Determination of hydrogen peroxide concentration using a handheld Raman spectrometer: Detection of an explosives precursor

It has been shown that a handheld Raman spectrometer can be used to determine hydrogen peroxide concentration in aqueous solutions in seconds. To allow quantitative analysis, the aqueous peroxide samples were mixed 50/50 (v/v) with a 4mol/dm3 sodium perchlorate solution which acted as the internal standard. Standard calibration using relative peak heights of the strongest perchlorate (932cm−1) and peroxide bands (876cm−1) gave an average error of 1.43% for samples in the range 5–30% peroxide. PLS regression of the same data set gave an average error of 0.98%. In addition, the concentrations of the samples were estimated by searching spectra against a library of standard spectra prepared using the same range of peroxide concentrations at 5% increments and with the same perchlorate internal standard. It was found that the library searching method classified all the test samples correctly, matching either the spectra of the same concentration, if they were present, or matching to the closest concentration if an exact match was not possible. This method thus provides a very rapid technique to allow determination of hydrogen peroxide concentrations in the field, for example at suspected improvised explosives manufacturing sites, without complex calibration procedures.