Page 4 - 1_Environmental analysis

SCA-130-101

The organic fraction is only 1% of the total ■ TOC-L Series
carbons. A TOC determination via the The sample preparation for the NPOC
difference method (TOC = TC - IC) will not be method (acidification and sparging) is auto-
appropriate in this case, as the calculated matically done in the TOC-L analyzer. The
TOC value is prone to large statistical errors. removing of the TIC can be performed either
in the syringe of the ISP-Module or in the
Example: autosampler with the external spare kit.
TC = 100 mg/l (RSD = 2%) ± 2 mg/l The ISP (integrated sample preparation)
(98 – 102 mg/l) module consists of an 8-port valve and a
IC = 98 mg/l (RSD = 2%) ± 1,96 mg/l syringe with sparging gas connection. In
(96,04 – 99,96mg/l) addition to acidification and sparging in the
syringe, the ISP also enables automatic
Based on error propagation the total error is ± dilution. This feature facilitates an extended
3,96 mg/l measuring range, dilution of highly
contaminated samples and the preparation of
TOC (calc.) = 2 mg/l ± 3,96mg/l a series of calibration samples from a stock
(- 1,96 - 5,96 mg/l) solution. The ISP module can therefore
considerably reduce time-consuming sample
The total error is bigger than the TOC-result, handling steps.
negative results are possible.
■ Example of drinking water analysis:
According to European Standardization EN NPOC-Method
1484 (instructions for the determination of Acidification: 1,5%
total organic carbon and dissolved organic Sparge time: 5 minutes
carbon), the difference method can only be
applied when the TIC value (total inorganic
carbon) is smaller than the TOC value. 10
For drinking water analysis the NPOC 9
method (non purgeable organic carbon) is 6
therefore used. The drinking water sample is Signal[mV]
first acidified to a pH value of 2. This way the 3
carbonates and hydrogen carbonates are
transformed into carbon dioxide. The CO 2 is 0
then removed via sparging with carrier gas. -1 0 7 14
The amount of volatile and therefore Zeit[min]
purgeable organic carbon can be disregarded
in drinking water. What remains is a solution ■ Recommended analyzer / Configuration
of non-volatile organic carbon compounds. TOC-L CPH
These can be oxidized to CO 2 and detected ASI-L (40ml), External Sparge-Kit.
via NDIR.
TOC-V WP with ASI-V (40ml)