Warfarin sodium stands out as the primary oral anticoagulant for treating pulmonary embolism, necessitating individualized dosage adjustments guided by post-administration blood concentration, typically maintained in the range of 2.23?2.30 nmol/mL. Common quantitative methods such as mass spectrometry (MS), liquid chromatography-mass spectrometry (LC-MS), and high-performance liquid chromatography-fluorescence detection (HPLC-FLD) suffer from the problems of expensive equipment, high consumable costs, and long analysis time (>30 min). In contrast, terahertz (THz) spectroscopy offers a solution by acquiring molecular fingerprinting properties. When combined with density functional theory (DFT) simulation, it is capable of predicting molecular spectral properties and analyzing vibrational modes. This combination has been widely used in drug studies. This study aims to establish a new method using THz spectroscopy for rapid qualitative and quantitative analysis in the clinical detection of warfarin sodium. The proposed method achieves high-sensitivity quantitative analysis of warfarin sodium with two indexes, and the minimum detection limit reaches 0.01 nmol/mL, which is lower than the clinical blood concentration.

This study employs the quantum chemistry software Gaussian 09 to theoretically analyze the molecular vibrational properties of warfarin sodium. Specifically, the DFT/B3LYP/3-21G basis set is used to predict the vibrational properties in the range of 10?16 THz. Concurrently, a Fourier transform infrared spectrometer is employed to perform qualitative and quantitative analysis on warfarin sodium. The samples for analysis are prepared by doping 20 μL warfarin sodium solutions on high-resistance silicon surface, followed by drying under vacuum conditions at 20 ℃. THz absorption spectra of warfarin sodium solutions, with concentrations in the range of 2?100 nmol/mL, are obtained at a resolution of 4 cm^-1.

In this study, qualitative experimental tests on 2 mg warfarin sodium are performed to obtain the THz characteristic absorption spectrum. The results reveal clear absorption peaks at 11.10, 11.94, 13.05, 13.74, and 15.43 THz, along with a shoulder peak at 14.01 THz (Fig. 1). Meanwhile, the molecular theoretical spectrum of warfarin, obtained by DFT calculation, demonstrates six characteristic absorption peaks within the frequency range of 10?16 THz. These theoretical peaks are located at 11.07, 11.70, 13.28, 13.82, 14.27, and 15.71 THz (Fig. 2). Comparison of the theoretical spectra with the experimental spectra exhibits consistency (Table 1), and different experimental peaks arise from different molecular vibrational modes (Fig. 3). For quantitative analysis, experimental peaks at 12.05, 13.79, and 15.58 THz are selected owing to their distinct vibration modes and strong absorbance. The peak area and intensity of these peaks exhibit linear relationships with the concentration of warfarin sodium solutions (Fig. 4 and Fig. 5), with correlation coefficients exceeding 0.96, conforming to Beer-Lambert law. Based on these results, the detection sensitivity and limit of detection (LOD) are further determined (Table 2). The lowest LOD reaches 0.01 nmol/mL, which is lower than the clinical blood concentration. Therefore, a rapid and reliable quantitative analysis method for warfarin sodium is established based on its multiple THz characteristic peaks.

In this study, a rapid qualitative and quantitative analysis method for the anticoagulant drug warfarin sodium is developed based on THz spectroscopy. Through THz spectral experiments and DFT calculations, it is clarified that six characteristic peaks of warfarin sodium exist in the range of 10?16 THz, corresponding to the frequencies of 11.10, 11.94, 13.05, 13.74, 14.01, and 15.43 THz, respectively. The attribution of these peaks is analyzed, and a qualitative identification method for warfarin sodium is established. Subsequently, the THz spectra of warfarin sodium solutions with different concentrations are analyzed. The correlation between drug concentration and the peak intensity, along with the peak area is analyzed, and the quantitative detection curve of warfarin sodium is given. The sensitivity and detection limit are calculated. The results demonstrate that the peak intensity and peak area increase linearly with the increase in warfarin sodium concentration (the correlation coefficient is >0.96). Based on the peak area at 15.58 THz, the detection limit reaches 0.01 nmol/mL, which is lower than the clinical blood concentration (2.23?2.30 nmol/mL). This study proposes a rapid quantitative detection method of warfarin sodium and contributes to the development of blood drug concentration monitoring technology.