High-end LaMotte test equipment

[richwill]

I've been collecting water parameter data (automatically) since I first setup the tank. Recently I've been lusting after more sophisticated monitoring equipment from LaMotte. Does anyone have experience with their Colorimeter or Spectrophotometer?

http://www.lamotte.com/WEB-SITE/AQU/HOME-AQU.HTM

- Richard

[JohnL]

[moved]

[Randy Holmes-Farley]

Richard:

I don't have any personal experience with those items. If anyone does, please chime in.

I know that many people have a similar system from Hach and seem quite happy with it (www.hach.com). Maybe they will chime in about it.

FWIW, I do have a spectrophotometer (not LaMotte, but a Perkin Elmer), but haven't yet used it in conjunction with any test kits.

[Gamera]

With respect to instrumentation, it looks like a pretty simple spectrophotometer. In fact, it looks like a hand-held spec-20.

THe parameters on it look decent for a handheld, though you can easily get much better performance (for more money, naturally).

My only experience has been with HP and Perkin-Elmer specs though. If you can afford these, I highly recommend them. :p

If you can afford the creme de la creme, I would recommend setting up your own with optics from Melles-Griot. It's not too expensive, and well worth the price. :D

[mx_tang]

I have a Lamotte SMART Colorimeter. The new model is the SMART2 Colorimeter, but that's why I got mine for a cheaper price.

One note on the colorimeters or even the spectrophotometers. They have been calibrated with 40+ test factors ranging from aluminum to zinc. We would probably be most interested in nitrate, phosphate, iron, iodine, and the like. The problem with these factory set programmed test factors is that they are intended to be used in freshwater.

If you want to test anything in saltwater, you're going to need to set up your own calibration curves and baselines. This is kind of a pain to do, but necessary if you want to get accurate results. I'm sure there are some test factors that aren't that far off between fresh and saltwater, but why even buy a one thousand dollar colorimeter if you only want something so inaccurate.

The problem with the user defined test factors is that it can only store 10 tests using your own reagents or Lamotte reagents. You could use Salifert or any reagent, granted that you have a known standard to compare the test kits with.

If you are calibrating in freshwater, there's no problem because you can easily obtain distilled or DI water, then add a known solution. CV1+CV2=CV3, right (where C= concentration and V= volume)? No problems there. If you know that your water has 0ppm or 0% anything except the hydrogen and oxygen molecules, CV1= CV3. Calibration is fairly straightforward.

But, when we use salt like Instant Ocean, Tropic Marin, or any other brand, we don't really know the concentration of solutes in there. For example, Instant Ocean claims to have 0 phosphates and nitrates, but is it really 0? Depending how much phosphate and nitrate we have in a known solution, we haven't accounted for this minute amount that might not be measurable with other test kits. I believe my colorimeter reads up to .1 ppm, but in the lab, we usually don't use that sig fig. Maybe that's not a big deal to some people.

Here's where it gets tricky, though. What if we're trying to test for calcium, or Iron, or something else that is absolutely in the synthetic salt. We need to rely on the manufacturers claims that they have some set range or test it against another test kit. The former might give us some really inaccurate readings to calibrate anything further with and the latter probably won't give us results too much better than that test kit itself.

I suppose you could go to the lab and ask the chemical supply house to get or make some pure sodium chloride or even try to get table salt. Mix it with DI or distilled water, then test it against a known solution. This might or might not work. There could be some interference doing it this way, but I definitely know there will be interference using synthetic salts. Personally, I haven't even started running calibrations because the time it takes is just not worth it. But, I suppose staring at an aquarium until I fall asleep, apparently, is worth my time. But honestly, I am just too lazy to do it, since I am not paranoid about test factors at the moment.

Now, if you're still reading this, and you can get a known standard somewhere or make up a batch, you need to input the data. No problem here. It's very straightforward. After you're done, or you've inputted enough data points to get a nice calibration curve, you test it with another known that's not one of the data points you used. This just tests if you correctly mapped the colorimeter. Spectrophotometers are a little more advanced because they aren't just finding color change, but %transmission and absorbancy. Basically, they calibrate the same way, though.

After all this is said and done, you've got yourself an expensive, and hopefully precise, piece of testing equipment. The accuracy is another monster altogether depending how well you set up your calibration curves and your known solutions. But even these devices can give inaccurate readings if the test tubes, cuvettes, or whatever are dirty, scratched, and have fingerprints on them.

I just figure that to make the known standard becomes costly. I waste reagents on plotting x amount of data points to not even be sure if the saltwater I mixed up truly has what I think it has in there. And I don't test on an hourly, or even daily basis, so it's not worth the hassle in the long run to test only 10 factors that I can plug and chug in the colorimeter less than 52 times a year. There's probably tons of other sources of error doing this BTW, but I figure if you buy something of this magnitude, you're going to have some idea of what you're doing. And, on the bright side, I don't need to change the test factor again unless I want to increase/decrease the range (.1-1ppm vs 1pm-10ppm). Yet, on the dark side, Murphy's Law tells me I'll accidentally delete the entire program and have to redo EVERYTHING.

I think I talked so much, my soapbox has petrified...
Mike

[Randy Holmes-Farley]

Mike:

Thanks very much for the detailed info!

[mx_tang]

You're welcome Randy. I just joined recently, so you'll have to excuse the belated post. To be honest, if someone in the water treatment industry wanted the colorimeter, I am sure I would sell it for wholesale cost because I just couldn't really do as much as I had originally planned for this device. Perhaps people with freshwater planted tanks or aquaculture could even use it to monitor water parameters, but I don't do any of those things.

I read back on some older posts and I believe Richwell's original intent was to set it up and monitor his aquarium. The problem with these kits are that they do not use monitors or probes to continually check water parameters. You still need to "get your hands wet" and do manually run the tests.

Since this thread is also about high tech equipment, I'll tell you what I am going to get as far as testing kits go. For alkalinity and calcium tests, I am absolutely bored to death dropping in reagents for titrations. So, I have decided to buy a dual magnetic stirrer (or two small ones). I'm going to drip in my calcium reagents until the color change is almost there, then use a syringe with a smaller drop volume to finish off the titration. This way, I take my 20ppm calcium test and can make it accurate to 5ppm. If I got a finer syringe with smaller graduations, such as a 10uL one, then my accuracy would be even less than 5ppm. Total cost would be $50 for cheap magnetic stirrer, $5 for the stir bar if not included, and $10 for a dozen 1mL syringes. I do have access to micropipets, but those things are really expensive. Probably 10 times the amount for a cheap magnetic stirrer.

Mike

[Habib]

This way, I take my 20ppm calcium test and can make it accurate to 5ppm. If I got a finer syringe with smaller graduations, such as a 10uL one, then my accuracy would be even less than 5ppm.

How sharp is the color change?

If you want such a high repeatability I assume that the calcium concentration is maintained within a very narrow range.

In such a case I would suggest to add say 95% of the titrant at once and then continue with the titration drop by drop.

I lost a lot of tiny stir bars in the siphon and they have to be cleaned after each use.

then use a syringe with a smaller drop volume to finish off the titration

Most regular syringes (I am not talking about chromatography syringes) will have a luer lock or some thing very close to it. The drop size of the bare syringe will be too large. A syringe with a smaller gradation does not mean that you can achieve that resolution. In most cases the drop size will determine that.
The largest stepsize counts (dropsize or syringe grad.)

[mx_tang]

Originally posted by Habib
This way, I take my 20ppm calcium test and can make it accurate to 5ppm. If I got a finer syringe with smaller graduations, such as a 10uL one, then my accuracy would be even less than 5ppm.

How sharp is the color change?

It goes from pink to dark purple. I don't want to say it's extremely sharp, but noticeable.

If you want such a high repeatability I assume that the calcium concentration is maintained within a very narrow range.

In such a case I would suggest to add say 95% of the titrant at once and then continue with the titration drop by drop.

It's maintainted between 450-480ppm. I test weekly and it doesn't drop below this because I have a lot of water and not much calcium uptake for the amount of water I have.


then use a syringe with a smaller drop volume to finish off the titration

Most regular syringes (I am not talking about chromatography syringes) will have a luer lock or some thing very close to it. The drop size of the bare syringe will be too large. A syringe with a smaller gradation does not mean that you can achieve that resolution. In most cases the drop size will determine that.

Yes, that's what I was eluding to, Habib. I think the bottle is approximately 20drops/mL, a bare syringe goes down to 40 drops/mL, and the one I am currently using goes down to 80drops/mL. Although it's not the smaller graduations that give it accuracy, it's the actual drop size. My syringe comes from Gliss and came in the Red Sea Calcium Pro test kit. I no longer use those reagents, but I have taken the syringe with the needle attachment.

Mike

[Randy Holmes-Farley]

While the calcium tests are more complicated, an alkalinity test is actually quite easy to run with a pH meter and an acid standard. There, you can make it as precise as you can measure liquids.

FWIW, I have a good UV/Vis spectrometer, but I rarely use it for reef tests for the very reasons that you mention: the need for standard curves, etc. That's the nice thing about the kits: they've done all that for you (and hopefully, did it correctly :D ).

[cayars]

<a href=showthread.php?s=&postid=620814#post620814 target=_blank>Originally posted</a> by Randy Holmes-Farley
While the calcium tests are more complicated, an alkalinity test is actually quite easy to run with a pH meter and an acid standard. There, you can make it as precise as you can measure liquids.


Digging up an old post. :)

Does anyone know how to do what Randy mentioned above? If so could you explain it please.

Thanks,
Carlo

[bertoni]

Well, all you need is a standard acid solution, an accurate measuring device, and a pH meter that can be calibrated at 4 and 7. Hydrochloric acid would do, but the concentration must be very precisely known. The testing involves titrating the acid until the pH is about 4.2.

We can probably do the math if you're still interested.

[cayars]

Yes very interested. Have both the measuring device and pH meters to do this. Getting the Hydrochloric acid should not pose a problem either.

Thanks so much bertoni!

Carlo

[cayars]

Bump

[bertoni]

Do you have an acid product chosen? We need the concentration.

[cayars]

No because I'm not sure exactly what type should be used.

If you know how to do the calc then by all means pick the acid and strength but try and make it something easy to come by.

Carlo

PS Much appreciated

[fish tanked]

digression I know but... I use a Hach DR850 colorimeter and have had great luck with it... It came as part of a water quality testing kit that included the colorimeter and a nice titrator etc. > I dont have much experience with the LaMotte stuff thought they may be great too...
Compensating for various chemical interferences and doing calibrations can be time consuming though with any colorimeter. Just my short thought...

[cayars]

What salt water tests are you using the DR850 for? Which have you found a problem with that requires a SW standard?

Carlo

[fish tanked]

Orthophosphates, Nitrates, Nitrites, Ammonia,
Chlorine ( free and total) , are the ones I usually almost daily for the colorimeter. Occasionally I will use some others.

Chloride interferes with the NO3 test so I had to take 9 samples of DI water and adjust them to 3 sets of 3 samples of set salinities. 3 samples @ 0ppt salinity, 3 samples @16ppt and 3 @32ppt. Next, I added a know quantity of a nitrate standard solution to each of the three salinity sample sets. I then ran the colorimeter test on each sample and used a formula to average the difference across the slope of salinities and nitrate levels. I then multiply the average error determined by my calculations by the results the colorimeter gives me on my sample. I think I explained that correctly.
It is a pain in the ***, but only have to do it once.
Quite a few of the tests for this colorimeter have interferences but the manual lists them all and has procedures for compensating. Most of the interferences are also huge levels of random things I am not likely to come across. So far the NO3 is the only one I have used that I have had an interference issue with. I assume that this is the case with another brand's colorimeter using this same testing method.