Pyrolysis fingerprint

In both cases, GC fingerprint libraries must be built before quantitative analysis can be routinely carried out. In analysis of QTLC by laser pyrolysis scanning (LPS), the TLC plates are placed in a chamber after development, and were irradiated with an IR laser to produce a high temperature at the location of the spot. The analyte is swept by a carrier gas to a GC, and detected with FID or ECD. The technique combines the separation power of TLC and the detection modes of GC [846]. 

With recent developments in analytical instrumentation these criteria are being increasingly fulfilled by physicochemical spectroscopic approaches, often referred to as whole-organism fingerprinting methods.910 Such methods involve the concurrent measurement of large numbers of spectral characters that together reflect the overall cell composition. Examples of the most popular methods used in the 20th century include pyrolysis mass spectrometry (PyMS),11,12 Fourier transform-infrared spectrometry (FT-IR), and UV resonance Raman spectroscopy.16,17 The PyMS technique... 

Instrumental drift results from variations in the physical conditions of a pyrolysis mass spectrometer over time.127 It leads to variation in spectral fingerprints taken from the same material on different occasions. Short-term (<30 days) instrument reproducibility was examined by Manchester et al.57 who used PyMS to differentiate strains of Carnobacterium over a four-week period. Excellent reproducibility was obtained as separation of the five type strains was sustained and spectra did not change significantly over the four weeks. 

Meuzelaar, H. L. Kistemaker, P. G. A technique for fast and reproducible fingerprinting of bacteria by pyrolysis mass spectrometry. Anal. Chem. 1973, 45, 587-590. 

This example belongs to chemotaxonomy, a discipline that tries to classify and identify organisms (usually plants, but also bacteria, and even insects) by the chemical or biochemical composition (e.g., fingerprint of concentrations of terpenes, phenolic compounds, fatty acids, peptides, or pyrolysis products) (Harbome and Turner 1984 Reynolds 2007 Waterman 2007). Data evaluation in this field is often performed by multivariate techniques. 

The introduction of non-volatile components into an MS has typically been via the pyrolysis of whole fermentation liquors. Pyrolysis is the thermal degradation of a material in an inert atmosphere or a vacuum. It causes molecules to cleave at their weakest points to produce smaller, volatile fragments called pyrolysate [23]. An MS can then be used to separate the components of the pyrolysate on the basis of their mass-to-charge ratio (m/z) to produce a pyrolysis mass spectrum, which can then be used as a chemical profile or fingerprint of the complex material analysed [24]. 

Pyrolysis MS (PyMS) has been applied to the characterisation and identification of a variety of microbial systems over a number of years (for reviews see [25-27]) and, because of its high discriminatory ability [28-30], presents a powerful fingerprinting technique applicable to any organic material. Whilst the pyrolysis mass spectra of complex organic mixtures may be expressed in the simplest terms as sub-patterns of spectra describing the pure components of the mixtures and their relative concentrations [24], this may not always be true because during pyrolysis intermolecular reactions can take place in the pyrolysate [31-33]. This leads to a lack of superposition of the spectral components and to a possible dependence of the mass spectrum on sample size [31]. However, suitable numerical methods (or chemometrics) can still be employed to measure the concentrations of biochemical components from pyrolysis mass spectra of complex mixtures. 

Fig-1 a Normalised pyrolysis mass spectra of Penicillium chrysogenum this complex fingerprint can be used to type this organism, b Normalised pyrolysis mass spectra of 200 pg pure Penicillin G this somewhat simpler biochemical profile is one of the range of penicillins produced by Penicillium chrysogenum... 

A few pyrolysis studies done on yeasts and yeast-like fungi did not attempt to analyze individual polysaccharides but to obtain a fingerprint characterization [67], It was also common to use statistical techniques such as factor analysis for the data interpretation. It was not unusual to find N-acetylamino sugar units in fungal polysaccharides. These units showed characteristic peaks in Py-MS that allowed the distinction of different materials. 

Another application of peptide pyrolysis is the study of silk. Pyrograms of minute pieces of fiber can be pyrolysed to identify the fingerprint of natural silk. 

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