Attention: Habib / Salifert Mg Test?

[skidrow52]

I usually wash the syrine and containers with RO water and let it dry before the next use, I think if I dont do so the dried residue of the reagent may alter the results! I dont know if what I do is correct or no, any comments?

It's not necessary to clean the syringes. That could be a cause of issues, depending on what you're using. RO/DI might be fine, but I still would just empty them and leave it at that.

 

[Randy Holmes-Farley]

Rinsing the syringe is a fine plan. Wiping the outside if there is a lot sticking to it may be useful. The inside fluid won't evaporate or matter, and the outside should generally not have much fluid on it to evaporate, but if it does, it won't generally get into the next test except after dilution in the stock acid, so the effect will be pretty minor (IMO).

 

[tegee]

IMHO...I don;t think any test kit should give higher readings when new and slowly give lower readings as the test kit is used up. I really like the ease of use of Salifert, but my patience is wearing thin. I have slowly moved to test Calcium and Mag with Elos and Alk with Hanna.

As has been mentioned many times, hobby test kits are frustrating at best. But I have become frustrated with all the excuses of Salifert and this evaporation theory???

 

[rayjay]

I think the evaporation of the titrating fluid is the most likely reason for what is happening.

 

[bertoni]

I agree that evaporation could be the key problem here. My kits seem to last a long time, but I keep all the solutions capped whenever possible. When I draw a syringe full of titrant, I open the bottle, draw the solutions, and then cap the bottle right away, for example. I'm not sure that's necessarily going to solve everyone's problems, though.

 

[tegee]

I agree that evaporation could be the key problem here. My kits seem to last a long time, but I keep all the solutions capped whenever possible. When I draw a syringe full of titrant, I open the bottle, draw the solutions, and then cap the bottle right away, for example. I'm not sure that's necessarily going to solve everyone's problems, though.

I do the same and with the Cal and Mag I get inconsistant reading from beginning of test kit until the end. And this issue with the "newer" Mag kit has got me really questioning the accuracy of Salifert kits. So I am going to have to accept it being off from their older version 150-200ppm. So my Mag reading, and subsequent adjustments in Mag solutions have been for not???

As mentioned, I will continue to use Salifert, but only for convenience and rely much more on Hanna and Elos for Alk, Cal, Mag and Phos.

 

[tegee]

I agree that evaporation could be the key problem here. My kits seem to last a long time, but I keep all the solutions capped whenever possible. When I draw a syringe full of titrant, I open the bottle, draw the solutions, and then cap the bottle right away, for example. I'm not sure that's necessarily going to solve everyone's problems, though.

I do the same and with the Cal and Mag and I still I get inconsistent reading from beginning of test kit until the end. I REALLY take great care when using any test kit to proper close lids and completely clean after each use.

And this issue with the "newer" Mag kit has got me really questioning the accuracy of Salifert kits. So I am going to have to accept it being off from their older version 150-200ppm. So my Mag reading, and subsequent adjustments in Mag solutions have been for not???

As mentioned, I will continue to use Salifert, but only for convenience and rely much more on Hanna and Elos for Alk, Cal, Mag and Phos.

 

[jmsalt1]

I agree that evaporation could be the key problem here. My kits seem to last a long time, but I keep all the solutions capped whenever possible. When I draw a syringe full of titrant, I open the bottle, draw the solutions, and then cap the bottle right away, for example. I'm not sure that's necessarily going to solve everyone's problems, though.

Like Tegee, I consider myself close to obsessive compulsive about closing and tightening bottles of reagents when in use and between tests, regardless of brand. I keep the kits away from extreme temps., high humidity, and don't keep them in a stand with a sump or any of the other excuses that have been floated to explain why the Salifert kits seem to have shorter shelf life's once in use than is implied by what I am beginning to believe are irresponsibly long purported expiry dates. Why not just come clean and disclose that they are too generous once they have been put into typical use by hobbyists? I don't doubt that the kits might be able to sit unopened for years and still be effective but the clock starts ticking once they are put to use. Set honest expectations for the kits because at this point it is hurting their credibility. I think the addition of reference solution / sample is a good start. Not sure if that is becoming a standard part of any of the Salifert kits but thought Habib might have mentioned it for CA or MG.

 

[rayjay]

If you are not using the test kit all that often so that it's use spreads out more than a year, consider that the evaporation is going to take place even with the best of intentions.
With cap on and near full bottle there is little air in the bottle. As used, the amount of air increases.
Now, as you uncap the bottle and insert the syringe you disturb the air inside, allowing for some of the saturated air to escape and new dryer air to enter.
Over many uses, this process gradually but exponentially increases the amount of evaporation leading to a stronger solution giving lower results.