Hanna Nitrate HR Accuracy

[CG2000]

I tested my Nitrates this morning with my Hanna and was shocked to see it read 8ppm as 3 days ago it read 1.2ppm and I'd done a water change.

So I ran it again, got 3.9, and again and got 0.8. This leaves me to beleive this Hanna is no more useful than a random number generator. I kept the 3 vials and I can see the colors are different, so I doubt that it's the checker itself, its as if the reagent is behaving differently sachet to sachet.

I'm confident I'm getting all the powder in and following the instructions accurately. I clean the exterior of the vials with a microfiber cloth before testing also.

 

[Dan_P]

I tested my Nitrates this morning with my Hanna and was shocked to see it read 8ppm as 3 days ago it read 1.2ppm and I'd done a water change.

So I ran it again, got 3.9, and again and got 0.8. This leaves me to beleive this Hanna is no more useful than a random number generator. Have other folks had this issue? Could I be doning something dumb or is it likley that the checker is faulty?

Two things. Take a look at the accuracy. I believe it is plus/minus 2 ppm. It is not really a low range test method. Also, there seems to be some lots of reagent that give low or inconsistent results. I do not use any reagent that is more than off white in color and does not flow easily.

 

[BZOFIQ]

Mine has been very consistent. I get repeatable results.

Can't say the same thing for all of the "eggs"

 

[Randy Holmes-Farley]

It’s important to orient the cuvette the same way each time, and to make sure the outside is clean.

That said, many of the test we use are just not as reproducible as we would like.

In general, I use the HR nitrate and think it works ok, but I have not taken the same measurement repeatedly to see the reproducibility.

 

[CG2000]

Mine has been very consistent. I get repeatable results.

Can't say the same thing for all of the "eggs"

Two things. Take a look at the accuracy. I believe it is plus/minus 2 ppm. It is not really a low range test method. Also, there seems to be some lots of reagent that give low or inconsistent results. I do not use any reagent that is more than off white in color and does not flow easily.

From their website it claims the following, so a typical reef aquarium would be within the right range. Seems like my reading are at least +/- 4ppm assuming the middle one is correct. Could be upto +/- 8 ppm if the lowest one is correct.

Range: 0.0 to 75.0 ppm (as NO3–)
Resolution 0.1 ppm
Accuracy @ 25°C (77°F) ±2.0 ppm ±5%


It's got to be the reagent. I'll buy a new pack and see.

If anyone else feels like doing 3 tests back to back to compare results I'd be interested to see what you get!

 

[areefer01]

I've run daily tests for a couple of months as part of the the Trident NP internal testing. I have had a love, hate (dislike), relationship with Hanna's nitrate test kit.

Tips I've come to follow:

• Be consistent with using the same test cuvette and cap
• Make sure you face the cuvette the same way each time if the markets still visible
• For consistency sake, use a reliable 10 ml syringe to fill cuvette
• Use the same cuvette for the zero (C1) and reading (C2) steps to ensure accuracy, don't cheat
• Shake vigorously for 2 minutes per the instructions
• Test at the same time if trending, and pull from the same source
• If testing to calibrate or run back to back tests, collect a pint of water for your sample - don't go back to the well

As already noted there is a margin of error. Also important to note this is a hobby grade test kit. To calibrate the NP sometimes I will use my tank water. I will collect a pint of water to draw the sample while also using to finish the Tridents calibration. Same sample, water source. If there is a test anomaly I will either toss it out and use the average of 3 or will retest for a 5th then remove.

I've had a bad set of (Hanna) reagents even though they did not fall within the expiration date. I reached out to Hanna and they replaced. I have had tests vary day by day and this is how I found the cuvette and cap issue. Once I started to use the same set numbers became consistent. I've also seen odd results and got them back to normal after replacing the battery. Also no name vs energizer made a difference. Go figure.

I guess my point is that be consistent in what you, we, can control. This worked best for me. I calibrate the Trident NP every 2 months if the reagent lot numbers are different in case anyone is wondering why I have this.

Hanna HI782 Nitrate HR, Hanna Phosphate HI713:

	nitrate	phosphate
test 1	31.4	1.53
test 2	41.3	1.52
test 3	33.7	1.49
test 4	30	1.5
avg	34.10	1.51

More recent 2/16 calibration run:

	nitrate	phosphate
test 1	23.3	0.64
test 2	24.5	0.68
test 3	25.4	0.79
test 4	22.3	0.65

 

[CHSUB]

I get the exact same results with ICP and Hanna LR, actually even better with Hanna. However, the Hanna HR imo is less reliable than Salifert, so not junk but close.

.

 

[CG2000]

Thanks for the info, I have no idea why I bought a HR not LR, seems like LR is better suited to what we do.

Here you can see the 3 curvettes next to each other. The 3 samples came from the same sample cup from the tank and were mixed within minutes of each other. You can clearly see the differtence in color, so I find it hard to believe this is anything but variation in the reagent sachets (which are not expired by the way).

 

[Randy Holmes-Farley]

For my nitrate target range, the HR is the right one, not the LR.

 

[Dan_P]

Thanks for the info, I have no idea why I bought a HR not LR, seems like LR is better suited to what we do.

Here you can see the 3 curvettes next to each other. The 3 samples came from the same sample cup from the tank and were mixed within minutes of each other. You can clearly see the differtence in color, so I find it hard to believe this is anything but variation in the reagent sachets (which are not expired by the way).

Most people find the LR procedure very tedious. I use the LR method because my system runs low in nitrate and I don’t check nitrate that often. The tedious test procedure is tolerable

 

[BZOFIQ]

Thanks for the info, I have no idea why I bought a HR not LR, seems like LR is better suited to what we do.

Here you can see the 3 curvettes next to each other. The 3 samples came from the same sample cup from the tank and were mixed within minutes of each other. You can clearly see the differtence in color, so I find it hard to believe this is anything but variation in the reagent sachets (which are not expired by the way).

The color "develops" with time hence the difference between your oldest mixed vs your fresh mixed.

The meter requires a button hold for a 7 minute timer to initiate before the sample is tested.

My friend never did that and too was getting wrong results until I told him. Some people just dont RTFM!

 

[scubajoe]

From their website it claims the following, so a typical reef aquarium would be within the right range. Seems like my reading are at least +/- 4ppm assuming the middle one is correct. Could be upto +/- 8 ppm if the lowest one is correct.

Range: 0.0 to 75.0 ppm (as NO3–)
Resolution 0.1 ppm
Accuracy @ 25°C (77°F) ±2.0 ppm ±5%


It's got to be the reagent. I'll buy a new pack and see.

If anyone else feels like doing 3 tests back to back to compare results I'd be interested to see what you get!

I have had this issue for a while now. I have been a chemist for over 30 years so I am pretty sure I can run a simple nitrate test consistently. I even use a balance to see how much reagent is coming out eat time and usually get between 0.18-0.19 g. I have not seen a pattern with the amount of reagent dispensed. I set my timers and shake vigorously for two minutes, I use eye glass cleaning towels to wipe the cuvette. I am using the large vial in the all in one tester. I read it twice today back to back and got 5.9 and then 8.5. Not really loving the variability but I take the higher of the two readings each time. I do not think I ever get close to the same value twice.

 

[areefer01]

I do not think I ever get close to the same value twice.

Here are some back to back tests I ran the other day.

 

[JeffB418]

THere are 2 items critical to this tester. 1) 2 minutes after you add reagent and 2) shake vigorously during those 2 mins. try to hit 2 mins exactly, no more no less. over reaction at this stage will cause off readings. and not enough reaction/shaking will also affect results. the best method I've found to get consistent readings is to use a micro stirrer assembly like this one https://www.autoaqua.com.tw/en/ss-100.html That unit will mix the sample in the same way required for this test I've been told by people much more knowlegable than I about the science behind this test.

 

[smoorman11]

Has anybody done a cap study for the weight of the reagent powder. To see if there are variations in the amount of reagent in each "envelope"?

 

[BriDroid]

Most people find the LR procedure very tedious. I use the LR method because my system runs low in nitrate and I don’t check nitrate that often. The tedious test procedure is tolerable

It is a pain, but my system seems to run low even dosing ammonium/urea, so once a week or two isn't so bad just to make sure my dosing isn't going haywire.