TEST METER FOR TESTING NITRATES

[Rick Mathew]

That's really cool. There's clearly an effect, but it is small enough we can ignore it. I'm interested in why the trend is negative for the 5ppm sample.

That is an interesting question....I might consider moving out beyond 5ppm and see what happens...

 

[EmdeReef]

Just got my nitrite checker:

- Red Sea - between 2-4
- Salifert - between 2-5
- Hanna - 3.94

I’ll do a few more and will send an ATI test, but seems pretty good for now. tonight is my fuge lights on day so expect nitrates to be much lower in the morning.

 

[Rick Mathew]

Just got my nitrite checker:

- Red Sea - between 2-4
- Salifert - between 2-5
- Hanna - 3.94

I’ll do a few more and will send an ATI test, but seems pretty good for now. tonight is my fuge lights on day so expect nitrates to be much lower in the morning.

Great...Thanks for sharing the results...will be interested in your ATI results...

 

[Dr. Dendrostein]

Randy: After you asked me this question I decide to go back to my original work on the HI-764 Salinity Effect and retest it. This time I did the experiments paying much more attention to the accuracy of my work and I got some surprising results...Below are the results

EFFECTS OF SALINITY ON NO3 MEASUREMENTS USING HI-764 CHECKER

OK…I just completed the repeat experiments of the Effect of Salinity on the nitrate test procedure using the HI-764. I did this experiment in total 2 times because I did not believe my first results. The second set of experiments confirmed the first set. The chart below shows the results graphically.

The procedure was as follows:

1) Make a 50 ppm N03 standard from RODI water and HACH N03N Standard

2) Mix RODI water with the 50 ppm standard to get the desired ppm for the test (1,3,5)

3) Weigh and mix the required amount of reagent grade sodium chloride to get the desired salinity in PPT (0,29,31,52)

4) Measure the salinity to confirm. (Milwaukee Refractometer)

5) Run the Nitrate test described above using HI-764 Hanna Meter. (3 replicas at each level)…36 total tests including replicas

6) Record and plot and analyze the result

PREPARED SAMPLES

As you can see the slopes are “0” which I interpret to mean no effect as a function of salinity level!


So what is different from my previous work, which indicated a salinity effect?



1) First work was done with a different meter HI-736 & HI-96702

2) My first work with the HI-764 and salinity effects was not carefully done. It was just checking to see if there was an effect and there is probable error in the work. I expected an effect so when I saw the differences in the measurements I concluded there was one and let it go at that.

3) The batch of Red Sea Reagents are different from previous measurements

4) Much more care was taken in this last set of tests then previous work.

5) The moon was full when I did the previous work! :rolleyes:

All of that being said I am going to put this out there for comments…any Thoughts?

I saw your test regiments. I wonder if you need to freeze then store in frig. Reason, if any bacteria present, with time will decalibrate regiments. Freezing kills bacteria. I wonder.

 

[Rick Mathew]

I saw your test regiments. I wonder if you need to freeze then store in frig. Reason, if any bacteria present, with time will decalibrate regiments. Freezing kills bacteria. I wonder.

That is an interesting question! When i make up a batch of standards I only make up what is necessary for the test sequence...the picture is actually the leftovers from the sequence...However I do keep larger quantities of the master standard (50 ppm) which would be subject to bacteria...I am going to pop that in the frig.....thanks for the tip

rick

 

[SeaDweller]

I saw your test regiments. I wonder if you need to freeze then store in frig. Reason, if any bacteria present, with time will decalibrate regiments. Freezing kills bacteria. I wonder.

Freezing doesn’t kill all types of bacteria.

 

[Dan_P]

Rick, I see that you caught our attention:-)

As the need to monitor high nitrates has arisen, and diluting has issues, I resorted to the Hanna Total Cl2 Checker to measure the Red Sea color. Its readings correlate very nicely to the Hanna LR Phosphate Checker (I have a standard curve for that one) where the ranges overlap. Since I am interested only in monitoring nitrate going away in my carbon dosing experiments, the accuracy is sufficient.

By the way, I treated myself to a Pasco visible spectrophotometer. No major scientific insights with it yet but it helped me develop a KMnO4 chemical oxygen demand test using the Hanna Total Cl2 Checker. Checkers still easier to use and my preferred tool.

 

[JimWelsh]

I treated myself to a Pasco visible spectrophotometer.

I'm jealous. I should be paying more attention to this thread than I currently am, but this sounds like some really great stuff you guys are doing over here!

 

[Rick Mathew]

Rick, I see that you caught our attention:)

As the need to monitor high nitrates has arisen, and diluting has issues, I resorted to the Hanna Total Cl2 Checker to measure the Red Sea color. Its readings correlate very nicely to the Hanna LR Phosphate Checker (I have a standard curve for that one) where the ranges overlap. Since I am interested only in monitoring nitrate going away in my carbon dosing experiments, the accuracy is sufficient.

By the way, I treated myself to a Pasco visible spectrophotometer. No major scientific insights with it yet but it helped me develop a KMnO4 chemical oxygen demand test using the Hanna Total Cl2 Checker. Checkers still easier to use and my preferred tool.

Dan: That is awesome...will be interested in how the new spectro adds to your knowledge and or flexability


rick

 

[Miguel Medina]

[QUOTE = "Rick Mathew, post: 5510716, miembro: 66447"] Y = 0.04581221 * x + 0.5017498

Eso sería increíble ... Gracias

rick [/ QUOTE]
¿Puedes ayudarme a entender esta fórmula para compararla con Ppb and move it to know the no3?

 

[Rick Mathew]

[QUOTE = "Rick Mathew, post: 5510716, miembro: 66447"] Y = 0.04581221 * x + 0.5017498

Eso sería increíble ... Gracias

rick [/ QUOTE]
¿Puedes ayudarme a entender esta fórmula para compararla con Ppb and move it to know the no3?

The "X" in the formula is the reading you get from the meter during the test procedure. When you put that meter value in the above formula in place of the "X" the answer you get is the NO3 level in ppm not ppb.

Example: Test Meter Reading Results (X) 50 2.79 ppm NO3 (Y)= 0.04581221 * 50+ 0.5017498

Hope this helps

 

[JimWelsh]

Example: Test Meter Reading Results (X) 50 2.79 ppm NO3 (Y)= 0.04581221 * 50+ 0.5017498

Careful -- I just might call the sig fig police on you. That's a heck of a lot of decimal places you got going on there.

 

[Rick Mathew]

The more the merrier...;)... my motto..

 

[Miguel Medina]

Me ha ayudado a entender mejor que Rick era simple, con los traductores se ha vuelto más complicado.
Sé que está trabajando recientemente con el HI-736, ¿sería correcta esta formulación?
1º A partir de una lectura de 125.
Y = -.000003258494 x (250) +.01296094 x (125) +.0534317 = 0.65 ppm

 

[Rick Mathew]

Me ha ayudado a entender mejor que Rick era simple, con los traductores se ha vuelto más complicado.
Sé que está trabajando recientemente con el HI-736, ¿sería correcta esta formulación?
1º A partir de una lectura de 125.
Y = -.000003258494 x (250) +.01296094 x (125) +.0534317 = 0.65 ppm

Actually the 250 value should be 15625 ...it is 125 squared (125*125)....However see comments below

Miguel: For the HI-736 I did some additional work I would recommend a much simpler regression formula which for the most part returns equally good values Y=0.0125 * x where x is the meter reading

Using your meter reading of 125 this would give a value of 1.62 ppm using the older regression and 1.56 ppm using the new regression formula...the difference of .06 is not significant and the equation is much simpler and because it is linear you can use a dilution procedure to expand the range of the meter...Although I have not verified that because I switch my work to the HI-764 ..Hope this helps

 

[Miguel Medina]

ok. Rick

 

[Randy Holmes-Farley Verified Community Expert]

Careful -- I just might call the sig fig police on you. That's a heck of a lot of decimal places you got going on there.

Maybe the meter is that good. :D

 

[Potatohead]

Could you not use the diluted Red Sea results (the one you use one ml of sample water, 15ml RO water, and multiply results by 16) with this method? Multiply your results by 16 at the end to have the scale go higher? Or would it not work right?

Or instead of one ml x 16, use 2ml x 8, or 4ml x 4, etc.

 

[Rick Mathew]

Maybe the meter is that good. :D

If only!!!... :-)

 

[Rick Mathew]

Could you not use the diluted Red Sea results (the one you use one ml of sample water, 15ml RO water, and multiply results by 16) with this method? Multiply your results by 16 at the end to have the scale go higher? Or would it not work right?

Or instead of one ml x 16, use 2ml x 8, or 4ml x 4, etc.

I don't see why not ...Beer's Law says it should be so..who am I to argue with him :-)...

My procedure is do the measurement using standard amount (16mL) ...If the reading exceeds the meter range then dilute the tested sample by 1/2 and remeasure...multiply meter results by 2 and plug results into regression formula ...the reaction color appears to be stable for several minutes...seems to work