Algae Posted March 21, 2011 Share Posted March 21, 2011 Hey Mike. Can you post your xls chart as an attachment in this thread? BTW I have heard that alk titration kits have a limited shelf life (and ph meters are good for 6 months). The Elos kit is a pita in indoor flourescent lighting. Sent from my VM670 using Tapatalk Quote Link to comment Share on other sites More sharing options...
reefnjunkie Posted March 21, 2011 Share Posted March 21, 2011 \(and ph meters are good for 6 months). Sent from my VM670 using Tapatalk what have you heard regarding the life of PH probes I know they need to be recalibrated (more than I do) but I have not read or forgot the life, I assume until I braek the glass bulb (laugh) Quote Link to comment Share on other sites More sharing options...
Algae Posted March 21, 2011 Share Posted March 21, 2011 what have you heard regarding the life of PH probes I know they need to be recalibrated (more than I do) but I have not read or forgot the life, I assume until I braek the glass bulb (laugh) I tried to reference the 6 month statement and couldn't find it. I may have been subject to He said/She said syndrome (which I dislike a lot). If I remember right it was that the electrode may sit on a shelf at the distributor for 6 months and at the retailer for 6 months thereby reducing the useful life. Randy Holmes and Milwaukee say that the useful life is 18-24 months. There have been people that have got 5 years out of a probe. I have had two go out on me. One at 9 months (Milwaukee) and the other at 1 year (Neptune standard). When they go out they will either jump all over the scale or be very slow to respond. The last one I bought was, effectively, $21 at BRS. I have ordered PH probes from China for about the same. BRS does test theirs before shipping. Back to the Alk/Phosphate thread! Quote Link to comment Share on other sites More sharing options...
madmike Posted March 21, 2011 Share Posted March 21, 2011 I keep a jar of 4ph test solution nearby and dunk the ph meter in it every once in awhile... if it within range I keep on testing, once it it out of range I recalibrate. As meters go bad they seem to need calibration more and more. I usually get 18-24 months out of mine and that seems reasonable. Remember to calibrate the meter with 4ph and 7ph because our endpoint is now 4.2, not the standard 8 or so of a reeftank. Quote Link to comment Share on other sites More sharing options...
grassi Posted March 21, 2011 Share Posted March 21, 2011 It is better to use standards for this kind of test. If you want to use a ph probe (and accept the error they introduce) you should use an instant lab grade ph meter, not a probe made to be used in full time immersion, like the "lab grade" we use in the hobby. They cost around $500+ The ph probe is useful for quick readings. You can find a lot of info on some threads of Randy Holmes Farley on RC or some writings on reefmagazine. Quote Link to comment Share on other sites More sharing options...
reefnjunkie Posted March 21, 2011 Share Posted March 21, 2011 I would suspect that if you are using a probe like the extra one I have hooked up to Apex to show me the PH in my tank (so I can say "neat my PH is 7.8" (laugh)) and I drop in a calibration solution of 4 and it reads 4, isn't that gonna work? As much as I drop stupid amounts of money on this "addiction" I will never drop that cash for a lab grade- Dont read that poorly, I hear what you are saying, I just figure if the probe reads 4 will soaking in a solution of 4 I am good to go, especially giving the range I used to get with all the other test kits- Quote Link to comment Share on other sites More sharing options...
grassi Posted March 21, 2011 Share Posted March 21, 2011 To reply to you question: if you calibrate (well) your probe you can be sure that the water in your tank is near to that ph value. But that does not mean that it is the real ph or that it will read so well to be used as a tritration test. Just think about how much time your probe takes to calibrate Give that much time to your probe to read when testing alk, and co2 will make it useless. Also, the accuracy of a ph meter depends on many other aspects. You have to rinse properly the probe. You have to stir the solution without adding to much co2 and so on. The pH electrodes change their response as a function of temperature, and so does the standard. I didn't suggest to buy a lab grade instant ph meter, but to test with standards instead of the probe. So if you want an approximative alk value, go with your probe. If you want an accurate value go with the standards or a good ph meter If you want the best of the 2 worlds, just use a good alk test kit: easy and enough accurate. This is not just my thinking, but from a guy who has a BA in chemistry and biology and a PhD in chemistry from Harvard University You can find some infos about the ph probe calibration and the related issues here: http://www.reefcentral.com/forums//showthread.php?p=16422790 There is a thread somewhere on RC where Holmes-Farley is discussing the alk test with a ph probe, I can't find it right now... Quote Link to comment Share on other sites More sharing options...
madmike Posted March 21, 2011 Share Posted March 21, 2011 Grassy, Holmes-Farley uses a ph probe and sulfuric acid to test his alk, he stated he's been doing it for years this way Quote Link to comment Share on other sites More sharing options...
madmike Posted March 21, 2011 Share Posted March 21, 2011 If you want the best of the 2 worlds, just use a good alk test kit: easy and enough accurate. Why would a test kit be the best of both worlds? Most color titration endpoint testkits don't even color change at ph 4.2, they all have different endpoints that IMO can vary alk reading by alot. There is an interesting thread on RC that show different kits changing color anywhere from 3.9-4.5. I'll take a few hundredths difference with my ph probe vs a few tenths off any day Quote Link to comment Share on other sites More sharing options...
grassi Posted March 21, 2011 Share Posted March 21, 2011 The test kits with 2 dyes can have a 10% error in titration. With the muriatic acid there are so many factors that you can introduce that you are probably gonna go over that 10%. This is what Randy was saying: "There is still the issue of how accurate the concentration on the bottle actually is. Is it just a target level that the company shoots for in manufacturing, or is it an actual measured result for that batch. The answer may actually be different for different companies. "The remaining concern is how accurately can you measure liquid volumes. Most people do not have a good way to do that with sufficient accuracy. If you do, this is an OK method, although you should be careful with the concentrated acid as it is nasty. If you are off by 5% in each step (initial dilution, second dilution, and then in the titration step), then the result might be off by 15%. The actual procedure involves many volume measurements, and typical DIYers will be off on all of these to some extent. So the quality of the result depends very strongly on the quality of your volume measurements." He might use this method, but I'm not a chemist, like many of us, so it is really possible that I will introduce a 15% (or more) error, which is higher that what I can get with no hassle from a La Motte or Hatch. This is why I think is for me and the average person, the best of the 2 worlds. Quote Link to comment Share on other sites More sharing options...
madmike Posted March 22, 2011 Share Posted March 22, 2011 There is still the issue of how accurate the concentration on the bottle actually is. Is it just a target level that the company shoots for in manufacturing, or is it an actual measured result for that batch. The answer may actually be different for different companies. You are referring to someone who is making a dilution of muriatic acid from home depot etc. for the titration which yes could be all over the place. We are purchasing laboratory grade 1N sulfuric acid used in labs that is standardized so IMO there is no 10-15% error in accuracy as long as you can measure aprox 3ml during your titration you will be just fine Quote Link to comment Share on other sites More sharing options...
grassi Posted March 22, 2011 Share Posted March 22, 2011 I'm with you for the acid source. Not for the accuracy of a cheap full time immersion probe, even if recalibrated one minute before the test. I use this method as well sometimes since I posted it here a few months ago. But I believe more the La Motte Quote Link to comment Share on other sites More sharing options...
Algae Posted March 23, 2011 Share Posted March 23, 2011 I'm with you for the acid source. Not for the accuracy of a cheap full time immersion probe, even if recalibrated one minute before the test. I use this method as well sometimes since I posted it here a few months ago. But I believe more the La Motte How easy is the La Motte to read? I just ordered one. I have a La Motte Nitrate tester and really like it btw. Quote Link to comment Share on other sites More sharing options...
grassi Posted March 23, 2011 Share Posted March 23, 2011 How easy is the La Motte to read? I just ordered one. I have a La Motte Nitrate tester and really like it btw. I like it. The color change is easy to read. The test is fast to after a couple of times that you have done it. You will like it Quote Link to comment Share on other sites More sharing options...
Algae Posted March 23, 2011 Share Posted March 23, 2011 Thanks Alessandro! Very cool! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.