Page 16 - Application Handbook - TOC

Sum parameter – Total Organic Carbon
Determination of particulate organic
carbon after filtration
SCA-130-107 (glass fiber suspension)
A limnological research laboratory tackled the
problem of determining the particulate TOC
content of the sample independently of DOC
(Dissolved Organic Carbon) content. The
water sample was filtered through filters of
varying pore sizes. Particles of varying sizes
remain on the filter. The question arose, how
particulate TOC can be best measured.
Fig. Used glass fiber filter
A possibility would be to shred the filter and
disperse it in water, and to measure the
obtained suspension directly using the TOC
system. This requires use of TOC-free glass
fiber filters. This uncommon question requires
a field test. Based on the melting range of
glass fiber (about 550 °C) it was necessary to
ensure that the glass fiber content would not
clog or deactivate the catalyst (680 °C) and to
establish where the oxidizing power
diminishes.
■ The field test
A TOC analyzer with autosampler was used
for the field test. After calibration of the TOC
system, the test solution was measured 10
times. The test solution consisted of a glass
fiber suspension in hydrochloric acid (five
glass fiber filters dispersed in 500 mL) that
was continuously stirred during
measurement. To test the catalyst, a
standard solution with a TOC of 50 mg/L was
th
injected after each 10 measurement. After
100 injections and visual inspection of the
catalyst and the catalyst tube, the measuring
cycle was somewhat increased. Function of
the catalyst was now checked using the
standard test solution only after every 20
injections of the glass fiber suspension.
After a total of 450 injections, no visible
change of the catalyst could be detected. Nor
did the oxidative properties change or
deteriorate in any way. Reproducibility of the
results also did not reveal any change.