Anelli Carlo, Pellicorio Vanessa, Bello Valentina, Merlo Sabina
Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Via Ferrata 5, 27100 Pavia, Italy.
Department of Drug Sciences, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy.
Sensors (Basel). 2024 Apr 26;24(9):2754. doi: 10.3390/s24092754.
Contactless and label-free detection of urea content in aqueous solutions is of great interest in chemical, biomedical, industrial, and automotive applications. In this work, we demonstrate a compact and low-cost instrumental configuration for label-free, reagent-free, and contactless detection of urea dissolved in water, which exploits the absorption properties of urea in the near-infrared wavelength region. The intensity of the radiation transmitted through the fluid under test, contained in a rectangle hollow glass tubing with an optical pathlength of 1 mm, is detected in two spectral bands. Two low-cost, low-power LEDs with emission spectra centered at λ = 1450 nm and λ = 2350 nm are used as readout sources. The photodetector is positioned on the other side of the tubing, in front of the LEDs. The detection performances of a photodiode and of a thermal optical power detector have been compared, exploiting different approaches for LED driving current modulation and photodetected signal processing. The implemented detection system has been tested on urea-water solutions with urea concentrations from 0 up to 525 mg/mL as well as on two samples of commercial diesel exhaust fluid ("AdBlue™"). Considering the transmitted intensity in presence of the urea-water solution, at λ = 1450 nm and λ = 2350 nm, normalized to the transmitted intensity in presence of water, we demonstrate that their ratio is linearly related to urea concentration on a wide range and with good sensitivity.
水溶液中尿素含量的非接触式无标记检测在化学、生物医学、工业和汽车应用中备受关注。在这项工作中，我们展示了一种紧凑且低成本的仪器配置，用于对溶解在水中的尿素进行无标记、无需试剂和非接触式检测，该配置利用了尿素在近红外波长区域的吸收特性。在两个光谱带中检测通过光程长度为1毫米的矩形空心玻璃管中所包含的被测流体传输的辐射强度。两个发射光谱中心波长分别为λ = 1450纳米和λ = 2350纳米的低成本、低功率发光二极管用作读出源。光电探测器位于玻璃管的另一侧，在发光二极管前方。利用发光二极管驱动电流调制和光电探测信号处理的不同方法，比较了光电二极管和热光功率探测器的检测性能。所实现的检测系统已在尿素浓度从0到525毫克/毫升的尿素 - 水溶液以及两个商用柴油尾气处理液（“AdBlue™”）样品上进行了测试。考虑到在尿素 - 水溶液存在下，在λ = 1450纳米和λ = 2350纳米处的传输强度，并将其归一化为在水存在下的传输强度，我们证明它们的比值在很宽的范围内与尿素浓度呈线性关系且具有良好的灵敏度。
