Test Kit Procedures

[melev]

DaveJ, thank you for providing us with some good suggestions for using test kits.

Here is the article:

Notes From The Trenches – Test Kit Procedures
http://reefkeeping.com/issues/2009-03/nftt/index.php

[Art_Vandelay]

Aren't you suppossed to leave the air bubble in. The test kit accounts for that. The bubble's volume is equal to the volume from the tip to the first line. If you push the air bubble out you are putting more than 5mL of water. You would be putting 5mL + the volume that the bubble would consume. All the increments on the side of the hypo are equal from 5 to 1.

[DaveJ]

Originally posted by Art_Vandelay
Aren't you suppossed to leave the air bubble in. The test kit accounts for that. The bubble's volume is equal to the volume from the tip to the first line. If you push the air bubble out you are putting more than 5mL of water. You would be putting 5mL + the volume that the bubble would consume. All the increments on the side of the hypo are equal from 5 to 1.

Manufactures may vary... but no, typically the volume is total volume, no air included. Bubbles form of different sizes so how could they 'build' in the bubble already?? For proper measurement, it should be without air at all.

Here is an quote from Hamilton Company, one of the worlds largest fluid measuring device manufactuers.... this is taken out of their operational manual for one of the syringe lines.

Trapped Air - Eliminate trapped air, which is compressible and affects syringe accuracy and precision, by completely priming the syringe with sample. Immerse the needle point 2 to 3 mm into the sample solution. Then draw and dispense sample into the solution until bubbles are no longer visible in the syringe barrel. Alternatively, remove air bubbles by turning barrel upright and allowing the air bubbles to rise to the needle exit. Then dispense both the air bubbles and the sample. Clean the exterior surface of the needle with a lint free tissue. Avoid wicking sample with the tissue by making sure it does not come in contact with the needle opening.

[melev]

What I do is fill the syringe with tank water, press it all out, and refill it. That usually works.

Alternately, I depress the plunger until the next graduated milliliter whole number, like 4. If the test only requires 2ml, I press out that much, stopping at the 2ml mark on the syringe (if I started at 4).

[Art_Vandelay]

thanks guys

[cthedaytrader]

I think what you are referring to is on the Sailfert test kits, with the titration kits such as Ca, the kit accounts not for an air bubble, but for the amount of reagent in the pipette tip, which is not accounted for in the syringe. So in this case there should be a gap of air between the plunger and the line. But on normal syringes you should get the air out.

[SirVilhelm]

Are the Salifert kits accurate? I am having an algae problem but the Salifert PO4 kit say's my nitrates are 0 and PO3 kit is about the same.

[melev]

It is possible to get a zero reading with a tank full of algae, because it is bound up in the plants. Pull out a lot by hand, and measure again the next day. Blow off your rockwork too... Get the detritus in suspension so it can be skimmed out.

[luther1200]

Yes, the air in the Salifert kits is accounting for the added volume of the pipette(plastic tip). And I think they are accurate.

[buildinboats]

Originally posted by luther1200
Yes, the air in the Salifert kits is accounting for the added volume of the pipette(plastic tip). And I think they are accurate.

That's not quite the case. It doesn't matter what the volume of the air trapped in the titration syringe is. What does matter is the amount of fluid you are pushing out of the syringe, and that column of fluid moves linearly with the movement of the plunger. In other words, if you move the plunger from a 1.0 ml starting point to the 0.6 ml mark the fluid in the syringe below the air bubble has traveled the same distance or .4 ml. Just make sure the tip is fully submerged the entire time you are drawing up the titrant.

[melev]

Nice avatar, buildinboats. Walter is awesome.

[kgross]

Originally posted by SirVilhelm
Are the Salifert kits accurate? I am having an algae problem but the Salifert PO4 kit say's my nitrates are 0 and PO3 kit is about the same.

Most Salifert kits are good, but the phosphate kit is not that good. Its zero level can still be way above NSW levels for phosphate.

About the only test kits I know of that have a low enough range are the meters and the D+D marine/Merk hobbiest test kit. Most of the others anything below .1ppm can read zero.

Kim

[DaveJ]

Originally posted by kgross
Most Salifert kits are good, but the phosphate kit is not that good. Its zero level can still be way above NSW levels for phosphate.

About the only test kits I know of that have a low enough range are the meters and the D+D marine/Merk hobbiest test kit. Most of the others anything below .1ppm can read zero.

Kim

Elos has sub .1ppm. It has .01, .05 levels up to 1 mg/l. So that is two color shade differences until it reaches that .1ppm level. Its accurate enough for our purposes.

[Randy Holmes-Farley]

Just to be 100% clear for everyone, when using syringes with titration kits, one should NOT try to remove the air that reflects trapped air between the tip end and the plunger end at the start of the plunger movement.

If you tipped the syringe upside down, blew out that air, and sucked up more fluid, you now have more fluid inside the syringe plus tip than the barrel readings indicate.

That is still not a problem unless you also take pains to push it out when using a full syringe. Normally, say if you dosed 0.74 ml with a 1 ml syringe, the syringe will just be holding more liquid at the end, but it did not impact the fluid added in the titration. But if you get down to the end of the syringe and try to blow it all out, say by sucking up air and blowing out the liquid, you will have dosed more than 1 mL, and so now will get an inaccurate reading.

[Art_Vandelay]

Thats what I was saying , Randy... thankyou! For example, the salifert test kit for calcium comes with a 2 mL syringe. The test calls for 2 mL of water to be used. When you suck up water into the syringe you always get air. I agree... you should NOT push the air out and draw in more water. You would have the 2mL indicated on the syringe as well as the additonal volume of water from the zero mark to the tip. Results would be inaccurate.

Here is a tip to use with the calcium salifert kit. I always use a bigger 5 mL syringe, fill it PAST the 5 mL mark and then dispense water/air into a waste cup until the air is out and the plunger is exactly at the 5 mL mark. I then dispense the syringe into the mixing vial given with kit until I reach the 3 mL mark on the syringe. This way I know the syringe has put out exactly 2 mL of WATER, regardless of the trapped air.

[DaveJ]

Originally posted by Art_Vandelay
Thats what I was saying , Randy... thankyou! For example, the salifert test kit for calcium comes with a 2 mL syringe. The test calls for 2 mL of water to be used. When you suck up water into the syringe you always get air. I agree... you should NOT push the air out and draw in more water. You would have the 2mL indicated on the syringe as well as the additonal volume of water from the zero mark to the tip. Results would be inaccurate.

Here is a tip to use with the calcium salifert kit. I always use a bigger 5 mL syringe, fill it PAST the 5 mL mark and then dispense water/air into a waste cup until the air is out and the plunger is exactly at the 5 mL mark. I then dispense the syringe into the mixing vial given with kit until I reach the 3 mL mark on the syringe. This way I know the syringe has put out exactly 2 mL of WATER, regardless of the trapped air.

Hate to continue to disagree... even with what Randy is saying. The manufacturers are pretty clear on their instructions. The amount of the water or chemical in the syringe is based on a full syringe from the tip of the plastic to the marking on the body. The manufacturer I quote above makes mention about their needle and avoiding sucking fluid into that, but the body needs to be full. Again, there is no way they can manufacture a bubble estimate into the measuring markings.

Also in the article there is no mention about clearing it out and sucking more out of the sample into the syringes. It simply says the technique is to tip it upside down, clear the bubble, then push water out into a waste container until the plunger reaches the proper marking point on the body of the syringe. This assumes you have more in there than you are trying to measure, example 6ml mark with a little air, as opposed to 5ml with air and sucking up the difference after clearing the air. Any cross contamination should be avoided and that means no sucking of more or squirting back into the sample and re-drawing the sample.

Choose the method that works for you, or what you choose to believe, but the manufacturers are very specific on their recommendations. If you are in doubt, contact the test kit manufacturers to see what their specific guidelines are. As I said, some may vary, but they will not be able to estimate the size of any gap or bubble in the body of the device.

[Randy Holmes-Farley]

Hate to continue to disagree... even with what Randy is saying. The manufacturers are pretty clear on their instructions.

The owner of Salifert came here in person many times and carefully explained to us that they did expect air in the syringe:

For example:

"The amount of air is a typically 0.22 ml.

The tip should be mounted firmly on the syringe. When drawing in lquid the tip should always be immersed in the liquid.

The amount of air which you see now is the amount between the end of the tip and the bottom of the piston.

This does not influence the measurement because the air pocket remains in place and when the syring is filled to the 1.00 ml mark there will be exactly 1.00 ml titrant.

The tip allows you to make a measurement with a higher resolution because the drop size (volume of liquid) is very small."
http://archive.reefcentral.com/forum...ad.php?t=95183

[luther1200]

If a syringe has a movement of 1ml, and you put a tip with .02ml volume on it, then suck in a liquid.You will have air in the syringe, and still have 1ml of liquid in there. But the syringe will only read .08 to account for the tip. If you got all the air out you would now have 1.2ml in the syringe. Which would give you a false reading, if you were anly supposed to put in 1ml.

[Kenmx10]

Randy, I use alcohol to clean my vials everytime I use them to remove any chemicals left behind that water wouldnt cut. Then I flush them out with tap water and shove a piece of paper towel in to wipe it out. Could this affect the readings in any way?

[Randy Holmes-Farley]

Randy, I use alcohol to clean my vials everytime I use them to remove any chemicals left behind that water wouldnt cut. Then I flush them out with tap water and shove a piece of paper towel in to wipe it out. Could this affect the readings in any way?

No, I do not think that is any concern, unless the vials are inadequately cleaned and then are used in different types of tests.

[kaskiles]

There are two different syringes; sample collecting and titration. The syringe DaveJ is talking about clearing the air bubble from (in the Reefkeeping article) is the sample collecting one, not the titration.

The Salifert instructions say to leave the air in the narrow titration syringe, I'm not sure it would even be possible to tap that air out...

I haven't read any test kit instructions on the sample collection syringe air bubble, but I normally try to avoid those because they seem to form in all different sizes for me (inconsistent amount of air).

[FFrankie]

Very interesting read and article. Thanks DaveJ.

[Randy Holmes-Farley]

The Salifert instructions say to leave the air in the narrow titration syringe, I'm not sure it would even be possible to tap that air out...

Sure you can, just as has been suggested: blow out the air and refill with liquid. Many people have asked this same question for many years, and despite Salifert trying to make it clear the air is normal, many users do not understand it.

[FFrankie]

Originally posted by Randy Holmes-Farley
The Salifert instructions say to leave the air in the narrow titration syringe, I'm not sure it would even be possible to tap that air out...

Sure you can, just as has been suggested: blow out the air and refill with liquid. Many people have asked this same question for many years, and despite Salifert trying to make it clear the air is normal, many users do not understand it.

I have to agree, what's not to understand? The instructions say to firmly place the needle in place. Some air will get into the syringe and this is normal and will not affect the test results. I have always done it this way and never had any problems with my results.
BTW, How does the Elos Ca++ test compare to the Salifert for ease and accuracy? I have yet to try the Elos for Ca++.

[fitz302]

does anyone know where to get the wide body test tubes?