Irregular Phosphate readings

[Ziggy17]

The lot number on both boxes that I used the reagents were Lot#0962 expire 2028

 

[Shirak]

Have you tried picking up a different phosphate test kit? Or have a LFS test if they have a good tester? Seems to me you need to verify which is the correct value.

I know you said the phosphate measure seems to match the color of the sample after testing but what if it's actually the high one that is correct and the others are incorrect due to bad reagent? The tester wouldn't know the difference and would measure the lighter color sample as it sees it. Would a bad packet of reagent read the .1 as .6? I don't know but I guess it's possible if a bad packet could read .6 as .1?

 

[Ziggy17]

Have you tried picking up a different phosphate test kit? Or have a LFS test if they have a good tester? Seems to me you need to verify which is the correct value.

I know you said the phosphate measure seems to match the color of the sample after testing but what if it's actually the high one that is correct and the others are incorrect due to bad reagent? The tester wouldn't know the difference and would measure the lighter color sample as it sees it. Would a bad packet of reagent read the .1 as .6? I don't know but I guess it's possible if a bad packet could read .6 as .1?

If I take 20 tests and only 3 were high, the likelihood of the 17 being false is not likely in this case. And I used a Salifert kit which was showing .1 ish, but hard to tell as the colour wall isn’t easy to read.

If it was only .6- .1 it would be easily to pass off as an error. But to go from 2.34 a linear decrease to .1 is a different conversation.

 

[Shirak]

Which is why I suggested another test kit which you apparently did so that is good. Salifert reading around .1 confirms the Hanna reading around the same value is correct. So either something is making the other oddball test way off in your sample or there is something wrong with a few of the reagent packets? Not sure there is a way to know for certain except if you get an odd test on the Hanna can you also test with the Salifert? Maybe. If you take enough of a sample to do a Salifert test with the same sample water when you get a Hanna result way out there. Could at least tell you if it's actually the sample or the Hanna reagent.

 

[Ziggy17]

If you take enough of a sample to do a Salifert test with the same sample water when you get a Hanna result way out there. Could at least tell you if it's actually the sample or the Hanna reagent.

That’s a good point, and I’ll do that.

It still leaves an unknown and I’m not a fan. I suppose the linear fashion of the decrease could be coincidence, but I’m not convinced in 3 coincidences in a 15 minute time span. Something in the water sample drove the numbers up and back down rather quickly.

 

[Dan_P]

That’s a good point, and I’ll do that.

It still leaves an unknown and I’m not a fan. I suppose the linear fashion of the decrease could be coincidence, but I’m not convinced in 3 coincidences in a 15 minute time span. Something in the water sample drove the numbers up and back down rather quickly.

Until this week, Hanna reagent issue was always low on my list of possible causes for testing issues.

I did many silicate tests over the past week, some being replicated. I worked with 3 lots of reagent C. Expiration date 2027 or 2028. The symptom was 1 ppm variation in the silicate reading. The swings in readings were correlated with the coloration of the powder. High reading when the reagent was nearly colorless (correct value), low reading when the reagent was highly colored. I was lucky because my problem reagent was color coded. I have a boat load of reagent lots and needed to test, so, I discarded any reagent if its olor was more than off white. Here is the information that might apply to your situation.

The reagent color variation occurred in the same lot AND since the packets were still attached in strips, occurred every other one. I hypothesize that the bulk reagent used to fill the packets was not a well mixed blend of lots or there was local decomposition of the bulk reagent during storage in one lot. Whatever the cause for bad reagent being unevenly distribute in the bulk, the point is that there can be variation within a given lot of packaged reagent. The individual packet quality might be consecutively good or bad, or gradually go from bad to good, or some other type of variation pattern. By the way, bad reagent might not be colored and gives no visual clue to the variation.

 

[Randy Holmes-Farley Verified Community Expert]

The reagent color variation occurred in the same lot AND since the packets were still attached in strips, occurred every other one. I hypothesize that the bulk reagent used to fill the packets was not a well mixed blend of lots or there was local decomposition of the bulk reagent during storage in one lot. Whatever the cause for bad reagent being unevenly distribute in the bulk, the point is that there can be variation within a given lot of packaged reagent. The individual packet quality might be consecutively good or bad, or gradually go from bad to good, or some other type of variation pattern. By the way, bad reagent might not be colored and gives no visual clue to the variation.

Wow, that's really interesting.

I doubt anyone here, or even Hanna tech reps, know some of the manufacturing details that might contribute to such issues, but it is certainly possible that a manufacturing machine might fill or seal more than one packet at a time, with materials running through different supply lines, and maybe even from different bulk packs of powder . Thus, the every other one, if it holds for more examples, is an interesting key to understanding.

As an aside, back in the early 1990's I worked for GTE Laboratories which was owned by the same parent company (GTE) as Sylvania. I'd have to say that one of the most interesting and eye opening things I learned during my time there was how Sylvania light bulbs were made on fully automated assembly lines. It was incredible how those lines were designed and implemented. Some of these sorts of things are way more complicated than typical consumers understand.

 

[Dan_P]

Wow, that's really interesting.

I doubt anyone here, or even Hanna tech reps, know some of the manufacturing details that might contribute to such issues, but it is certainly possible that a manufacturing machine might fill or seal more than one packet at a time, with materials running through different supply lines, and maybe even from different bulk packs of powder . Thus, the every other one, if it holds for more examples, is an interesting key to understanding.

As an aside, back in the early 1990's I worked for GTE Laboratories which was owned by the same parent company (GTE) as Sylvania. I'd have to say that one of the most interesting and eye opening things I learned during my time there was how Sylvania light bulbs were made on fully automated assembly lines. It was incredible how those lines were designed and implemented. Some of these sorts of things are way more complicated than typical consumers understand.

An old TV program “How It’s Made” presented a 10 minute video on the manufacturing of incandescent light bulbs. Automation galore.

I laughed at the ease these machines blow, connect and seal glass, remembering my efforts to make a cold trap that would hold a vacuum.

 

[Lasse]

I have seen reports here in Sweden with rise in PO4 after treating a dinoflagellate blom with UV-C. However - not so high and not so fast decline as you report - more days than hours. Dinoflagellates are known for its ability to absorb and utilize PO4 in much lower concentrations compared with competing algae and also for their ability to "store" P as polyphosphate in their tissues. Something linked to your problems with dinoflagellates is stil my main track.

That 50 different bags from two different batches - at least 3 would contain a bad reagent and that you from this 50 bags pick the three that have nearly an linear decrease between each others in the right order may be the reason...... if so - do not buy any lotteri tickets for the last of your life - IMO - your life's most magical event have already happens

Sincerely Lasse

 

[Ziggy17]

Dan P, thank you very much for doing that. It makes sense that it could happen. I wonder if Hanna would be open to learning about this and issue warnings on certain lots that display an irregular reading based on possible mixing issues.