Suez Total Organic Carbon - March 2020 - 14

Percent Recovery Results

Table 1. Accurate Weigh of Stock Solutions for Vials
Vial

Stock Used

Stock Weight
(g)

Total Weight
(g)

TOC (ppm c)

TOC Blank = 35 ppb C

1

100 ppm C

25

500

5.0

Theoretical
ppm C

Vial Set
#2

Vial Set
#3

Vial Set
#4

% Recovery
Average

2

100 ppm C

3

100

3.0

5.0

103%

101%

101%

101%

3

100 ppm C

5

500

1.0

3.0

102%

102%

102%

102%

4

100 ppm C

25

500

0.5

1.0

98%

99%

102%

100%

5

100 ppm C

3

100

0.3

0.5

102%

103%

104%

104%

0.3

98%

99%

98%

99%

Table 1 was used to accurately weigh out the stock solutions into
vials. Then each vial was filled with 20 mL of low-TOC water. Four
sets of vials were created (20 vials) for this study. One set was used
for the linearity test, and the remaining were used to determine
percent recovery, accuracy, and intra-assay precision as described
in ICH Q2(R1).

TOC analysis of cleaning agent test standards
The prepared cleaning agent test standards were then analyzed for
TOC content. Each vial was analyzed with four replicates, with the
first replicate being rejected. The average, standard deviation and %
RSD were calculated. The average of the water blank that was used
to prepare the stock solutions was also recorded and factored into
the final results. The blank value was used to subtract the water
background from the test standard solution results.

Linearity Test Results
TOC Blank = 35 ppb C
Theoretical ppm C

Vial Set #1

% Recovery

% RSD

5.0

5.40

102%

1.1

3.0

3.10

101%

0.4

1.0

1.10

104%

1.1

0.5

0.55

99%

1.0

0.3

0.32

98%

0.3

R2= .998

Slope = 1.01

y-intercept = 0.004

Linearity
Results

14

summary
The data generated from this study demonstrate that alkaline
cleaning agents can be analyzed for organic carbon content by TOC
analysis with Sievers Analyzers. The analysis determined that the
method is sensitive enough and linear over the 0.1 to 5 ppm C range,
as demonstrated by an R2 value of .998. Precision and accuracy were
demonstrated with relative standard deviation (RSD) values less than
three percent and average recovery values of 99% to 104%. The limit
of detection was based on repetitive measurements of the reagent
water used to make the stock solutions. This limit of detection for the
analyte was determined to be 0.814 ppb C.
TOC analysis offers an effective way to measure cleaning agent and
product residues, monitor cleaning processes, and reduce overall risks.
Suez Total Organic Carbon - March 2020

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