Testing Alkalinity, specifically with Salifert Tests

[ReeferMadness80G]

I’ve noticed that on more than one occasion with different different kits (only salifert) that often times I will test alkalinity and get a result, it won’t usually be what I’m expecting, so I say, “let’s test it again” I run the test once more and get the result I expected initially, so I test again to get best 2 out of 3 and end up with the same result as the 2nd test. Why does the first test always seem void? I do the exact same thing every time. I’ll try and break it down for you a different way if you’re still a little lost.

(Decide to test Alkalinity)
1. Grab test kit
2. Administer test
3. Read results
“Hmm, I thought for sure I would’ve tested around 7.7-8 dkh, let me test again to be sure”
(Repeat above steps 1-3 exactly)
“I got 7.8 dkh this time, maybe I should test again to be sure”
(Repeat above steps 1-3 exactly)
“ I got 7.8dkh again, weird but I guess that’s my results”

Anyone else experience this?

 

[hybridazn]

Are you rinsing the volute with rodi water? If using tap or even tank water it could be enough to effect the 1st test.

 

[ReeferMadness80G]

Are you rinsing the volute with rodi water? If using tap or even tank water it could be enough to effect the 1st test.

I use tap. But if I do the same with all the test tubes would they still cause error on the first test only?

 

[hybridazn]

I use tap. But if I do the same with all the test tubes would they still cause error on the first test only?

No it should be the same across the board then.

Is it possible that there is still residue from the previous rounds of tests lingering before the next test causing the 1st test to be different?

 

[ReeferMadness80G]

No it should be the same across the board then.

Is it possible that there is still residue from the previous rounds of tests lingering before the next test causing the 1st test to be different?

Not really. I rinse them out after each test and I rinse them again before each test, albeit it’s tap water, I also give them a quick drying with a paper towel. I’m going to run a test now after rinsing with ro water to see what that yields

 

[ReeferMadness80G]

Ok, new test yielded same as tests 2 and 3

 

[cmcoker]

Are you rinsing the titration syringe? I imagine if there is a drop or 2 of the reagent left and it dries out, but mixes with the new titrant that could maybe cause a shift. How far off is the first reading generally? A lot or a little?

 

[ReeferMadness80G]

Are you rinsing the titration syringe? I imagine if there is a drop or 2 of the reagent left and it dries out, but mixes with the new titrant that could maybe cause a shift. How far off is the first reading generally? A lot or a little?

No I don’t rinse the syringe ever, it’s usually off by
0.4-0.8dkh

I thought I should add, I usually give the syringe a few plunges up and down in the solution before I suck up 1ml for my testing. I do that to get air bubbles out.

 

[red13]

Not sure if it will help, but I always pre rinse the vials and syringe that I fill the vials with tank water. I get pretty consistant results.

 

[ReeferMadness80G]

Not sure if it will help, but I always pre rinse the vials and syringe that I fill the vials with tank water. I get pretty consistant results.

Thanks, I will have to try that. My results are consistent, however It’s usually after that initial test.

 

[Reefltx]

No I don’t rinse the syringe ever, it’s usually off by
0.4-0.8dkh

I thought I should add, I usually give the syringe a few plunges up and down in the solution before I suck up 1ml for my testing. I do that to get air bubbles out.

With salifert, it’s not correct to do that.

 

[ReeferMadness80G]

With salifert, it’s not correct to do that.

Hey thanks, what specifically is not correct? so I can fix that. Thanks bud

 

[Blanch]

It happens the same to me with magnesium test of salifert. I dont know why.

 

[nigelmansell]

Hey thanks, what specifically is not correct? so I can fix that. Thanks bud

Plunging the thingy up and down to get rid of the air

 

[ReeferMadness80G]

Plunging the thingy up and down to get rid of the air

Why would that be wrong? I get the air bubbles out yeah, but the air pocket at the top bc of the tip remains the same. I’m not sure how getting exactly 1ml in my syringe is wrong vs having a few air bubbles inside of it being right.

 

[Blanch]

As you said, i do exactly the same things for the first measure than the followings but the real measure is the second one. Everytime that happens i contrast the results with the nyos magnesium test and they have the same values.

 

[madweazl]

Why would that be wrong? I get the air bubbles out yeah, but the air pocket at the top bc of the tip remains the same. I’m not sure how getting exactly 1ml in my syringe is wrong vs having a few air bubbles inside of it being right.

The bubbles in the syringe dont matter; additionally, squirting the reagent that was in the tip back in the reagent may contaminate the reagent.

 

[ReeferMadness80G]

The bubbles in the syringe dont matter; additionally, squirting the reagent that was in the tip back in the reagent may contaminate the reagent.

I have thought of that. However, let’s remember my results are correct and consistent after initial test 1. But I am taking that into consideration and will rinse syringe with ro water now

 

[Charterreefer]

I’ve noticed that on more than one occasion with different different kits (only salifert) that often times I will test alkalinity and get a result, it won’t usually be what I’m expecting, so I say, “let’s test it again” I run the test once more and get the result I expected initially, so I test again to get best 2 out of 3 and end up with the same result as the 2nd test. Why does the first test always seem void? I do the exact same thing every time. I’ll try and break it down for you a different way if you’re still a little lost.

(Decide to test Alkalinity)
1. Grab test kit
2. Administer test
3. Read results
“Hmm, I thought for sure I would’ve tested around 7.7-8 dkh, let me test again to be sure”
(Repeat above steps 1-3 exactly)
“I got 7.8 dkh this time, maybe I should test again to be sure”
(Repeat above steps 1-3 exactly)
“ I got 7.8dkh again, weird but I guess that’s my results”

Anyone else experience this?

I'm assuming you are using the high resolution test.
I sometimes get a reading where I feel I should add one more drop to get a pink instead of a reddish color or it might look like there's a hint of blue left. Could it be from that? Maybe your on the fence (about the color) with the first test. That's what happens to me sometimes.

 

[madweazl]

I have thought of that. However, let’s remember my results are correct and consistent after initial test 1. But I am taking that into consideration and will rinse syringe with ro water now

There is no way to know if the results are correct or not. Regardless of which tests you perform in the future, discard the remaining reagent once the test is complete.