Another calcium test reading high

[crpeck]

Hi Habib,

I have been using a Seachem calcium test for the last year and just bought a Salifert Ca test to replace it since I've been using the Salifert for Alkalinity.

The discrepancy between the Seachem and the Salifert Ca is 100 points. Seachem 380 ... Salifert 480+. The Seachem kit came with a reference solution of 400. When I test the reference solution with the Seachem, I'm right on at 400. The Salifert puts it off the chart at 500+.

I've done each test 3 times and double checked the directions ... I really think I'm doing it right. The only place the directions are not clear is after you add Ca reagent #2. After the powder (#1) it says "Don't mix yet", but then it never tells you when to mix. I'm assuming you mix after adding the 8 drops of reagent #2.

The batch number on my Ca-3 is: T0403-D NV

I just got it last week from Premium Aquatics online.

Have there been any problems with these tests? Is there some other way I can independently check it?

Thanks for your help!
Cathy

[dragon_slayer]

Cathy
not sure if a new kit has changed but all my Ca test kits have been 6 drops not 8.

hth
kc

[crpeck]

Thanks ... I just checked the directions again. They say that this is a new version, Febr. 2004 and say you can't interchange the reagents with the older version. Maybe I got new instructions with old reagent?? The instructions definitely say 8 drops.

Good idea though ...

Cathy

[Salifert]

What you did sound OK for the new version.

Just to be sure, you did 2 ml of sample right?

If you did then I think the Seachem's standard is probably not OK, you took also 2 ml from it I assume.

We can re check that batch for you.

FWIW I'm not aware of any problems with the calcium kits, which was one of your questions.

[crpeck]

Thanks for checking.

Yes, I used 2 ml of sample and also 2 ml of the reference liquid. It seems odd that the Seachem tests the reference at the proper amount .. 400 but the Salifert does not. I guess theoretically if they developed the reference using the same wrong standard as the test, then both would be consistently wrong. It's kind of scary to think I've been off that much on my calcium for so long.

I appreciate the double check. I think I will test the reference using another test as well and see how it turns out.

Thanks SO much!
Cathy

[dragon_slayer]

Cathy

why dont you mix up some new salt mix and test it. that way you'll get a better idea which one is correct.

kc

[Salty Irishman]

Kathy, I to have recently experienced the same thing! I seem to think that the seachem kit with a calibration sample is the correct reading. I can't imagine that my calcium is over 500 which is what the Salifert kit is telling me, which is a test for strontium and
tests for calcium along the way. Seachem is the calcium test I will rely on . Keep us posted as to what your further test reveal. Thanx

[crpeck]

I just tested the SeaChem reference (400) with a Red Sea Ca test and also got 400 ... or close to it. The Red Sea is a little harder to pick up the color change, which is why I quit using it. But if anything, the tendency with the Red Sea is to keep going with the titrant to get a noticable color change so if anything I would be more likely to test too high than low.

I redid the Salifert again ... going very slowly and carefully and giving it a little longer to change color between drops. It started going from pink to purple at 430, but didn't go blue until at least 450.

So right now, it seems to me that the Salifert is still testing high but when I give it more time to change color between drops it doesn't test as high as when I did the test quickly.

The Red Sea test I had here was pretty old. To be fair, I should probably buy a new kit of some kind and run it again. I'm starting to run out of the reference solution doing all these tests.

[Salty Irishman]

Cathy,

So you're giving the reagent more than 20 seconds after each drop to change color and that lowered the end result by 50. If that's the case I'll have to give it a try and let ya know what I find. I've run this test many times trying to see what I may have been missing but never really tried simply giving the reagent more time to interact and change color before adding the next drop.

As I stated eariler this test kit is to test Strontium but gives calcium levels before you actually get to the Stromtium, and always the calcium comes back 100 higher than the Seachem, and I'm never able to detect Strontium even after I have just dosed the tank, so I am leary about the whole test. If there is something I'm missing along the way it is also affecting my final Strontium reading and I would really like to resolve what is going on.

Thanks for the input, I will try slowing down as well and let ya know how I make out.

[crpeck]

I wouldn't say I gave it 20 seconds between each drop. I went fast up to about the 300 -350 reading and then went really slow between drops. Probably more like 8 seconds or so. It sounds like we're talking about 2 different test kits as well. Salifert has such a great reputation I was thinking it was just a batch problem rather than a test problem.

Good Luck and let me know what happens.

Cathy

[Salifert]

Cathy:

FYI I'll be able to answer this thread later today.

[Salifert]

There was one more person asking questions for the same batch number and we could not find back the archieved reagents for that batch.

Today we made another attempt and could still not find them.

I checked today many batches for the new version kit as you have it and they are all OK.

A MO will see if they have still that batch you have and run tests comparing with other batches. I hope they can do this today or tomorrow and will let you know.

Still I would like that you get another kit just to be extra sure.

Please e-mail name and address to salifert@hotmail.com


FWIW I would not rely on the Seachem standard bcause that might have been calibrated using their kit.

Also it might not be marine water at all. Does it get very turbid just like the aquarium water after adding the first liquid reagent?

If not then it certainly is not a marine water matrix and if it get's turbid it might be.


Habib (Salifert)

[crpeck]

Thanks, Habib

I'll look at the reference more carefully with another test and let you know. I appreciate all your efforts. I knew there was a reason I like Salifert

It will be helpful to get this figured out as I'm in the process of correcting a Ca and Alkalinity imbalance that accidentally occurred because I was trying to use dosers that malfunctioned for my 2 part additive. I need to know as precisely as possible these levels so I can straighten out the balance in my tank.

Thanks again!
Cathy

[Joboo]

Been searching this forum because I also am having issues with the SAME batch. I see that Cathy also tested with Red Sea and received simliar readings as the Seachem.

Habib, are you saying that BOTH of these testkits as well as the reference sample are inaccurate?? Why is it always a problem with the OTHER company?? And why is it that the only batch you can't seem to find is the one in question?

I not trying to be difficult but it seems that its always the OTHER companies fault. I think you guys need to start looking internally for the answers.


Thanks
John

[Habib]

John:

In your other thread in Reef Discussion forum I already told that we can't find archieved samples of that particular batch.

Here is some of the communication with a MO company of approx. 2 weeks ago. I have left his name out.


quote:
--------------------------------------------------------------------------------

Salifert wrote on 07/01/2004 10:48 AM:
xxxxxxxx:

Which batch numbers did you use?
Comparuison of the T0403-D NV with any other Ca-3 reagent batch ending with NV would be of tremendous help.

We made a last attempt to find the archieved ones but did not find them.

If you used another batch number as well then we can compare the results. I just checked several other new version batches and they are OK.

TIA

Habib


quote:
--------------------------------------------------------------------------------




And why is it that the only batch you can't seem to find is the one in question?


If you are suggesting that we are trying to hide something then you are wrong. The above pm illustrates this.

I not trying to be difficult

Not at all.

but it seems that its always the OTHER companies fault

I have not said that. In your other thread you say that Oceanic gave you a calcium value for that batch of 485 ppm and you find with the Salifert a 13% higer value.

I told you that difference can a.o. also be caused by them mixing to another salinity than what you did. I requested a RC member yesterday the phone number of Oceanic (and got it) because I want to talk with them about their testing procedure and at which salinity etc.

Behind the scene we are doing much more to find the correct answers.


Hope that explains a few things.

[Habib]

John:

Perhaps the following might be of some help.

Do you mix the Oceanic salt according to the instructions or do you have to add more salt per water volume to get the desired salinity (your refractometer reading).

TIA

[Joboo]

Originally posted by Habib
John:

Perhaps the following might be of some help.

Do you mix the Oceanic salt according to the instructions or do you have to add more salt per water volume to get the desired salinity (your refractometer reading).

TIA

I mix until I get the desired results testing with my Refractometer at 2 hours after mix and 24 hours. What does this have to due with the Red Sea and Seachem acheiving the same results and your test 50 ppm higher?

[Habib]

What does this have to due with the Red Sea and Seachem acheiving the same results and your test 50 ppm higher?

Nothing

[Joboo]

Habib,

I'm just trying to justify spending $23 for a test that may not be accurate. I think to really clear this up I am going to look around for a couple of reference samples. Hopefully if I can find more than two or three I can get more accurate results.

Thanks
John

[Joboo]

Originally posted by Habib
John:

Perhaps the following might be of some help.

Do you mix the Oceanic salt according to the instructions or do you have to add more salt per water volume to get the desired salinity (your refractometer reading).

TIA

Please explain why this is important?

[Habib]

Originally posted by Joboo
Please explain why this is important?

I will do so after my kids are gone to bed.

It is almost 7 pm over here in Holland and the kids are very naughty.

I'll be back in an hour or so.

[crpeck]

Hi John,
It makes sense to me that any salt, including Oceanic is going to formulate the Calcium and everything else to a standard salinity that may be lower. If you add more than the standard half cup per gallon to achieve a higher salinity, then calcium and everything else will probably be a tad more concentrated as well on a per gallon basis.

That may explain why the Oceanic tests high, but it still doesn't explain why the test kits get such different results. Habib was sending me a different Salifert batch so I can test the two against each other. I haven't done anything yet about trying to find different reference solutions ... let me know what you find out with that.

I have a chemistry graduate student watching my tank while I go out of town next week. I was talking to her about some of the problems I had getting consistent pH and calcium readings and she offered to run some tests for me in the lab at the University.

I'll let you know how those turn out.

Thanks for your help, Habib and thanks for the bump on this John. Good to know I'm not crazy or doing something stupid in running the test.

Cathy

[crpeck]

p.s. Habib ... it's good to know that kids all over the world are the same in the respect that they get naughty any time you're on the computer or the phone. Must be universal.

[Habib]

Cathy:

was sending me a different Salifert batch so I can test the two against each other.

I had directed your MO to this thread and asked to send you one without any costs. I'll check with them since I have not had a reconfirmation.

Must be universal.

Fortunately it is universal.

[Habib]

Originally posted by Joboo
Please explain why this is important?

Cathy did give a nice explanation.

The more salt you add per gallon of water the higher the salinity will be but also everything (except pH) will increase.

Roughly adding 10% more salt the salinity will increase by 10% so will the calcium, magnesium and alkalinity.

So when IOceanic says 485 ppm calcium to you then we need to know at what salinity.

I had an hour ago a lengthy call with Oceanic and have spoken with Matt. He seemed to recall your case (or perhaps it was someone else)



Oceanic salt has normally (according to them) a calcium concentration of 420 - 480 ppm and the recent batches are at 480 ppm.

This when the salt is mixed with RO water giving a s.g. of 1.0215 - 1.0225 at 77 F

A 10% higher salinity would correspond to approx. 1.0237 - 1.0247 at the same temperature.


Now let's look at your data (from your other thread):

The specific Gravity for the water sample was 1.025(maybe 1.0245, hard to tell) using a refractormeter recently calibrated with same RO/DI water.

Bye the way, All test kits were well in the expiration date range. Salifert test kit was purchased back in April while the other 2 testkits purchased yesterday.

Here are the results

Salifert - 550ppm
Hagen - 640ppm
Aquarium Pharmaceuticals - 480ppm - 500ppm


If the s.g. is at a comparable temperature etc than the calcium value should be approx. 10 % higher than the 485 ppm (reported by Oceanic).

That corresponds to 535 ppm. This corresponds IMO quite well with the Salifert.


FYI I discussed the high level of calcium in Oceanic and they agreed with me because they have formulated it for a lower salinity than most reefers use it. I advised them to lower the calcium somewhat.


HTH