Are test kits affected by sample temperature? What about ICP?

[JRCooke]

Apologies if this has been asked before and if it sounds a bit daft.

Couple of days ago I got a tropic Marin hydrometer, made up some fresh salt water to 1.0263 @ 25 Celsius then left it for a few days with no heater or circulation. A few days later I thought to myself “I’ll send a sample off for ICP and see how it stacks up”. I put a pump in to circulate for a while but no heater, took a sample and sent it off, I await the results.

In the mean time i want to test the water and wondered if I should heat it? What do you think?

and will the sample be heated for ICP testing? Does it matter?

thanks to anyone with the knowledge that replies

 

[Gtinnel]

Salinity is absolutely effected by temp. Some testers have temperature compensation build in though.
As for an ICP test I don't have any idea how they do it in regards to salinity.

 

[JRCooke]

Salinity is absolutely effected by temp. Some testers have temperature compensation build in though.

Sorry, my bad, I should have included that in my question, I know that. I measure SG @ 25 Celsius.
Once it’s mixed and if tested cold could it affect say alkalinity, calcium, magnesium etc on hobby home test kits?

 

[Gtinnel]

Sorry, my bad, I should have included that in my question, I know that. I measure SG @ 25 Celsius.
Once it’s mixed and if tested cold could it affect say alkalinity, calcium, magnesium etc on hobby home test kits?

I don't know that but that was the reason I clicked on the thread because I wonder the same thing about other parameters. It seems like it would be easy to test. If no one replies with an answer tonight I may try it with alkalinity and my Hanna checker. I'll get a water sample and test it at room temp, from the fridge, and warmed up and see what difference I get.

I would think that they would change some but probably not enough to matter, but that's just a guess.

 

[JRCooke]

I don't know that but that was the reason I clicked on the thread because I wonder the same thing about other parameters. It seems like it would be easy to test. If no one replies with an answer tonight I may try it with alkalinity and my Hanna checker. I'll get a water sample and test it at room temp, from the fridge, and warmed up and see what difference I get.

I would think that they would change some but probably not enough to matter, but that's just a guess.

That would be interesting.

its my time and electricity bill that drives the question. I just don’t want to heat the water again

 

[taricha]

Once it’s mixed and if tested cold could it affect say alkalinity, calcium, magnesium etc on hobby home test kits?

The major effect is going to be reaction time for colorimetric kits like hanna. It'll usually just be a little slower when cold, probably not a different result.
Titrations shouldn't be affected much by reasonable cooler temps.
(there are always some surprises possible though.)

 

[JimWelsh]

will the sample be heated for ICP testing?

Yes, to around 10,000 degrees F (similar to the temperature of the surface of the Sun).

 

[kingjames_dc5]

I don't know that but that was the reason I clicked on the thread because I wonder the same thing about other parameters. It seems like it would be easy to test. If no one replies with an answer tonight I may try it with alkalinity and my Hanna checker. I'll get a water sample and test it at room temp, from the fridge, and warmed up and see what difference I get.

I would think that they would change some but probably not enough to matter, but that's just a guess.

I to have always wonder this but never took the time to give it a go. I would be very interested to see the results.

 

[Randy Holmes-Farley]

Salinity is absolutely effected by temp. Some testers have temperature compensation build in though.
As for an ICP test I don't have any idea how they do it in regards to salinity.

Just to clarify, salinity is not substantially impacted by temperature, but some of the methods of detecting salinity are impacted.

 

[Randy Holmes-Farley]

I don't know that but that was the reason I clicked on the thread because I wonder the same thing about other parameters. It seems like it would be easy to test. If no one replies with an answer tonight I may try it with alkalinity and my Hanna checker. I'll get a water sample and test it at room temp, from the fridge, and warmed up and see what difference I get.

I would think that they would change some but probably not enough to matter, but that's just a guess.

As folks note, titration kits (most alk, calcium, and magnesium) will not be impacted much by normal rom temperature, but the timing or results of color change/match kits can be:

Hach Silica kit:

Silica Test Kit, Model SI-5

Silica test kit with color disc covers 0-30 and 0-600 mg/L ranges with 1 and 20 mg/L increments.

www.hach.com

"The sample temperature must be 15–25 °C (59–77 °F) for accurate results."

 

[Gtinnel]

Just to clarify, salinity is not substantially impacted by temperature, but some of the methods of detecting salinity are impacted.

I find it amazing how little the average hobbyist knows about the most basic of parameters in salinity. For years I understood that salinity was impacted by temp, but you're saying it isn't (significantly at least). So it's just our testing devices reading the salinity wrong when the temp is outside of a traditional range?

 

[Gtinnel]

I to have always wonder this but never took the time to give it a go. I would be very interested to see the results.

I was busy last night with school events for my kids but I should have plenty of time this evening to do it. I'll let you know what results I get.

 

[JRCooke]

Thanks to those guys with the knowledge for the detailed answers. Appreciate it.

 

[Randy Holmes-Farley]

I find it amazing how little the average hobbyist knows about the most basic of parameters in salinity. For years I understood that salinity was impacted by temp, but you're saying it isn't (significantly at least). So it's just our testing devices reading the salinity wrong when the temp is outside of a traditional range?

This is a bit of a complex question when you get right down to it, and depends on how you define salinity. But the big "changes" that folks see with salinity measuring devices with temperature are because the the devices themselves are typically measuring a different property (refractive index, conductivity, or density, for example), and that property changes with temperature. So the correlation between, say, refractive index and salinity itself is temperature dependent.

Think of it this way; If salinity is defined in its most simple way (grams of solids per 1 kg of total fluid (35 ppt = 35 g/kg)), then if you take one kg of that seawater and change the temperature, all of the solids and water come along to the new temperature, and the salinity is necessarily unchanged.

 

[Gtinnel]

So this evening I took a cup of tank water and got a sample and tested alk with my Hanna and got 8.1. I then put the cup of water in my freezer for an hour or so and then tested and got 8.0 (which honestly I was surprised I was able to get an accurate (I'm guessing its accurate) reading since the cuvette was frosting over while trying to test. Then I put the same cup of water in a sink with hot water in it until the sample was warm and I got a 8.4 on my Hanna.

Then let the cup cool down to room temp and tested again and got 8.4 also.

I guess all I proved was that my test was very unscientific. I'm not sure why my last 2 tests were higher but warm and the last room temp tests still gave the same reading, so my guess is for alk temp doesn't matter. Which seemed to be stated by several people on the thread before I did my pointless test.

 

[Randy Holmes-Farley]

I'm not sure why my last 2 tests were higher

Actually, IMO you showed that to within the claimed uncertainty of the Hanna checker, temperature is unimportant as all of those are essentially the same:

Alkalinity Checker Handheld Colorimeter - HI772 | Hanna Instruments

Hanna Instruments alkalinity checker bridges the gap between alkalinity test kits & advanced instrumentation by giving direct saltwater alkalinity results in dKH.

www.hannainst.com

Accuracy @ 25°C/77°F

±0.3 dKH ±5% of reading"

 

[Gtinnel]

Actually, IMO you showed that to within the claimed uncertainty of the Hanna checker, temperature is unimportant as all of those are essentially the same:

Alkalinity Checker Handheld Colorimeter - HI772 | Hanna Instruments

Hanna Instruments alkalinity checker bridges the gap between alkalinity test kits & advanced instrumentation by giving direct saltwater alkalinity results in dKH.

www.hannainst.com

Accuracy @ 25°C/77°F

±0.3 dKH ±5% of reading"

Well I appreciate the comment, and here I assumed it was some kind of testing flaw that caused my two higher readings.

Wait, so if my alkalinity is 8 then 5% is .4 plus the .3 means the testers accuracy is only guaranteed to be within .7 of the actual alkalinity? If I'm right then that is a huge variance, I wonder if most people realize that?

I never bothered to look up the accuracy of it, ecspecially since I rarely use it.

 

[Randy Holmes-Farley]

Well I appreciate the comment, and here I assumed it was some kind of testing flaw that caused my two higher readings.

Wait, so if my alkalinity is 8 then 5% is .4 plus the .3 means the testers accuracy is only guaranteed to be within .7 of the actual alkalinity? If I'm right then that is a huge variance, I wonder if most people realize that?

I never bothered to look up the accuracy of it, ecspecially since I rarely use it.

It is true that many folks think test methods are more accurate than they really are, especially digital ones.

In this case, the best Hanna claims is 8.0 +/- 0.4 dKH. So 7.6 to 8.4 dKH when it reads 8.0 dKH.

If you test the same sample multiple times it may give a more narrow range of results (say, 7.9 to 8.2), but that does not mean the true answer is within that range.

 

[Gtinnel]

It is true that many folks think test methods are more accurate than they really are, especially digital ones.

In this case, the best Hanna claims is 8.0 +/- 0.4 dKH. So 7.6 to 8.4 dKH when it reads 8.0 dKH.

If you test the same sample multiple times it may give a more narrow range of results (say, 7.9 to 8.2), but that does not mean the true answer is within that range.

I like most people just hear the popular brands of testers and use them without looking into how accurate they actually are.

 

[JRCooke]

I like most people just hear the popular brands of testers and use them without looking into how accurate they actually are.

Thanks for trying.

It was very good of you and in a way has answered my questions.
With yours and others input I now know I can get a fairly accurate result within test apparatus accuracy without worrying about heating the sample up to 25. Which is useful because sometimes I take a cup of water, get distracted and don’t test till a bit later.

thanks again