SPME-GC

Yang, M. J. Orton, M. L. Pawliszyn, J. Quantitative Determination of Caffeine in Beverages Using a Combined SPME-GC/MS Method, /. Chem. Educ. 1997, 74,... 

Macpherson T, CW Greer, E Zhou, AM Jones, G Wisse, PCK Lau, B Sankey, MJ Grossman, J Hawari (1998) Application of SPME/GC-MS to characterize metabolitres in the biodesulfurization of organosulur model compounds in bitumen. Environ Sci Technol 32 421 26. 

Bentivenga, G., D Auria, M., Fedeli, P., MaurieUo, G., and Racioppi, R. (2004). SPME-GC-MS analysis of volatile organic compounds in honey from Basilicata. Evidence or the presence of pollutants from anthropogenic activities. Int. J. Food Sci. Technol. 39,1079-1086. 

SPE-HPLC and SPME-GC (cf. Sections 7.1 and 7.2). For meaningful results it is crucial to dispose of the correct interface between the various combined techniques. 

Applications The potential of a variety of direct solid sampling methods for in-polymer additive analysis by GC has been reviewed and critically evaluated, in particular, static and dynamic headspace, solid-phase microextraction and thermal desorption [33]. It has been reported that many more products were identified after SPME-GC-MS than after DHS-GC-MS [35], Off-line use of an amino SPE cartridge for sample cleanup and enrichment, followed by TLC, has allowed detection of 11 synthetic colours in beverage products at sub-ppm level [36], SFE-TLC was also used for the analysis of a vitamin oil mixture [16]. 

Sandra and David [37] have reported on validation studies for SHS-HSGC, Py-HSGC, on-line LVI-GC, on-line SPME-GC, on- and off-line SPE-GC, on-line and off-line derivatisation-GC, SBSE-TD-GC, and PTV-LC(SEC)-GC. 

Principles and Characteristics As mentioned already (Section 3.5.2) solid-phase microextraction involves the use of a micro-fibre which is exposed to the analyte(s) for a prespecified time. GC-MS is an ideal detector after SPME extraction/injection for both qualitative and quantitative analysis. For SPME-GC analysis, the fibre is forced into the chromatography capillary injector, where the entire extraction is desorbed. A high linear flow-rate of the carrier gas along the fibre is essential to ensure complete desorption of the analytes. Because no solvent is injected, and the analytes are rapidly desorbed on to the column, minimum detection limits are improved and resolution is maintained. Online coupling of conventional fibre-based SPME coupled with GC is now becoming routine. Automated SPME takes the sample directly from bottle to gas chromatograph. Split/splitless, on-column and PTV injection are compatible with SPME. SPME can also be used very effectively for sample introduction to fast GC systems, provided that a dedicated injector is used for this purpose [69,70],... 

The main characteristics of on-line SPME-GC coupling are given in Table 7.10. Although the SPME sampling regime itself (room-temperature operations) is not harsh, other parts of the analytical system (such as the... 

Table 7.10 Main characteristics of on-line SPME-GC coupling...

GC injection port) may well be. This was clearly demonstrated by a comparison between cryotrapping/direct injection, cryotrapping/SPME, and solid-phase (Tenax-GC) extraction for sampling of odorous sulfur compounds [71], Thermally labile compounds are likely to break down in the GC injection port/column/transfer line. Instead of SPME-GC, the recently developed SPME-HPLC [72] might be more applicable to analysis of such thermally unstable compounds. 

SPME-GC and SPE-GC are complementary rather than competitive techniques. SPE requires at least 100 p,L, of which only a small fraction is actually used for subsequent GC or HPLC analysis. This problem is addressed by SPME. Although SPME-GC is an attractive technique, its precision (RSDs, 3-20%) is often not as good as in SPE-GC (RSDs, 1-10%). 

Organotin compounds (biocides and polymer stabilisers) in water were analysed by means of HS-SPME-GC and GC-MS (SIM) [296],... 

MacPherson, T. Greer, C.W. Zhou, E., et al., Application of SPME/GC-MS to Characterize Metabolites in the Biodesulfurization of Organosulfur Model Compounds in Bitumen. Environmental Science Technology, 1998. 32(3) pp. 421—426. 

Headspace solid phase microextraction (HS-SPME). With this extraction technique, it is possible to concentrate volatile compounds thus allowing their detection even at trace levels, as in the case of volatile and semi-volatile terpenes in archaeological findings [7,31]. Chapter 10 outlines how resinous materials are investigated using HS-SPME-GC/MS. 

SPME/GC MS in the Characterisation of Terpenic Resins 275 10.3.3 Application to Research on Olibanum [26]... 

Table 10.3 Main components detected by headspace SPME/GC MS in the six reference olibanum samples with certified botanical origin and in three olibanum samples without botanical origin... 

Table 10.6 Terpenes detected by headspace SPME/GC MS in four samples from the tomb of Khnoumit (Dachour, Egypt)...

These results demonstrate clearly that headspace SPME/GC-MS is well adapted to the detection of volatile or semi-volatile terpenes from resins or gum resins. The method is rapid and simple. A moderate heating (80°C) of the sample allows the extraction of less volatile compounds such as particular diterpenes or diterpenoids which are more specific. 

SPME/GC/MS is an efficient technique to reveal the presence of resinic substances in archaeological samples. Indeed, volatile terpenes are still present in very old archaeological samples (4000 years old), particularly in the case of compact matrixes, and can be trapped by the SPME fibre. In comparison with methylene chloride extraction, SPME is very specific and allows the direct analysis of the volatile terpenes content in complex mixtures including oils, fats or waxes. For this reason, headspace SPME is the first method to use when analysing an archaeological sample it will either allow the identification of the resin or indicate further sample treatment in order to detect characteristic triterpenes. The method is not really nondestructive because it uses a little of the sample but the same sample can be used for several SPME extractions and then for other chemical treatments. 

M. Ryhl Svendsen, J. Glastrup, Acetic acid and formic acid concentrations in the museum environment measured by SPME GC/MS, Atmos. Environ., 36, 3909 3916 (2002). 

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