Page 24 - 3_Chemical industry

SCA-130-311

■ Measurement method and results ■ Further considerations
The oxidation products of H2O2 pose no harm
Measurement type: NPOC
to the liquid handling system, catalyst and de-
Addition of acid: 1.5%
tectors of the TOC-L. The samples themselves
Sparge time: 5 minutes
however should be placed in septum-sealed
Injection volume.: 50 μL
vials in the autosampler, to exclude accidental
spilling of the aggressive substance.
40
The injection volume for both TOC and TNb
30
determination can be increased further to be
Signal[mV] 20 able to measure in lower ranges.
10
0 Higher concentrated solutions (e.g. 55%) can
-4
0 2 4 6 8 10
Time[min] be measured as well. Unstabilized solutions

Fig.2: 3 NPOC Injections of 30% H2O2. might tend to create foam when applying the
NPOC method. In such cases it is advised to
Multiple injections of the untreated 30% hydro-
use the difference method (TOC=TC-IC) to
gen peroxide solution were conducted suc-
prevent bad reproducibility.
cessfully and with good reproducibility.

To investigate matrix influences, a potassium
hydrogen phthalate solution was subsequently
added to increase the TOC content by 10 and
20mg/L respectively. Concurrently, a mixed
Potassium nitrate and Ammonium sulfate so-
lution was added to increase the TNb by 1 and
2mg/L (Figure 3).

NPOC TNb RSD
Sample
[mg/l] [mg/l] [%]
H2O2 (30%) 19,4 2,76 1,0
H2O2 (30%) 29,0 3,71 1,5
(spiked with 10mgC/l
and 1mgN/l)
H2O2 (30%) 38,9 4,71 0,5
(spiked with 20mgC/l
and 2mgN/l)
Fig.3: Results of original and spiked H2O2

The NPOC and TNb contents were found pre- ■ Recommended analyzer / configuration
cisely according to the added amounts. The TOC-LCXH
validity and efficiency of the measurement TNM-L for TNb determination
method was thereby considered verified. ASI-L with external sparge kit