Objective: In order to guide the on-line detection of active components of Traditional Chinese Medicine

the on-line analysis method of NIRS was established for NH4Cl solution by using the near infrared spectroscopy technology. In addition

the impact of bubbles on the detection result was evaluated. Method: The near-infrared spectroscopy technique was used to determine the content of NH4Cl. The prediction model was established using partial least squares (PLS) method after rejecting outliers. Result: The predicted value calculated by the established model was quite close to the true value

which indicated a nice performance of the near infrared spectrometer in quantitative ability. The correlation coefficients (R2) and the root-mean-square error of cross-validation (RMSECV) of the quantitative calibration model were 0.991

0.493 respectively. The root-mean-square error of prediction (RMSEP) was 0.222. The relative prediction error (RESP) was less than 10% when the concentration of NH4Cl was higher than 1.504 g ·L-1. In addition

the results showed that the impact of the bubble on the detection result was so small that it could be neglected. Conclusion: The error level of near-infrared spectroscopy technology could satisfy the on-line detection of traditional chinese medicine.