The influence of different integration time on stoichiometric analysis in near infrared grating spectrometers

Grating spectrometers are widely used in NIR spectroscopic analysis as a spectrum acquisition instrument. The sensitivity of the spectrometer can be varied by changing the integration time. In this paper, we study the influence of varying integration time on Stoichiometric analysis. The NIR spectra of different intralipid suspensions measured at five integration time were collected, which were then used to establish a model to predict the intralipid suspensions concentration by using the partial least squares regression (PLSR) method. “Cross-validation method” was used to evaluate the errors caused by the different integration times. Experimental results showed that the model accuracy is different based on the root-mean-square error of the calibration set (RMSEC), which ranged from 0.0016 to 0.3488. With the method of “Cross-validation,” all the root-mean-square errors of the prediction set (RMSEP) were larger than the RMSECs, up to two orders of magnitude. This study demonstrates that the integration time has a nonlinear relationship with the light intensity obtained by the spectrometer, this nonlinearity will affect the measurement accuracy. Therefore, we should pay attention to the influence by varying integration time on the measurement in the stoichiometric analysis.