A Method to Evaluate Spectral Analysis by Spectroscopy

Abstract

Visible and near infrared spectroscopy has been widely used to develop a method for rapidly determining organic carbon in soils or sediments (SOC). Most of these studies concentrated on how to establish a good spectral model but ignored how to evaluate the method, such as the use of detection range (max and min), resolution and error for SOC spectral analysis. Here, we proposed a method to evaluate the spectral analysis of SOC. Using 96 sediments sampled in the Yellow Sea and Bohai Sea, China, we established three spectral models of SOC after collecting their spectral reflectance by Agilent Cary 5000, ASD FieldSpec 4 and Ocean Optics QEPro, respectively. For both the calibration set and validation set in each spectrometer, the predicted SOC concentrations followed a distribution curve (function), in which the x-axis was the SOC concentrations. Using these curves, we developed these four technical parameters. The detection ranges were the SOC concentrations where the curve was near to or crossing with the lateral axis, while the detection resolution was the average difference between the two neighboring SOC concentrations. The detection errors were the differences between the predicted SOC and the measured SOC. The results show that these technical parameters were better in the bench-top spectrometer (Cary 5000) than those in the portable spectrometers when analyzing the same samples. For the portable spectrometers, QEPro had a broader detection range and more consistent detection error than FieldSpec 4, suggesting that the low-cost QEPro performed as well as the high-cost FieldSpec 4. This study provides a good example for evaluating spectral analysis by spectroscopy, which can support the development of the spectral method.

Analysis of brines for the content of the main substance and impurities of magnesium and calcium salts by the sonoluminescence method

“…Метод сонолюмінесценції є єдиним методом хімічного аналізу, придатним для експресного визначення вмісту NaCl у розсолах прямо в свердловині [7][8][9][10][11][12].…”

“…Визначали вміст NaCl та солей MgCl 2 і CaCl 2 у розсолі. Для уникнення припинення кавітації і, як результат, зникнення сонолюмінесценції внаслідок дегазації розчину, подавання аргону не припиняли [7,8]. Весь процес аналізу проходив в автоматизованому режимі.…”

Prediction of Potassium Content in Rice Leaves Based on Spectral Features and Random Forests

“…Because the chemical determination of potassium requires the destruction of rice leaves, the Agilent Cary 5000 (Agilent Technology, Santa Clara, CA, USA) equipped with an integrating sphere was used to measure the reflectance before measuring the content of potassium. Compared with the portable spectrometer, it has the advantages of a wider detection range (350-2500 nm), higher resolution (1 nm), and lower error [55]. When measuring, the target leaf was fixed on the bracket, with the light spot focused on the designated area.…”