Salifert Test Kits bad after a year?

[george9]

Hi all,
To preface this -the salifert kits I've been using are the same since November 2021. They all expire in early 2024 so I figured they were good.

I recently bought another 3 pack of the alk, mag and ca tests since my I needed a new alk test and it was cheaper to buy all 3. Well I am noticing some disparities in results thats suggesting my old kits likely are going bad.

Last week I tested mag with my old kit and it was 1200 which is too low for my tank so I slowly have been adding a bit more mag to get the level up to 1350. It was up to 1350 according to the old test as of early this week. I test again today and its right back down to 1230 which makes 0 sense. I then used the new mag test and it shows a 1410ppm concentration which is a bit high but more likely after all of the mag I have been adding. I did test again with the old test kit and get a completely different result of 1370 which tells me the higher value is more likely than the lower one and that this old mag test is garbage.

Same issue with calcium. I tested with the old kit and got 410 which I thought was a bit low (I usually am at 450). Tested with the new one and got 480 ppm which is a tad high.

My alk tests (new and old) are matching okay.

I noticed the new salifert mag test doesn't have the old powder any more and is more like the alk kit. Is it something with these two powder based tests (ca and mg) that go bad? Is it good practice to just not trust a test kit thats been in use for about a year? Maybe I should just be buying new kits every 6-8 months or so.

I also noticed on the new tests that when the plunger is filled to 1.0mL, the actual liquid level in the chamber varies. With the old tests, all of the liquid lines would be at .85mL when the top of the plunger hit 1.0mL. With the new tests, I noticed the liquid level is all over the place between each 3 test kits when the plunger sits at 1.0mL. Is this a potential problem?

Thanks for any advice you can provide!

 

[MnFish1]

Hi all,
To preface this -the salifert kits I've been using are the same since November 2021. They all expire in early 2024 so I figured they were good.

I recently bought another 3 pack of the alk, mag and ca tests since my I needed a new alk test and it was cheaper to buy all 3. Well I am noticing some disparities in results thats suggesting my old kits likely are going bad.

Last week I tested mag with my old kit and it was 1200 which is too low for my tank so I slowly have been adding a bit more mag to get the level up to 1350. It was up to 1350 according to the old test as of early this week. I test again today and its right back down to 1230 which makes 0 sense. I then used the new mag test and it shows a 1410ppm concentration which is a bit high but more likely after all of the mag I have been adding. I did test again with the old test kit and get a completely different result of 1370 which tells me the higher value is more likely than the lower one and that this old mag test is garbage.

Same issue with calcium. I tested with the old kit and got 410 which I thought was a bit low (I usually am at 450). Tested with the new one and got 480 ppm which is a tad high.

My alk tests (new and old) are matching okay.

I noticed the new salifert mag test doesn't have the old powder any more and is more like the alk kit. Is it something with these two powder based tests (ca and mg) that go bad? Is it good practice to just not trust a test kit thats been in use for about a year? Maybe I should just be buying new kits every 6-8 months or so.

I also noticed on the new tests that when the plunger is filled to 1.0mL, the actual liquid level in the chamber varies. With the old tests, all of the liquid lines would be at .85mL when the top of the plunger hit 1.0mL. With the new tests, I noticed the liquid level is all over the place between each 3 test kits when the plunger sits at 1.0mL. Is this a potential problem?

Thanks for any advice you can provide!

Not sure what you mean - about the liquid level. However - I would buy a third test (or ask your LFS to test it) - that will give you a better idea what's going on?

 

[george9]

Not sure what you mean - about the liquid level. However - I would buy a third test (or ask your LFS to test it) - that will give you a better idea what's going on?

Thinking that’s the best way to narrow this down with a third test.

On the salifert test, you’re supposed to draw in the test solution into the syringe until the plunger is at 1.0mL. I remember watching a YouTube video about the correct way to perform the test and they said when the plunger is at 1.0 mL, the liquid level between the plunger and the air gap should be at .85 mL which they are on my old test kits.

With the new test kits, im not sure if the plungers are slightly different but when I draw the test liquid to 1.0 mL on them, the liquid level varies between .8mL and .9ml and is never consistent anymore. Trying to think back hard to college chemistry but not sure if this has a bottom line impact to the test results? lol

 

[stevolough]

There certainly can be a difference each time. I always draw a little in and then put plunger back down a couple of times then I draw it in slowly till fluid level is on 85 and plunger on 1. I’ve seen a variation of up to .10 without doing it slowly and making sure plunger is bottomed out. Not really a huge problem if it’s a little off as long as you are doing it the same way each time.

 

[MnFish1]

You just have to account for the air Many people fill the whole syringe - thinking it's the right way - in fact - (hard to explain for me) - you ignore the dead-space.

 

[george9]

There certainly can be a difference each time. I always draw a little in and then put plunger back down a couple of times then I draw it in slowly till fluid level is on 85 and plunger on 1. I’ve seen a variation of up to .10 without doing it slowly and making sure plunger is bottomed out. Not really a huge problem if it’s a little off as long as you are doing it the same way each time.

I usually draw and release a few times to make sure I’m not getting any air but I can never draw in a consistent .85.

The alk syringe will go to .81, the calcium will go to .86 as well as the magnesium one. Maybe it comes down to tiny differences in manufacturing between the different syringes?

I tested the old syringes with the new tests and they draw to .85 just like they do with the old liquids. The differences between the new and old syringes is throwing me off and if the solutions are the same it will lead to test error for sure I am thinking. Maybe I am worrying too much about it but minute .1 mL differences change the results of the test otherwise it wouldn’t be a huge deal. The instructions themselves say to just be concerned where the plunger level is and don’t mention how large the air gap should actually be

 

[MnFish1]

I usually draw and release a few times to make sure I’m not getting any air but I can never draw in a consistent .85.

The alk syringe will go to .81, the calcium will go to .86 as well as the magnesium one. Maybe it comes down to tiny differences in manufacturing between the different syringes?

I tested the old syringes with the new tests and they draw to .85 just like they do with the old liquids. The differences between the new and old syringes is throwing me off and if the solutions are the same it will lead to test error for sure I am thinking. Maybe I am worrying too much about it but minute .1 mL differences change the results of the test otherwise it wouldn’t be a huge deal. The instructions themselves say to just be concerned where the plunger level is and don’t mention how large the air gap should actually be

I think you might be doing it incorrectly

 

[george9]

I think you might be doing it incorrectly

What is the correct way to do it? The way I understood it is you need to draw the test solution into the syringe until the bottom plunger hits 1.0mL. Despite the instructions not saying anything about this, my concern is how each syringe seems to have a slightly different size air gap between the plunger and actual liquid level that seems to come down to differences in the syringes themselves or the pink tips. The instructions simply say the air gap is normal but don’t say what size the air gap should be

 

[Dan_P]

Hi all,
To preface this -the salifert kits I've been using are the same since November 2021. They all expire in early 2024 so I figured they were good.

I recently bought another 3 pack of the alk, mag and ca tests since my I needed a new alk test and it was cheaper to buy all 3. Well I am noticing some disparities in results thats suggesting my old kits likely are going bad.

Last week I tested mag with my old kit and it was 1200 which is too low for my tank so I slowly have been adding a bit more mag to get the level up to 1350. It was up to 1350 according to the old test as of early this week. I test again today and its right back down to 1230 which makes 0 sense. I then used the new mag test and it shows a 1410ppm concentration which is a bit high but more likely after all of the mag I have been adding. I did test again with the old test kit and get a completely different result of 1370 which tells me the higher value is more likely than the lower one and that this old mag test is garbage.

Same issue with calcium. I tested with the old kit and got 410 which I thought was a bit low (I usually am at 450). Tested with the new one and got 480 ppm which is a tad high.

My alk tests (new and old) are matching okay.

I noticed the new salifert mag test doesn't have the old powder any more and is more like the alk kit. Is it something with these two powder based tests (ca and mg) that go bad? Is it good practice to just not trust a test kit thats been in use for about a year? Maybe I should just be buying new kits every 6-8 months or so.

I also noticed on the new tests that when the plunger is filled to 1.0mL, the actual liquid level in the chamber varies. With the old tests, all of the liquid lines would be at .85mL when the top of the plunger hit 1.0mL. With the new tests, I noticed the liquid level is all over the place between each 3 test kits when the plunger sits at 1.0mL. Is this a potential problem?

Thanks for any advice you can provide!

If your syringe fill is not the same or variable, that is the likely source of variation in test results.

You will really need to purchase a reference standard to test your tests. Multi-parameter versions, i.e., PO4, NO3, Ca, etc, are available so you can test several test kit types.

 

[elysics]

As long as in the end the air gap is still in the syringe and it didn't come out at some point instead of the liquid when you were doing the test, then it doesn't matter how big it is, the liquid that came out is the same either way

 

[Randy Holmes-Farley]

I show the correct way to use ANY syringe here. There should be air in the syringe representing air in the tip.

Reef Chemistry Question of the Day #161 Using a Syringe

Reef Chemistry Question of the Day #160 I have just drawn tank water into a syringe with a tip (shown below, including a blowup of the barrel). The blue coloration shows where the fluid is. When I started to draw fluid in, the tip and syringe were empty and the plunger was all the way in...

www.reef2reef.com

 

[rockyb]

They do tend to be off after 8-12 months

 

[Cory]

Male sure your pink tip is on tight and the same for both test kits.