Dear all,through my method validation and process to determine LOQ through signal to noise ratio, we found through series of concentration that I reach to concentration show signal to noise ratio =9.1 and show very good %RSD for peak area less than 10 ( around 8) and was the first concentration archive % RSD less than 10…so we pick this concentration as LOQ level… Is it OK or must be signal to noise ratio 10 to be LOQ level?!
LOQ determination by S/N method is not correct method.LOQ value varies with noise so you can use slope method.
We try use slope equation and try Loq equation which submitted in USP 41… Both produce low undetectable concentration by hplc… (the method we validate is compendial method)