A double modulation

Dowrey A E and Maroott C 1982 A double-modulation Fourier transform infrared approaoh to studying adsorbates on metal surfaoes Appl. Spectrosc. 36 414-16... 

FIGURE 31.2 Pictorial depiction of a double module hollow fiber Uquid membrane set up. HFM—Hollow fiber module F— Feed O— Organic extractant S—Strip or receiver phase and P—Pump. (Reproduced from Mohapatra, P.K. and Manchanda, V.K., Indian J. Chem., 42A, 2925, 2003. With permission.)... 

Once having determined the optimal operating conditions for the selective recovery of nickel, some tests with a real effluent coming from the Thai stainless steel industry were carried out in a double module operation (i.e., two HFSLM modules in series) for the maximum recovery of nickel ions. For a single module operation the recovery of nickel ion was 58% while, by operating with a double module operation, its recovery increased to 87% and the amount of Ni remaining in the feed solution after passing double-module operation was 1 mg L, which was in accordance with the permissible limits of Thailand. 

Let us consider a double-modulation FT-IR spectrometry experiment in which a target sample and a reference sample are effectively placed between an infrared source and an interferometer, and the infrared beam from the source irradiates the target and reference samples alternately with a modulation frequency of/. The single-beam spectra of the target and reference samples may be denoted, respectively, by B (v) and 5 (5). As the infrared beam which has passed through the target and reference samples has been modulated with frequency / , its spectmm B v, t), a function of time t, is expressed in the following form. 

Figure 11.4 Schematically illustrated interferograms obtained by double-modulation FT-IR spectrometry, (a) F (x) unmodulated part of an interferogram, (b) F lx) modulated part of an interferogram, and (c) F(x) interferogram of a double-modulation FT-IR measurement.

Nafie LA, Lipp ED and Zimba CG (1981) Fourier transform infrared circular dichroism a double modulation approach. In Sakals J (ed) Proceedings of the 1981 International Conference on Fourier Transform Infrared Spectroscopy, pp 457-468. SPIE. 

Polarization Modulation in FTIR Spectroscopy (PM-FTIRS). Recently, Kunimatsu, Golden, and coworkers have coupled the polarization modulation technique with Fourier transform infrared spectroscopy and applied the new method to electrochemical studies (Figure 20). In their work, a double modulation technique is employed, using a photomodulator working at high frequency (78 kHz) and a polarizer, both inserted in the optical path. 

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