TOC cube

vario TOC cube

 

TOC / TC analyses in soil with the vario TOC cube

The vario TOC cube can easily be reconfigured from liquid to solid mode, AN-A-160409-E-01
so that the instrument can analyse virtually any type of sample: from
liquid, particulate containing samples, semi-solids to actual solid
samples.

For the TC analyses the samples have been weighed into tin boats. instrument:
vario TOC cube
For TOC analyses the samples have been weighed into silver boats and solid TC
acidified using a 1M HCl solution. The acidified samples have been dried
one hour at 100 °C and have then been packed into tin boats, in order to sample:
enhance the combustion temperature to > 1000 °C (in order to combust 20 – 210 mg
the silver completely). The samples cannot be acidified in the tin boats soil
directly since the strong acid will damage the tin packing material. solid

Two certified soil samples have been analysed in order to test the
performance of the vario TOC cube. Furthermore, three soil samples have
been analysed.

sample weight [mg] TC [%] weight [mg] TOC [%]

soil 4.1% TC 50 – 100 4.10 ± 0.022 50 – 60 3.87 ± 0.029

soil 13.1% TC 20 – 30 12.7 ± 0.040 30 – 40 12.4 ± 0.085

soil-1 70 – 170 1.49 ± 0.006 40 – 80 1.15 ± 0.061

soil-2 170 – 210 1.80 ± 0.008 50 – 70 1.43 ± 0.034

soil-3 30 - 60 3.31 ± 0.028 30 - 70 2.46 ± 0.046

The soil standards have been analysed with a high accuracy and
precision. A complete recovery of carbon was achieved. The TC and TOC
content of the three soil samples could be analysed with high precision.

Besides the excellent performance for liquid samples, the vario TOC cube
can also analyse solid samples without limitations.

 

Fast determination of TOC in seawater with the vario AN-W-060408-E-02
TOC cube

The analysis of saline samples strongly reduce the lifetime of the quartz
glass combustion tube and the catalyst of the vario TOC cube. Using a
simple change in setup, by combining a low combustion temperature
with a bottom closed ash finger containing quartz wool, saline samples
can be analysed with the vario TOC cube without restrictions.

The combustion tube temperature of the vario TOC is reduced to 680°C, instrument:
so that the sample does not spatter when it enters the hot combustion vario TOC cube
tube. Moreover, a bottom closed ash finger containing ca. 1 cm quartz TOC
wool is used, in which all salt residues are captured.
sample:
Various seawater samples with different salinity are analysed. The 0.2 ml
samples are acidified with HCl to a pH of 2 in order to outgas the TIC in sea water
the sample container and to only analyse the TOC fraction. liquid

sample Salinity [%] TOC [mg/l] SD [mg/l RSD [%]

Atlantic Ocean ca. 3.5 1.89 0.044 2.4

North Sea ca. 3.5 6.78 0.073 1.1

Baltic Sea ca. 0.8 4.63 0.148 3.1

Red Sea ca. 4.0 2.64 0.046 1.7

The relatively high TOC content in the samples indicate that they are
taken close to the sea surface. The high relative standard deviation in
the Atlantic Ocean and Baltic sea samples are caused by carbon
containing particulates abundant in the samples.

By reducing the combustion tube temperature to 680°C and using a
bottom closed ash finger containing quartz wool when analysing saline
samples, the alkaline residues of the sample do not get in contact with
the combustion tube and catalyst. Due to this complete matrix
separation, the vario TOC cube can be run with saline samples
automatically over a long time (more than 600 analyses on one
combustion tube and ash finger).

The vario TOC cube is very well suited for the analysis of seawater
samples. The low TOC content in seawater can be determined with a
high precision.

 

TOC in industrial process water with vario TOC cube

During specific industrial processes, the quality of process water has to AN-W-070109-E-01
be monitored. The vario TOC cube is very suited for the routine analyses
of industrial process water, since it is designed for fully automatic
analyses of total organic carbon (TOC) over a wide concentration range.

The samples have been acidified externally with HCl in order to remove instrument:
the TIC from the samples. vario TOC cube
TOC
Average TOC concentrations of three different types of industrial process
water, together with their absolute and relative standard deviations are sample:
presented below. All samples have been analysed three times. 0.2 ml
water
sample TOC [mg/l] SD [mg/l] RSD [%] liquid
ipw 1 1.28 0.010 0.80
ipw 2 51.5 0.16 0.30
ipw 3 99.9 0.40 0.40

The TOC content of the different process water samples could be analysed
with a very high precision (relative standard deviation < 1%).

The results show that the vario TOC cube is suitable for the analyses of
industrial process over a large range of TOC concentration values.

 

TOC analysis in drinking water with vario TOC cube AN-W-100309-E-01

The total organic carbon (TOC) content is one of the standard parameters
which is routinely determined in drinking water. The vario TOC cube is
designed for this task and operates according to the international
standard ISO 8245 on “Water quality - Guidelines for the determination
of total organic carbon (TOC) and dissolved organic carbon (DOC)”.

Drinking water samples have been collected from cities and villages in instrument:
the neighbourhood of Elementar Headquarters. The samples have been vario TOC cube
acidified externally with HCl in order to remove the TIC from the samples. TOC (NPOC)

The direct mode (determination of NPOC after removing the TIC by sample:
acidification and sparging) is the standard procedure for drinking water 0.8 ml
analysis due to the unfavourable TOC:TIC ratio (TOC << TIC). water
liquid
Probe TOC [mg/l] abs. std [mg/l] rel. std [%]
Hanau 0.89 0.006 0.66
Mörfelden 1.89 0.002 0.11
Bad Kissingen 1.33 0.002 0.13
Gelnhausen 0.43 0.006 1.36
Mainz 1.49 0.016 1.08
Bad Soden – Salmünster 0.21 0.004 1.90
Alzenau 1.25 0.0004 0.03
Birstein 0.20 0.0003 0.14

The relatively low TOC content of all drinking water samples could be
determined with a very high precision. No effect of TIC cloud be
observed, underlining the high sparging efficiency of the vario TOC cube.

The vario TOC cube is very suitable for the analysis of TOC in drinking
water and fulfils the requirements of the international standard ISO 8245
on “Water quality – Guidelines for the determination of total organic
carbon (TOC) and dissolved organic carbon (DOC)”.

 

The analysis of low TOC concentrations in brine using AN-W-121110-E-01
the vario TOC cube

The analysis of saturated salt solutions (brine) strongly reduce the
lifetime of the quartz glass combustion tube and the catalyst of a TOC
analyser. Due to the excellent matrix separation of the vario TOC cube,
strong saline samples can be analysed automatically over a long time
without interruption for maintenance. Moreover, concentrations down
below 1 ppm provide no problems for the vario TOC cube since the matrix
separation enables high injection volumes up to 0.5 ml.

The combustion tube temperature of the vario TOC is reduced to 680°C to instrument:
avoid melting of the salt. Moreover, a bottom closed ash finger (crucible) vario TOC cube
containing ca. 1 cm quartz wool is used, in which all salt residues are TOC
captured.
sample:
A 28% brine solution is prepared containing 2 ppm TOC and analysed on 0.2 ml
the vario TOC cube over a longer time period. The solution is diluted with brine
water (1:1) before analysis. liquid

28% Brine (10 analyses) average SD RSD
TOC [mg/l] [mg/l] [mg/l] [%]

2.237 2.176 2.204 0.071 3.23
2.146 2.194
2.319 2.146
2.267 2.297
2.116 2.146

Due to impurities in NaCl, used for the preparation of the Brine solution
the found TOC concentration is higher as the nominal value of 2 ppm.

By reducing the combustion tube temperature to 680°C and using a ash
crucible containing quartz wool when analysing brine samples, the
alkaline residues of the sample do not get in contact with the
combustion tube and catalyst. Due to this complete matrix separation,
the vario TOC cube can be run with brine samples automatically for more
than 100 samples when using an injection volume of 100 µl.

We recommend flushing the instrument with water (using the flush
sequence function in the software) between brine samples for even
more analyses without interruption.