My hacks for consistent tests

[HawkeyeDJ]

My eyesight isn't as good as t used to be, neither is my memory. So I've come up with some hacks that others may find helpful.

The horizontal black line is 1-2mm above the white line as a guide for the top of the meniscus. I've marked my alk and nitrate cuvettes in a similar manner.

Placed a black dot on the tester to help align the cuvette consistently.

The appearance of the reagent packs are almost identical. Not anymore.

 

[exnisstech]

Good tips. I use a 10ml syringe and don't rely on the marks on the cuvettes. I use the same syringe for all tests. I never thought about aligning the cuvettes the same each time.

 

[HawkeyeDJ]

Good tips. I use a 10ml syringe and don't rely on the marks on the cuvettes. I use the same syringe for all tests. I never thought about aligning the cuvettes the same each time.

I've been told there can be subtle irregularities in the glass, which could skew inconsistent results if not aligned the same each time.

I've used a syringe to 'calibrate' the cuvette initially.

I also used acrylic clear coat nail polish to cover the Sharpie markings. Keeps them fresh and intact when I clean the cuvettes following testing.

 

[Randy Holmes-Farley]

FWIW, exact volumes are not that critical in most side viewed color tests.

 

[aSaltyKlown]

I use a 10ml syringe and the stock vile and make sure the 10ml lable is always facing front.
I do like the coloring of the reagents, I've added the wrong one at times and this would definitely help.

 

[EricR]

10 mL syringe for me and don't even look at the Hanna vial lines.
*when I checked a few they were accurate but I had one that was obviously not marked the same

I do like the highlighting idea since I have once or twice grabbed/used the wrong packet but seems like a bit too much effort for me personally.

 

[Pod_01]

FWIW, exact volumes are not that critical in most side viewed color tests.

Out of curiosity:
1) Why would the exact volume not impact the results as much?
2) How much off can it be? 5%, 10%, 20%…

When I use Hanna test I try to be on the line (I never measured the line) just for consistency. Reason being if it is off it is consistently off. But the comment makes it sound that I am overthinking it.

 

[19Mateo83]

Out of curiosity:
1) Why would the exact volume not impact the results as much?
2) How much off can it be? 5%, 10%, 20%…

When I use Hanna test I try to be on the line (I never measured the line) just for consistency. Reason being if it is off it is consistently off. But the comment makes it sound that I am overthinking it.

I always wondered why their 10ml line was actually like 8ml

 

[dschuffert]

Thanks for the tips; they are beneficial! I am now coloring my packets with a highlighter, too!

 

[sean151]

The point he's probably making is that if you're slightly below or above the line we're talking less than a 5% variance. For a 10mL vial, the adjustment between below and above the line (at the meniscus) is going to be closer to 0.1-0.5mL depending on the individual. Translating to 1-5% variance. What really matters is hitting the same mark every run as then you're actually measuring the same amount.

Salifert titration tests can have large jumps between drops (Ca and Mag), so even then you're very wishy-washy on exactly what numbers you're getting. Which leads back to importance on run to run consistency vs. hitting exact numbers. With Hanna packets good luck getting 100% out of the packets, but again consistency between runs is the key.

 

[Randy Holmes-Farley]

These are the reasons that the exact volume in such tests is not very important:

1. The absorbance is viewed through the sides, so the depth does not impact the results the way it would if you viewed down through the sample (as in some other kits).

2. Unless you are at the very highest level of analyte that the kit can quantify, it has excess reagents present to allow for chemical reactions with all of the ions that may be present. Thus, if the chemical reagents are added to a slightly larger volume of tank sample, there are still plenty of reagents present to react with the analyte (say, nitrate) and form the needed color.

 

[Randy Holmes-Farley]

The point he's probably making is that if you're slightly below or above the line we're talking less than a 5% variance. For a 10mL vial, the adjustment between below and above the line (at the meniscus) is going to be closer to 0.1-0.5mL depending on the individual. Translating to 1-5% variance. What really matters is hitting the same mark every run as then you're actually measuring the same amount.

I mean it may not cause ANY variance.

Try it.

Others have, and the effect is minimal.

 

[HawkeyeDJ]

I mean it may not cause ANY variance.

Try it.

Others have, and the effect is minimal.

I get what you're saying. I'm sure the manufacturers take into consideration their customers may not be as precise or consistent in their measurements, so the tests have to allow for variations from operator to operator.

What are your thoughts or experience regarding titration drops?

I'm thinking specifically of the Red Sea Magnesium test. It takes only 2ml of tank water. Reagent A must be a series of 5 drops, mixed and spaced apart by 15 seconds. Reagent B is 5 drops mixed for 20 seconds, then reagent C is 1 ml titrated until color change.

Seems to me that there is a lot of room for variation and/or error for such a small amount of tank water. Should I be concerned?

 

[Randy Holmes-Farley]

In a titration test, the things that matter are the tank water volume measurement and the titrant volume dispensed to the endpoint. The exact volume of drops of reagents of various sorts will not matter.

 

[Freenow54]

My eyesight isn't as good as t used to be, neither is my memory. So I've come up with some hacks that others may find helpful.

The horizontal black line is 1-2mm above the white line as a guide for the top of the meniscus. I've marked my alk and nitrate cuvettes in a similar manner.

Placed a black dot on the tester to help align the cuvette consistently.

The appearance of the reagent packs are almost identical. Not anymore.

Use Salifert syringe they have a flat plunger way easier

 

[Gribbles]

I always wondered why their 10ml line was actually like 8ml

Omg yes, lol. That's bugged the heck outta me and I always figured I was in the wrong

 

[HawkeyeDJ]

I do like the highlighting idea since I have once or twice grabbed/used the wrong packet but seems like a bit too much effort for me personally.

I do all the marking when I first open the box. I also separate the packets from the chain at that time. When I'm ready to do my weekly tests, I don't have the patience for annoying details like closely reading labels to make sure I've got the right one. Color coding makes it easy and fast.

 

[vahegan]

These are the reasons that the exact volume in such tests is not very important:

1. The absorbance is viewed through the sides, so the depth does not impact the results the way it would if you viewed down through the sample (as in some other kits).

2. Unless you are at the very highest level of analyte that the kit can quantify, it has excess reagents present to allow for chemical reactions with all of the ions that may be present. Thus, if the chemical reagents are added to a slightly larger volume of tank sample, there are still plenty of reagents present to react with the analyte (say, nitrate) and form the needed color.

I think this does not apply, say, to Hanna's KH checker, in whiich color depends on the resultant pH after adding the reagent (acid and dye mix), which depends on the exact amount of buffer in the water sample.

 

[Randy Holmes-Farley]

I think this does not apply, say, to Hanna's KH checker, in whiich color depends on the resultant pH after adding the reagent (acid and dye mix), which depends on the exact amount of buffer in the water sample.

That would be true, yes. Volume is important in all alk test methods that reefers use.