Near-infrared spectroscopy bioprobe estimation of metabolites' responses to Pb in Cladophora rupestris.

Near-infrared (NIR) spectroscopy was used as a bioprobe to estimation chlorophyll, total sugar, proline, and metallothionein (MT) response to Pb (0, 1, 2.5, 5, 7.5, 10, and 20 mg/l) in Cladophora rupestris. Spectra between 3775.94 and 12315.19 cm were analysed using a partial least-squares regression (PLS). Principal component analysis (PCA) was performed by evaluating the distance between the C. rupestris samples treated with different concentrations of Pb. Results showed that 4000-7500 cm of raw NIR spectra from C. rupestris was linked to carbohydrates and stretching of N-H, and the O-H overtone was associated with proline and MT. NIR spectroscopy technique coupled with PLS quantitative analysis model has high potential. Multiplicative scatter correction and standard normal variate combining first-order derivative with S-G smoothing filter are superior to the other models. The root mean square error of cross of chlorophyll, total sugar, proline, and MT was 0-1, indicating the accuracy of the model is high. The R values of chlorophyll, total soluble sugar, proline, and MT between measured and predicted values were higher than 0.99. PCA analysis indicate clear boundaries in the spatial distributions of seven Pb concentrations, indicating that NIR spectroscopy has high potential as a tool assisting bioprobes for estimating metabolites' responses to Pb in Cladophora rupestris.