Aztec 600 ISE ammonia and fluoride
Single-stream ion-selective analyzers
Appendix A – Reagents and Standard Solutions
76
OI/AXM630–EN Rev. I
Appendix A – Reagents and Standard Solutions
A.1 Reagent and Standard Solutions – Ammonia-ISE
A standard set of reagents for the Aztec 600 ISE ammonia
analyzer comprises 1 reagent, a low calibration standard and a
high calibration standard.
A.1.1 Reagent
The ammonia reagent is a mixture of EDTA-di-sodium salt and
alkali solution (NaOH-sodium hydroxide) held in a 10 l container.
The EDTA in the reagent is added to prevent blockages in the
analyzer's internal pipework. Blockages are caused when, due
to the high pH, metal ions (for example, calcium and
magnesium) present in the sample form insoluble hydroxides.
EDTA combines with the metal ions to prevent this happening. It
also prevents hardness precipitation and inaccuracies caused
by complexing of ammonia with some metal ions.
The sodium hydroxide releases the available ammonia in a free
form by adjusting the pH of the sample solution to a value
greater than 11.
A.1.2 Standard Solutions
2 standard solutions of known concentration appropriate to the
measuring range are required for analyzer calibration:
Low ammonia standard solution
(factory default is 1.214 mg/l NH
3
= 1 mg/l NH
3
-N)
High ammonia standard solution
(factory default is 4.856mg/l NH
3
= 4 mg/l NH
3
-N)
A.2 Reagent and Standard Solutions – Fluoride-ISE
A standard set of reagents for the Aztec 600 ISE fluoride
analyzer comprises 1 reagent, a low calibration standard and a
high calibration standard.
A.2.1 Reagent
The fluoride reagent is a Hexametaphosphate buffer solution
held in a 10 l container.
The Hexametaphosphate adjusts the pH of the sample to 5.25
to prevent the formation of hydrogen fluoride (HF) and hydroxide
ions that act as an interferent. The buffer also complexes other
potential interferents such as aluminium and iron.
A.2.2 Standard Solutions
2 standard solutions of known concentration appropriate to the
measuring range are required for analyzer calibration:
Low fluoride standard solution
(factory default is 0.5 mg/l F)
High fluoride standard solution
(factory default is 1.5 mg/l F)
A.3 Reagent and Standard Solution Consumption
The reagent consumption rate depends on the selected
operating mode:
Standard operating mode – 10 liters (2.6 gal [US]) every
2 months
Economy operating mode – 10 liters (2.6 gal [US]) every
3 months
The standard solution consumption rate is dependant on both
the selected operating mode and the frequency and type of
calibration but is typically:
Standard operating mode – 2.5 liters (0.7 gal [US]) every
2 months
Economy operating mode – 2.5 liters (0.7 gal [US]) every
3 months
However, ABB recommend that the standard solution is
replaced every 3 months to ensure accuracy.
Typical reagent and sample flow rates are:
Standard operating mode
–
Reagent – 0.12 mls (0.003 fl oz [US]) per minute
–
Sample – 2 mls (0.07 fl oz [US]) per minute
Economy operating mode
–
Reagent – 0.085 mls (0.002 fl oz [US]) per minute
–
Sample – 1.43 mls (0.05 fl oz [US]) per minute
Warning.
Ensure personal protective equipment (PPE) such as
gloves
and
eye protection
are worn during any
maintenance and that any spillages are cleaned-up.
Observe all health and safety procedures for handling
chemicals.
Note.
There are 2 options of ammonia reagent solution. For
applications that may typically be expected to exceed
300 ppm NH
3
, it is recommended that reagent
AWRS620/0304 is used. For most other applications,
reagent AWRS620/0301 is likely to be suitable.
Note.
Solutions as low as 0.25 mg l
-1
NH
3
-N at an ambient
temperature of 25 °C and under normal light conditions can
be prepared with care, but must be used immediately. A
solution prepared in this way loses 10 % of its concentration
over a 7 day period, making it unsuitable for long-term use.
Note.
The user has the ability to assign different standard
concentration values. It is strongly recommended that the
appropriate standard solutions are selected to suit the
application measuring range.
