Feasibility of Terahertz Time-Domain Spectroscopy to Detect Tetracyclines Hydrochloride in Infant Milk Powder

We report the use of terahertz time-domain spectroscopy (THz-TDS) to detect tetracyclines hydrochloride (TCsH) in infant milk powder for the first time. Four kinds of TCsH exhibited their unique spectral features in the region of 0.3-1.8 THz. The main spectral features of these TCsH were still detectable when mixed with infant milk powder with concentrations at 1%-50%, even in the ternary mixtures. The results from chemometrics analysis showed that qualitative and quantitative detection of TCsH in infant milk powder could be successfully achieved. The residual predictive deviation (RPD) values of all these TCsH models were all higher than 2, indicating these models were considered good and could be used in screening purposes. The RPD values of TCH, DTCH, and CTCH models were higher than 3, which were considered excellent for prediction purposes. These preliminary results indicated that THz-TDS combined with chemometrics analysis was suitable for detecting the presence of TCsH residues in a food matrix.