bracketing standard technique

[upamaniah]

hi,
is there any statements regarding useage of bracketing standard system in quantification analysis as well as the acceptance creteria by any regulatory body or any institution
almost all of my senior analysts says no, in such a case from where we taking as a reference.
thanks in advance
vijay
india

[Srinivas SK]

Hello

Bracketing is a well accepted validation and quantitation technique. If you could offer more information on what your application problem is, nature of sample, concentration levels, etc.. perhaps I could help out.

Rgds,

S.K Srinivas

[upamaniah]

hi sir,
thanks for the reply.
its about the general ovi analysis by gc-head on/headspace of drug substances.
especially triethylamine, pyridine, tfa, acetic acid we are doing by hean on injection of sample 100mg/mL with respective standard concentrations.
i was analysing triethylamine content (1000ppm) in promipexole dichloride monohydrate and ropinrole hydrochloride drug substances.
the later didn't give any great issues, but former drug giving problems like regenearion of column(db1-30mX0.53mmx5.0µm). i quickely understand that the sample moity as well as dihydrochloride gives rise some problems. hence i injected a b.std after my sample. i didn't get any peak for tea rt. next day i took regeneartion techniques and injected the same std preparation and found reproducing. keeping this in mind i am started injecting a std after every six samples in all projects. my seniors are differing this is not necessary as there is no written subject.
hence my quiery.
thanks and regards,
vijay

[Srinivas SK]

Dear Vijay:

I don't see anything wrong in your reasoning. It is normal practice to inject a standard after a few sample injections. I'd recommend it myself. It would be better if you could add an internal standard, and calculate peak height ratios, if reproducibility is an issue.

As far as I know, TEA tends to get strongly retained on a DB-1 column and regular regeneration is required.

Also, check the sample load. I think 100 mg/ml on a 0.53 megabore is on the higher side.

Do let me know how this turns out. This is an interesting problem.

Best regards,

Srinivas

[upamaniah]

hi sir.
about sample concentration:
for 100mg/mL sample con. std working con. will be 100ppm for a limit of 1000ppm. in agilent it is giving area of 120 (1µL) for a split ratio of 1:10, (i can go for 1:5 there i am getting repeatablity problem). this area is quite low for the validation purpose. sometime back i worked out for ceftriaxone sodium sample having 300 ppm as limit. there i used splitless injection of extracted tea from sample matrix in inorganic basic condition to ethylacetate. i am trying the same way for this sample too, if i get good recovery i am bit lucky.
thanks for the comments soon i will let you know about the results.
one guy asked about using 0.53mm column in gcms in this forum
i replied kindly look in to it and give suggestions.
vijay