Page 4 - 3_Chemical industry

SCA-130-301

To investigate matrix influences, a potassium The relative standard deviation over all
hydrogen phthalate solution was measurements was 3.4%. The following
subsequently added to the 18.5% graph shows the progression of the TOC
hydrochloric acid solution to increase the values of the hydrochloric acid injections.
TOC by 5 ppm (Figure 3 and Table 1).

Fig.4: Result of longterm stability

Blank values and standards (10 ppm) were
Fig.3: Results of original and spiked hydrochloric
solution alternately measured between the individual
measurements.
Figure 3 and Table 1 show the results of the
individual measurements of the hydrochloric
acid as well as the measurements of the
spiked hydrochloric acid.

TOC result of 18,5% hydrochloric acid in mg/l
Injection Original Spiked with
5ppm TOC
1 4,901 10,46 Fig. 5: Sequence of hydrochloric acid, blank (pure
2 4,858 10,24 water) and Standards (10 mg/l)
3 4,91 10,39
4 4,716 10,64
5 4,728 10,28 ■ Recommended analyzer / configuration
6 4,739 10,35  TOC-L CPH with a normal sensitive catalyst
7 4,966 10,34 (without glass wool at the bottom of the
8 4,71 10,36
9 4,662 10,42 catalyst tube)
10 4,733 10,33  B-Type scrubber with SnCl 2 solution
11 4,659 10,11  Copper bead scrubber with pH paper
12 4,625 10,27  Bypassing the blank check vessel
13 4,552 10,06
Mean value 4,75 10,33  Substituting water for phosphoric acid (IC
SD 0,12 0,15 vessel)
RSD in % 2,6 1,4  OCT-L 8-port sampler

Tab. 1: Values of each injection

■ Long-term stability
To investigate the long-term stability of the
method, the 37% hydrochloric acid solution
was again diluted to a ratio of 1:2 with water
and injected 76 times (150 µL).