Follow marine ammonia trends with the right refill
Keep routine saltwater ammonia checks going with the three-reagent refill for HI784 and the documented HI83399 Marine Ammonia method. The method measures ammonia and ammonium together and reports the result as NH₃ mass—useful for monitoring changes, not a direct free-ammonia toxicity reading.
Manufacturer photograph of the marine reagent refill; packaging shown is representative.
Select the right method
Choose for marine samples and a 0.00–2.50 ppm result reported as NH₃. The combined NH₃/NH₄⁺ measurement is not TAN-N or NH₃-N, and is not a measurement of only free, unionized NH₃. No numerical salinity operating interval is asserted.
Three matched reagents for 25 tests
HI784-25 replenishes HI784A-0, HI784B-0 and HI784C-0 for 25 marine ammonia tests. The current formulation uses liquid A with powder B and C. Match your refill to the current instrument instructions rather than using obsolete drop-count directions.
Choose the current liquid-and-powder workflow
The current HI784 Checker method uses a measured 1 mL dose of liquid A with powder B and C; the documented HI83399 Marine Ammonia method also uses this formulation. Have accurate, clean measuring tools ready and follow the full PDF for your instrument. Do not combine the current reagents with the old 18-drop/12-drop method.
Interpret the result on the correct mass basis
The blue-green salicylate reaction measures ammonia and ammonium together. HI784 Checker and the documented HI83399 Marine Ammonia method report the combined result as NH₃ mass—not nitrogen mass (TAN-N or NH₃-N). This is not a direct free, unionized NH₃ toxicity reading: estimating that portion needs separate pH and temperature information and an appropriate marine equilibrium interpretation.
Fresh samples make trends more useful
For HI784 Checker and the documented HI83399 Marine Ammonia method, prepare the sample immediately after collection: ammonia can dissipate during storage and bias results low. Keep the prepared cuvette (sample plus reagents) at 18–29 °C. Complete powder dissolution, clear cuvette surfaces and bubble-free readings support consistent repeat checks.
Prepare your existing setup for the next test
Have the HI784 Checker or HI83399 with its named Marine Ammonia method, a clean cuvette and cap, 1 mL syringe with tip, transfer pipette, scissors and lint-free wiping material ready separately. This is a reagent refill, not a meter or complete accessory kit; the documented method needs no heated digestion.
Practical handling
Wear the protective equipment specified in the component SDS, avoid contact with reagents and dispose of used solutions according to the SDS and local requirements. Check the supplied lot label and component SDS before use.
Frequently Asked Questions
What buying need does HI784-25 cover?
It replenishes the matched marine ammonia chemistry for an HI784 already owned or the documented HI83399 Marine Ammonia method. Choose it for routine monitoring of combined ammonia/ammonium in marine water, not as a generic freshwater reagent replacement.
Does the 2.50 ppm range mean TAN-N?
No. The 0.00–2.50 ppm scale is reported as NH₃ mass, although the method measures NH₃ and NH₄⁺ together. TAN-N and ammonia-nitrogen use nitrogen mass and cannot take the same numerical label without conversion.
Is this a direct measurement of toxic free ammonia?
No. It measures combined ammonia/ammonium, not only unionized NH₃. Estimating the unionized fraction needs separate pH and temperature information and an appropriate marine equilibrium interpretation; the result alone is not a toxicity verdict.
Should I use the old 18-drop and 12-drop directions?
No. The current 07/25 HI784 method uses 1 mL liquid A and powder packets B and C. Follow the current instrument manual and the instructions matching your actual reagents; do not mix old and new physical reagent versions.
What is the current timing sequence?
After A and B, add sample to 10 mL, dissolve gently for 60–90 seconds, stand 30 seconds and zero. After adding C, dissolve for 30 seconds and develop for 15 minutes. The HI784 manual allows 10 minutes only below 1.00 ppm; do not apply that exception universally.
Can I collect the sample now and test it later?
The instructions call for preparation immediately after collection. Ammonia can dissipate from stored samples and produce low measurements. Keep the prepared cuvette within 18–29 °C and follow the full method.
Do I need a heater or a specific salinity in ppt?
No heated digestion is specified. The documented application is marine water, but no numerical ppt or PSU operating interval is established here. Do not infer suitability for an unusual brine from the marine label alone.
How should I plan for capacity and reusable tools?
Hanna states 25 tests; repeats and quality-control checks consume that capacity too. Have the meter, clean cuvette and cap, accurate 1 mL syringe with tip and transfer pipette ready separately. The capacity rating does not specify physical bottle or packet counts. Use the supplied lot label for expiry information.
