Islam Meez, Seetohul L Nitin, Ali Zulfiqur
School of Science and Technology, University of Teesside, Borough Road, Middlesbrough TS1 3BA.
Appl Spectrosc. 2007 Jun;61(6):649-58. doi: 10.1366/000370207781269846.
A novel implementation of broadband cavity enhanced absorption spectroscopy (BBCEAS) has been used to perform sensitive visible wavelength measurements on liquid-phase solutions in a 2 mm cuvette placed at normal incidence to the cavity mirrors. The overall experimental methodology was simple, low cost, and similar to conventional ultraviolet-visible absorption spectroscopy. The cavity was formed by two concave high reflectivity mirrors. Three mirror sets with nominal reflectivities (R) of R = 0.99, 0.9945, and 0.999 were used. The light source consisted of a high intensity red, green, blue, or white LED. The detector was a compact charge-coupled device (CCD) spectrograph. Measurements were made on the representative analytes, Ho(3+), and the dyes brilliant blue-R, sudan black, and coumarin 334 in appropriate solvents. Cavity enhancement factors (CEF) of up to 104 passes for the high reflectivity mirrors were obtained. The number of passes was limited by relatively high scattering and absorption losses in the cavity, of approximately 1 x 10(-2) per pass. Measurements over a wide wavelength range (420-670 nm) were also obtained in a single experiment with the white LED and the R = 0.99 mirror set for Ho(3+) and sudan black. The sensitivity of the experimental setup could be determined by calculating the minimum detectable change in the absorption coefficient alpha(min). The values ranged from 5.1 x 10(-5) to 1.2 x 10(-3) cm(-1). The limit of detection (LOD) for the strong absorber brilliant blue-R was 620 pM. A linear dynamic range of measurements of concentration over about two orders of magnitude was demonstrated. The overall sensitivity of the experimental setup compared very favorably with previous generally more experimentally complex and expensive liquid-phase cavity studies. Possible improvements to the technique and its applicability as an analytical tool are discussed.
一种新型的宽带腔增强吸收光谱法（BBCEAS）已被用于对置于与腔镜垂直入射的2毫米比色皿中的液相溶液进行灵敏的可见波长测量。整体实验方法简单、成本低，且与传统紫外可见吸收光谱法类似。该腔由两个凹面高反射率镜构成。使用了三组标称反射率（R）分别为R = 0.99、0.9945和0.999的镜组。光源由高强度红、绿、蓝或白色发光二极管组成。探测器是一台紧凑型电荷耦合器件（CCD）光谱仪。对代表性分析物Ho(3+)以及亮蓝-R、苏丹黑和香豆素334染料在合适溶剂中进行了测量。对于高反射率镜，获得了高达104次通过的腔增强因子（CEF）。通过次数受腔中相对较高的散射和吸收损耗限制，每次通过约为1×10(-2)。使用白色发光二极管和R = 0.99的镜组，在单次实验中还获得了Ho(3+)和苏丹黑在宽波长范围（420 - 670纳米）的测量结果。实验装置的灵敏度可通过计算吸收系数的最小可检测变化量α(min)来确定。其值范围为5.1×10(-5)至1.2×10(-3)厘米(-1)。强吸收剂亮蓝-R的检测限（LOD）为620皮摩尔。展示了浓度测量约两个数量级的线性动态范围。该实验装置的整体灵敏度与之前通常实验更复杂且昂贵的液相腔研究相比非常有利。讨论了该技术可能的改进及其作为分析工具的适用性。
