If you use a syringe take a look...

[MD]

This was news to me. I always used the stopper on a syringe to indicate the level. Not so apparently. Take a look.

link http://www.murphysmachines.com/how_to/how_to_syringe.html

Made a difference in my readings.

 

[MD]

Everyone already knew this? I'm Surprised.

 

[sue711]

That's ridiculous, I'm an RN and that is not the method for measuring doses in a syringe. The stopper is designed to accommodate for the tapered end of the syringe, their method actually overdoses.

 

[khaosinc]

I was gonna say...

I used the normal measuring method for injecting stuff in to my stomach for months and never had a problwm

 

[bertoni]

You can measure from either the plunger or the liquid level, as long as you're consistent with the meniscus (and keep the syringe perfectly vertical). I just measure from the plunger since it's easier and more accurate.

 

[balto777]

That's ridiculous, I'm an RN and that is not the method for measuring doses in a syringe. The stopper is designed to accommodate for the tapered end of the syringe, their method actually overdoses.

I agree that the stopper is designed to accomodate the shape of the syringe. Look at the triangle in the stopper and the triangle in the syringe tip and they match. So what they are doing is not necessary.

However, the method that is being demonstrated does not overdose either. The amount being used is the difference between the two numbers exactly. The extra that you are saying is being overdosed (the amount in the triangle part of the syringe) is there both before and after the application. The biggest problem with this method is the amount of waste produced since you should not put the leftover fluid back into the chemical bottle.

 

[MD]

That's ridiculous, I'm an RN and that is not the method for measuring doses in a syringe. The stopper is designed to accommodate for the tapered end of the syringe, their method actually overdoses.

I believe you since you are a RN but i have three different syringes. One from a Salifert kit, one from a Elos kit that are both 5 ml,and a 1 ml from a Salifert kit. If I measure 1ml 5 times and and use the method shown in the link with a 5 ml syringe they are close. If I use the plunger the results are very different. Also if I use the plunger to compare the two 5 ml syringes they are different. None of the results match a line in a test tube that indicates 5 ml from an API test kit.

This makes me question the accuracy of my test results. I asked this question on Elos forum here and the link was provided by them. Maybe I'm splitting hairs and it's not really an issue but the results of my calcium test show that it makes a difference.

I would just like to be as precise as I can, but perhaps consistent is good enough?

 

[Randy Holmes-Farley]

Everyone already knew this? I'm Surprised.

We have discussed this a million times, and there are many ways to accurately use a syringe. The only important thing is how far the plunger end moves while dispensing fluid. Whether there is air above the liquid, and how much, is not important.

 

[MD]

Everyone already knew this? I'm Surprised.

We have discussed this a million times, and there are many ways to accurately use a syringe. The only important thing is how far the plunger end moves while dispensing fluid. Whether there is air above the liquid, and how much, is not important.

I understand that, what I am questioning is the difference between both syringes when they both indicate 5ml when using the stopper lined up with the 5ml line. Sorry if you have discussed this a million times, guess I should have searched it. Thanks.

 

[Aquarist007]

You can measure from either the plunger or the liquid level, as long as you're consistent with the meniscus (and keep the syringe perfectly vertical). I just measure from the plunger since it's easier and more accurate.

I do too and I am assuming you don't draw up the air initially either?

 

[cody6766]

I never saw anything like that in any of my microbiology or chemistry classes, so I would think it's not a requirement to get an accurate measurement. BUT, like everyone said, its still accurate as long as you keep the syringe level and watch your miniscus. It's just an extra step for the same results IMO.

 

[kareem314]

That is a bizarre way to use a syringe. I have used many types of syringes and never used that method. That method would kill someone when I make IV bags at work. If you are unsure about your technique, just practice. It won't take long to get the hang of things.

 

[tdevries]

I'll chime in with the experience of another chemist, and it's perfectly acceptable (even preferred) to have the liquid being measured/transferred in contact with the syringe plunger. This other method with an air buffer should be fine, too, but either way you do it watch out for bubbles in the liquid.

 

[TheH]

I guess the two methods are only different if you are going to deplete the syringe all the way down to the tapered tip?

 

[MD]

I did some retesting against a small graduated cup like the ones used to manually dose 2 part. It appears there was a slight variation between my two syringes but I don't believe enough to be an issue. The API test tube marked 5 ml was way off. I used both methods, plunger vs air gap and they were the same. My issue was what I was checking against. I actually wish I never posted this to begin with, should have thought of checking it that way before.Thanks for the feedback.

 

[Randy Holmes-Farley]

I guess the two methods are only different if you are going to deplete the syringe all the way down to the tapered tip?

That still should not make a difference.