Volatilization trace analysis

Gas Chromatography. Gas chromatography is a technique utili2ed for separating volatile substances (or those that can be made volatile) between two phases, one of which is a gas. Purge-and-trap methods are frequently used for trace analysis. Various detectors have been employed in trace analysis, the most commonly used being flame ioni2ation and electron capture detectors. 

Volatile analytes. As residue analysis is also trace analysis in the lower ppm (mg kg ) to ppb ( ug kg ) range, concentration steps usually involve evaporation of solvents (sometimes with traces of water present) to near dryness. The volatility of analytes can be deduced from their elution temperatures in GC, and thus whenever an analyte elutes from a nonpolar GC phase of film thickness <0.25 qm below approximately 150 °C, losses due to co-evaporation during concentration by the rotary evaporator or by a stream of nitrogen need to be avoided. 

Bronlc acids containing electron-capturing subsitituents were developed by Poole and co-workers. Table 8.19 (451,535,536). In terms of volatility, stability of derivatives, and response to the electron-capture detector the 3,5-bis(trifluoromethyl)benzeneboronic acid, 2,4-dichlorobenzeneboronic acid, and 4-bromo-benzeneboronic acid were recommended for general applications. In particular, the 3,5-bis(trifluoromethyl)benzeneboronate derivatives are remarkably volatile, more so than the benzeneboronates, and are suitable for the analysis of bifunctional compounds of low volatility. All the benzeneboronate derivatives are susceptible to solvolysis which is the primary limitation to their general use for trace analysis. 

Difficult matrix introduction (DMI) is another recently introduced way of automating trace analysis in complex and dirty matrices [101]. The technique may be used for both liquid and dirty solid samples. In DMI a sample extract or sample matrix (solid) is introduced directly into a microvial in the injector. Volatiles are desorbed directly... 

Advantages and disadvantages of HS-GC over regular GC are summarised in Table. 4.26. HS-GC fingerprinting chromatograms obviously include only the volatile components present and do not provide a complete picture of sample composition on the other hand, when solvent extraction is used, all the soluble sample constituents are removed, including also those having no appreciable vapour pressure at the equilibration temperature. Headspace analysis enhances the peaks of volatile trace components. 

Radtke-Granzer, R., Piringer, O. G., Problems in the quality evaluation of roasted coffee by quantitative trace analysis of volatile flavor components, Dtsch Lebensm Rundsch, 77, 203, 1981. (CA95 95570j)... 

Nearly every area of measurement science can boast of progress in measuring ever-smaller quantities of chemicals, but several stand out in their stunning trace-analysis capabilities. Trace-metal analysis has come to be dominated by methods that volatilize the sample and then either measure its spectroscopic emission or absorption, or measure the masses of the gaseous metal ions using mass spectrometry. Volatilization is accomplished by various thermal means that include flames, furnaces, and inductively coupled or microwave plasmas. The com-... 

Splitless Trace analysis (ppb) possible Cold trapping and solvent effects provide sharp peaks More complex than split Limited to temperature programming Several parameters to optimize Loss of low-volatility, labile analytes... 

Volatile amines from Ci to C(, and ammonia were separated on a PoraPLOT column, with or without a temperature gradient, depending on volatility. The method is applicable to determination of the purity of manufactured amines. Trace analysis of these amines can be performed by capillary GC-FID and of ammonia by GC-ELCD101. 

WAUTERS, E., E.WALRAVENS, E.MUYLLE and G.VERDUYN (1983). An evaluation of a fast sampling procedure for the trace analysis of volatile organic compounds in ambient air. Environm Monitor.Assessm. 3, 151-160. 

Friant, S.L. and Suffet, I.H. Interachve effects of temperature, salt concentration, and pH on head space analysis for isolahng volatile trace organics in aqueous environmental samples. Anal. Chem., 51(13) 2167-2172, 1979. 

D. H. Fine and D. P. Rounbehler, Trace analysis of volatile N-nitroso compounds by combined gas chromatography and thermal energy analysis. Journal of Chromatography, 1975,109(2), 271-279. 

D. H. Fine, D. Lieb and F. Rufeh, Principle of operation of the thermal energy analyzer for the trace analysis of volatile and nonvolatile N-nitroso compounds. Journal of Chromatography, 1975,107(2), 351-357. 

Ideal for gaseous/volatile analytes, high retention for trace analysis For polar analytes, especially for alcohols Developed for high-performance liquid chro-matograpy applications, e.g. surfactants Ideal for a broad range of analyte polarities, good for C3-C20 range... 

Similar to the analytical procedure for trace analysis in high purity GaAs wafers after matrix separation, discussed previously,52 the volatilization of Ga and As has been performed via their chlorides in a stream of aqua regia vapours (at 210 °C) using nitrogen as the carrier gas for trace/matrix separation.58 The recoveries of Cr, Mn, Fe, Ni, Co, Cu, Zn, Ag, Cd, Ba and Pb determined after a nearly quantitative volatilization of matrix elements (99.8 %) were found to be between 94 and 101 % (except for Ag and Cr with 80 %). The concentrations of impurities measured by ICP-DRC-MS (Elan 6100 DRC, PerkinElmer Sciex) after matrix separation were compared with ICP-SFMS (Element 2, Thermo Fisher Scientific) and total reflection X-ray fluorescence analysis (TXRF Phillips). The limits of detection obtained for trace elements in GaAs were in the low ngg-1 range and below.58... 

GC has been used extensively for the separation and determination of volatile organic molecules, and most aspects of this application area are fully documented in monographs on this technique. In the inorganic trace analysis area, however, fewer species possess the required volatility, and applications tend to be limited to the separation of volatile species of low molecular weight (such as methyl derivatives of As, Se, Sn, Hg) and the separation of semi-volatile organo-metals, metal halides, metal hydrides, metal carbonyls and metal chelates. For organo-metal species, the type of detection system required varies with the nature of the analyte, and the options include electron capture detection, flame photometric detection (sometimes ICP), AAS and MS. 

Wolska, L., C. Olszewska, M. Turska, et al. 1998. Volatile and semivolatile organo-halogen trace analysis in surface water by direct aqueous injection GC-ECD. Chemosphere 37 2645-2651. 

B. Middleditch, A. Ziatkis, et al., Trace analysis of volatile polar organics problems and prospects, J. Chromatogr. Sci., 26 150-152 (1988). 

Water. A laboratory engaged in careful electrochemical work with aqueous solutions or in trace analysis will need facilities for the preparation and storage of highly purified water. Water commonly is contaminated with metals in both dissolved cationic form and in the form of colloidal or particulate matter that is not ionized appreciably.70 Frequently it also is contaminated by bacteria and by organic impurities that cannot be removed by ordinary or oxidative distillation because of the steam volatility of the impurities.71... 

The most sensitive analysis was achieved with pentafluorobenzoate, which permits up to 10 12 g of thymol to be determined. Clarke et al. [74] compared the characteristics and ECD responses of acyl derivatives of amines. Table 4.7 shows some of their results. It follows that a different type of acyl derivative is suitable for each type of amine and at the same time other characteristics, which are not reported in the table, must also be taken into consideration. TFA derivatives have better chromatographic characteristics than chloroacetates and usually are preferred, despite their lower responses. The highest sensitivity was obtained by Clarke et al. for HFB derivatives. Other workers [75] drew attention to the dependence of the responses of haloacyl derivatives on the detector temperature. Its significance can be particularly important in trace analysis, when it is necessary to work at the maximal sensitivity of the detector. In each instance when an acyl derivative is used a compromise must be found among the sensitivity required, volatility of the derivatives, reagent availability and other factors. 

Four techniques based on mass spectrometry are widely used for multi-elemental trace analysis of inorganic compounds in a wide range of sample types. These techniques are thermal ionization (TI), spark source (SS), glow discharge (GD) and inductively coupled plasma (ICP) mass spectrometry. In these techniques, atomization and ionization of the analysed sample are accomplished by volatilization from a heated surface, attack by electrical discharge, rare-gas ion sputtering and vaporization in a hot flame produced by inductive coupling. 

Westendorf, R.G. "Trace Analysis of Volatile Organic Compounds in Foods by Dynamic Headspace Gas Chromatography" presented at the 35th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy Atlantic City, N.J. March, 1984. 

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