Laser pyrolysis, analytical method

A new method for the quantitative determination of pesticides is laser-pyrolysis scanning (LPS). No color reaction or visualization procedure is necessary simply the TLC plates are placed in a chamber after development and irradiated with an infrared laser to produce a high temperature at the location of the spot. The analyte is swept by a carrier gas to a gas chromatograph and analyzed by an appropriate sensitive GC detection method. 

Ion-mobility mass spectrometry (IM-MS) has emerged as an important analytical method in the last decade [74]. In IM-MS, ions are generated by pyrolysis, electrospray, laser desorption, or other ionization techniques prior to their entry into a gas-filled mobility drift cell. In this cell, ions drift at a velocity obtained from an electric field based on their shapes or dipoles in the case of differential mobility spectrometry (DMS). The greater the cross section of an analyte is (i.e., the larger the ion... 

This chapter is only concerned with spectroscopic techniques applicable to polymer/additive analysis insofar as not reported under the specific headings of laser ablation (c/r. Chp. 3.2) or laser pyrolysis (c/r. Chp. 3.5). Laser spectroscopy, which is no substitution of conventional methods but a valuable addition of the analytical toolbox, has extensively been reviewed [1,98]. Chemical spectroscopy with lasers [9] and applications of laser spectroscopy were described in monographs [1,3,99]. 

Cl in conjunction with a direct exposure probe is known as desorption chemical ionization (DCI). [30,89,90] In DCI, the analyte is applied from solution or suspension to the outside of a thin resistively heated wire loop or coil. Then, the analyte is directly exposed to the reagent gas plasma while being rapidly heated at rates of several hundred °C s and to temperatures up to about 1500 °C (Chap. 5.3.2 and Fig. 5.16). The actual shape of the wire, the method how exactly the sample is applied to it, and the heating rate are of importance for the analytical result. [91,92] The rapid heating of the sample plays an important role in promoting molecular species rather than pyrolysis products. [93] A laser can be used to effect extremely fast evaporation from the probe prior to CL [94] In case of nonavailability of a dedicated DCI probe, a field emitter on a field desorption probe (Chap. 8) might serve as a replacement. [30,95] Different from desorption electron ionization (DEI), DCI plays an important role. [92] DCI can be employed to detect arsenic compounds present in the marine and terrestrial environment [96], to determine the sequence distribution of P-hydroxyalkanoate units in bacterial copolyesters [97], to identify additives in polymer extracts [98] and more. [99] Provided appropriate experimental setup, high resolution and accurate mass measurements can also be achieved in DCI mode. [100]... 

A variety of volatilization/ionization methods have been applied to polymers a recent review or key paper is cited here for each. Extensive reviews that include mass spectrometry of pol5mrers can be found in Analytical Chemistry Other to )ical reviews are field desorption, laser desorption, plasma desorption, fast-atom bombardment, pyrolysis, and electrospray ionization. The present review will focus on polymer characterization using secondary-ion mass spectrometry (SIMS) in the high mass range comparison with other methods will be presented where appropriate. 

Additive analysis may be carried out by examination of extracts or dissolutions of the polymer, by non-destructive spectroscopic (in-polymer) testing of solid or melt, or by degradative testing using thermal methods mainly through the examination of volatiles released ( thermal extraction ). In this Chapter we consider thermo-analytical and pyrolysis methods applied to polymer/additive formulations as received Chp. 3 deals with laser desorption techniques. 

---