How to measure properly when conducting water tests?

[Dom]

So I use Red Sea test kits. Those of you that are familiar with them know that some test kits offer a red-tipped syringe device which holds reagent.

As an example, the calcium test kit calls for 10ml of sample water. Then using the red-tip syringe, you draw up 1ml of reagent. The problem is that when drawing up reagent, I always end up drawing up a bubble so that I'm only starting with .9ml instead of 1ml.

I've tried everything; drawing slowly, taking the red tip off before drawing... nothing seems to work, and I still get the bubble.

I make allowances and get by with it. And when you are using .7-.8ml of reagent to complete an ALK test, you're running high.

Fortunately, I have reagent left over, even when I'm starting with .9ml.

So what am I doing wrong?

Thanks
Dom

 

[Randy Holmes-Farley Verified Community Expert]

So I use Red Sea test kits. Those of you that are familiar with them know that some test kits offer a red-tipped syringe device which holds reagent.

As an example, the calcium test kit calls for 10ml of sample water. Then using the red-tip syringe, you draw up 1ml of reagent. The problem is that when drawing up reagent, I always end up drawing up a bubble so that I'm only starting with .9ml instead of 1ml.

I've tried everything; drawing slowly, taking the red tip off before drawing... nothing seems to work, and I still get the bubble.

I make allowances and get by with it. And when you are using .7-.8ml of reagent to complete an ALK test, you're running high.

Fortunately, I have reagent left over, even when I'm starting with .9ml.

So what am I doing wrong?

Thanks
Dom

That is not a correct assumption or usage.

There should ALWAYS be air in the syringe and it does not impact volume. It reflects air in the tip. the liquid volume matches the movement of the plunger, regardless of air presence.

This has more:

Reef Chemistry Question of the Day #161 Using a Syringe

Reef Chemistry Question of the Day #160 I have just drawn tank water into a syringe with a tip (shown below, including a blowup of the barrel). The blue coloration shows where the fluid is. When I started to draw fluid in, the tip and syringe were empty and the plunger was all the way in...

www.reef2reef.com

 

[jeffp1]

The bubble is supposed to be there. The other .1 ml is in the tip

 

[WVNed]

Nothing
The bubble doesn't matter.
The bubble comes from the air in the tip.
But when you move the plunger you have displaced a volume of say 1ml. Yes the bubble in in the body but the rest of your 1ml is now in the tip.
So when you push the plunger back down 1 ml comes out.

Randy beat me. I was looking for that

 

[Glenner’sreef]

Hey Dom, Very consistent problem. So follow me on this one. I too get bubbles when I put the water sample syringe into the DT. But I totally submerge the small syringe into the water and pump the little syringe until all bubbles are out. And it works getting the bubbles out. Likewise, I do close to the same thing when withdrawing reagent from any bottle. Place syringe in bottle, tip near bottom of bottle and pull and pust syringe plunger back and forth. I don’t see any evidence of bubbles after doing this. Good luck.

 

[Glenner’sreef]

Agree with previous posts! Thought you were having problems with additional bubbles thus throwing off you test.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, pipettors/syringes we use in research labs keep ALL of the liquid in the disposable tip, and get none in the barrel that would require cleaning. Only air is ever present in that barrel.

 

[sealife4life]

Me too! I started using the Red Sea kit and wondered the same. My initial draw is always above the .9 but not full ml. So I aligned it with the .9 and assume .1 in the needle part.

 

[sealife4life]

Don’t know if I should be assuming in this hobby either

 

[infinite0180]

FWIW, pipettors/syringes we use in research labs keep ALL of the liquid in the disposable tip, and get none in the barrel that would require cleaning. Only air is ever present in that barrel.

yes and then we shoot the tip in the garbage lol

 

[Dom]

Me too! I started using the Red Sea kit and wondered the same. My initial draw is always above the .9 but not full ml. So I aligned it with the .9 and assume .1 in the needle part.

But why wouldn't the manufacturer account for the .1 in tip and start the syringe markings where the reagent starts? If someone came along and looked at that syringe, they would think .1ml had already been used, wouldn't they?

 

[sealife4life]

I guess it needing air in the syringe but it’s confusing because other syringes work differently.

 

[Dom]

@Randy Holmes-Farley

I just read your thread on the proper use of syringes (I think it was #161).

So if I am understanding you, the plunger lined up with the 1ml mark is correct. We have .9ml in the syringe, and .1ml in the tip.

The .1ml air bubble is what was in the tip and the volume the plunger used.

 

[Randy Holmes-Farley Verified Community Expert]

I guess it needing air in the syringe but it’s confusing because other syringes work differently.

ALL syringes work this way. ALWAYS ignore air and go by the travel of the plunger.

Even medical syringes for injection work this way. Docs force out the air because they do not want to inject air, not because it "improves" the measure of liquid dispensed. The volume dispensed is exactly measured by the plunger travel when dispensing.

 

[Jekyl]

The air is supposed to be there and is accounted for.

 

[Randy Holmes-Farley Verified Community Expert]

@Randy Holmes-Farley

I just read your thread on the proper use of syringes (I think it was #161).

So if I am understanding you, the plunger lined up with the 1ml mark is correct. We have .9ml in the syringe, and .1ml in the tip.

The .1ml air bubble is what was in the tip and the volume the plunger used.

It is the travel of the plunger against the markings on the barrel that matters. The difference between the start and finish is the liquid dispensed when the syringe is held vertically (that is, tip down). It doesn't matter what you see inside the barrel (within reason).