Low-Content Quantitation in Entecavir Tablets Using 1064 nm Raman Spectroscopy

Abstract

The nondestructive and high sensitive analysis of a low content of an active pharmaceutical ingredient (API) was a difficult problem, especially in a complex system of pharmaceutical formulations. In this paper, a rapid and no sample preparation method was developed, which used a 1064 nm Raman spectrometer to detect entecavir monohydrate (ETV-H) in Baraclude tablets. Entecavir was a drug approved by FDA for the treatment of chronic hepatitis B and became the first choice in the market. The wavelength selection results displayed that the signal-to-background ratio of the Raman spectrum with 1064 nm excitation wavelength was 14 times that of the commonly used 785 nm wavelength. The partial least squares (PLS) method was used to calibrate concentration models containing 0.1% to 1.0% w/w% ETV-H in calibration set samples. Different preprocessing methods were used to eliminate the background interference and extract more spectral information. Calibration samples were used to choose the best performing model. Then, all the calibration samples combined with the best performing models’ parameters successfully predicted the content of ETV-H in Baraclude tablets. Combining baseline processing and standard normal variate (SNV) with PLS, the model showed a good result with an R2 of 0.973, RMSEC of 0.05%, and RMSEP of 0.03% on the spectral region of 1350–1700 cm−1. The limit of detection of this model was 0.17%. These results showed that 1064 nm Raman spectroscopy technology could be an alternative analytical procedure to quantify low-content API in intact tablets.