Hach 1950Plus - Preparing Calibration Standards; Preparing Phosphoric Acid Solution

Page 50
Preparing Calibration Standards
UVTOCReagents and Standards.fm
Section 3
3.4 Preparing Calibration Standards
3.4.1 Organic Calibration Standards
Danger: Some of the compounds
approved for use in the analyzer
are toxic even at low
concentrations. Take appropriate
precautions when handling them
See Safety Note 1 on page 183 for
Spanish, French, German, or
Italian translations.
Typically, the ideal TOC calibration standards are prepared with either
reagent-grade ethylene glycol or reagent-grade KHP. Standards should not be
preserved with hydrochloric acid. Table 6 describes the concentrations for
these and other calibration solution compounds that have been approved for
use in the analyzer. Add the amounts shown (in milliliters or grams) to a clean
one liter volumetric flask and dilute to one liter with distilled or DI water. These
are considered aqueous solutions. If other values are required, ratio
accordingly. Never mix two or more calibration standards.
Dispose of calibration standards as prescribed by the manufacturer or the
local/national regulatory agency.
1 mg/L = 1000 µg/L
3.5 Preparing Phosphoric Acid Solution
Example: Prepare 20 L of 0.6M H
3
PO
4
(see Table 7).
Caution: Phosphoric acid is a
strong and corrosive reagent.
Handle with appropriate care. Eye
protection is required when
handling phosphoric acid. Wash
your hands thoroughly with soap
and water immediately after
handling this reagent. Scratching
or touching your skin before
washing your hands may cause
skin irritation. See Safety Note 6
on page 184 for Spanish, French,
German, or Italian translations.
1. Obtain a 20-L container with a lid that closes securely. Make sure that the
container is clean and has been flushed with distilled or DI water.
2. Add 14 liters of DI water to the container.
3. Slowly add 819 mL of 85 wt % phosphoric acid to the container.
Dilute with DI water to measure a total of 20 liters.
4. Mix by shaking the container with the top on.
5. Place the acid input tube into the acid container, making sure that the
tube is bottomed in the container.
Table 6 Preparing Organic Calibration Solutions
Calibration Standard Amount to add to a 1-L Flask Resulting concentration
Organic Compounds 100 mg/L 1000 mg/L
Ethylene glycol 0.233 mL 2.33 mL
Ethanol 0.242 mL 2.42 mL
Methanol 0.337 mL 3.37 mL
KHP 0.212 g 2.12 g
Acetic acid 0.250 g 2.50 g
Sucrose 0.238 g 2.38 g
1,4 Benzoquinone 0.150 g 1.50 g
Urea 0.500 g 5.00 g