Reef Chemistry Question of the Day #161 Using a Syringe

[Jeff Hall]

You are wrong. (sorry this was not the post that was wrong - this one was correct) but the one where the doctors and nurses were asked was wrong.

I'm glad you explained why I was wrong

 

[MnFish1]

I'm glad you explained why I was wrong

You were wrong because you misread the type of syringe tip, and multiple people explained why you were wrong - I was just responding again - because you seemed to ignore what everyone else wrote - and asked people at your workplace (who were also wrong). Wasn't meant to be contentious.

 

[Daltrey]

I'm glad you explained why I was wrong

He wasn’t saying you were wrong only that you weren’t right. There is a big difference.

 

[Jeff Hall]

You were wrong because you misread the type of syringe tip, and multiple people explained why you were wrong - I was just responding again - because you seemed to ignore what everyone else wrote - and asked people at your workplace (who were also wrong). Wasn't meant to be contentious.

I am sorry I have angered you. You are correct in every way. I have no idea how to use a syringe nor does anyone I work with and I am sorry I entered the discussion.

 

[MnFish1]

I am sorry I have angered you. You are correct in every way. I have no idea how to use a syringe nor does anyone I work with and I am sorry I entered the discussion.

You asked why you were wrong - I answered you (twice) - and in doing so said I was not trying to be contentious. If you want to play some kind of drama card - ok - do so, but dont put emotions or words in my 'mouth'/'typing' that aren't there - I haven't ever been 'angered'

 

[Jeff Hall]

You asked why you were wrong - I answered you (twice) - and in doing so said I was not trying to be contentious. If you want to play some kind of drama card - ok - do so, but dont put emotions or words in my 'mouth'/'typing' that aren't there - I haven't ever been 'angered'

You have yet to tell me how I am wrong. Please explain. Again sorry I have made you angry.;Poto;Rage

 

[MnFish1]

You have yet to tell me how I am wrong. Please explain. Again sorry I have made you angry.;Poto;Rage

Here - are your messages - below each is whats wrong...

The answer is 1.6. I may not know everything about reefing but any half decent nurse knows how to use a syringe...

The example provided is using a pipette tip not a needle - as @Daltrey explained to you - there is much more volume in the pipette tip than a syringe/needle.

Actually on second thought, you would have to flip the syringe around to get the accurate amount its definitely not 2.8 mL because there is way to much air in the syringe but it's most likely not 1.6mL either because there is a small amount of fluid still in the tip. If you flipped the syringe around you could accurately measure it.

Flipping the syringe has nothing to do with it - if you read the problem as posed in the question. And - per the poster - the answer is 2.9 ml. Definitely.

So you are telling me there is 1.3mL of fluid in the tip of that syringe? I find that hard to believe and I think you are wrong. I understand your logic but in order to get an accurate measurement you should flip syringe the other way

He was right, you were wrong.

I'm staying out of this because I am at work and have asked multiple nures and physicians about this and they agree with what I thought which is the answer is neither 1.6 or 2.9 but somewhere inbetween and closer to 1.6. You need to flip the syringe to get the answer.

You're still wrong (and so are the people you questioned at work ) for the same reasons as before

Yeah but if your syringe is not completely submerged in the fluid you could introduce more air into the syringe thus making your results innaccurate, and I know for a fact that a needle does not contain 1.3mL of air. IMO the volume of air actually in a syringe is most likely negligable because it's so small.

There is no needle on this syringe, its a pipette tip - which can easily hold 1.3 cc. You were wrong.

As to me being angry - no. Frustrated - a little. Because several people took time to explain why you were wrong and it seemed like you didnt want to listen.

 

[Jeff Hall]

Here - are your messages - below each is whats wrong...



The example provided is using a pipette tip not a needle - as @Daltrey explained to you - there is much more volume in the pipette tip than a syringe/needle.



Flipping the syringe has nothing to do with it - if you read the problem as posed in the question. And - per the poster - the answer is 2.9 ml. Definitely.



He was right, you were wrong.



You're still wrong (and so are the people you questioned at work ) for the same reasons as before



There is no needle on this syringe, its a pipette tip - which can easily hold 1.3 cc. You were wrong.

As to me being angry - no. Frustrated - a little. Because several people took time to explain why you were wrong and it seemed like you didnt want to listen.

Okay so I see where Daltrey explained why I am allegedly wrong, but not you. I still wouldn't trust this method of reading a syringe or pippette because if any where to get in while drawing up the fluid it would totally skew the results. Flip the syringe/pipette the other way get all the air out and that will give you a truly accurate reading that will not be skewed by air entering the syringe or different air pressures within the syringe and outside of the syringe. If I am continuing to frustrate you I appolo

Here - are your messages - below each is whats wrong...



The example provided is using a pipette tip not a needle - as @Daltrey explained to you - there is much more volume in the pipette tip than a syringe/needle.



Flipping the syringe has nothing to do with it - if you read the problem as posed in the question. And - per the poster - the answer is 2.9 ml. Definitely.



He was right, you were wrong.



You're still wrong (and so are the people you questioned at work ) for the same reasons as before



There is no needle on this syringe, its a pipette tip - which can easily hold 1.3 cc. You were wrong.

As to me being angry - no. Frustrated - a little. Because several people took time to explain why you were wrong and it seemed like you didnt want to listen.

 

[cmcoker]

I'll just say that flipping it and trying to get the air out would probably introduce more error for people using these for aquarium test kits. Most of the pipettes are opaque so you can't see if you flicked all the air out of the tip or not. KISS is going to be best for the majority of users, esp those that are not in the medical field.

I am a Veterinary technician, and use syringes daily. Teaching people how to give their pets insulin regularly reminds me that using a syringe properly is a learned skill.

All of the alkalinity test kits (that I have used) instruct the user to leave the air bubble, so teaching people how to use the syringe as described by the test manufacturer is the best way to go and the purpose if this thread.

 

[MnFish1]

Okay so I see where Daltrey explained why I am allegedly wrong, but not you. I still wouldn't trust this method of reading a syringe or pippette because if any where to get in while drawing up the fluid it would totally skew the results. Flip the syringe/pipette the other way get all the air out and that will give you a truly accurate reading that will not be skewed by air entering the syringe or different air pressures within the syringe and outside of the syringe. If I am continuing to frustrate you I appolo

You're wrong because with a pipette tip there can easily be 1.3 ml of dead space (which you said wasn't possible). You said the answer to the question was definitely NOT 2.9 ml (you were wrong). You were wrong when you said 'The answer is 1.6. ...' because the answer is 2.9 ml. These were the posts where I said you were 'wrong'.

If you look at the instructions for using these tips with syringes (like reef test kits) there is no need to empty out all of the air. The reason its done in medicine is because most fluid from injection vials is drawn with the needle on the tip facing upwards into the vial - meaning that some air remains near the tip of the needle - thus it needs to be expelled before injecting into the patient. Using a pipette tip on a syringe, the tip is facing downward into the solution being drawn up - leaving any 'air' at the upper end of the syringe (near the barrel) - this means that the fluid that is drawn up - is the accurate amount - the air at the barrel end is left in the syringe when the plunger is pressed all the way in.

Of course if you expel every bit of air from a syringe, this will be as accurate - but unless the person is using the pipette/syringe incorrectly, not more accurate. But with each use, you will waste reagent if you expel all of the air.

 

[Jet915]

Yikes, so I just got the salifert Mg kit and was reading it accounting for the air bubble. I guess my Mg is low and not normal!

 

[Randy Holmes-Farley]

Yikes, so I just got the salifert Mg kit and was reading it accounting for the air bubble. I guess my Mg is low and not normal!

Let us know how low it is. It really doesn't need to be very high.

 

[Jet915]

Let us know how low it is. It really doesn't need to be very high.

Well, I initially tested my Mg for the first time a week ago and based on the end of the plunger, it was 950! I thought I read it wrong so I read it based on the air bubble and it was around 1250 so I dosed some Mg. I tested it again yesterday and my Mg was 1320 (based on the air bubble and not the end of the black plunger). My calcium is 440 and I use reef salt so I'm kinda surprised my Mg would be around 1000. Is it normal to be that low? I just got some SPS a few weeks ago and started kalkwasser for the last week. I wont be home till tomorrow but I'll retest my Mg again.

 

[Randy Holmes-Farley]

I doubt it was low.

1250 ppm is OK anyway, but so is 1320 ppm. So is 1400 ppm.

All of those possibilities are fine.

900 is not.

 

[Jet915]

I doubt it was low.

1250 ppm is OK anyway, but so is 1320 ppm. So is 1400 ppm.

All of those possibilities are fine.

900 is not.

So am I not doing my test correctly?? I dont want to dose Mg unnecessarily but i'm wondering why my Mg would be so low in a mixed reef tank with some sps frags. I'll test again tomorrow using the end of the black plunger and not the air bubble and see what I get. Thanks!

 

[Randy Holmes-Farley]

So am I not doing my test correctly?? I dont want to dose Mg unnecessarily but i'm wondering why my Mg would be so low in a mixed reef tank with some sps frags. I'll test again tomorrow using the end of the black plunger and not the air bubble and see what I get. Thanks!

I'm not saying you are doing something wrong, but I'm not sure what you are doing. It is one thing to get a properly dispensed volume, and another to look things up on a chart that assumes a certain starting point.

If you used the bottom of the bubble both times, it should be OK, but 900 ppm is not at all likely unless your salinity is way too low.

 

[Jet915]

I'm not saying you are doing something wrong, but I'm not sure what you are doing. It is one thing to get a properly dispensed volume, and another to look things up on a chart that assumes a certain starting point.

If you used the bottom of the bubble both times, it should be OK, but 900 ppm is not at all likely unless your salinity is way too low.

My salinity is 1.024 and has been that for several months. I'll test it tomorrow and take some pics of the syringe. Thanks for your responses, much appreciated!

 

[Jet915]

Well, I checked my Mg today and it was 1280 doing it the correct way so I did something wrong the first time, thanks for your help.

 

[Randy Holmes-Farley]

Well, I checked my Mg today and it was 1280 doing it the correct way so I did something wrong the first time, thanks for your help.

You're welcome.

Happy reefing.

 

[SharkRacer]

And the answer is...B. 2.9 mL

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.

@Randy Holmes-Farley - This was SUPER helpful, especially the last part where you explain why/how the medical work approaches this differently. That was helpful in understanding this concept of the syringe volume.