saifbham
New Member
Hi all,
This may be helpful to some here.
Recently my Salifert test kit gave me incorrect readings consistently, possibly due to evaporation concentrating one or more reagents.
Hence I (partially) made my own calcium test kit in the lab to check against the commercial kit. I say partially as I am still using reagent "Ca-1" (but I believe I know what to substitute it with). At the very least I think this is helpful in making sure our Calcium test kits are still giving us accurate readings.
The kit consists of the following:
-1M NaoH solution (pH adjustment, magnesium precipitation)
-0.01M Disodium-EDTA (titrant)
-Reagent "Ca-1" from Salifert Calcium test kit (BUT I think it can be substituted with Eriochrome Black T) (indicator).
Instructions:
-Add 2 ml of saltwater from tank
-Add the indicator (enough to give a strong colour usually seen with comercial test kits)
-Add 0.28-0.3ml of 1M NaOH (using a 1ml syringe)
-Titrate by adding the EDTA solution in a dropwise manner.
-Use this equation to calculate Ca2+ concentration in ppm: =
("volume of titrant used"/2)*0.01*1000*40
Stock solution for the kit (I am sure many can work this out but I thought I would post this to save some time):
-1M NaOH: Dissolve 4g in100ml water.
-0.01 EDTA: Dissolve 3.723g of Disodium EDTA dihydrate in 1L of water.
The EDTA solution has to accurately made as it is the titrant.
I have tested this kit with my tank water and the results match with those from a brand new Salifert kit. I need to make a reference calcium solution to further test this. I have not purchased Eriochrome Black T yet to test it. I will update if and when I have obtained some. It would be very much appreciated if someone could also test this. Also (if you can obtain some) testing Eriochrome Black T as an indicator would be very useful.
Thanks and happy reefing,
Saif
This may be helpful to some here.
Recently my Salifert test kit gave me incorrect readings consistently, possibly due to evaporation concentrating one or more reagents.
Hence I (partially) made my own calcium test kit in the lab to check against the commercial kit. I say partially as I am still using reagent "Ca-1" (but I believe I know what to substitute it with). At the very least I think this is helpful in making sure our Calcium test kits are still giving us accurate readings.
The kit consists of the following:
-1M NaoH solution (pH adjustment, magnesium precipitation)
-0.01M Disodium-EDTA (titrant)
-Reagent "Ca-1" from Salifert Calcium test kit (BUT I think it can be substituted with Eriochrome Black T) (indicator).
Instructions:
-Add 2 ml of saltwater from tank
-Add the indicator (enough to give a strong colour usually seen with comercial test kits)
-Add 0.28-0.3ml of 1M NaOH (using a 1ml syringe)
-Titrate by adding the EDTA solution in a dropwise manner.
-Use this equation to calculate Ca2+ concentration in ppm: =
("volume of titrant used"/2)*0.01*1000*40
Stock solution for the kit (I am sure many can work this out but I thought I would post this to save some time):
-1M NaOH: Dissolve 4g in100ml water.
-0.01 EDTA: Dissolve 3.723g of Disodium EDTA dihydrate in 1L of water.
The EDTA solution has to accurately made as it is the titrant.
I have tested this kit with my tank water and the results match with those from a brand new Salifert kit. I need to make a reference calcium solution to further test this. I have not purchased Eriochrome Black T yet to test it. I will update if and when I have obtained some. It would be very much appreciated if someone could also test this. Also (if you can obtain some) testing Eriochrome Black T as an indicator would be very useful.
Thanks and happy reefing,
Saif
