Red Sea Pro Alkalinity has new endpoint color.

[cmcoker]

Just throwing this out there, if you buy one of the "New and improved" Red Sea Pro Alkalinity refill kits the endpoint color has changed. The new endpoint is green.

I just got a refill and was a bit confused with where I was supposed to stop. The new test will go from blue to green to yellow.

I contacted Red Sea and the new endpoint is when you turn green. Yellow is overshooting the color change. They are waiting on new reference cards to come in.

Happy reefing!

 

[JimWelsh]

Good ol' bromocresol green. Sounds like someone forgot to include the methyl red!

 

[cmcoker]

Good ol' bromocresol green. Sounds like someone forgot to include the methyl red!

Ha, yeah. Looking around further, they have a picture on their website where you can see a new reference card, endpoint is green.
Looks like they are going with this as the new and improved kit. I wonder if it's from all the complaints about the reddish pinkish endpoint.

Since you are a chem guy, do you think the change in dyes is going to affect the test results? Assuming the user does everything correctly

 

[JimWelsh]

It depends on how sharp the color change at the endpoint is, and how close that endpoint is to the actual equivalence point of the titration. More specifically, I guess it depends on how close the endpoint of the new indicator is to the endpoint of the old indicator, in terms of users transitioning from the old test to the new one. Like most all the tests we do, consistency from test to test is more important than nailing down some specific number.

While I'm really just joking about the "someone forgot to include the methyl red" part, it is true that for alkalinity titrations where the human eye is the detector, the classic indicator is a mixture of bromocresol green and methyl red, because this creates a sharper endpoint that is more easily detectable by most people than using bromocresol green alone. Bromocresol green alone tends to be seen as green for too long by the eye for there to be a distinct, sharp endpoint. While I have no insight into what Red Sea is actually doing here, the simple fact is that there just aren't that many pH indicator dye substances that operate over the pH range needed for this test. Bromocresol green alone does transition from blue to yellow over the range of interest. Another candidate is bromophenol blue, which also changes from blue at a higher pH to yellow at a lower pH, but its pKa is a bit low for this titration (about 3.85). So, maybe they're using a mixture of bromocresol green and bromophenol blue, but I'm just guessing. Perhaps they know of some other indicator dye that I'm not aware of.

 

[Randy Holmes-Farley]

Ha, yeah. Looking around further, they have a picture on their website where you can see a new reference card, endpoint is green.
Looks like they are going with this as the new and improved kit. I wonder if it's from all the complaints about the reddish pinkish endpoint.

Since you are a chem guy, do you think the change in dyes is going to affect the test results? Assuming the user does everything correctly

Depends on exactly what it is.

Chemistry and the Aquarium: What is Alkalinity? ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/2002/2/chemistry


Interestingly, many test kits use more than one pH indicating dye. Using more than one dye at the same time permits the endpoint to be sharper. For example, bromcresol green has a broad color transition between pH 3.8 (yellow) and 5.4 (blue-green) and methyl red has a broad transition between pH 4.4 (red) and 6.2 (yellow). A mixture of the two (used in the Hach alkalinity kit) has a sharp transition (orange to blue-green) around pH 5.1 in fresh water (which may be slightly different in salt water).

Five point 1 you say? Based on the discussion above, is that low enough? Well, the Hach kit was designed for use in fresh water where the pKa of the bicarbonate is much higher than in seawater, and in that situation, it is appropriate. In seawater, however, it is marginal. My tank water took 3.4 meq/L to get down to pH = 5.03, and then an additional 0.4 meq/L to get down to pH 4.00. Consequently, this kit (and others with a similar dye mix) may be missing out on 10% of the alkalinity simply because it isn't titrating low enough. This difference obviously isn't significant to most reef keepers, but is something to keep in mind when doing such things as comparing test kits to standards (in seawater) or to each other.

 

[Centerline]

This is funny as yesterday I left my Hanna alk checker at work and used my RedSea Pro for the first time in several months. I knew the alk should have been at 10 so when it turned YELLOW instead of red I stopped. 9.5 - tada!
I added the rest of the solution and it almost turned orange. And now we have green.

 

[cmcoker]

Well just for fun, I used a 40ml sample of saltwater I mixed last night (Red Sea Blue Bucket, 35ppt) in a small glass bowl and used their titrant until I called it green, no longer a trace of blue to my eyeballs. I used 2.3ml, which gave me an approximate alkalinity of 8.1dkh (2.3ml / 4 = 0.58ml), pH measured 4.3. The label of the salt bucket claims alkalinity at 7.8-8.2dkh when mixed to 35.5ppt.
I used the same water and repeated sample in their test vial, used 0.57ml so about the same, just under 8.1dkh.

So I will continue to use the test kit as I am comfortable with it after running a few tests, but think it's gonna be really impossible for someone who is blue-green color blind!

 

[Damien Buckley]

I have the new kit too and the 'over' indicator is a nice introduction. I was concerned however as when I performed the first test with it, it returned 12.6dkh whereas the remainder of the last bottle was returning 10.1. I spoke to Red Sea and was able to make a loose standard solution using RO & Foundation B. The new key measured smack-on at 10.1dkh for the standard which, assuming I had it mixed well, was almost exact. The old bottle was returning 8 which I am putting down to it having gone off over time with repeated openings. Now to let my alkalinity drop slowly. I thought it was 10…

 

[cmcoker]

I have the new kit too and the 'over' indicator is a nice introduction. I was concerned however as when I performed the first test with it, it returned 12.6dkh whereas the remainder of the last bottle was returning 10.1. I spoke to Red Sea and was able to make a loose standard solution using RO & Foundation B. The new key measured smack-on at 10.1dkh for the standard which, assuming I had it mixed well, was almost exact. The old bottle was returning 8 which I am putting down to it having gone off over time with repeated openings. Now to let my alkalinity drop slowly. I thought it was 10…

I thought I was around 8dkh (I was), and didn't know what color I was supposed to stop at, thought yellow at first which gave me like a 9.5 or so, glad I didn't just assume and go with that.

 

[Damien Buckley]

I thought I was around 8dkh (I was), and didn't know what I was color to stop, thought yellow at first which gave me like a 9.5 or so, glad I didn't just assume and go with that.

Yeah I thought the new kit was out as I tested against the old reagent and an (admittedly very old) API kit which both agreed at 10. I was going to return the new kit but having tried the standard solution I realised the old kits were wrong.

I quadruple checked it against the standard Red Sea alkalinity kit from the Marine Care kit I no longer use and that agreed with the new Pro kit. I also noticed the old standard kit has the green endpoint and yellow 'over' indicator too so it would appear that Red Sea have switched the Pro reagent to whatever used to be their standard alkalinity kit. Go figure…

Either way, I'm advised by Aviad at RS that the lighter colour with this reagent will last and perform more consistently which is welcome if true as I found the previous Pro reagents would go off and start trending down in results up to 1-2dkh towards the end of the bottle and as the reagent changed from a solid red colour to more tangerine like the new reagent.

 

[Damien Buckley]

I thought I was around 8dkh (I was), and didn't know what color I was supposed to stop at, thought yellow at first which gave me like a 9.5 or so, glad I didn't just assume and go with that.

I'm pretty confident that my standard solution was somewhere near 10dkh but will also test next time I mix up some Coral Pro salt out of interest.

 

[jason2459]

This is to bad. I thought the Alk kit was perfectly fine and easy to read. They need to spend time on fixing their Mg kit and not on one that didn't need improving.

 

[Randy Holmes-Farley]

This is to bad. I thought the Alk kit was perfectly fine and easy to read. They need to spend time on fixing their Mg kit and not on one that didn't need improving.

lol

 

[NU2REEFIN]

Well just for fun, I used a 40ml sample of saltwater I mixed last night (Red Sea Blue Bucket, 35ppt) in a small glass bowl and used their titrant until I called it green, no longer a trace of blue to my eyeballs. I used 2.3ml, which gave me an approximate alkalinity of 8.1dkh (2.3ml / 4 = 0.58ml), pH measured 4.3. The label of the salt bucket claims alkalinity at 7.8-8.2dkh when mixed to 35.5ppt.
I used the same water and repeated sample in their test vial, used 0.57ml so about the same, just under 8.1dkh.

So I will continue to use the test kit as I am comfortable with it after running a few tests, but think it's gonna be really impossible for someone who is blue-green color blind!

So do you read at the bottom of the black plunger or the top of the remaining test fluid?

 

[Randy Holmes-Farley]

So do you read at the bottom of the black plunger or the top of the remaining test fluid?

Plunger.

 

[Randy Holmes-Farley]

This question of the day goes into great detail on how to read a syringe and why:

Reef Chemistry Question of the Day 161 Using a Syringe
https://www.reef2reef.com/threads/reef-chemistry-question-of-the-day-161-using-a-syringe.226267/

Answer is here:

https://www.reef2reef.com/threads/r...61-using-a-syringe.226267/page-5#post-2625685

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.

 

[NU2REEFIN]

This question of the day goes into great detail on how to read a syringe and why:

Reef Chemistry Question of the Day 161 Using a Syringe
https://www.reef2reef.com/threads/reef-chemistry-question-of-the-day-161-using-a-syringe.226267/

Answer is here:

https://www.reef2reef.com/threads/r...61-using-a-syringe.226267/page-5#post-2625685

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.

Wonderful answer!!!! Thank you so much for the clarification.