Rapid qualitative and quantitative analysis of chlortetracycline hydrochloride and tetracycline hydrochloride in environmental samples based on terahertz frequency-domain spectroscopy

Owing to the advantages of transient, broadband, low-energy, transmission and high frequency accuracy, terahertz frequency domain spectroscopy (THz-FDS) has been introduced and pioneered for determining chlortetracycline hydrochloride (CCH) and tetracycline hydrochloride (TCH) in environmental samples, such as chicken, rice and soils. Their THz fingerprint spectra were located in the range of 0.4-1.1 THz, with the peaks at 0.49, 0.60, 0.76, 0.90 and 1.03 THz for CCH and at 0.52, 0.67, 0.79, 0.92 and 1.05 THz for TCH, respectively. By simple pressing treatment, dry soil, chicken and rice samples spiked with standards can be used for direct analysis. For the quantitative analysis, partial least squares regression (PLSR) algorithms were utilized for optimizing the analysis accuracy, calculation and prediction. Lower root mean square error of cross validation (RMSECV < 0.1689), calibration (RMSEC < 0.0623), prediction (RMSEP < 0.1280) and higher correlation coefficient (R > 0.9089) for these two compounds in soil, chicken and rice samples have been obtained. Our results indicated that THz-FDS combined with PLSR model could be a useful analytical technique for monitoring CCH and TCH in environmental samples.