Mistake in Salifert NO3 Test Instructions????? Need input!

[Mike and Donna]

I just switched to the Salifert Prof-Test Nitrate test kit. Prior to the switch, I got a reading of 10 mg/l from a SeaTest kit (both on the low-range and high-range tests.)

I used the Salifert medium range procedure which calls for 1 ml of liquid plus the chemicals and got a reading of 25 mg/l NO3, and this was after a 50% water change! The reading today, after a 25% water change was about 20 mg/l...so it was "internally consistent."

Just for grins, I tried the low-range test (which uses 10 ml of water plus an additional chemical.) I got a reading of 2.5 mg/l (had done another 25% water change.) Hmmm...sort consistent with the old SeaTest trend. So, I thought, what if the medium range test was supposed to be 10 ml of water (like all the other Salifert tests) instead of 1 ml. I tried the test with 10 ml and voila! It tested about 2.5 mg/l,now consistent with the low-range Salifert and both of the SeaTest kits.

My conclusion is that there must be a misprint on the instructions.

Anyone have this experience?????

 

[M.E.Milz]

I have posted something about this apparent "error" in the testing procedure in the past, but never got any responses. I get the same inconsistancies (10 fold difference). So which do you think is correct, the low range or the medium range?

 

[danmhippo]

& I always thought my PO4 has always been high

I didn't ask that question fear of being treated as an ass!

 

[Mike and Donna]

My conclusion is that the instructions for the medium-range are wrong. If I use 10ml water instead of 1ml, then the readings of both the low-range and medium-range Salifert tests are consistent...and they are roughly the same as the SeaTest kits.

 

[ThePuz1]

Just some input on this subject. Up until recently I was using a test kit that came with my setup. My nitrates were always 10 to 20 ppm. I purchased Salifert NO3 test, and found my levels to be 75 to 100. I almost had a cow. I did 5 H2O changes {25%} in the last week.Level is now 25, But I never questioned the test. Makes alot of sense though.I couldnt figure out why there was such a big difference in the two tests. I feel so much better that this is consistant with other people.

 

[AnotherGoldenTeapot]

I've never had a problem with that test so I think the instructions are printed correctly. It makes sense to me that you need to use ten times more water in the narrow-range test too.

Does the SeaTest test measure the same form of nitrate as the Salifert one?

 

[Jimmy G]

I agree with AGT that the directions for the test are correct. Are you guys remembering to divide the result by 10 when you do the Low Range test?The Low Range test is to be used when you get a reading "significantly" lower than 10 ppm on the Medium Range test.

 

[bertoni]

The Salifert instructions have worked for me,
too.

 

[M.E.Milz]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote

I agree with AGT that the directions for the test are correct. Are you guys remembering to divide the result by 10 when you do the Low Range test?The Low Range test is to be used when you get a reading "significantly" lower than 10 ppm on the Medium Range test.

Yes. I have done this test dozens of times with different kits. I always end up with the SAME COLOR following either low-range test or the medium-range (wherein one uses 10 times the amount of the water sample). This results in the same ppm reading on the card (for exmple, 25 ppm). However, if then divide the result of the low-renge result by 10, you end up with a ppm reading that is 10 times less than the result of the medium-range reading (for example, 2.5 ppm).

I have even asked others to follow the preceedures exactly with their kit, and they have gotten the same 10 fold difference.

If you are in the habit of only using one of the testing preceedures, you would never discover the discrepency. In other words, if you always use the medium-range test, you might consistantly read 30-40 ppm. If you always use the low-range test, then you might consistantly read 3-4 ppm.

 

[Chucker]

Has anyone contacted Salifert about this apparent error? They're the ones who would know.

 

[VP]

Are both tests measuring NO3 or N-NO3. See paragraph 7 here for conversion rates: http://www.algone.com/nitrates.htm conversions from N-NO3 to NO3. This may be your problem. Just a thought.

[ February 26, 2002: Message edited by: VP ]</p>

 

[Anonymous]

In general, a low range titration will use a larger sample.

I'll give an example. Normally when testing for chlorides in boiler water, you draw a 100 ml sample from feed water (going into the boiler) and titrate it. If you don't detect anything but still have chlorides building up in the boiler, you do a low range test--the low range test requires a much larger sample. This sample is concentrated and then titrated.

Nitrate test kits aren't the most accurate out there. I would expect it to be within +/- 25% at best. Besides, NO3 isn't toxic--you don't need a pinpoint number--ballpark is good enough.

Ty

[ February 26, 2002: Message edited by: tyoberg ]</p>

 

[Mike and Donna]

The other difference with Salifert is the addition of a third chemical to the process. Have no idea what it is...


Guess I'll write to Salifert to try to get some insights. Unfortunately, I can't find a web site for them...and I don't speak Dutch.

Aber, Ich spreche ein bischen Deutsche. (Please don't flame! This is a remnant of high school German...and I was graduated in 1966!)

 

[Anonymous]

At lower NO3 concentrations, the effects of interfering ions will be greater to the point that they may significantly contribute to error--my guess is that the extra chem. is to mitigate that error, probably by getting rid of the interfering ions.

Ty

 

[AnotherGoldenTeapot]

Faulty reagents are a possibility I guess. I know that other manufacturer's have had problems with the shelf-life of their nitrate tests e.g. Seachem.

Any nitrite would interfer with the results too.

The instructions are correct though.

You either have a faulty test, are mistkan in its use (not likely), or you have "special" water that the test does not work with. My money is on you having a faulty test kit.

 

[Anonymous]

I dunno about that--he's using the low range test outside of the conditions that they recommend.

 

[M.E.Milz]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> The instructions are correct though.

You either have a faulty test, are mistkan in its use (not likely), or you have "special" water that the test does not work with. My money is on you having a faulty test kit.
<hr></blockquote>

I have ruled these possibilities out.

I have followed both of the recommended procedures (ie, low-range test & medium-range test) exactly, and have consistantly obtained a ten fold difference in the result between the procedures. The difference between 5ppm and 50ppm is not insignificant.

I have done this on different tanks (I have 3 tanks, 1 reef tank and 2 FOWLR tanks), and have obtained the same ten fold difference (except for the reef tank, which usually has zero nitrates).

I have asked at least one other person to conduct the same procedures on one of my tanks, using their own Salifert test kit, and they also obtained the same ten fold difference.

The only reasonable explanation is an error in the instructions for one of the two procedures.

What I have not done is compare the results of the Salifert test procedures with other test kits to determine which of the Salifert procedures is in error.

 

[Chucker]

Again, has anyone contacted Salifert? It is their kit after all.....

 

[bertoni]

Okay, I thought I remembered testing with both
ranges on the Salifert and getting them to agree,
but I tried them again anyway.

The tests worked as documented for me. They both
gave me (sigh) 2.0 ppm nitrate. Looking down
through the top, they weren't the same color at
all.

This isn't to say that you're doing anything
wrong. I've had tests give me implausible
results.

I also tested with a SeaTest kit and got 4.0 ppm.
Sigh. I'll try again with the SeaTest since
tonight was the first time I used it. Maybe
that's as close as we can expect?

[ February 28, 2002: Message edited by: Jonathan Bertoni ]</p>

 

[Mike and Donna]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by tyoberg:
<strong>I dunno about that--he's using the low range test outside of the conditions that they recommend.</strong><hr></blockquote>


How can you conclude that? Maybe the medium-range is being using out of range.....