Frustrated Red Sea with titration syringe

[b4tn]

I cant seem to get consistent levels in the titration syringe's. Instructions say that the air gap is normal under the plunger to allow for the .1 ml in the tip. My issue is that the gap changes anywhere from .05-.2 and is different every time I take the tip off to clean it. When one drop can make such a big difference in color changes I feel like this would really mess with the tests. Does anyone have any tips to fix this? I was thinking about using the one syringe and tip I have that seems to be the most consistent and just use it for all the tests.

 

[wildwilly1]

I too had trouble with this . what I do is draw reagent into syringe with tip on . then remove tip empty syringe and draw back into syringe 1ml . then put tip back on seems to work good that way I have exactly 1ml in syringe and tip is full at start of test and end of test so only have to read what was actually used from the syringe. hope this helps

 

[redfishbluefish]

With the plunger all the way at the bottom of the syringe, draw in titrant solution up past the 1 ml mark. Lift the syringe out of the solution and expell titrant to the 1 ml mark. By doing this you have "compressed" the extra air to a set volume that shouldn't change as you do the titiration. That volume of air is the volume of the tip on the syringe. That's why you don't have to get rid of it.

Now here's one more tip that has to do with good laboratory practices.....don't return any titrant to the mother bottle once you are done with the titration. This reduces (eliminates) the likelyhood of contaminating the mother liquid. Just shoot it into the vial once you've made your final reading.

Hope this helps.

 

[miyags]

All I know is the air gap in my alk is almost twice as large as my cal. Quality control has gone down hill, on almost everything in this hobby.Its ridiculous to buy three different test kits, and pick the middle number. Thermometers are the same way.

 

[Randy Holmes-Farley Verified Community Expert]

I think you may have a misunderstanding of how syringes work.

I cant seem to get consistent levels in the titration syringe's. Instructions say that the air gap is normal under the plunger to allow for the .1 ml in the tip. My issue is that the gap changes anywhere from .05-.2 and is different every time I take the tip off to clean it. When one drop can make such a big difference in color changes I feel like this would really mess with the tests. Does anyone have any tips to fix this? I was thinking about using the one syringe and tip I have that seems to be the most consistent and just use it for all the tests.

It actually makes NO DIFFERENCE what the air gap is. You could put on a three foot tip, and the liquid would NEVER even enter the barrel, and yet the movement of the plunger will exactly draw in and dispense the amount of fluid that is measured by the travel of the plunger in the barrel. It is the difference in position of the plunger (often most easily measured by the movement of the end of the plunger) after movement that is the only thing that matters.

 

[jgraz]

I simply refuse to use the Red Sea alk kit. Or any kit that tells me that there is supposed to be air in the syringe. I used to have the same issue drawing up the titrant. The air gap was always different. And if that's the case then it's not possible that it accounts for titrant in the tip.

I have switched to the Hanna for alk and love it. It's pretty much the same price as a new Red Sea kit and refills are cheaper I believe.

And to be honest my back up is a API. IMO there is something to be said for ease of use and when I'm just ball parking it, API works just fine.

 

[jgraz]

I think you may have a misunderstanding of how syringes work.



It actually makes NO DIFFERENCE what the air gap is. You could put on a three foot tip, and the liquid would NEVER even enter the barrel, and yet the movement of the plunger will exactly draw in and dispense the amount of fluid that is measured by the travel of the plunger in the barrel. It is the difference in position of the plunger (often most easily measured by the movement of the end of the plunger) after movement that is the only thing that matters.

I understand your point here but how does that account for the fact that sometimes the air gap smaller or larger when using the same syringe and tip. While always bringing the plunger to the 1ml mark.

 

[Randy Holmes-Farley Verified Community Expert]

I understand your point here but how does that account for the fact that sometimes the air gap smaller or larger when using the same syringe and tip. While always bringing the plunger to the 1ml mark.

How tightly you push the tip onto the fitting will change the air gap. If using different tips, and if the tips are slightly different volumes inside, that will also change it.

 

[jgraz]

I have seen many threads questioning this air gap and how it seems to change from test to test. So since the air gap seems to be a point of contention how can it be avoided?
What I was doing was drawing up little titrant the turning the syringe upside down and pulling back on the plunger to move the air to the tip side. Then pushing plunger to expel all the air. Then drawing up more titrant to the 1 ml mark. If pushed the plunger all the way down the extra titrant stays in the tip. Aside from the obvious bit of wasted titrant is this sound?

 

[wildwilly1]

thinking bout switching to salifert for calcium and magnesium. any thoughts on these good or bad

 

[wildwilly1]

I have a hanna for alk and love it

 

[Randy Holmes-Farley Verified Community Expert]

I have seen many threads questioning this air gap and how it seems to change from test to test. So since the air gap seems to be a point of contention how can it be avoided?
What I was doing was drawing up little titrant the turning the syringe upside down and pulling back on the plunger to move the air to the tip side. Then pushing plunger to expel all the air. Then drawing up more titrant to the 1 ml mark. If pushed the plunger all the way down the extra titrant stays in the tip. Aside from the obvious bit of wasted titrant is this sound?

I agree that users are often confused, but it is not something to be concerned with. There is no desirability in avoiding the air gap. Ever (well, not that I can think of, anyway). It is part of how a syringe works and does not introduce error unless you try to eliminate it and are only partly successful (see below). Every chemist who designs kits and uses syringes knows this and plans accordingly. Some may not explain it very well in their instructions, but it is a fact, and some make this fact clear in discussions of syringes (Habib Sekha, owner of Salifert, for example). I've used syringes that cost hundreds of dollars each, and there is always air from the tip. It is just they way they are supposed to work. The volume of the air from the tip doesn't matter. The fluid drawn in will be exactly dispensed when the plunger hits the bottom of the barrel (if that's where you started drawing from). No more and no less.

What you did is OK as long as you leave the tip full, but it is no better than leaving the tip full of air. The worst thing you can do is somehow fill the air gap with fluid (as you did) and then going to pains to get that last bit of liquid dispensed, instead of leaving it in the tip. You will have dispensed more than the syringe volume of fluid. In short, the syringe volume plus the tip volume, leading to error.

 

[jgraz]

Thank you for the explanation. I don't go through pains to get all the liquid out I know it's there for a reason.

Oddly enough when using the tip on the Hanna Checker the reagent never even makes it into the syringe and I never questioned it at all. It's just these little tips that I just can't wrap my head around

 

[b4tn]

I think you may have a misunderstanding of how syringes work.



It actually makes NO DIFFERENCE what the air gap is. You could put on a three foot tip, and the liquid would NEVER even enter the barrel, and yet the movement of the plunger will exactly draw in and dispense the amount of fluid that is measured by the travel of the plunger in the barrel. It is the difference in position of the plunger (often most easily measured by the movement of the end of the plunger) after movement that is the only thing that matters.

You know, if I stop and think about it... you are right. The Gap would only make a difference if you where using the entire contents of the syringe. The distance that the plunger moves is the amount of fluid used. Makes total sense now lol

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, expensive pipettes (fancy syringes) have digitally adjustable plungers, but all of the liquid stays in the tip. You cannot eve see inside the barrel and no liquid ever enters the barrel. That way, you can discard the tip and not need to clean the pipette itself.

Here's what one looks like:

http://www.coleparmer.com/Product/T...pette_Pipette_F2_1_10_mL_Red_Each/EW-25013-24

 

[jgraz]

FWIW, expensive pipettes (fancy syringes) have digitally adjustable plungers, but all of the liquid stays in the tip. You cannot eve see inside the barrel and no liquid ever enters the barrel. That way, you can discard the tip and not need to clean the pipette itself.

Here's what one looks like:

http://www.coleparmer.com/Product/T...pette_Pipette_F2_1_10_mL_Red_Each/EW-25013-24

Maybe I'll pick a few up. Lol

 

[wildwilly1]

so u just draw the plunger up to the 1ml mark right

 

[Randy Holmes-Farley Verified Community Expert]

so u just draw the plunger up to the 1ml mark right

Yes, if it says dispense 1 mL, then you start with the plunger tight to the bottom, and pull it up until the lower end of the plunger aligns with the 1 mL mark.

 

[wildwilly1]

my plungers are not flat they have a nipple in the center so draw it up to the very bottom of the nipple or the bigger rpound part

 

[Randy Holmes-Farley Verified Community Expert]

my plungers are not flat they have a nipple in the center so draw it up to the very bottom of the nipple or the bigger rpound part

Right. Sometimes the bottom of the barrel is not flat but shaped to keep fluid from being trapped in a corner, as in the picture below. Usually the side of the barrel when pushed all of the way in lines up at 0 mL. So you take measurements from the leading edge of the plunger where it touches the side of the barrel (at tip of arrow), not at the leading tip of the plunger which can be further ahead in the middle of the barrel: