All chapter are use full for ADJUSTMENT of chromatography, TLC etc 

In such case some questions arias that

Why adjustment in chromatography ?
How adjustment justified ?

Adjust chromatography

If your method is validated and method are submitted in DMF so
[Different lab may different working processer different instrument, column manufacture different  may be fail in sst which may mention in monograph such case ]

a. Meet system suitability criteria
b. Meet relevant performance characteristics (resolution, Rt, Palt count etc(column manufacture different such case)
c.  why sst or monograph condition not achieved in your lab 
i. Change in Instrument /equipment
ii. Change column manufacture 
iii. Change in reagent /chemicals
iv. Different in operation (one lab to another lab)

How adjustment justified

a. By verified SST
b. By verified any other relevant performance characteristic 
3. Important considerations 
a. Change other those indicated in gc<621> revalidation of procedure
b. Once adjusted, procedure can’t be re-adjusted with without re-validation 
c. Cumulative effect must be evaluated