I have problem with Reference standard for HPLC

[ultima_86]

Hi everyone, I am using Amoxcillin trihydrate reference standard (86.0% Amoxcillin, as is). I used the reference standard to calculate my raw material Amoxcillin trihydrate and got the result about 87.2% but the specification is 95.0% - 105.0% anhydrous substance (I have not used either convertion formula using molar mass of Amoxcillin and Amocillin trihydrate or substration of moisture yet)
My question is that: “Is the content of my reference standard 86.0% of Amoxcillin trihydrate or 86.0% of Amoxcillin (as is)?”
Any support would be highly appreciated. Thanks in advance!

[vmu]

Theoretical content of C16H19N3O5S in C16H19N3O5S·3H2O is 100*365.40/419.45 = 87.1%.

USP RS
https://static.usp.org/pdf/EN/reference ... R106H0.pdf
Molecular Formula: C16H19N3O5S·3H2O
...use a value of 869 ug of amoxicilline per mg of material on the as is basis.

EP CRS
https://crs.edqm.eu/db/4DCGI/db/4DCGI/l ... 0000_6.pdf
AMOXICILLIN TRIHYDRATE CRS batch 6
The “as is” content is: 85.9% of C16H19N3O5S (for 0577, 0260).

[TylerSmith123]

Hi Ultima,

According to the European pharmacopeia, and what I learned, the "as-is" weight is the weight of only the Amoxicillin (C16H19N3O5S) aka the 87.2% (by weight). While the remaining ~13% is probably mostly the water content of the hydrate, and the smallest bit of impurities (probably only 0.5% of the total weight). However, you are on the correct pathway with your conversions, I've seen a few examples on here of people who forget the conversion between salt and free base or acid. I hope that answers your question! And here's a link to the Eu pharmacopeia page for their Amoxicillin standards used in monographs:
EDIT: Vmu jumped on this one much quicker and has all the necessary info I would have linked!

Have a nice one,
Tyler

[vmu]

the "as-is" weight is the weight of only the Amoxicillin (C16H19N3O5S)

"As is" is an attribute of a ref. material, not an attribute of any of the constituents of the ref. material. It means that you don't need to do any additional calculations and actions (e.g., drying, determination of water and/or residual solvents content, etc) to find the amount of the substance of interest in the sample of RS you take. You only need to multiply the weight of the RS sample you take by the value of the weight fraction of the substance stated in the RS certificate.

[ultima_86]

Many thanks to all of your answers. My problems have been solved.