ca monitor

[Randy Holmes-Farley]

I would not trust any ion selective electrodes in seawater, except fluoride, without seeing a detailed discussion stating that they can work without excessive interferences from other ions under those circumstances.

[chask]

I have had a little chemistry but I shunned biology during my studies - didn't relish the idea of cutting up frogs and mice etc. It also has been many many years since I have even seen a chemistry classroom or lab so this may be a pretty dumb question/suggestion.

Would it be possible to correlate a reading from an ion meter to a chemical test result to estimate greater accuracy in future readings with the ion meter?

What I am thinking is a procedure akin to calibrating a pH meter but use sea water samples from the tank for the calibration solutions so that the other ions are present in the test samples. Take enough for three samples being sure to get enough for a few standard chemical tests of each calibration sample. Test the water in one sample for the ion of concern. Then add known amounts of the ion to known volumes of the other samples to create a total of three concentrations. Use a chemical test kit to verify the ion concentration in the other two samples. Then use the ion meter to test the three samples. Wouldn't this procedure provide sufficient information to calibrate the ion meter for reasonably accurate use? Or will the other ions that might contaminate the ion meter readings change in concentration out of proportion with the ion of concern?

chask

[Randy Holmes-Farley]

The Pinpoint meter does include calibration fluids. Whether they are suitable for the range of different water chemistries that reef aquarists encounter is the question.

What I am thinking is a procedure akin to calibrating a pH meter but use sea water samples from the tank for the calibration solutions so that the other ions are present in the test samples.

That is what I plan to do using ICP/AA for the detection method. I would not assume that any kit is demonstrably accurate enough to determine the accuracy of a different method.

[Randy Holmes-Farley]

Lou Dell (owner of American Marine) has sent me some info that I can post here that may be of interest to folks:

"The Calcium PVC membrane is pretty resistant to most minor interferences. Magnesium within a relatively normal range should not really change the results significantly. Regardless a stabile Magnesium level will always show the real differences in Ca++ levels on any system.
The calibration fluids are basically 32-33 ppt salt level with a Magnesium background 1200-1400 ppm + the appropriate Calcium level.
This probe is very expensive IMO and it should be kept clean as possible. My recommendation is for the hobbyist to set up a monitoring station whereby 3 cups, test tubes (I use shot glasses) are set up. Cal fluid in the first two and tank sample in the last. Store the probe in any of the 2 clean calibration fluids and take a new sample as often as you wish to determine the Calcium level.
This probe is definately not like a pH or temperature probe and will react much slower. pH is usually 10 seconds or so; Calcium may take as long as 40 seconds (an etentity in the advanced reefkeepers life!)
Many people will continuously monitor and this can be achieved but you have to be mindful of :
1-putting the probe at the proper level relative to the water level
2-replenish the electrolyte fluid when needed
3-re-calibrate when readings change significantly
4-must use an AC Kit; battery will work continuously for only a few days
5-shorter probe life"

[alrha]

sheeesh. basically its not as simple as a simple pH monitor. for all that hassle, i would probably find it easier to just use a test kit.

[Bojan]

Randy do you have any idea, what is probe lifetime, if I will use this probe continuously.

[Randy Holmes-Farley]

No, I do not know what the probe lifetime would be. Sorry.

[PaintGuru]

Yeah for that price I would probably stick with titrations (come on, titrations are fun!!!), especially if the probe requires replacing often. Still, another cool gadget to waste some money on!

[gobygoby]

joining in. Sounds like a good idea....but I was hoping for something that takes a constant reading and ment for 24/7 use. Oh well.....

Goby

[tstone]

My recommendation is for the hobbyist to set up a monitoring station whereby 3 cups, test tubes (I use shot glasses) are set up. Cal fluid in the first two and tank sample in the last. Store the probe in any of the 2 clean calibration fluids and take a new sample as often as you wish to determine the Calcium level.

If this unit is accurate then this sounds reasonable enough. If the probe will last a while using this method then it may be worth while.

[NCNBilly]

Don't forget the all important 4th shot glass full of Jameson for when you are done.

[Habib]

Originally posted by NCNBilly
Don't forget the all important 4th shot glass full of Jameson for when you are done.

[Bojan]

I received Ca monitor yesterday and because I like such toys, I started to test Ca monitor immediately. I exactly followed instructions in user guide for calibration with 100 ppm and 1000 ppm calibration fluid.

After calibration my Ca monitor measured 1023 ppm , when I put probe in 1000 ppm calibration solution. Because declared accuracy of Ca monitor is 2%, this is acceptable.

During measurent of Ca level in calibration solution I found out, that measured value directly jump frrom 1000 ppm to 1023 ppm. This is quite strange to me, looks like that resolution of measurements is 2%.

After that I put electrode in my sump, approximately 5 cm (2 inches) deep in water and my Ca monitor measured 426,6 ppm after 2 minutes , when measured value stabilized. I also measured Ca with my Salifert Ca test and I got result 390 ppm with Salifert test.

I left probe in the sump in the same possition all night and today in the morning I read 407 ppm on my Ca monitor, so during the night result changed from 426,6 ppm to 407 ppm.


The second

[Randy Holmes-Farley]

Thanks for the update.

The second

You were saying?

[alrha]

wow. i feel like it doesnt really help that way. first of all, it doesnt give you the piece of mind of knowing your Ca, b/c you may end up worried about the calibration. and at 390 i would add a dose of Ca but at 420 i wouldnt, so the accuracy seems to need perfecting on this thing.

[Bojan]

I will continue to test Ca monitor.

Today I will test Salifert Ca test with 100 ppm and 1000ppm calibration solutions . I suppose that new calibration solution, which I received together with Ca monitor, is trustworthy. What do you think Randy ?

After that I will test how much Ca monitor depends on temperature. I will measure the same sample , but I will heat sample to different temperatures 20, 25, 30 degress C.

[hammerhead]

Cool this is what I'm waiting for some comparative testing.

[Randy Holmes-Farley]

I suppose that new calibration solution, which I received together with Ca monitor, is trustworthy. What do you think Randy ?

I don't know. I'd presume it is accurate, as it should be easy to make.

[hammerhead]

Make sure the Calibration solution is the same temp as the test sample.

[gbr]

Received my "monitor" two days ago. First off I would like to say that I am going to be calling Pinpoint because maybe I got a bad unit and if that is the case I will correct this post.

Because I did not read the instructions or this forum prior to buying the unit I did not realize that this is not a calcium monitor. It is a calcium tester. FWIW, 2ml of this, 1 spoon of that, 8 drops of this and a squirt of that is just as easy as this new tester so I would recommend that everyone keep their wallets closed. (unless you are bidding on my tester on eBay )

I broke in the probe for two hours and calibrated the unit as per the instructions. I was excited to see what the tank read so under the house I went to drop the probe into the sump. 300...323...385...xxx...xxx...600 plus...well that can't be right I thought. So I recalibrated. This time the unit settled on 389. I tested with Salifert and got 400 so I was happy. I left the unit off and the probe in the sump, came back two hours later and turned it on...323...another hour later 316. errrrr. Salifert still says 400 of course. So I calibrate again...this time before calibration I put the probe in the 1000+ solution to see what the probe read...over 2000 something...probe in RO/DI...5...probe in 100+ solution...123. Immediately after calibration I put the probe in the 1000+ solution and got over 2000 again. Now obviously there is something wrong with the probe or the unit but this is very frustrating. I own 4 other pinpoint monitors (pH, ORP, Salinity, Temp) and have had great success but this one is faulty at best.

The manufacturer recommends using shot glasses to set up a "monitor" station and leave the probe in one of the solutions. Well unless you are covering the glass, wouldn't any evaporation drive up the calcium content in that glass and completely throw off the calibration? This is nonsense...unless of course you own the company and calibration fluid is free. At $16 for a new calibration fluid kit everytime you taint the fluid and $147 for a new probe every year and a half to two years...my fault...I should have done more research I guess...the lazy shall be punished.

Randy, I know you are busy but could you just pop that thing out of the box, break in the probe and test your tank water...ya know ya want to.

[Randy Holmes-Farley]

Thanks for the info.

The manufacturer recommends using shot glasses to set up a "monitor" station and leave the probe in one of the solutions. Well unless you are covering the glass, wouldn't any evaporation drive up the calcium content in that glass and completely throw off the calibration?

I haven't gone through the directions yet, but yes, evaporation will change the values. Maybe you are supposed to cover them, or use fresh fluid for the actual callibration.

Randy, I know you are busy but could you just pop that thing out of the box, break in the probe and test your tank water...ya know ya want to.



I'll be doing some careful tests after my vacation (which starts tomorrow).

[Boomer]

I'll be doing some careful tests after my vacation (which starts tomorrow).

AGAIN !!!

You deserve all the vacation you can get.

[Randy Holmes-Farley]

Thanks, Boomer.

[loudell]

Hi, I hope I can chime in here. I designed the Calcium Monitor and may be able to help a bit.
The PINPOINT Calcium Monitor can monitor, if you wish, and there are several ways to accomplish this. My suggestion to set up a 3 cup monitoring station is is an easy method that verifies your calibration immediately before and keeps the probe very clean by ultimately returning it to a clean calibration fluid or the probe storage bottle. You can monitor the calcium in your system and take 100 samples an hour if you want using the 3 cup method. This gives you a good sample read and keeps the probe clean, also at a proper fluid level and algae free.
If you want to put the probe in your system you should put it in an area of very low flow. Corner of a sump maybe. All types of electrodes will become very unstable at different higher flow rates, pH and ORP as well. The Calcium Probe has a low tolerance for high flow. Also the Calcium Probe should be placed about an inch into the sample so that the fluid level of the electrolyte is higher than the level of your sample.
To verify if you have a good location for the Calcium probe take a cup sample and look for the same steady number in a proper area of your sump or corner of your tank.
Keep in mind that if you add calcium, it will take some time to throroughly mix with your system and register in the probe area of lower turbulance.
gbr, if you dropped the probe in the sump then no wonder some readings were wacky. The users manual have already been re-written to help make it easier to use. You may have gotten the first instruction set. The new instructions are on the website at www.americanmarineusa.com
I'm truly sorry if you had a bad experience, many people have not. If you would like to return your meter I'm sure there would be no problem.

[Randy Holmes-Farley]

Thanks for chiming in, Lou.