Beforeinstrumental analysis, we shall choose a reliable analytical procedure whichfulfils the requirements including specificity, sensitivity and accuracy. In pharmaceuticalanalysis, liquid chromatography coupled with mass spectrometer (LC-MS) iswidely used. However, there are some errors introduced during the measurementsdue to instability of the analytical instruments5.Therefore, there is a need to develop methods for calibration to eliminate theerrors.
In general, LC-MS system is calibrated in each batch analysis using avariety of chemical standards4.Instrumental performance is monitored through many indexes like retention time,mass accuracy, limit of detection, repeatability, reproducibility, sensitivity,etc. To ensure the mass accuracy ofmass spectrometer, some reference standards should be used regularly tocalibrate the mass shift, like CsI, tyrosine, peptide standard, etc.
For some specific analysis likeparallel reaction monitoring (PRM), calibration of retention time of liquidchromatography between runs could be conducted using specific calibrationstandards, like iRT.6Moreover, toensure the stability of analytical system over a long period of time, qualitycontrol charts (Shewhart charts) should be drafted to determine the above-mentionedindexes.Regular equipmentmaintenance and cleaning are also required and mainly accomplished by professionaltechnicians or engineers from instrument manufactures.3.
Sample collectionIn general,samples are collected from different sources, including raw materials,intermediate products, finished products and packaging materials, see Figure 1. In detail, the content of activepharmaceutical ingredients (API) should be measured to ensure the quality ofthe raw materials. Then samples collected from intermediate products are usedto monitor the production processes and optimize the procedure if necessary.Finished products are collected for stability studies and microbiologicalanalysis.
In addition, some packaging material should be sampled and thenensured to be inert to the pharmaceutical components.