School Me on Hanna 713 PO4 Checker

[Buzz1329]

This may well be the most boring post ever posted on RC. But here goes. I’ve gone through dozens of tests (and packets of reagent) with the Hanna 713 PO4 Checker, but still can’t seem to get consistent results. For example, on the last batch of tests (3 tests per tank), I got results ranging from .23 to .03 on one tank and .09 to .0 on the other

Obviously, the problem is my use of the test kit and not the kit itself since so many are using it successfully. Maybe if I describe my methodology, someone can school me on what I’m doing wrong.

1. I open test reagent packet using scissors. I shake/collect the reagent into one corner of the packet, crimp the end of the packet that the reagent has collected into so that I can dump the reagent into the test tube more easily.
2. I clean the outside of test tube with cloth provided with kit.
3. I fill test tube with water from dt, using syringe, shake tube, and discard water.
4. I then fill test tube with 10 ml of water from dt using same syringe.
5. When rinsing and filling test tube I grasp tube with the cloth provided.
6. I press the button on the checker, and when it flashes add/press C1, I place the test tube containing 10 ml of dt water into checker.
7. I again press the button and when I get the add/press C2 message, I remove tube from checker and pour reagent into tube. This can take up to 20-30 seconds. And despite my best efforts to get all the reagent into the tube, I find that after completing the test, and I shake out the reagent packet, there is always some reagent left in the packet.
8. Using test kit cloth to grasp the test tube, I then vigorously shake the tube for 1 minute and 45 seconds, Because it takes so long to add reagent to the tube, I find that if I go beyond 105 seconds, the checker may reset itself and I have to start from scratch. At 90 seconds I slow shaking to allow bubbles in tube to dissipate. From my perspective it sometimes looks like there is some undissolved reagent floating in the tube. And obviously, my calculation of seconds may not be 100% accurate.
9. I then put test tube back into checker, press and hold button and wait for 3 minute countdown.

So what am I doing wrong?

Is there another way of getting reagent into the test tube more efficiently?

Is there some problem with the way I shake the tube to mix the reagent?

OMG, you must stop whatever you’re doing and help me immediately! Or . . . what? My tanks will continue to have the same PO4 levels they’ve always had. Actually, I think you can take a few deep breaths, maybe deal with some pressing personal issues, and then – if you feel like it – shoot me some tips.

Thanks,

Mike

 

[bertoni]

I haven't used that device personally, so I can't help with the details. A lot of people have been successful with it. A fair number have had problems, particularly with individual batches of reagents. You might want to contact Hanna with the batch numbers, to see what they have to say. My guess is that you are dealing with a bad batch of reagents, but the meter might have issues, too.

 

[Buzz1329]

I haven't used that device personally, so I can't help with the details. A lot of people have been successful with it. A fair number have had problems, particularly with individual batches of reagents. You might want to contact Hanna with the batch numbers, to see what they have to say. My guess is that you are dealing with a bad batch of reagents, but the meter might have issues, too.

Thanks, as always.

What do you use to test for PO4?

Mike

 

[mitchrapp]

Check this thread out:

http://www.reefcentral.com/forums/showthread.php?t=1961215

Cutting the side and top of the reagent packet and forming a funnel really works well to get it all out. There's a video in that thread. Now that I look at the packet, they do outline where to cut - just never knew that meant to cut both the top and side off.

 

[Fish Keeper82]

You do basically what I do with a few exceptions:

1. I tap on the reagent packet very good before I open it to pack it all at the bottom. I then open the packet and pinch it right in the middle of the cut and spread it from this mid point to a top and bottom leaving a some what diamond shape as if your looking in the packet .Then I re-tap very lightly on packet with intent to get the reagent all in the middle on the bottom. I have very little reagent that does not make it in the vial this way. I started doing it this way when I found it seemed too much reagent would stay in the corners.

2.When you push button for add/C1 the lid must be closed since there will be added light from top that will effect this zero calibration.( you didn't specify so thought id mention it.) This might be the only thing that would get those far off readings. Bubbles and not adding all reagent I don't think would get you that wide a range, so I would guess reagent is bad.
3. I only shake vigorously for about 1 min, then I slowly invert the vial the rest of the time. I find this gets rid of most of the bubbles.
4. Shouldn't make a difference but I gather the test water from the exact same part of the tank.
5. I take readings before first feeding of the day seeing how most all PO4 is from food.

Hope this helps.

keep in mind the accuracy of this tester +/- .04
attached are my results for last 2 months ( the larger .05 in brown letters is day I changed GFO after the .05 reading and you can see the decline and rise in the next tests... I will be changing GFO soon again)

 

[Fish Keeper82]

Here is my full chart since my initial PO4 testing when I had my rocks leaching PO4. It shows consistency in readings of the meter.

 

[bertoni]

The Hach and Salifert kits have worked well enough for me, although I'm not particularly worried about getting a very precise number. People have gotten credible results from the Hanna equipment, too. You might just need a bit of customer support.

 

[outssider]

you don't need to shake vigorously .....watch the hanna video on you tube...

There are a lot of ways to get all the reagent out of the packet in less than 5 seconds...you just need a better technique and practice...

 

[Fish Keeper82]

you just need a better technique and practice...

Even if the OP had a few bubbles and missed a bit of reagent I doubt the reading would be as far as he is having. I only say this cause I had trouble my first few tests and results were still close.

The checker in use has an accuracy of +/-.04ppm.

Lets say his actual PO4 was .04.... the test could show a result of anywhere from 0 to .08 . That's as close of accuracy this test is rated for.

But his reading was in range from .23 to .03. Worst case lets say the .03 is at the far low tolerance. That would mean .11 would be the high with an actual of .07ppm. To have a reading 4 times the rated accuracy at .23 would indicate to me a severe error in testing( which by the posted steps I doubt) bad reagent or a bad checker.

The most my tests accuracy have been from each other( back to back tests) has been .02 difference.

 

[Buzz1329]

Thanks everyone for your advice.

I'll use your suggestions and see if I can get usable results. .

Mike

 

[dkeller_nc]

One thing that is important is that you re-insert the vial with reagent and water into the meter in the same orientation as you did for the blank (with tank water only). That's pretty easy to do - simply orient the "10mL" mark toward you both times.

As for getting the reagent into the tube, I find it much simpler to cut a small piece of wax paper, crease it down the middle, and pour the reagent packet onto it before turning the meter on. That allows you to set the edge of the crease onto the lip of the vial, and pour all of it in when the time comes. Others have ordered micro-funnels for this purpose. I've worked in various chemistry laboratories for a few decades, so I suppose others may find the wax paper more difficult and the micro-funnel easier, but I haven't found it necessary.

 

[outssider]

One thing that is important is that you re-insert the vial with reagent and water into the meter in the same orientation as you did for the blank (with tank water only). That's pretty easy to do - simply orient the "10mL" mark toward you both times.

As for getting the reagent into the tube, I find it much simpler to cut a small piece of wax paper, crease it down the middle, and pour the reagent packet onto it before turning the meter on. That allows you to set the edge of the crease onto the lip of the vial, and pour all of it in when the time comes. Others have ordered micro-funnels for this purpose. I've worked in various chemistry laboratories for a few decades, so I suppose others may find the wax paper more difficult and the micro-funnel easier, but I haven't found it necessary.

I tap the reagent into a corner of the packet then I cut the reagent packet diagonally...kind of make a funnel out of the diagonally cut packet by creasing opposite sides then pour the reagent out the crease ....but actually I like your idea better...,

 

[hogfanreefer]

I never shake as that creates bubbles that you may not see that affect the result. I use the timer on my cell phone and invert the tube back and forth for 2 minutes. The reagent is most often in excess if I understand the test clearly. The 3 minute count down allows any undissolved reagent to settle out of the way of the photometer.

That said, I changed to the 736 ultra low range and have had MUCH more consistent results (usually within 0.01 or less). I believe it's a better unit.