Wait a second...
Nepřihlášený uživatel
You are here: UCT PragueCentral Laboratories → Laboratory of Organic Elemental Analysis
iduzel: 25101
idvazba: 31765
šablona: stranka_submenu
čas: 25.11.2017 08:54:12
verze: 3887
uzivatel:
remoteAPIs:
branch: trunk
Obnovit | RAW

Laboratory of Organic Elemental Analysis

The elemental analyses are focused on the determination of following elements – carbon, hydrogen, nitrogen, sulfur, chlorine, bromine, iodine and phosphorus. Analytical methods are based on a sample high-temperature burning in oxygen atmosphere and with a subsequent detection of selected burning products.
Solid or liquid samples can be analysed, e.g. pure chemicals, fuels, coal, heavy oils, plant materials, wood, cellulose etc. Some soils, sands, clays, sediments and other samples being partially or predominantly inorganic can be analyzed. The samples are always destroyed by burning (analyses are destructive).

Analyses

1. Simultaneous determination of carbon, hydrogen, nitrogen and sulfur from one sample
Vario EL Cube analyzer is used for this determination. The analyzer is equipped with a TCD detector and additionally IR detector which is used for determination of the low sulfur content ( below 100 ppm).

Simultaneous C, H, N, S determination is based on high-temperature (up to 1200°C) combustion of the sample in the oxygen stream. Gaseous products of combustion (N2, CO2, H2O a SO2) are purified, separated and finally determined by TCD. Typical samples are organic chemicals but lot of inorganic matters can be  analyzed as well.

If your sample contains fluorine in any form and quantity, then the sulfur content cannot be determined. Fluorine containing samples can be analyzed only by the Vario EL III analyzer. In the case of flourinated samples, we can only do the determination of carbon, hydrogen and nitrogen content.

2. Trace and semi-trace determination of halogens and sulfur
We are able to determine even very low content of halogens (not fluorine) and sulfur. These analyses are carried out by the Mitsubishi TOX – 100 analyzer.

Trace and semi-trace determination of halogens:
The sample is burnt in the oxygen-argon atmosphere. Hydrogen chloride produced by sample burning flows into the titration cell where the microcoulometric titration by Ag+ ions takes place. Ag+ ions are automatically generated by Ag - electrode.


Trace and semi-trace determination of sulfur:
The sample is burnt in the oxygen-argon atmosphere. Sulfur dioxide produced by sample burning flows into the titration cell where the microcoulometric titration by I3- ions takes place.

Trace determination of sulfur is disturbed by nitrogen and halogens. If the determination has to be done, your samples cannot contain nitrogen and halogens.
Trace determination of halogens (not fluorine) is disturbed by high sulfur and nitrogen content. If the determination has to be done, your samples can contain sulfur and nitrogen up to 10 %wt. In the case of samples of unknown chemical composition, we have to do the simultaneous C, H, N, S determination at first.

3. Determination of chlorine-, bromine- and iodine content
Methods of classical argentometry are used for the determination of the halogens content. However methods are slightly modified to be able to analyse low quantity of halogens. The sample weight needed for the analysis is depended on the expected halogen content.

The sample is burnt in the oxygen atmosphere inside of the Erlenmeyer flask. Gaseous products of burning are absorbed into the working solution of hydrogen peroxide that is subsequently transfered into the titration flask. The halogen content is determined by potentiometric titration using silver nitrate as titrant.

Your sample has to be a solid and easy burnable matter.
If the estimated halogen content is bellow 5 wt% then the sample mass needed for one analysis is at least 100 mg. If the estimated halogen content is above 5 wt% then the sample amount needed for one analysis is 20 mg.

4. Phosphorus determination
The sample is burnt in the oxygen atmosphere and mineralized. The phosphorus content is determined by a modified complexometric titration.

The sample must not contain alkali earth metals.
If the estimated phosphorus content is low (approx. 0.1 wt%) then the sample amount must be at least 800 mg in one analysis!

Updated: 1.2.2016 16:48, Author: Josef Chudoba

UCT Prague
Technická 5
166 28 Prague 6 – Dejvice
IČO: 60461373 / VAT: CZ60461373

Czech Post certified digital mail code: sp4j9ch

Copyright: UCT Prague 2015
Information provided by the Department of International Relations and the Department of R&D. Technical support by the Computing Centre.
switch to full version