GC-ICP-MS

GC is based on the distribution of a volatile (gaseous) analyte between a gaseous mobile phase and a liquid stationary phase present on a solid support. The analyte mixture must be volatilised 

we distinguish between separation on packed columns and on capillary columns. Briefly, packed columns have a large inner diameter (2-6 mm) and are filled with an inert support coated with the liquid stationary phase, while capillary columns are open tubes with small inner diameter, the liquid stationary phase coating the inner wall. 

For speciation analysis using GC coupled to ICP-MS, it is imperative that the species in question is volatile or can be volatilised without degradation or destruction. Only a few species are directly accessible for GC-ICP-MS analysis, e.g. peralkylated organometallic compounds, element hydrides or carbonyls. Many of the species of interest are partly alkylated molecules, present in ionic form either in the water phase or in soU, sediments and biological materials. These compounds must be derivatised prior to GC-ICP-MS analysis, which usually necessitates an extraction step from the matrix, with subsequent derivalisation to the volatile compound and a final extraction into an adequate medium for GC injection. 

In principle, the connection of a GC to an ICP-MS is straightforward - the outlet of the GC column is connected to the torch injector, either directly or via a transfer line. In reality, this simple approach bears several constraints  

The GC itself is a versatile tool, enabling, e.g., injection via thermodesorption of species preconcentrated on a solid phase microextraction (SPME) fibre, or the use of cold injection systems for volatile species, and of course is applicable to a wide range of species just by choosing appropriate columns and separation conditions. 

In contrast to the MIP source, ICP s have received limited attention as detectors for gas chromatography. One reason for this includes the fact that ICP s have traditionally been used for the determination of metals. The analytical utility of the ICP for the detection of non-metals such as carbon and the halogens is limited by the relatively small degree 

Chong and Houk [87] have reported on the coupling of ICP-MS to packed-column GC. Potentially this hyphenated technique would not only provide sensitive element-selective detection, but also would allow for the determination of atomic ratios or empirical formulas. The information derived would be complementaiy to molecular information available using GC-MS with conventional ionization methods. 

The interface between GC column and ICP consisted of a glass-lined stainless-steel tube which was attached to the end of the column. The other end of the tubing was inserted into the quartz injector tube of the ICP torch. The end of the transfer line was positioned approximately 2 cm. from the tip of the injector in order to eliminate arcing of the plasma to the stainless-steel tubing. An auxiliary argon nebulizer flow was necessary to form an ion rich central channel in the plasma. 

---

Prange A, Jantzen E (1995) Determination of organometallic species using GC-ICP-MS. Journal of Analytical Atomic Spectrometry, 10 105-109. 

GC-FTIR, GC-AED, GC-ICP-MS, cf. Chapter 7), fast GC separations (1996) and most recently the development of sophisticated injectors with temperatureprogramming capability and high-resolution systems (GC-ToFMS). As a result, modem GC systems are quite advanced (Scheme 4.3) and GC is one of the most widely applied instrumental techniques. 

GC-AAS has found late acceptance because of the relatively low sensitivity of the flame graphite furnaces have also been proposed as detectors. The quartz tube atomiser (QTA) [186], in particular the version heated with a hydrogen-oxygen flame (QF), is particularly effective [187] and is used nowadays almost exclusively for GC-AAS. The major problem associated with coupling of GC with AAS is the limited volume of measurement solution that can be injected on to the column (about 100 xL). Virtually no GC-AAS applications have been reported. As for GC-plasma source techniques for element-selective detection, GC-ICP-MS and GC-MIP-AES dominate for organometallic analysis and are complementary to PDA, FTIR and MS analysis for structural elucidation of unknowns. Only a few industrial laboratories are active in this field for the purpose of polymer/additive analysis. GC-AES is generally the most helpful for the identification of additives on the basis of elemental detection, but applications are limited mainly to tin compounds as PVC stabilisers. 

Figure 7.15 Schematic of the GC-ICP-MS interface. Reproduced by permission of Agilent Technologies...

Table 7.33 reports the main characteristics of GC-ICP-MS. Since both GC and ICP-MS can operate independently and can be coupled within a few minutes by means of a transfer line, hyphenation of these instruments is even more attractive than GC-MIP-AES. GC-ICP-MS is gaining popularity, probably due to the fact that speciation information is now often required when analysing samples. Advantages of GC-ICP-MS over HPLC-ICP-MS are its superior resolution, resulting in sharper peak shapes and thus lower detection limits. GC-ICP-MS produces a dry plasma when the separated species reach the ICP they are not accompanied by solvent or liquid eluents. This reduces spectral interferences. Variations on the GC-ICP-MS... 

Microwave plasma detection has been reviewed [351], also in relation to GC [352,353], Coupling of chromatography (GC, SFC, HPLC) and capillary electrophoresis (CE) with ICP-MS and MIP-MS detectors has also been reviewed [181,334,335]. Various specific GC-ICP-MS reviews have appeared [334,337,345,346,354,355]. 

ICP-MS is being used more frequently in combination with a front-end separation technique such as GC, as a specific and highly selective detector for a variety of speciation applications. GC-ICP-MS is a powerful... 

Other techniques used for organotin speciation comprise GC-FAAS, GC-GFAAS, GC-ICP-MS, HPLC-FAAS, HPLC-GFAAS, HPLC-DCP (after continuous on-line hydride generation), HPLC-ICP-AES, HPLC-ICP-MS, etc. [555], Whereas ICP-AES does not provide an adequate response for ng levels of tin, ICP-MS can detect sub-ng to pg levels. GC-ICP-ToFMS... 

Speciation analysis of organometal compounds by means of GC-MIP-AES and GC-ICP-MS has been reviewed [565], as has as metal speciation by HPLC... 

In contrast to combined systems, hyphenated techniques consist of two or more analytical systems each of which is independently applicable as an analytical technique. Usually, the connection is realized by means of an interface and the system is controlled by a computer. With regard to integrated sample treatment, separation and transfer, hyphenated methods like GC-MS, HPLC-MS, GC-IR, GC-IR-MS, GC-AAS, GC-ICP-MS, MS-MS, and... 

Bayon M, Camblor MG, Alonso JI, Sanz-Medel A. An alternative GC-ICP-MS interface design for trace element spedation. J. Anal. At. Spectrom. 1999 14 1317-1322. 

The determination of volatile elemental species in biological or environmental samples, such as body fluids, tissues, soils, plants or water, generally requires a careful preconcentration and clean-up procedure in order to separate the analytes from matrix material. Several existing sample preparation procedures and applied measurement techniques (especially GC-ICP-MS in combination with... 

Phosphoric acid triesters in human blood plasma have been determined by GC-ICP-MS after SPME,27 after their separation from blood plasma, with detection limits of 50ngl-1 for tripropyl phosphate, 17ngl 1 for tributylphosphate and 24ngl 1 for triphenylphosphate. 

Donard and co-workers reported on the application of double-focusing sector field GC-ICP-MS with a single ion collector and multi-collector arrangement for trace metal speciation.2... 

Several working groups have analyzed platinum group elements (PGEs) as possible markers of anthropogenic pollution in aerosols (in airborne particulates from automobile exhaust to check the emission of catalysts), mainly by ICP-MS.49 50 Airborne particles were also investigated with respect to selected element species (e.g., of Hg and Pb) by GC-ICP-MS.51,52... 

Argon plasmas are used in optical emission spectrometry to atomise and ionise elements leading to the emission of characteristic spectral lines. Hence, a plasma torch (7-8 000 K) can be used for ionisation in mass spectrometry. Ions produced in the plasma are introduced into the mass analyser through a small orifice (called a skimmer) placed in the axial direction. Because the mass spectrometer is operated under a vacuum, the ions are sucked into the mass analyser through the skimmer. An aqueous solution of the sample can be aspirated into the plasma or, alternatively, the plasma can be placed at the exit of a gas chromatograph (e.g. speciation of organo-metallic compounds by GC/ICP-MS). Since all chemical bonds are broken in the plasma, the only accessible information is that concerning the concentration of monoatomic ions (Fig. 16.19). 

One of the first reported couplings of GC-ICP-MS was by Van Loon et al. [115], who used a coupled system for the speciation of organotin compounds. A Perkin-Elmer Sciex Elan quadrupole mass filter instrument was used as the detector with 1250 or 1500 W forward power. The GC system comprised a Chromasorb column with 8 ml min 1 Ar/2 ml min-1 02 carrier gas flow with an oven temperature of 250°C. The interface comprised a stainless-steel transfer line (0.8 m long) which connected from the GC column to the base of the ICP torch. The transfer line was heated to 250°C. Oxygen gas was injected at the midpoint of the transfer line to prevent carbon deposits in the ICP torch and on the sampler cone. Carbon deposits were found to contain tin and thus proved detrimental to analytical recoveries. Detection limits were in the range 6-16 ng Sn compared to 0.1 ng obtained by ETAAS, but the authors identified areas for future improvements in detection limits and scope of the coupled system. 

---