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Appendix C
5/20/2009
8
In a 1000 ml volumetric flask, add 172 ml of concentrated hydrochloric
acid to ~600 ml of deionized water. Dilute to 1000 ml with deionized
water.
7.6 Organic Carbon Stock Standard: Potassium Hydrogen Phthalate (KHP)
Standard, 1000 mg/l
Potassium hydrogen phthalate (HOCOC
6
H
4
COOK),
Dried at 45
!
C
2.125 g
Deionized water
1000 ml
In a 1000 ml volumetric flask, dissolve 2.125 g of potassium hydrogen
phthalate in ~800 ml of deionized water. Dilute to 1000 ml with deionized
water. Make fresh every 4 - 6 months. Store at 4
!
C.
7.7 Inorganic Carbon Stock Standard: Sodium Hydrogen Carbonate/ Sodium
Carbonate (NaHCO
3
/Na
2
CO
3
) Standard,
1000 mg/l
Sodium Hydrogen Carbonate (NaHCO
3
)
1.75 g
Sodium Carbonate, Anhydrous (Na
2
CO
3
) 2.205 g
Deionized H
2
O
500 ml
In a 500 ml volumetric flask, dissolve 1.75 g NaHCO3 and 2.205 g
Na2CO3 in ~300 ml deionized H2O. Dilute to 500 ml with deionized
H2O. Make fresh every 4 months. Store at 4
°
C.
7.8 Blanks – Two blanks are used in calculations for this analysis.
7.8.1
ASTM D1193, Type I water is used for the Laboratory
Reagent Blank. The LRB is comprised of the instrument
blank plus the organic content found within the TYPE I
water. The area of the LRB is subtracted from the area of
the standards.
7.8.2
For ambient water samples, the LRB cannot be used,
because the samples have no added Type I water. Because
the instrument has an internal blank that is not constant, the
instrument blank is determined to be the
absolute value
of
the y intercept. This value is subtracted from the area of the
samples.
7.8.3
If the ambient water sample is diluted with TYPE I water,
then the LRB must be used in the calculation.
7.8.4
This does not apply to TIC samples. The instrument blank
for inorganic carbon is insignificant, so no blank is
subtracted from the samples.
7.9 Quality Control Sample (QCS) – For this procedure, the QCS can be any
certified dissolved sample which is obtained from an external source. If a
certified sample is not available, then use the standard material (KHP).