Page 80 - PBL71 OI/AXM630-EN AZTEC 600 SS (WIRO)
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Aztec 600 ISE ammonia and fluoride
Single-stream ion-selective analyzers Appendix A – Reagents and Standard Solutions
Appendix A – Reagents and Standard Solutions
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.
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:
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:
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OI/AXM630–EN Rev. J
Note. There are 2 options of ammonia reagent solution. For applications that may typically be expected to exceed 300ppm NH3, it is recommended that reagent AWRS620/0304 is used. For most other applications, reagent AWRS620/0301 is likely to be suitable.
Low ammonia standard solution
(factory default is 1.214 mg/l NH3 = 1 mg/l NH3-N)
High ammonia standard solution
(factory default is 4.856mg/l NH3 = 4 mg/l NH3-N)
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.
Note. Solutions as low as 0.25 mg l-1 NH3-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.
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
