Capillary electrophoresis trace analysis

Limits of detection become a problem in capillary electrophoresis because the amounts of analyte that can be loaded into a capillary are extremely small. In a 20 p.m capillary, for example, there is 0.03 P-L/cm capillary length. This is 1/100 to 1/1000 of the volume typically loaded onto polyacrylamide or agarose gels. For trace analysis, a very small number of molecules may actually exist in the capillary after loading. To detect these small amounts of components, some on-line detectors have been developed which use conductivity, laser Doppler effects, or narrowly focused lasers (qv) to detect either absorbance or duorescence (47,48). The conductivity detector claims detection limits down to lO molecules. The laser absorbance detector has been used to measure some of the components in a single human cell (see Trace AND RESIDUE ANALYSIS). 

P. Britz-McKibbin and S. Terabe, On-line preconcentration strategies for trace analysis of metabolites by capillary electrophoresis. J. Chromatogr.A 1000 (2003) 917-934. 

Kfivankova, L., Pantiickova, P., Gebauer, P., Bocek, P., Caslavska, J., and Thormann, W. (2003). Chloride present in biological samples as a tool for enhancement of sensitivity in capillary zone electrophoretic analysis of anionic trace analytes. Electrophoresis 24, 505—517. 

M. A. Ruggiero and F. M. Lan9as, Approaching the ideal system for the complete automation in trace analysis by capillary electrophoresis , in Proceedings of the 3rd Latin American Symposium on Capillary Electrophoresis, Buenos Aires, Argentine, November 30-December 2. p. 1 (1997). 

Da Silva, C.L., E.C. de Lima, and F.M. Tavares (2003). Investigation of preconcentration strategies for the trace analysis of multi-reside pesticides in real samples by capillary electrophoresis. J. Chromatog. A, 1014 109-116. 

Cengiz, S. and Sakul, O. (2001). Capillary electrophoresis in forensic soil analysis. Trace Elements Electrolytes 18, 87-91. 

A high-sensitivity cell for the Agilent Capillary Electrophoresis System has recently been developed. The cell increases detection sensitivity by an order of magnitude compared to standard detection [61]. This new cell is expected to increase substantially the utility of CE/CEC for the detection of enantiomeric purity of chiral drugs and trace analysis in biological and environmental samples. 

For clcmcnt-speciPc detection in GC, a number of dedicated spectrometric detection techniques can be used, for example, quartz furnace AAS or atomic Bu-orescence spectrometry (AFS) for Hg, or microwave-induced plasma atomic emission spectrometry (MIP-AES) for Pb or Sn. However, ICP-MS is virtually the only technique capable of coping, in the on-line mode, with the trace element concentrations in liquid chromatography (LC) and capillary electrophoresis (CE) efBuents. The femtogram level absolute LoDs may still turn out to be insufficient if an element present at the nanogram per milliliter level splits into a number of species, or when the actual amount of sample analyzed is limited to some nanoliters as in the case of CE or nanoBow HPLC. The isotope spcciPcity of ICP-MS offers a still underexploited potential for tracer studies and for improved accuracy via isotope dilution analysis. 

Figure 8 Automated high-throughput RNA analysis by capillary electrophoresis. Typical batch processing profiles of a 96-well sample plate. Total RNA sample preparations from rice (traces 1-76 from top), arabidopsis (traces 77-95), and yeast (trace 96) 6 pL each in 96-well plate. Conditions 50-pm-i.d. capillary, =10 cm (L = 30 cm) sieving medium, 1% PVP (polyvinylpirrolidone, MW= 1.3 MDa), 4 M urea, 1 xTBE, 0.5 pM ethidium bromide =500 V/cm 25°C. RNA samples were diluted in deionized water and denatured at 65°C for 5 min prior to analysis. Sample tray was stored at 4°C in the CE instrument during processing. Injection vacuum (5 s at 3.44 kPa). Separation matrix was replaced after each run, 2 min at 551 kPa. (Reproduced with permission from Ref. 102.)...

Hou L, Wen X, Tu C, and Lee HK. Combination of liquid-phase microextraction and on-colunm stacking for trace analysis of amino alcohols by capillary electrophoresis. J. Chromatogr. A 2002 979 163-169. 

Analysis of the chiral pollutants at trace levels is a very important and demanding field. In recent years, capillary electrophoresis has been gaining importance in the direction of chiral analysis of various racemates. A search of the literature cited herein indicates a few reports on the chiral resolution of environmental pollutants by CE. It has not achieved a respectable place in the routine chiral analysis of these pollutants due to its poor reproducibility and to the limitations of detection. Therefore many scientists have suggested various modifications to make CE a method of choice. To achieve good reproducibility. 

Gas chromatography-mass spectrometry (GC-MS) provides a standard method for accurate quantification of plant hormones, but requires pre-derivatizing those to volatile compounds that may affect the yield of the analyzed compounds as hydrolysis of the derivatives, multiple-products formation, and limited volatility occur. Capillary zone electrophoresis was used to determine dissociation constants of cytokinins [284,285], to explore their separation and possible quantification [274,286], Main disadvantage of the method in trace analysis is a relatively high limit of detection coming from the restricted injection volumes that are typically in the nanoliter range. This limitation may be overcome by the use of sensitive detection systems (e.g. mass spectrometry) and/or the development of on-line stacking methods [287]. 

Applications of cze include the detection of trace amounts of DNA and the separation of peptide fragments. Furthermore, this technique is beneficial to forensic scientists because restriction mapping can be performed, allowing assays for DNA to be carried out at the scene of a crime (see Forensic testing). It is also possible to interface capillary electrophoresis on-line with a mass spectrometer as a sample introduction technique in the analysis of amino acids and proteins (70). Further improvements in capillary electrophoresis include the need to increase column capacity. Most reported separations involve the resolution of only 20—30 components, whereas high resolution hplc is capable of resolving several hundred components in a mixture (see Chromatography). 

The determination of iodine in seawater helps in understanding the marine environment. A variety of analytical methods have been proposed for the quantitative determination of iodine in seawater. This chapter discusses the methods employed for the separation and determination of iodine in seawater. These methods include capillary electrophoresis (CE), ion chromatography (IC), high-performance hquid chromatography (HPLC), gas chromatography (GC), spectrophotometry, ion-selective electrode, polar-ography, voltammetry, atomic emission spectrometry (AES), and neutron activation analysis (NAA). The advantages and hmitations of these methods are also assessed and discussed. Since iodine is present in the ocean at trace levels and the matrices of seawater are complex, especially in estuarine and coastal waters, the methods developed for the... 

Aside from conventional electrophoretic methods, capillary electrophoresis (CE) is considered as a novel electrophoretic technique for protein separation with advantages of being easy, rapid, automatic, using trace amount of test samples, and qualitative as well as quantitative within one analysis... 

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