QC for test kits?

SallyWho · Oct 18, 2021

Does anyone know if there are commercially available quality controls for test kits? I know the Hanna checkers have calibrators, but I don't think I've heard of any manufacturer having QC. I work in a hospital laboratory, and not being able to do QC to absolutely ensure that the test kits are working correctly drives me bananas!

I can probably use RODI as a negative control for several of the analytes, but that's assuming the RODI water doesn't have any nitrates, nitrites, phos, ammonia, etc. Positive controls though? Not a clue!

BanjoBandito · Oct 18, 2021

Depending on the test manufacturer, I would directly contact them and ask for calibration advice/samples. PH is used by buffers, refractometers use pure water, the bare bones answer is test something you know to be fact, then go off it.

Randy Holmes-Farley · Oct 18, 2021

I assume that by positive control you just mean a standard.

yes, there are commercial standard for many things.

What kit do you want to evaluate? Some are easier than others. Some are sold by hobby companies that you have to decide how much you trust them.

Malcontent · Oct 18, 2021

Mixed-Parameter Standard, NIST, Wastewater, Low Range

www.hach.com

Nitrogen-Ammonia Standard Solution, 50 mg/L as NH₃-N, pk/20 - 2 mL PourRite Ampules

www.hach.com

I've had ammonia standards get contaminated by ammonia in the air so if I was buying again I'd consider those single use sealed ampules.

You probably also need a micropipette to dilute the standards to the desired range.

fryman · Oct 18, 2021

The trident comes with a standard with each set of reagents. They are using the best practice I've seen in tbe hobby which is surprising. They are even better in this regard than hanna. But the trident is crazy expensive.

Hanna sells a cal standard for the alk checker but it's pretty close to useless.

1) the hanna alk standard comes with 2 pre-mixed vials, for C.1 and C.2. So, this "calibration" does not assess lot-to-lot variation of hanna reagents, which I've found to be significant (+/- 0.3 dkh).

2) the hanna alk standard gives a single data point (for checker itself only) at 5.0 dKH. Why do I care about 5.0? I've found the hanna checker to be +/-0.1 dkh at 5.0 but more like +/-0.4 dkh at 8.0. You'd never know that just using a single data point at 5.0

I don't know if the other hanna cal standards are better, or if anyone else has standards.

Randy Holmes-Farley · Oct 18, 2021

fryman said:
The trident comes with a standard with each set of reagents. They are using the best practice I've seen in tbe hobby which is surprising. They are even better in this regard than hanna. But the trident is crazy expensive.

Hanna sells a cal standard for the alk checker but it's pretty close to useless.

1) the hanna alk standard comes with 2 pre-mixed vials, for C.1 and C.2. So, this "calibration" does not assess lot-to-lot variation of hanna reagents, which I've found to be significant (+/- 0.3 dkh).

2) the hanna alk standard gives a single data point (for checker itself only) at 5.0 dKH. Why do I care about 5.0? I've found the hanna checker to be +/-0.1 dkh at 5.0 but more like +/-0.4 dkh at 8.0. You'd never know that just using a single data point at 5.0

I don't know if the other hanna cal standards are better, or if anyone else has standards.

I agree that most Hanna standards are not standards at all, but machine testing materials to simply verify the electronics are working as expected.. They do not assess the actual function of the reagents or the method at all.

Gtinnel · Oct 18, 2021

I've never used it to know how reliable it is, but there is a reference solution that you can buy on BRS that gives known values for the most common saltwater parameters.
You can use this to verify your tests and testing methods.

Saltwater Multi Reference Solution

The only reference solution based on a saltwater matrix that includes 8 of the most popular parameters for saltwater aquariums in a single solution. Fauna Marin’s Multi-Reference Solution is used to check your home water test kits for accuracy. Using your water test kits at home, you can measure...

www.bulkreefsupply.com

Dave_J · Dec 2, 2021

I've been checking against stock salt water.

Randy Holmes-Farley · Dec 3, 2021

Dave_J said:
I've been checking against stock salt water.

How do you know the levels in it?

Dave_J · Dec 3, 2021

The manufacturer’s representation.

Randy Holmes-Farley · Dec 3, 2021

Dave_J said:
The manufacturer’s representation.

Thanks. Such representations are often self serving, if not completely incorrect. I'm not saying it is necessarily wrong here, but in general it may not be a good way to understand what to use and why and how.

That's part of the reason for this forum: to sort true chemical facts from manufacturer fantasy.

Dave_J · Dec 3, 2021

Here’s something I found a while back.

Aquarium Frontiers Feature

Randy Holmes-Farley · Dec 3, 2021

Dave_J said:
Here’s something I found a while back.

Aquarium Frontiers Feature

Craig's work is more than 20 years old. I would not assume any mixes still match those values.

Dan_P · Dec 4, 2021

SallyWho said:
Does anyone know if there are commercially available quality controls for test kits? I know the Hanna checkers have calibrators, but I don't think I've heard of any manufacturer having QC. I work in a hospital laboratory, and not being able to do QC to absolutely ensure that the test kits are working correctly drives me bananas! I can probably use RODI as a negative control for several of the analytes, but that's assuming the RODI water doesn't have any nitrates, nitrites, phos, ammonia, etc. Positive controls though? Not a clue!

If you want to ensure every test kit is working, there is no short cut. You have to run at least one reference sample, even better use 3 at different concentrations. Otherwise you are just trusting that the manufacturer is doing a good job. If you ask them about QC, they will of course tell you that “they are doing a good job”, which is a waste of time.

The good news is that you can buy a multi-parameter reference standard with nitrate, phosphate and other analytes in one bottle. I don’t recall the name though. @Rick Mathew uses it.

Rick Mathew · Dec 4, 2021

Dan_P said:
If you want to ensure every test kit is working, there is no short cut. You have to run at least one reference sample, even better use 3 at different concentrations. Otherwise you are just trusting that the manufacturer is doing a good job. If you ask them about QC, they will of course tell you that “they are doing a good job”, which is a waste of time.

The good news is that you can buy a multi-parameter reference standard with nitrate, phosphate and other analytes in one bottle. I don’t recall the name though. @Rick Mathew uses it.

Here is the referance standard Dan_P is referring to