Is it possible or acceptable to use a spectrophotometer to measure Test Article concentrations, or does this have to be performed via HPLC?
If the spectrophotometry test method is valid, meaning that it provides reliable data with acceptable specificity, linearity, accuracy, and precision, then it is perfectly fine. If the matrix for the test article is simple and non-interfering, then spectrophotometry might do the job. HPLC is often chosen to measure concentrations because it can separate the test article from interfering components in the matrix. No matter what method/instrument is used to measure concentration, you’ll want a method of calibration with a reference standard material.
If you have option to use both techniques for analysis , then u must go for HPLC b/c it shows the real picture due to seperation technique, there are many draw backs by using UV/Vus spectrophotometer, it can not seperate the analyte. if you are confident in UV/Vis spect method, problem in developing the HPLC method and proper analytical method validation is perform then you may use spectrophotometer however It is more prefer that the method should be stabilty indicating method so your first chioce should be any seperartion technique instead of UV/Vis spect for your convinence.
Now a days in most labs HPLC is prefred for assay determination, other tests like dissolution and uniformity of contents are prefered to be done on UV as it is simple, less time consuming and economical. Related substance test can only be done on HPLC or other chromatographic techniques.
In current practices, Regulator are enphasizing to develop SIM (stabilty indicating methods) and For SIM methods, the testing methodology should be specific like HPLC n GC. so HPLC and other specific testing technique must use for analysis.