Hach Lange 2100AN, Инструкция по эксплуатации инструмента

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SECTION 3,
continued
37
3.2.1 Formazin Stock Solution
Make Formazin dilutions used for instrument calibration from a 4000-NTU stock
solution equivalent to the Hach Cat. No. 2461-49 turbidity standard supplied with
the instrument. This prepared stock solution is stable for up to one year from the
date received when properly stored. Thoroughly mix the 4000-NTU stock solution
prior to use for making standards. If desired, 4000 NTU stock solution can be
prepared using hydrazine sulfate and hexamethylenetetramine (also available from
Hach). Hach Company recommends using the prepared standard for best accuracy
and long term data comparability. Preparation of 4000 NTU stock solution from
raw materials is temperature and technique dependent. Prepared stock solution
from Hach is manufactured under the tightest quality control standards. Formazin
product purchased in the future will be equivalent to the standard delivered with
the new instrument. Refer to Section 3.2.6 on page 43 for preparation instructions.
3.2.2 Dilution Water
Use high-quality, low-turbidity water (<0.5 NTU) to prepare the Formazin
dilutions required to calibrate the instrument. The 2100AN Turbidimeter provides
automatic correction for <0.5 NTU turbidity contributed by dilution water (refer
to Section 2.3.3 on page 19).
Distilled, demineralized or deionized water usually is sufficient, as is most filtered
tap water. If the purified water exceeds 0.5 NTU, filter it to meet the turbidity
requirements as described in Section 2.3.3.1 on page 20.
3.2.3 Preparing Recommended Formazin Dilutions
Note: Instead of diluting a formazin stock solution, StablCal
®
stabilized formazin
suspensions may be used. Order StablCal Calibration Kit for the 2100AN Turbidimeter,
Cat. No. 26595-00 (bottled) or Cat. No. 26595-05 (ampuled).
Hach Company recommends use of 20-, 200-, 1000- and 4000 and 7500-NTU
Formazin standards for calibration of the Model 2100AN Turbidimeter. Prepare
Formazin dilutions immediately before calibration, and discard the dilutions after
use. While 4000-NTU stock solutions are stable for up to one year, diluted
solutions deteriorate more rapidly. Prepare dilutions of 20, 200 and 1000 NTUs
according the directions in Table 2. The dilution water also is used to make an
initial blank measurement.
Note: When measuring turbidity less than 4000 NTU, the 7500 NTU calibration data point
does not have to be included in the instrument calibration. After measuring the 4000
NTU standard, press CAL/Zero to complete the calibration procedure, store the other
5 calibration data points and return to the measurement mode.
The 7500-NTU Formazin standard is provided in an ampule ready for use. Do not
open the ampule or use the contents as dilution stock. The standard is stable for
one year from the date it is received. Replace this calibration standard annually.