Hach-Lange POLYMETRON 9245 User Manual - Manual (Page 23)

21
Analyzer Overview
3.4 Conditioning reagent
Hach Lange highly recommends the use of Diisopropylamine (DIPA) as the conditioning
reagent. Other reagents such as ammonia or ethanolamine can be applied, providing the
specification limitations imposed by amines other than DIPA are clearly understood.
The following graph ( Figure 5 below) shows the curves obtained using DIPA and ammonia as
conditioning reagents. As can be seen, the DIPA curve remains linear at a much lower sodium
concentration resulting in better accuracy, repeatability, a lower detection limit, and a lower rate
of reagent consumption.
The following table shows the comparable values of detection limit, accuracy, repeatability, and
consumption for DIPA, ammonia, and ethanolamine:
Note: As Hach Lange recommends DIPA to be used as the conditioning reagent, all references relating to
the conditioning reagent throughout this manual will be to DIPA.
Figure 5 Calibration curves obtained with DIPA and NH
3
as reagents
DIPA
[C
6
H
15
N]
Ammonia
[NH
3
]
Ethanolamine
[H
2
N(CH
2
)
2
OH]
Lowest detection limit 0.01ppb 2ppb 5ppb
Accuracy (non-cationic applications)
The greater of
± 0.1ppb or ± 5%
of the reading
The greater of
± 1ppb or ± 5%
of the reading
The greater of
± 2ppb or ± 7%
of the reading
Accuracy (cationic applications)
The greater of
± 2ppb or ± 5%
of the reading
The greater of
± 2ppb or ± 5%
of the reading
The greater of
± 2ppb or ± 7%
of the reading
Repeatability within a 10°C variation
The greater of
< 0.02ppb or ±1.5%
of the reading
The greater of
< 0.1ppb or ±1.5%
of the reading
The greater of
< 0.2ppb or ±2%
of the reading
Consumption of 1 liter at 25°C for a
pH measurement of 10 to 10.5
approx. 13 weeks approx. 3 weeks approx. 7 weeks