Salinity: DIY Calibration Standard consistent difference with Oceamo-MS ICP

[djkms]

Hello,

I am using Randy's DIY conductivity standard to calibrate my Hanna Salinity tester. Unlike most people I love this tester as its the only one that I know of on the market that can test to the tenth of a point.

I mix 6.2grams of Mortons salt to 182ml of RO/DI water to calibrate. I run ICP's every 2 months and my ICP consistently reads .06 higher than my Hanna checker calibrated with the DIY solution. I also add up all the elements to see if that number matches the salinity value on my ICP which it does.

Curious on the discrepancy To correct this I assume I would just add 6.1 grams of salt instead of 6.2?

My most recent ICP is attached. When I tested my water it read 35.4 but ICP came back 35.9

This is the scale I use to measure:
Amazon product

Any thoughts appreciated,
Kris

 

[mook1178]

The precision of the tester is 1 ppt. That means the tester and the icp are in agreeance if the results if both are less than 1 ppt from each other

 

[Reginald Reefer III]

I no longer use a refractometer type of salinity tester and solely use a hydrometer. It matches almost exactly to my monthly ICP-MS.

 

[djkms]

The precision of the tester is 1 ppt. That means the tester and the icp are in agreeance if the results if both are less than 1 ppt from each other

Valid point that I often forget with these testers, the stated accuracy. That being said it is consistently .06 higher so I may just add .1g less salt next go around and see how it compares to my next ICP. Thanks for the reply.

 

[mook1178]

IF it is really .06 ppt different, you are not making any difference to the animals in the tank for that adjustment. That is most likely in the ICP precision. Just because something reports to x digits does not mean that is an accurate measurement, Ie hanna reporting 0.1 ppt when the precision is 1 ppt.

 

[KStatefan]

Oceamo uses a conductivity meter for salinity on your results.

 

[djkms]

IF it is really .06 ppt different, you are not making any difference to the animals in the tank for that adjustment. That is most likely in the ICP precision. Just because something reports to x digits does not mean that is an accurate measurement, Ie hanna reporting 0.1 ppt when the precision is 1 ppt.

I dont disagree with your statement and this isnt about the health of the animals. its more an OCD thing trying to get values to match if I have the ability to do so.

 

[mook1178]

I dont disagree with your statement and this isnt about the health of the animals. its more an OCD thing trying to get values to match if I have the ability to do so.

Good luck! You are messing around and trying to make adjustments in the precision realm of either measurement.

 

[djkms]

Good luck! You are messing around and trying to make adjustments in the precision realm of either measurement.

Thanks, its actually one of the aspects I enjoy with reefing

 

[Randy Holmes-Farley]

Curious on the discrepancy To correct this I assume I would just add 6.1 grams of salt instead of 6.2?

My most recent ICP is attached. When I tested my water it read 35.4 but ICP came back 35.9

I agree that you are trying to be more accurate than the Hanna permits.

It only claims +/- 1 ppt under perfect conditions

You are seeing a difference of 0.5 ppt between your measurement and a measurement at a lab that is likely more accurate, but still has its own uncertainty.

So I do not see a concerning "discrepancy".