the bottom or on the walls of the vessels, if you have acidified them.
As Michael Päch wrote, don't use glass vessels at all if you have F-containing solution. But also don't use it in any case for your samples or standards (or the dilution solution), since you might get background concentration from Si dissolved out of the glass (this happens at neutral or alkaline pH).
It's not just about your standards and vessels...
You also should use a proper sample introduction system
(plastic nebulizer and spray chamber) and ceramic (torch) injector.
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