Hannah phos checker timing

[Fr4nkthet4nk]

I have the same problem. I use the two cuvettes.

 

[MnFish1]

Personally I think the 2 cuvette method makes sense. Using the 2 curettes in each test it should be easy to see If one or the other gives disparate reaulta. If so use one if not use two

 

[O'l Salty]

I use a magnetic stirrer for about 30 seconds.

 

[dede]

@dede The above is how you perform the method and why its done that way. By only allowing 3 minutes for the sample to react, you are getting an erroneous value.

I think there is a lot of confusion about timing here. I am shaking my vial probably about 2 1/2 minutes as it probably takes me 30 seconds to put the reagent into the vial. Then I add it back into the checker which then takes another 3 minutes to give the results.

@sghera64 Are you saying we need to shake the reagent in the vial for 5 minutes, my checker would time out by then. Or are you saying from the time the checker displays the C2 to the actual time the checker gives you a numerical reading needs to be at least 5 minutes, which makes more sense.

Or to be more clear, you need to mix the reagent in your vial for 2 to 3 minutes, then it sits in your checker for an additional 3 minutes at which point it will then display a numerical value.

 

[sghera64]

I think there is a lot of confusion about timing here. I am shaking my vial probably about 2 1/2 minutes as it probably takes me 30 seconds to put the reagent into the vial. Then I add it back into the checker which then takes another 3 minutes to give the results.

@sghera64 Are you saying we need to shake the reagent in the vial for 5 minutes, my checker would time out by then. Or are you saying from the time the checker displays the C2 to the actual time the checker gives you a numerical reading needs to be at least 5 minutes, which makes more sense.

Or to be more clear, you need to mix the reagent in your vial for 2 to 3 minutes, then it sits in your checker for an additional 3 minutes at which point it will then display a numerical value.

What I’m saying, and how I’m trying to clarify Hanna’s instruction sheet, is that the reagent needs to be in contact with the sample water for 5 minutes when the instrument makes its reading. How you get there may vary.

Many people simply add the reagent to the sample (at that point the 5 minute countdown begins). They mix the sample for 1-2 minutes, but start the 3:00 countdown timer 2 minutes after the reagent is added to the sample.

The critical point is: reading is taken 5 minutes after reagent goes into the sample water.

Hope that clears things up.

 

[Pmj]

Yes - you'd need a bigger sample size - and a broader range of potential values'. (ie. maybe the results are comparable when the PO4 is 35 or so - but wildly different then the PO4 is 150 (or 10). There just seems (to my small brain) no reason not to do the test the way the manufacturer tells you to do it.

My values are normally critically low, as in reading 2-10, as my PO4 crashes dealing with dinos for the past year, but I also does heavily at times, so I've seen the high end too. It's always basically what I would expect based on the amount dosed.

The reason to not follow it exactly is obvious, the timer shutting off the unit. If it didn't do that, I don't think there would be so many threads over the years about this unit. I don't know about everyone else, but on other tests, you get a feel for how it works and don't have to follow everything to the T. For example, shaking in between each reagent drop for alk tests, or a nitrate test getting pretty much where it's going to be very early on (like a minute in) as opposed to the 3 min or w/e it tells you to wait. Just my experience. If you are not confident in the results on any test, you should always follow the instructions to the T or confirm with new reagents or another test.

 

[Sleepydoc]

I have to agree about the auto shut-off time being too short; simply changing it from 3 minutes to 4 minutes would have made a world of difference.

I was using 2 cuvettes as that made the process timing much easier, but then I read that that can actually introduce errors, so now I’m back to racing to make sure it doesn’t take too long. I use the same process others have - I have my reagent packet open and ready, so I don’t waste any extra time, so it’s really not an issue for me. In spite of this minor annoyance, I still think the Hanna Checker is the best phos meter out there.

One question, though - after reading the control sample (C1,) you can either press and hold the button which starts a 3 minute timer, or press and release the button which does the reading immediately. Since you have to use the same cuvette, the soonest you can get a reading is 5 minutes (2 minutes mixing + 3 minutes for it to ‘develop.’) What’s the point of the press and release function?

 

[sghera64]

I have to agree about the auto shut-off time being too short; simply changing it from 3 minutes to 4 minutes would have made a world of difference.

I was using 2 cuvettes as that made the process timing much easier, but then I read that that can actually introduce errors, so now I’m back to racing to make sure it doesn’t take too long. I use the same process others have - I have my reagent packet open and ready, so I don’t waste any extra time, so it’s really not an issue for me. In spite of this minor annoyance, I still think the Hanna Checker is the best phos meter out there.

One question, though - after reading the control sample (C1,) you can either press and hold the button which starts a 3 minute timer, or press and release the button which does the reading immediately. Since you have to use the same cuvette, the soonest you can get a reading is 5 minutes (2 minutes mixing + 3 minutes for it to ‘develop.’) What’s the point of the press and release function?

You are correct in that it does not matter how you get to the five minute end-point: 1.) manually track the time and press and release the button while C2 is displayed, or 2.) press the button while C2 is displayed and hold until the 3 minute timer starts after 2 minutes of mixing.

The value of the 3 minute timer could be that once you and your hands are freed up after 2 minutes of mixing, you are free to move on to another task (such as testing Alk).

 

[Sleepydoc]

You are correct in that it does not matter how you get to the five minute end-point: 1.) manually track the time and press and release the button while C2 is displayed, or 2.) press the button while C2 is displayed and hold until the 3 minute timer starts after 2 minutes of mixing.

The value of the 3 minute timer could be that once you and your hands are freed up after 2 minutes of mixing, you are free to move on to another task (such as testing Alk).

No - my point was that if you are supposed to use the same cuvette for the control and the test and the device turns off after 3 minutes then there is no way you could ever use the press and release function since the soonest you could possibly test after running the control is 5 minutes.

(Edit - thinking about it some more, I'm guessing either it may be a standard control chip in the device or they figured out later on that you need to use the same cuvette)

 

[Sallstrom]

Haven't read all post so maybe this is posted already. Anyway, I do the tests like this.

Adds water to two cuvettes. Close the one that will be used in the checker (I always use the same one).
To the other one I add the powder and mix until the test water is clear.
Then I clean the outside of the first cuvette, put it in(10ml mark facing the way I want) and do the first step.
Then empty that cuvette and fill it with the water mixed with powder(using a clean pipette).
Clean it, put it in(facing the same way), and press again.

Hope you'll understand even though my English isn't the best

/ David

 

[Greenstreet.1]

I follow the instructions.

 

[sghera64]

I follow the instructions.

Rebel!

 

[Greenstreet.1]

Rebel!

[emoji23]
I see no reason to change what works for years and I have the po4 & ulr.
Well I do one thing differently I cut open the reagent before I do anything.

 

[mike werner]

I thought that was not recommended due to difference in cuvette shape/refraction

I read the same thing.for what it's worth I tried the 2 min.shake and a 1 min shake.i found no difference in the readings I get.i'm not sure 2 min. is necessary but that is what hanna recommends.