Quick detection and quantification of iron-cyanide complexes using fourier transform infrared spectroscopy.

The continuous release of persistent iron-cyanide (Fe-CN) complexes from various industrial sources poses a high hazard to the environment and indicates the necessity to analyze a considerable amount of samples. Conventional flow injection analysis (FIA) is a time and cost consuming method for cyanide (CN) determination. Thus, a rapid and economic alternative needs to be developed to quantify the Fe-CN complexes. 52 soil samples were collected at a former Manufactured Gas Plant (MGP) site in order to determine the feasibility of diffuse reflectance infrared Fourier spectroscopy (DRIFTS). Soil analysis revealed CN concentrations in a range from 8 to 14.809 mg kg, where 97% was in the solid form (Fe[Fe(CN)]), which is characterized by a single symmetrical CN band in the range 2092-2084 cm. The partial least squares (PLS) calibration-validation model revealed IR response to CN which exceeds 2306 mg kg (limit of detection, LOD). Leave-one-out cross-validation (LOO-CV) was performed on soil samples, which contained low CN (<900 mg kg). This improved the sensitivity of the model by reducing the LOD to 154 mg kg. Finally, the LOO-CV conducted on the samples with CN > 900 mg kg resulted in LOD equal to 3751 mg kg. It was found that FTIR spectroscopy provides the information concerning different CN species in the soil samples. Additionally, it is suitable for quantifying Fe-CN species in matrixes with CN > 154 mg kg. Thus, FTIR spectroscopy, in combination with the statistical approach applied here seems to be a feasible and quick method for screening of contaminated sites.