Salifert v. Seachem Ca Test Results

I want to know what are the true results.The sales person does not know why.She has used both test kits,both at home on her 2 salt tanks and at the tanks at the store.She told me she always gets a 100 ppm diff and she doesn't know why.I like the salifert syringe system better.You don't have to get ride of the air plus the drops are smaller,but whats the point if its off.I also happened to run into a customer with a cal meter.He has had it 2 months and it is starting to malfunction.He did not want to return it as I advised him.Since I had so many problems with it.I do hope they solve that bug.I liked the meter and if they fixed the problem I would buy another.
 
This sort of issue is why I frequently caution folks to not over interpret the results of tests.

I want to know what are the true results.

In my analysis of the calcium meter:

Electronic Calcium Monitoring
http://reefkeeping.com/issues/2005-04/rhf/index.htm

The Salifert kit was reasonably close to what I believe the actual value of my standard to be:

"For initial testing I chose to use as the "standard" a sample of artificial seawater that was mixed to an approximate salinity of S=35. I mixed a 44-gallon batch using Instant Ocean artificial salt mix and reverse osmosis/deionized (RO/DI) water to a conductivity of 52.7 mS/cm, and allowed it to settle for three weeks. I then proceeded to measure its calcium concentration by ICP-AES (inductively coupled plasma-atomic emission spectroscopy, an $80,000 analytical instrument. I was somewhat disappointed with my inability to use this sophisticated technique to get a precise answer. Despite taking five different samples and analyzing them at eight different emission wavelengths using two different calibration methods (five standard additions of known calcium concentrations to each sample, as well as comparison to a fixed 1000 ppm commercial calcium standard), I was unable to get consistent values. Some of the samples were acidified or filtered through submicron filter membranes to determine if solid materials were impacting the result (they were not). Overall, I took more than 200 measurements, each involving three replicate observations of the emission intensity. Nevertheless, the result was not very satisfying, with a substantial variation occurring between the different values. The average of every measurement taken was 336 ppm. With the uncertainty involved, however, I'd conclude that the true value was probably 340 Ã"šÃ‚± 40 ppm. I also measured the same sample once with a Salifert brand test kit and got 330 ppm calcium."
 
Randy,

I am not sure how to interpret your findings. "once with a salifert".... does this mean a single test? Could this just have been lucky? Do you have any idea why measuring the calcium in seawater is so hard?

Bean
 
Sure, it may have been a total fluke. :)

Measuring calcium in seawater with a test kit is hard because there are alot of other ions around that can interfere and are themselves present at variable concentration, such as magnesium and carbonate. I suspect that the Seachem standard contains neither, and so isn't a true seawater test, but rather just a check on performance.
 
So it would be safe to infer testing against a standard only shows that accuracy of the reagents/kit are "correct" with regards to the standard but may deviate in unforseen ways in the presence of seawater.

It gives me the feeling that a "target" calcium level is someplace between 300-500 and any place in there is good. If you get precipitation, then your a bit high.

Bean
 
So it would be safe to infer testing against a standard only shows that accuracy of the reagents/kit are "correct" with regards to the standard but may deviate in unforseen ways in the presence of seawater.

Yes, that would be my interpretation. :)

I'd try to keep calcium above 380 ppm, and then maintain adequate alkalinity, and things are generally OK. :)
 
Is there no reference that can be made to test the kits?. A tsp of lime in a gal? a known Ca supplement(esv, kent etc?) maybe a glass of milk:)
 
Hobster, I find a big bowl of Haagen Dazs mango ice cream works wonders.

Oh wait, you want to test calcium. I meant for everything else ;)
 
MiddletonMark said:
Hobster, I find a big bowl of Haagen Dazs mango ice cream works wonders.

Oh wait, you want to test calcium. I meant for everything else ;)
Click to expand...

I am more a of a Breyers Mint CC my self.
We have mass quanities of Mangos here if you ever want some shipped:) Had I known, I would have brought some last time we were up there .(In laws live in Madison and surrounding areas)
 
Will trade frags for Mangos :D

Holy cow, I'd say do it next time. They remind my of happy days living in Pakistan as a grad student a decade ago.
 
I guess I will test with both kits and settle for a 50 ppm inbetween.If I stay above the 400 ppm mark I am fine.My friend has the american pharm test kit and he says its supposed to be a good test kit for $11.99.I will ask him to bring it over just to see what that tests at.
 
i have had similiar results with the last 2 salifert CA kits when compared to Seachem's CA kit. My water tested ~400 with the Seachem kit and ~500 with the salifert. At first i thought i just got a bad salifert kit so i bought another and had similiar readings. To be honest im not too concerned as all my SPS are doing great but it sure would be nice to know what is going on with the CA kits these days.

Scott
 
Steve/Plumb,

I can get the Seachem Ca test kit in the US for $25 or less. I think the $45 CDN then would be about right? Maybe not.

Please let us know the results from American Pharmacy kit.

I think you're right, like Randy wrote. If you're over the target value, you're okay.
 
I usualy buy stuff from the U.S. its half the price.I found the Seachem for as low as $20 us.The US dollar is low about 25 to 30 cents so it would cost me about $26 cdn plus shipping.I send the stuff to my cousin and pick it up.His wife just came here I should have ordered it but I wanted to know.My friend came by I didn't have a chance to ask for his test kit but I will try and pick it up.I will retest with all 3 when I get it.
 
Randy/Chemists-

Is it possible that one of these kits actually reports mg/l instead of ppm? Would the difference between mass/volume measurement to the ratio of ions be enough to account for the discrepancy?
 
I kinda have a theory about this... Its about the air present in the sringe...

You see ( I am at the university at this moment so I dont have the salifert test instructions )...

When I fill the sringe the air present in it its about 0.2 ml ... If I dont drop anything in my test sample ... and I go to the test comparison table, it says that 0.8 ml = like 100 ppm Ca ( or something like that , right??? ) that has always bugged me a lot , and I dont know whats it about... I will try to see the instructions at night and then ill report to you .
 
Ive always liked the american pharm test kits and found them to read the same as salifert for alot less money.Last time i tested the calcium kits back to back they were real close.Also i tested a seatest kit at the same time and it was way off.When salifert and american pharm read 440-460 the seatest read 370.

Also as far as nitrate kits, i think the american pharm blows the salifert away.
 
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