Dear Quang Dao Duc

It is certainly recommended to prepare the standards (and samples!) also in 5% HCl to ensure Pt remains in solution.

Best regards

Bodo

Dear Quang Duc Dao,

I would first determine what concentration range you are going to make your sample and the standards. Then to make the standards dilute the 1000ppm standard to a low, medium and high standard (ex. 10, 20, 30ppm) in DI water to be able to make a calibration curve for the ICP-OES analysis. The concentration ranges will depend on if you are using radial or axial detection.

For making the samples to analyze, once you know the concentration range I would make them nominally the middle point of your calibration curve. To prepare the samples add the needed amount of Pt/g-C3N4 to hit your nominal concentration of Pt in your final volume and digest it in HCL or aqua regia. Since your standard is in HCL, HCL should be fine for the digestion. Usually only a few ml (~10ml) is needed per sample. Then stir the solution to allow it to mix and then heat it in an oven for 12h or overnight at 120C to dissolve the metal. Then dilute that solution with DI water to the desired final volume you pre calculated to get the desired Pt concentration.

From my experience it is best to pick a fixed volume such as 50ml in which you have a volumetric flask to be able to do the dilutions properly since ICP-OES is a very sensitive technique.

Thanks,

Blake MacQueen

https://core.ac.uk/download/pdf/37376609.pdf

Dear Black MacQueen,

Thank you for your answer. However, since the boiling point of HCl solution is 100C, how could I heat it overnight at 120C?

Quang Duc Dao ,

You want the solution to be boiling to help the digestion of the metals from my experience. What I and other I know have done is put them in digestion vials and keep the cap very loosely on them when putting them in the oven overnight. This prevents the gas from going into the oven etc. The solution won't boil vigorously at that temperature and the solution will remain. I have done this many times and have not had issues. Just slowly open the vials post heating in case any pressure built up in the digestion vial.

I hope that helps.

Dear Blake

I am not sure which kind of oven you are using but I would never recommend to a) heat HCl (or HNO3) solutions in a conventional laboratory oven, even to less than boiling and b) do that with closed vials. If loosely capped, HCl will partially evaporate and corrode any metal parts inside. If closed more tightly there may be sufficient pressure build up to rupture the vials.

If a dedicated high-pressure digestion system is not available, I would recommend to only heat the digestion mix on a hotplate - inside a fume hood ! - and without closing the vials tightly.

Best regards

Bodo

My research group has experience in the determination of platinum group of elements in Pt catalyst samples [1].

The following decomposition procedure was used:

1 g of the catalyst samples was weighed in a 50 ml beaker. 15 ml of

freshly prepared mixture of acids (5 ml conc. HNO3+15 ml conc. HCl)

was added to the sample and the beaker was covered with a watch

glass. The sample was left to stand for 1 h at room temperature in

order to prevent vigorous reactions. After that, the sample was heated

for 6 h on a water bath and allowed to cool down slowly to room

temperature. The content of the beaker was transferred quantitatively

into a 100 ml volumetric flask and filled up to the mark with distillate

water. The undissolved material (γ-alumina+silicates)

has settled down and the supernatant solution was subjected to

analysis by ICP-AES. The volume of the solid residue is less than 0.4% of

the final volume.

The final sample solution contains hydrochloride acid.

Hence, the platinum group of elements must be dissolved in aqua regia, but in the end of the dissolution procedure, the final solution contains hydrochloride acid.

Therefore, the calibration solutions must be prepared in 5% hydrochloric acid.

Reference

[1]. P. Petrova, S. Velichkov, N. Velitchkova, I. Havezov, N. Daskalova, “Problems, possibilities and limitations of inductively coupled plasma atomic emission spectrometry in the determination of platinum, palladium and rhodium in samples with different matrix composition”, Spectrochimica Acta Part B 65 (2010) 130–136, doi:10.1016/j.sab.2009.12.005.-

With kind regards, N.Daskalova