2 Stage Dissolution Calculation


I'm currently in the process of overhauling custom fields and report methods in our department. I don't have much experience with this and have a question about dissolutions.
Currently for our 2 stage dissolutions, we run each sample on one sample set method with the acid bath defined as Bath A and the buffer bath defined as Bath B. These dissolutions have 2 components that are being summed together for our total dissolved percent calculation.

Currently these are processed by first processing only standards and Bath A utilizing a result custom field 
Total_Dissolved_Percent_Acid = SUM(Dissolved Percent)

The values for the last pull generated above are input into a keyboard custom field called Percent_Released_2hr for every pull and vessel for Bath B.

Then this sample set is processed again. This time using only standards and Bath B utilizing a result custom field
Total_Dissolved_Percent_Buff = SUM(Dissolved Percent) + Percent_Released_2hr

As you can imagine this method allows for an endless number of typos that require a sample set to be reprocessed. I would like to turn this into only needing to process each sample set one time and at the same time remove the requirement of typing in the 2 hour value from Bath A for each vessel/pull in Bath B. 

My main problem lies with the syntax in custom field relating to dissolution. I haven't been able to find much help on the issue. I'd like to have it calculate all of the results for Bath B with one custom field but I'm not sure if it's possible. I am starting out by creating a calculation for just the total dissolution percentage for first time point in bath B (240 minutes). I have tried both a Peak and Result field type with the CF
But both times it tells me "TIME120.%.%Total_Dissolved_Percent_Acid is either a field name that doesn't exist or a key word which needs to be used in it's exact format."

Anyone have any pointers/ideas? 

Best Answer

  • Empower2019
    Answer ✓
    Thanks for that. I don't have much experience with dissolution so my advice is based on what I know of custom fields. You say each Bath B Vessel is filled with the corresponding value from the 120 min result for each vessel in Batch A. But you have 12 Bath A entries and 18 Bath B so where do the extra 6 values for Bath B come from? Unless that's a typo and it should be 12 and 12?

    In the sample set, Label the 12 Bath A entries as A1 to A12 and B1 to B12 for Bath B. You need two CFs. First- Use your Result Custom Field SUM(Dissolved Percent), make sure its set to search order Result Set Only, all sample and peak types. Call this custom field something simpler than your name, like Dissolved_Percent.

    Second custom field: Result, Enum, Calculated, Use as Field, search order Result Set Only, all Sample and Peak Type and call this Overall_Dissolved_Percent. Formula:


    For the translation table in the next screen, you get Value from 0 to 11 and a Translation field opposite each value. For the value 0, enter A1.%.(Dissolved Percent)+B1.%.(Dissolved Percent) (fc). This should give you the value for A1 and B1 combined. Same for position 1, enter A2.%.(Dissolved Percent)+B2.%.(Dissolved Percent) (fc) and so on until you get to Position 11. Copy the first formula to Wordpad, then its just a case of editing the labels and pasting it back in. Dont forget to put a space after the formula and then (fc) this is the only way Empower will return what you are looking for. Hope this helps. 


  • Hi. Can you maybe share a screenshot or two of your sample set. I'm struggling to see the exact issue as what you are trying to achieve, thanks.

    Your syntax for those custom fields is wrong, you need to put the field or custom field that you want the calculation done for in brackets, plus if you are using a summary you need a field like AVE, MAX, MIN, SUM, PROD or %RSD. Your Field wont be recognized by Empower because the syntax goes Label, Injection, Channel and then field in brackets so you have the label and the injections covered but Empower is looking for a channel called .%Total_Dissolved_Percent_Acid which of course doesn't exist. You need to drop the channel name and put the (.%Total_Dissolved_Percent_Acid) in brackets like that.

    An example sample set would help when trying to assist.

  • Here's a generic sample set method for the dissolution in question. 
    The Percent_Released_2hr is filled in for each Bath B Vessel with the corresponding value from the 120 minute result for each vessel in Bath A. Hopefully this makes things more clear.
  • It worked thank you so much!

    It took some tinkering and re-reading but it worked. You saved me so much time I really appreciate it.

    I'm looking into purchasing some of Waters' e-Learning modules pertaining to custom fields to help me with future calculations. Do you know if they go into the kind of detail explaining why a space is needed at the end of the formula or the (fc) at the end of the translation fields?
  • Glad it worked out. I had access to a testing project before I read your reply and there is an even quicker way to do this. Label all the Bath A/Bath B pairs the same so instead of A1 to A12 and B1 to B12, change to A1B1 then A2B2 then A3B3 right up to A12B12. So your first 12 samples of Bath A are labelled A1B1...up to A12B12 and then the second 12 samples of Bath B are ALSO labelled A1B1 up to A12B12.

    Keeping your first CF as it is SUM(Dissolved_Percent), create a second Result Real Calculated custom field, search order Result Set Only, all sample and peak type, the formula is:

    SAME.%..SUM(Dissolved_Percent) and call this CF RollingDissolved_Percent, please use this naming as its important that the name of the custom field begins with R (long story!) and make sure to add a "Summarize Custom Fields" line as the last line of the sample set, also checking that the processing column for this line is set to Normal and there is nothing in the Label Reference field for that line either. This will work for you because I see you run standards throughout the run and don't do a sliding bracket set-up in that you dont quantitate samples in a bracket fashion using the standard either side of the bracket- that set up often results in CFs not working at all when it comes to Amount.

    When you process the run, Empower sums the Dissolved_Percent values for all samples with the same label, so A1B1 will be summed giving you the total Dissolved Percent from Bath A first sample and Bath B first sample and so on for second sample of Bath A and second sample from Bath B. And this CF will work when using just one pair of samples or 100 pairs, whereas the one I sent you is limited to 12 labels. Another advantage to this CF is you can do summary functions on it in a report method so a table of all the results and you can do Min and Max and Mean etc on it, whereas the first CF cant do this.

    I'm not sure what the fc even stands for its so long since I did the courses. Yes the elearning courses can be helpful. Industry experience is best though to become proficient in custom fields.

  • I ended up slightly modifying the first CF you made. The sample set I sent didn't have any typos. Basically the way it works is half the sample is dissolved in bath A and the other half dissolves in bath B. The final dissolved amount from bath A is added to each transfer time for Bath B to get the total percent dissolved at each time point for bath B so instead of 

    A1.%.(Dissolved Percent)+B1.%.(Dissolved Percent) (fc)
    A2.%.(Dissolved Percent)+B2.%.(Dissolved Percent) (fc)

    it went

    A7.%.(Dissolved_Percent)+B1.%.(Dissolved_Percent) (fc)
    A8.%.(Dissolved_Percent)+B2.%.(Dissolved_Percent) (fc)

    for the first pulls from bath B and then

    A7.%.(Dissolved_Percent)+B7.%.(Dissolved_Percent) (fc)
    A8.%.(Dissolved_Percent)+B8.%.(Dissolved_Percent) (fc)

    for the second pulls from bath B and finally

    A7.%.(Dissolved_Percent)+B13.%.(Dissolved_Percent) (fc)
    A8.%.(Dissolved_Percent)+B14.%.(Dissolved_Percent) (fc)

    for the final pulls from Bath B.
    Due to the need to add the last pulls from bath A to all of the pulls of bath B I don't think the identical labeling CF will work.

    Once again thanks for your help. I'm sure I'll be back with more questions in the future