Tunze Calcium Test Kit

[DavidL]

Hi,

I recentley purchased a Tunze Calcium (Macherey-Nagel) test kit and I am wondering how I convert my value to ppm Ca++. The instructions said that if using seawater it has to be diluted 1:5 so I used 1ml of tank water and 5ml of distilled water. After following the directions I got a value of about 12 d or 2.2mmol/l. The instructions offer no further help in converting to ppm Ca++.

I decided to try to find ppm Ca++ so what I did was convert d to mg/l CaCO3 (1d=17.8mg/l CaCO3). So 12d = 213.6mg/l CaCO3. I previously used the Lamotte Ca test kit so looking back at their instructions I decided to multiply 213.6mg/l CaCO3 by 5.16 to get a value of 1,102.176. Then to get to ppm Ca++ I multiplied 1,102.176 by 0.4 to get a value of 440.8ppm Ca++. Are the steps I took to get ppm Ca++ correct?

Also in a number of places on the net (even the Tunze website) I read that the Tunze Ca test kit was suppose to be a colormetric type of test kit however in the directions it decribes its method as complexometric titration. Are these two different types of methods? I have used Lamotte, Salifert, and Seachem Ca test kits before and the Tunze kit is much like the others- It has three steps like the others however in step two where Lamotte, Salifert, and Seachem would use a powder/tablet indicator Tunze has a liquid indicator.

Thanks,
David

 

[rvitko]

It is very similar to the Seachem kit- it is a titration type test. The modified instructions printed by Tunze which explain the dilution and the need for 3 drops of Sodium Hydroxide instead of two also included a table which you follow to get the result in ppm- same as Seachem or Salifert. Colorimetric is less accurate for Calcium than titration. All the other Tunze tests are colorimetric and I think it is just an oversight as it is the only titration kit we offer. If you need a copy of the modified seawater instructions let me know. The Machery Nagel instructions are for use by a water supply company in testing Freshwater.

 

[DavidL]

The modified instructions printed by Tunze which explain the dilution and the need for 3 drops of Sodium Hydroxide instead of two also included a table which you follow to get the result in ppm

I must not have recieved the modified instructions printed by Tunze. The instructions that came with the kit said to use six drops of sodium hydroxide instead of two. Can three drops be used instead of six to conserve the sodium hydroxide? Also there was not a table printed that showed how to get results in ppm Ca++. There were only some conversions listed (1d=1.25e=1.78f=17.8mg/l CaCO3=10mg/l CaO) which is why I thought we had to calculate ppm Ca++ ourselves.

If you need a copy of the modified seawater instructions let me know

Yes, please post a copy of the modified instuctions.

Thanks,
David

 

[rvitko]

It would be best if you could email me because I have to substantially reduce the image quality for RC.

 

[rvitko]

Your box should have included four pieces of paper- a small green business card size paper with lot number and ISO certificate. A paper instruction sheet from Machery Nagel, A laminated instruction card and a Tunze printed aquarium instruction set. Please send me an email and I can send you the original instructions as a jpg that isn't reduced in size or quality- it is about 200K.

 

[DavidL]

Hi,

I sent you a pm.

The test kit came with everything except the Tunze printed aquarium instruction set.

David

 

[rvitko]

No problem- I scanned the instructions in high res and they were about 500K- if you have any problem let me know. Sorry for the mix up- it does happen once in a rare while.

 

[DavidL]

Hi,

I did not find the instructions to be helpful. It says to dilute 20ml of tank water to 100ml of distilled water. The test tube looks to be able to hold only about 25ml. I assume that the instructions meant to keep it at a 1:5 ratio so 1ml of tank water to 5ml of distilled water would be ok? It also says to add three drops of sodium hydroxide while the laminated instruction card says to use six drops- how many should I really add? What will be the affect of adding three or six drops on the value I get (I used six drops the first time I used the kit)? Also the table looks to correspond to the directions for the regular fresh water test not for the dilution instructions for the saltwater test. For instance it would take atleast three titrations following table 1 until we would get to the mininum Ca++ values reefers like to keep their Ca at. I got a value of 12d(though Iââ"šÂ¬Ã¢"žÂ¢m not sure its the real value because at the end I accidentally squirted the titration solution out) that would correspond to a value of 86 mg/l Ca++. I used the Seachem Ca test a few days ago where I got a value of about 450 so I know its not 86. Should I multiply the mg/l Ca++ value in the table by 6 (dilution factor) which would equal 516. The instructions say nothing about this.

Thanks,
David

 

[rvitko]

OK, the Dilution of 20ml of marine water to 100ml distilled is done to achieve greater accuracy. Logically if you were off by 1ml here you would have far less accuracy issues than if you were off by 1ml and did 1ml to 5ml. After doing this dilution you collect a 5ml sample in the test tube. To this you add 3drops of sodium hydroxide, 2 drops of indicator and then you take the d and trace across table one on the instructions. With a reading of 12 you have 430ppm. It is all in the table- completely ignore the Machery Nagel instructions

 

[DavidL]

I think I finally understand. So you recommend to mix 20ml of tank water to 100ml of distilled water then shake it around and then put 5ml of the 120ml mixture into the vial and then go from there (to bad another mixing beaker wasnââ"šÂ¬Ã¢"žÂ¢t provided). As to reading from the table I see where my problem was, I was looking at table two not one- opps.

Thanks,
David

 

[rvitko]

Here is the simple way- A mason jar will have a 100ml line- to this add 4 test tubes filled to the line- 5ml. This is how I do it. It is essentially identical to the seachem but with a higher resolution and it does more tests.