The measurement accuracy of portable infrared spectrometers is influenced by multiple factors. The following analysis is conducted from five dimensions: instrument performance, environmental conditions, sample characteristics, operating standards, and data processing:
1、 Instrument performance and calibration
-Light source stability: Fluctuations in light source intensity can directly affect the signal-to-noise ratio of spectral signals. For example, tungsten halogen lamps have a relatively flat spectral distribution in the near-infrared region, while LED light sources may have emission peaks at specific wavelengths. Improper selection can result in certain absorption features not being effectively detected. The decrease in luminous efficiency caused by aging of the light source or temperature changes can also introduce measurement errors.
-Optical system accuracy: Damage to gratings or prisms can reduce wavelength resolution, resulting in spectral peak shift or overlap. The performance of optical fibers cannot be ignored either. Longer fibers will increase light intensity attenuation, and the selection of numerical aperture needs to balance light collection capacity and stray light interference. In addition, a decrease in detector sensitivity or an increase in noise (such as changes in CCD dark current) can weaken the ability to capture weak signals.
-Calibration effectiveness: Regular use of standard substances for wavelength and intensity calibration is crucial. For example, the JY2000 spectrometer from Jingyi Optoelectronics ensures measurement consistency at different wavelengths through full band calibration. If rapid calibration checks are not performed before each measurement, data deviation may occur due to instrument drift.
2、 Environmental interference
-Temperature and humidity fluctuations: Temperature changes can cause thermal expansion and contraction of optical components, resulting in optical path deviation, especially for refrigerated spectrometers (such as JY6500). Excessive humidity may cause surface fogging of optical components, increasing light scattering losses; Environmental electromagnetic interference may introduce noise through circuit coupling.
-Vibration and stray light: External vibrations can cause instability in the optical path, and stray light in the environment (such as sunlight or artificial light sources) may mask the weak absorption signal of the sample. It is recommended to use the equipment in a constant temperature, low vibration darkroom and reduce dust pollution through sealed design.
3、 Sample Processing and Characteristics
-Sample uniformity and morphology: Uneven surface of solid samples can cause diffuse reflection differences, while liquid sample concentrations exceeding the linear response range (following Beer's law) can cause absorbance distortion. If the powder sample is not ground sufficiently, the difference in particle size will exacerbate the light scattering effect.
-Impurities and storage conditions: Bubbles or impurities in the sample can generate additional absorption bands, and improper storage (such as decomposition caused by high temperature or photochemical reactions caused by light) can alter its molecular structure. For example, after potassium bromide tablets adsorb water, they will produce hydroxyl absorption peaks in the infrared region that interfere with the measurement.
4、 Operational standardization
-Lack of standardization process: Failure to align optical paths according to regulations, insufficient signal acquisition time, or improper gain settings can all affect data quality. For example, taking the average of multiple measurements can reduce random errors, while ignoring environmental parameter records (such as real-time temperature and humidity) will limit the feasibility of subsequent data correction.
-Insufficient professionalism of personnel: When the operator does not have a deep understanding of the instrument principle, there may be problems such as incorrect selection of accessories (such as mismatched fiber type and sample), misjudgment of abnormal data, etc. Professional training (such as technical guidance provided by Jingyi Optoelectronics) can significantly improve operational reliability.
5、 Data Processing and Analysis
-Algorithm and parameter settings: Software algorithm defects (such as baseline correction errors, unreasonable peak fitting models) can directly distort the results. For example, Raman spectroscopy data without eliminating the influence of scattered light may overestimate the sample concentration. In addition, caution should be taken against data loss or format conversion errors during storage and transmission.
-Background subtraction and normalization: Incorrect deduction of environmental background (such as air absorption peaks) or failure to perform spectral normalization may result in false positive/negative results. Establishing a standardized database to assist in comparative analysis can effectively improve the accuracy of identifying complex samples.
Improving accuracy requires a systematic approach: regular maintenance and calibration of instruments, strict control of environmental conditions, standardized sample processing procedures, enhanced personnel training, and optimization of data processing algorithms. For high-precision demand scenarios, it is recommended to combine multiple devices for cross validation and establish a traceability system based on national standard materials.