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Author Topic: pH of Calcium Chloride issues  (Read 540 times)

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Mcant

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pH of Calcium Chloride issues
« on: January 03, 2017, 10:48:30 PM »

See Below
« Last Edit: January 03, 2017, 11:00:50 PM by Mcant »
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Mcant

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Re: pH of Calcium Chloride issues
« Reply #1 on: January 03, 2017, 11:00:07 PM »

Hi all,

Could I ask for a bit of input into an issue I've been investigating lately?

I received 2 batches of CaCl2 Dihydrate from a supplier with a CoA result expected below and above my specification (5.4 and 6.3 respectively) (my specification is 5.5-6.0)

On testing at a 10% w/v solution at 23 degrees =/- 2 degrees (our specification) we generated results of (6.37 and 6.70 respectively).

Following an initial RCA I came to conclusion of a genuine OOS result being generated.

Further testing was conducted since the supplier tested at a 5% w/v concentration, as well as a repeat at 10% w/v at 23 degrees C +/- 2 degrees.

Results were:  5%  - (5.77 / 5.99)
                        10% - (5.91 / 6.31)

The pH meter was calibrated and passed before every measurement and intermediate checked afterwards, the same pH meter was used to test other products by various other analysts on all days - of which no atypical results were generated.

A brand new pH probe was also installed and used after the initial OOS result.

on a visual comparison both batches look relatively uniformed with regard to particle size.

I'm thinking that the batches might have been taken from the "end of the pot" on the supplier's side leading to a lack of homogeneity?

These results seem to be coming out of a random number generator -  this issue aside the results initially taken were also nowhere near the CoA (and the difference between batches was fairly large).

Any input would be most appriciated!

Thanks in advance!  >:D 
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Mcant

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Re: pH of Calcium Chloride issues
« Reply #2 on: January 03, 2017, 11:01:38 PM »

it's probably worth noting all other tests NIR / Chemical IDs etc passed with no issues
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Arkcon

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Re: pH of Calcium Chloride issues
« Reply #3 on: January 04, 2017, 01:11:34 AM »

There are hundreds more variables to consider.  Lets try to work briefly with some for now

You have to return these lots, and the manufacturer has to replace, or retest and share their procedures with you.  If you're proud of the work you've done, and they're proud of their work.  This should be a non-issue.  We'll have to see how that goes, however.

What you're doing is problematical, however.  The pH electrode isn't a solid-state Star Trek tricoder-type device.  And I do get into arguments with people over this.  Everytime you stick it onto a solution, a trace of the filling solution gets replaced by the analyte.  That shouldn't be significant, but experimentally, you should evaluate your procedure:  How much, does the pH of the calibration stand deviate before and after these unknown samples?  You can't be more accurate and precise than that.
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That all depends on how reasonable we're all willing to be.  I just want my friends back, except for Cartman, you can keep him.

Mcant

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Re: pH of Calcium Chloride issues
« Reply #4 on: January 04, 2017, 03:46:26 AM »

Thank you for the input Arkcon, I'm not personally sure there are 100s of variables as such since the test is ridiculously simple and 99% of everything else tested by the same method and equipment has produced expected / passable results.

The batches have been returned / not being used in manufacturing. The issue is we've still have to report / investigate as to why the results were generated and the powers that be hate "inconclusive" as a reason if at all possible - that being said it's getting to the point at which we might sign it off as such.

I'm coming to the end of my reasoning as to why we've generated these results hence asking online, in case there was a pearl of wisdom.

Either way thanks for the input.  :-*
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