Liquid chromatography-atomic absorption spectrometry

With its different modes of operation, high-performance liquid chromatography (HPLC) is a most suitable technique for the separation of less volatile, polar, or even ionic analytes. HPLC separation provides a continuous eluent flow of typically up to 1 mL min which can easily be introduced into the nebuHser of a flame AAS system. The interface design generally is a critical factor, since it may induce additional peak broadening which reduces both sensitivity and resolution. 

The column effluent is directly introduced into the mixing chamber of the flame atomiser. Since the transport efficiency of flame AAS is usually only 5—10%, this explains why the sensitivity of this type of coupling is limited, particularly in comparison with GC-AAS. 

Graphite furnace AAS generally offers highly sensitive detection for small sample amounts, however the sequential nature of the drying, ashing, and atomisation steps make it difficult to interface it to a continuous separation technique like HPLC. As a simple solution, the autosampler of a commercial GF-AAS instrament may be modified in such a way that the effluent is passed through a PTFE flowthrough cell from which the autosampler periodically injects a small aliquot (10—50 pL) into the furnace. Of course, this does not provide a continuous on- 

Despite the better sensitivity of GF-AAS the coupling with HPLC has only found limited use, mainly due to the difficulties of coupling a continuous flow separation technique with the discrete nature of GF-AAS. Improvements may be expected by coupling HPLG and GF-AAS after on-line hydride generation as outlined for HPLC-FAAS, however, these techniques has not been thoroughly investigated. 

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High, K.A., Azani, R., Fazekas, A.F., Chee, Z.A. and Blais, J.-S. (1992) Thermospray-microatomizer interface for the determination of trace cadmium and cadmium-metallothioneins in biological samples with flow injection- and high-performance liquid chromatography-atomic absorption spectrometry. Anal. Chem., 64, 3197-3201. 

Liquid chromatography-atomic absorption spectrometry (LC-AAS) and liqnid chromatography-optical emission spectrometry (LC-OES) combine the separating power of LC... 

Chana, B.S. and Smith, N.J. (1987). Urinary arsenic speciation by high-performance liquid chromatography/atomic absorption spectrometry for monitoring occupational exposure to inorganic arsenic. Anal. Chim. Acta 197,177-186. 

High, K. A., Blais,J. S., Methven, B. A.J., and McLaren,J.W. (1995). Probing the characteristics of metal-binding proteins using high-performance liquid chromatography-atomic absorption spectroscopy and inductively coupled plasma mass spectrometry. Ajiafysr (London) 120(3), 629. 

Inductively coupled plasma atomic emission spectrometry Electrothermal atomic absorption spectrometry High pressure liquid chromatography... 

Zhang X, Cornelis R, De Kimpe J, and Mees L (1996) Arsenic speciation in serum of uraemic patients based on liquid chromatography with hydride generation atomic absorption spectrometry and on-line UV photo-oxidation digestion. Anal Chim Acta 319 177-185. 

In modern times, most analyses are performed on an analytical instrument for, e.g., gas chromatography (GC), high-performance liquid chromatography (HPLC), ultra-violet/visible (UV) or infrared (IR) spectrophotometry, atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry. Each of these instruments has a limitation on the amount of an analyte that they can detect. This limitation can be expressed as the IDL, which may be defined as the smallest amount of an analyte that can be reliably detected or differentiated from the background on an instrument. 

Principles and Characteristics Plasma source techniques are more widely used in connection with liquid chromatography than atomic absorption spectrometry (see Section 7.3.3). ICP is a natural complement to liquid chromatography, and HPLC-ICP procedures... 

Hydride Generation Atomic Absorption Spectrometry High Performance Liquid Chromatography High Performance Thin-Layer Chromatography High Resolution... 

Measurement techniques that can be employed for the determination of trace metals include atomic absorption spectrometry, anodic stripping voltammetry, differential pulse cathodic stripping voltammetry, inductively coupled plasma atomic emission spectrometry, liquid chromatography of the metal chelates with ultraviolet-visible absorption and, more recently, inductively coupled plasma mass spectrometry. 

Techniques for analysis of different mercury species in biological samples and abiotic materials include atomic absorption, cold vapor atomic fluorescence spectrometry, gas-liquid chromatography with electron capture detection, and inductively coupled plasma mass spectrometry (Lansens etal. 1991 Schintu etal. 1992 Porcella etal. 1995). Methylmercury concentrations in marine biological tissues are detected at concentrations as low as 10 pg Hg/kg tissue using graphite furnace sample preparation techniques and atomic absorption spectrometry (Schintu et al. 1992). 

The most important features of liquid membranes are that they olfer highly selective extraction, efficient enrichment of analytes from the matrix in only one step, and the possibility of automated interfacing to different analytical instruments such as liquid chromatography, gas chromatography, capillary zone electrophoresis, UV spectrophotometry, atomic absorption spectrometry, and mass spectrometry [82]. 

M. Grotti, P. Rivaro and R. Frache, Determination of butyltin compounds by high-performance liquid chromatography-hydride generation-electrothermal atomisation atomic absorption spectrometry, J. Anal. At. Spectrom., 16(3), 2001, 270-274. 

C. Schickling and J. A. C. Broekaert, Determination of mercury species in gas condensates by online coupled high-performance liquid chromatography and cold-vapor atomic absorption spectrometry, Appl. Organo-met. Chem., 9(1), 1995, 29-36. 

AMS = accelerated mass spectroscopy EDTA = ethylene diamine tetra acetic acid GFAAS = graphite furnace atomic absorption spectrometry ICP-AES = inductively coupled plasma - atomic emission spectroscopy NAA = neutron activation analysis ETAAS = electrothermal atomic absorption spectrometry SEC/ICP-MS = size-exclusion chromatography/ICP-AES/mass spectrometry HLPC/ICP-AES = high-performance liquid chromatography/ICP-AES LAMMA = laser ablation microprobe mass analysis NA = not applicable ppq = parts per quadrillion... 

Wrobel K, Gonzalez EB, Wrobel K, et al. 1995. Aluminum and silicon speciation in human serum by ion-exchange high-performance liquid chromatography-electrothermal atomic absorption spectrometry and gel electrophoresis. Analyst 120 809-815. 

Diemer, J. and Heumann, K.G. (1997) Bromide/bromate speciation by NTI-IDMS and ICP-MS coupled with ion exchange chromatography. Fresenius J. Anal. Chem., 357,74-79. Duan, YX., Wu, M., Jin, Q.H. and Hieftje, G.M. (1995) Vapour generation of nonmetals coupled to microwave plasma-torch mass-spectrometry. Spectrochim. Acta B, 50,355-368. Ebdon, L., Hill, S. and Jones, R (1987) Interface system for directly coupled high performance liquid chromatography-flame atomic absorption spectrometry for trace metal determination./. Anal. At. Spectrom., 2, 205-210. 

Hansen, S.H., Larsen, E.H., Pritzi, G. and Cornett, C. (1992) Separation of seven arsenic compounds by high performance liquid chromatography with on-line detection by hydrogen-argon flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry./. Anal. At. Spectrom., 1, 629-634. 

Basic techniques for speciation analysis are typically composed of a succession of analytical steps, e.g. extraction either with organic solvents (e.g. toluene, dichloromethane) or different acids (e.g. acetic or hydrochloric acid), derivatisa-tion procedures (e.g. hydride generation, Grignard reactions), separation (gas chromatography (GC) or high-performance liquid chromatography (HPLC)), and detection by a wide variety of methods, e.g. atomic absorption spectrometry (AAS), mass spectrometry (MS), flame photometric detection (FPD), electron capture detection (ECD), etc. Each of these steps includes specific sources of error which have to be evaluated. 

Figure 6.1 Bar-graph of MeHg in CRM 580. The results correspond to six replicate determinations as performed by different laboratories using various methods. MEANS indicates the mean of laboratory means with 95% confidence interval. Abbreviations-. CVAAS, cold vapour atomic absorption spectrometry CVAFS, cold vapour atomic fluorescence spectrometry ECD, electron capture detection GC, gas chromatography HPLC, high-performance liquid chromatography ICPMS, inductively coupled plasma mass spectrometry MIP, microwave induced plasma atomic emission spectrometry QFAAS, quartz furnace atomic absorption spectrometry SFE, supercritical fluid extraction.

Investigations of lead speciation in various environmental samples have relied upon gas and liquid chromatographic separations coupled to mass spectrometric and atomic absorption spectrometric detectors. The combination of atomic absorption spectrometry with gas chromatography (GC-AAS) has proved to be the most widely applied technique. Sample types have included air, surface water, air particulates, sediments, grass, and clinical materials such as blood. A review of speciation analyses of organolead compounds by GC-AAS, with emphasis on environmental materials, was published (Lobinski et al., 1994). 

Ebdon, L., Hill, S. and Jones, R (1987) Application of directly coupled flame atomic absorption spectrometry-fast protein liquid chromatography to the determination of protein-bound metals. Analyst, 112, 437-440. 

Momplaisir, G.M., Blais, J.-S., Quinteiro, M. and Marshall, W.D. (1991) Determination of arsenobetaine, arsenocholine and tetramethylarsonium cations in seafoods and human urine by high-performance liquid chromatography-thermochemical hydride generation-atomic absorption spectrometry.J.Agric. Food Chem., 39, 1148-1151. 

Mixtures of R3Sn+ compounds (R= -butyl. phenyl, cyclohexyl) were separated by ion exchange-high performance liquid chromatography-graphite furnace atomic absorption spectrometry [252], The small spread in calibration slopes in Fig. 4.10 signifies similar efficiencies for their separation and column recovery, as well as graphite furnace sensitivities. 

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