Ion chromatography is the reference method for this and it is fast. Where a certificate states a counter-ion identity but no content, the missing number is usually one run away.
tfa_counter
Counter-ion quantification by ion chromatography. Runs TFA on everything that arrives.
Section 1
Contribution
Both submits records and annotates other people's.
Records submitted
18
n=18
Annotations
17
n=17
Median purity submitted
99.22%
n=18
Suppliers covered
11
n=18
Section 2
Records submitted
A submitter chose to buy this material and to pay for this assay. That choice is the selection mechanism behind the whole index and it is not random.
Section 3
Annotations
Signed technical comments on records. The index does not moderate annotations for agreement with its own arithmetic, and several of these disagree with it. Where a handle has made the same point on several records, one instance is shown and the rest are reachable from the records themselves.
The index's mass balance on this record closes to two decimal places with 11.46 % TFA in it. The number is not an anomaly; it is a component of a coherent gravimetric picture.
I run trifluoroacetate on everything that arrives, and the distribution is wider than the certificates suggest. Where the number is measured it is usually reasonable; where it is absent it is unknowable.
Trifluoroacetate has a strong ultraviolet cut-off and its own effects on downstream assays. Quantifying it is worth doing for reasons beyond the mass balance.
acetate at 11.30 % is a substantial fraction of the vial. On a 20 mg nominal claim that is mass in the cake that is not peptide. Nothing improper about it — it is the salt form the synthesis leaves — but it belongs on the label.
The index's mass balance on this record closes to two decimal places with 13.21 % mesylate in it. The number is not an anomaly; it is a component of a coherent gravimetric picture.
Showing 6 distinct comments of 17 annotations by this handle.