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### Topic: P and Si on ICP-OES  (Read 1883 times)

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#### 1goga1

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##### P and Si on ICP-OES
« on: June 18, 2014, 04:12:53 AM »
Hello Guys, wonder if you could give me an advice.

So, im digesting HCFeCr (high-carbon ferrochrome) in microwave and i can digest my sample entirely in two ways.

1 - HNO3/HF solution

2 - HCl/HNO3 solution

Si

Ideally i would like to use these solution to obtain Si and P content in FeCr.

In first (HNO3/HF) case I understand that i will need to perform "complexation of HF" with saturated H3BO3.

Could you explain how i should perform this "complexation". I tried simply adding the saturated H3BO3 in sample, but it did not help, i still had huge concentrations of Si (from the chamber, which is made of quartz, Swiching to teflon is not an option right now). Should i perform another digestion in microwave with H3BO3 and shoould i use saturated solution or can i use crystaline H3BO3 (ive read, that it takes about 500mg of H3BO3 per mL of HF).

In second case (HCl/HNO3) - i recive extremely low contentrations of Si (like 3-4 times lover). Is it because Si is volotised during sample preparation or ... ? (During the digestion period, vessels are closed, so nothing can escape the vessel. Before opening them i wait untill they reach 20C).

P

Now, in both cases i get high results. Here i am completely lost. Problem is, that in most cases P is being determined on wavelength of 179,..nm (and it is performed in vacuum). Since i don`t have any vacuum chamber, I have to do it on 214,...nm (on 213nm - i get negative conc.)

Building matrix

For FeCr it is extremely hard, not just because it has about 69% of Chrome, up to 9% of cabron, rest is Iron and other elements, but also because this product is very "different" every time (depending on the manufacturer, on carbon content, heavy metall content like Mo, Co, W etc. )

I would like to know, on what elements i should keep my eyes on, when i am preparing this matrix solution for FeCr, only those, that are very close to Si and P in wavelength?

What acids are better for P and Si determination on ICP-OES? (are there any buffer solution for P or Si, like LaCl3 or CsCl that could help be clear the noise)

Any advices in ICP configurations are also appreciated (since i am a beginner user).