I find that if I clear it a few times and press hard the last time, I get solution up to at least .85 and sometimes .90. So its clear, the amount of reagent in the syringe can easily vary from test to test depending on how you draw it out. It's just weird.
Salifert Testing Question
- Thread starter Eric45
- Start date
I find that if I clear it a few times and press hard the last time, I get solution up to at least .85 and sometimes .90. So its clear, the amount of reagent in the syringe can easily vary from test to test depending on how you draw it out. It's just weird.
Happyschneider
New member
Believe me, I have PhD in biochemistry. I know exactly what I am doing with these tests
the bubble plays no role. The alk and calcium tests are a titration test, that is the whole point.
cambo123
New member
This is exactly the confusion I was trying to point out before. There is no scale/mapping/adjustment that accounts for the bubble. The bubble doesn't matter. The reading from the syringe directly correlates to the amount of regent dispensed which directly correlates to your all/calc/mag
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cambo123
New member
Oops tried to edit slightly and double posted
RCS82
New member
This is the way i look at it. If you pull the syringe back to fill it with fluid, the space of air will be in there. Then add the fluid drop by drop to the test vial, and the air space is still there. It really doesn't matter if that space contained air or testing fluid or jello.
Rybren
Well-known member
Here's a quote from Randy Holmes Farley on the subject of syringes.
"Here's how to think about how a syringe works:
When the plunger is pushed all the way in, the leading edge of the plunger aligns with the zero mL marking. That is true of nearly every syringe I've seen. When you begin to use it, the tip and barrel are empty, with the tip containing air and the barrel occupied by the plunger.
As you draw back the plunger with the tip in a liquid, the plunger creates a vacuum between it and the liquid, drawing in the liquid. The movement of the plunger draws in exactly the amount of liquid equal in volume to the travel of the plunger backwards (or upwards). So you can track how much fluid is taken up exactly by the travel of the plunger against the volume markings, regardless of what you see with the fluid (assuming it is functioning properly).
Some of the drawn in liquid will be in the tip, and some (or perhaps none, if it is all in the tip) will be in the barrel of the syringe. If the volume of the tip is larger than the volume indicated by the movement of the plunger, none will show in the barrel. Many modern pipettes work this way to avoid contaminating the barrel of the device. The device stays clean and the tip is discarded after each use.
Now, when you go to dispense the liquid, the plunger is pushed in, and all of the liquid is dispensed and the air is pushed back into the tip.
If you mistakenly tipped the syringe upward during dispensing, and blew out the air before the liquid, then when you push the plunger all the way in, there will still be liquid in the tip, and you probably won't know how much so you end up with a mismeasurement.
In the medical world, it can be super important to not inject air into a patient's bloodstream. In that case, the syringe must first be overfilled. It is then tipped up and all of the air blown out and some liquid may be blown out until the end of the plunger is exactly aligned with the volume marking you want to dispense. The syringe in total now contains the amount you want to inject, plus the volume of the the needle. Then you inject and when done, the needle is still full of liquid in the exact amount as before injection, and like before, the amount dispensed is exactly determined by the movement of the plunger. So this situation is no different except that you start and end with a full tip/needle. In a non-injection setting, you start and end with an air-filled tip.
So it doesn't matter how much liquid you see in the barrel. Only the movement of the plunger is important, whatever the use. "
"Here's how to think about how a syringe works:
When the plunger is pushed all the way in, the leading edge of the plunger aligns with the zero mL marking. That is true of nearly every syringe I've seen. When you begin to use it, the tip and barrel are empty, with the tip containing air and the barrel occupied by the plunger.
As you draw back the plunger with the tip in a liquid, the plunger creates a vacuum between it and the liquid, drawing in the liquid. The movement of the plunger draws in exactly the amount of liquid equal in volume to the travel of the plunger backwards (or upwards). So you can track how much fluid is taken up exactly by the travel of the plunger against the volume markings, regardless of what you see with the fluid (assuming it is functioning properly).
Some of the drawn in liquid will be in the tip, and some (or perhaps none, if it is all in the tip) will be in the barrel of the syringe. If the volume of the tip is larger than the volume indicated by the movement of the plunger, none will show in the barrel. Many modern pipettes work this way to avoid contaminating the barrel of the device. The device stays clean and the tip is discarded after each use.
Now, when you go to dispense the liquid, the plunger is pushed in, and all of the liquid is dispensed and the air is pushed back into the tip.
If you mistakenly tipped the syringe upward during dispensing, and blew out the air before the liquid, then when you push the plunger all the way in, there will still be liquid in the tip, and you probably won't know how much so you end up with a mismeasurement.
In the medical world, it can be super important to not inject air into a patient's bloodstream. In that case, the syringe must first be overfilled. It is then tipped up and all of the air blown out and some liquid may be blown out until the end of the plunger is exactly aligned with the volume marking you want to dispense. The syringe in total now contains the amount you want to inject, plus the volume of the the needle. Then you inject and when done, the needle is still full of liquid in the exact amount as before injection, and like before, the amount dispensed is exactly determined by the movement of the plunger. So this situation is no different except that you start and end with a full tip/needle. In a non-injection setting, you start and end with an air-filled tip.
So it doesn't matter how much liquid you see in the barrel. Only the movement of the plunger is important, whatever the use. "
With all due respect to your expertise, if the size of the bubble varies depending upon how hard the plunger is pressed by as much as 1/4 inch, the amount of reagent in the syringe will vary as well. Common sense, at least in my mind, would suggest that one would get different readings. Come on guys, get your heads out of the clouds and read the scale on the side of the syringe with different sized bubbles!
Dude what everybody is trying to explain is that it doesn't matter how much liquid is in the syringe (i mean visible) but how much exits! If you don't trust us take a small empty 1ml beaker, and play with the size of the bubble while dispensing (!) Liquid. You will ALWAYS get 1ml of liquid in the beaker no matter how big the air bubble is. In other words the size of the bubble depends on how well your syringe tip is primed which for the titration test is irrelevant...
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Being how this tests end result is measured, it very much matters how much reagent is drawn. IME tiny differences in this draw are normally +/- 1 dkh
I fully understand where the OP is coming from, that's why i said to remove all the previous reagent in the tip, at the end of the day what really matters is consistency.
I make sure mine are always reading .80 at the start, sometimes this takes purging it a few times.
I fully understand where the OP is coming from, that's why i said to remove all the previous reagent in the tip, at the end of the day what really matters is consistency.
I make sure mine are always reading .80 at the start, sometimes this takes purging it a few times.
Guys all you're measuring is how much reagent goes into the test tube. That's it. It doesn't matter how much air is in the syringe, one thing you know for a fact.there is at least 1cc I there (because that's how much your plunger moved while the tip was in the reagent liquid) and that is exactly how much you can dispense. The air you have there is just how much air was in the dead volume (space that the piston cannot directly influence I.e. The tip of the syringe) and that will go back to that place again (I.e. The tip of the syringe not the tube). And again do the test! You will never dispense more that how much the syringe plunger had moved (and as long as your tip was in reagent when moving that's all liquid no air) The end result is measured by how much the plunger moved from the 1cc Mark and however much that is it's liquid dispensed.
Happyschneider
New member
Look, I don't give a monkey about your respect for my "expertise" it is also not relevant as you cannot confirm that I said the truth
Point is that everyone agrees with you that the amount of liquid in the syringe varies. Where we disagree is that it matters.
The only thing I can think of why you might think it matters is that you don't look St where the plunger is at the end but where the liquid level is. I would agree that this then would make a huge difference but then it would be wrong anyway. Salifert table is standardised to read the amount based on where the plunger is.
There is a very easy way to settle this lengthy discussion. Take a solution (in two different vials). In one vial you do the test with 0.8 liquid in the syringe, with the other you take 0.85 liquid in the syringe. Do the test in both exactly as described in the manual of the test and you will see that both are within the accuracy of the test. Q. E. D.
it is also not relevant as you cannot confirm that I said the truth Point is that everyone agrees with you that the amount of liquid in the syringe varies. Where we disagree is that it matters.
The only thing I can think of why you might think it matters is that you don't look St where the plunger is at the end but where the liquid level is. I would agree that this then would make a huge difference but then it would be wrong anyway. Salifert table is standardised to read the amount based on where the plunger is.
There is a very easy way to settle this lengthy discussion. Take a solution (in two different vials). In one vial you do the test with 0.8 liquid in the syringe, with the other you take 0.85 liquid in the syringe. Do the test in both exactly as described in the manual of the test and you will see that both are within the accuracy of the test. Q. E. D.
Ugh
Ugh
hey Happy, you brought up your PHd, I just said I respect your training but disagree with your conclusion. The point here is not how much reagent goes into the test solution, but how much is left in the syringe when the color changes, as determined by the scale. And that reading will vary by as much as 1/4 of an inch depending, again, on how hard you press the plunger. For Mag., that 1/4 inch will show anywhere between 1350 and 1500, which I am sure is well beyond the margin of error.
So, once again, my question is: how hard do you press the plunger in when expelling air and drawing in reagent?
And if anyone thinks it doesn't matter, don't say it....please
Ugh
hey Happy, you brought up your PHd, I just said I respect your training but disagree with your conclusion. The point here is not how much reagent goes into the test solution, but how much is left in the syringe when the color changes, as determined by the scale. And that reading will vary by as much as 1/4 of an inch depending, again, on how hard you press the plunger. For Mag., that 1/4 inch will show anywhere between 1350 and 1500, which I am sure is well beyond the margin of error.
So, once again, my question is: how hard do you press the plunger in when expelling air and drawing in reagent?
And if anyone thinks it doesn't matter, don't say it....please
hey Happy, you brought up your PHd, I just said I respect your training but disagree with your conclusion. The point here is not how much reagent goes into the test solution, but how much is left in the syringe when the color changes, as determined by the scale. And that reading will vary by as much as 1/4 of an inch depending, again, on how hard you press the plunger. For Mag., that 1/4 inch will show anywhere between 1350 and 1500, which I am sure is well beyond the margin of error.
So, once again, my question is: how hard do you press the plunger in when expelling air and drawing in reagent?
And if anyone thinks it doesn't matter, don't say it....please
Salifert themselves say it doesn't matter. Do you believe them maybe? As for what you're saying, yes what matters is how much reagent goes in the tube, that's the very definition of the titration test.
Now, what do you look at when you measure your result to compare with the table? Where your liquid is? No, the cc mark where the bottom of the plunger ended. Let's say that's 0.1 cc's. Now that same piece was at the 1 cc mark when the test started. This yields 0.9 cc's dispensed in the test tube. Hence it doesn't matter how much is in the syringe but how much is dispensed. Salifert has made our life easier and gives us directly that when the bottom of the plunger is at 0.1 that means a certain number. That doesn't happen with a red sea test for instance where you have to calculate the difference (1 - 0.1 = 0.9 which they say means a certain Mg concentration).
Asking people not to tell you the truth is like asking to stay in the dark. It's not an opinion my friend, we're not doing politics. You can't disagree with facts.
Happyschneider
New member
Yes, I overreacted there, not easy to transport my special blend of self irony...
As others already stated, you want to measure the amount that goes into the test vial. Otherwise you will get wrong interpretations.
KSU_WILDCAT
New member
Eric slow down and take a deep breath. I was on board with you as well until I thought about it. I didn't believe it at first either. It doesn't matter really what the level is UNLESS YOU RUN OUT OF FLUID before the color changes. You are reading the plunger position not the fluid level. You move the plunger .1 ml you get .1 ml out (Remember, as long as there is fluid in the syringe. I understand in a CAL test with water near 500 ppm you may be close. Like I said before, when I draw mine up I make sure when the plunger is at 1.00 I have .85 ml of fluid in the syringe. This has worked for me. Remember just be consistent. I think me, along with you are thinking about this too much.
Justin, I agree with you. Not to be nit picky here but unless you drew air in the syringe by accident while pulling your plunger up you should have 1ml of liquid in there no matter what (since the movement of the piston was 1ml). Like we said before the amount of air depends on how much liquid is in the dead volume (red tip plus syringe plastic tip) when you start drawing in fluid which, as stated above, is irrelevant. The only way you can run out of fluid is if you have a sample that has a measured variable (calcium, alkalinity etc) higher than the test kit is designed (i.e. higher value than the 1ml of titrant available).
As long as you're careful not to pull air and that your syringe is fully submerged during reagent filling then you will be fine. That's why Salifert says it's been taken into account.
KSU_WILDCAT
New member
Agree
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