Chromatography limitations

Lab-on-a-chip/high-performance liquid chromatography Limit of detection... 

Dieldrin, endrin Insecticides reacted with BC13 prior to gas chromatography. Limit of detection 0.01 ppm [295]... 

Miscellaneous - Gas chromatography/thin layer chromatography. Limit of detection 1 50 xg/kg [334]... 

Chloro-2-methyl-phenoxyacetic acid and metabolites Ethenacetone heptane hexane (2 1 1 1) Derivatisation to pentafluorobenzyl derivatised after clean-up by thin layer chromatography then gas chromatography. Limit of detection 20 - 25 ng absolute [402]... 

Chloro-2-methyl- phenoxyacetic acid Dichloromethane extraction Extracts esterified with 2,3,4,5,6-pentafluorobenzyl bromide, petroleum ether extract analysed by gas chromatography, limit of detection 0.5 - 2 pg/kg [403]... 

Trifluralin, benefin Electron capture gas chromatography, limit of detection 50 pg absolute [483]... 

Again, the DEs reported by Flamm and Pakhomov were not defined but were given as >99.9 percent for GB and GD for Stage 1 only and >99.999 percent for the overall process (Bechtel, 1996). The GB and GD concentrations in the bitumen-salt product were generally below the gas chromatography limit of detection of 1 x 1(H mg/ml. 

The low efficiency and short migration distances typical of thin-layer chromatography limit useful separations to those with relatively large enantioselectivity factors. Absorption by the chiral selector can cause baseline instability and reduced sample detectability for quantitative measurements by scanning densitometry. The chiral sepa-... 

Affinity tail Affinity tag or type of chromatography Limitations References... 

The quadripolar spectrometers whose resolution is limited to about 2000 are of simpler design than the magnetic sectors and are less costly. They are often used in conjunction with gas chromatography (see section 3.3) for purposes of identification. 

Chromatographic techniques, particularly gas phase chromatography, are used throughout all areas of the petroleum industry research centers, quality control laboratories and refining units. The applications covered are very diverse and include gas composition, search and analysis of contaminants, monitoring production units, feed and product analysis. We will show but a few examples in this section to give the reader an idea of the potential, and limits, of chromatographic techniques. 

Despite their importance, gas chromatography and liquid chromatography cannot be used to separate and analyze all types of samples. Gas chromatography, particularly when using capillary columns, provides for rapid separations with excellent resolution. Its application, however, is limited to volatile analytes or those analytes that can be made volatile by a suitable derivatization. Liquid chromatography can be used to separate a wider array of solutes however, the most commonly used detectors (UV, fluorescence, and electrochemical) do not respond as universally as the flame ionization detector commonly used in gas chromatography. 

Micellar Electrokinetic Capillary Chromatography One limitation to CZE is its inability to separate neutral species. Micellar electrokinetic chromatography... 

Specifications and Analytical Methods. Vinyl ethers are usually specified as 98% minimum purity, as determined by gas chromatography. The principal impurities are the parent alcohols, limited to 1.0% maximum for methyl vinyl ether and 0.5% maximum for ethyl vinyl ether. Water (by Kad-Fischer titration) ranges from 0.1% maximum for methyl vinyl ether to 0.5% maximum for ethyl vinyl ether. Acetaldehyde ranges from 0.1% maximum in ethyl vinyl ether to 0.5% maximum in butyl vinyl ether. 

Volatile impurities, eg, F2, HF, CIF, and CI2, in halogen fluoride compounds are most easily deterrnined by gas chromatography (109—111). The use of Ftoroplast adsorbents to determine certain volatile impurities to a detection limit of 0.01% has been described (112—114). Free halogen and haHde concentrations can be deterrnined by wet chemical analysis of hydrolyzed halogen fluoride compounds. 

Methods for iodine deterrnination in foods using colorimetry (95,96), ion-selective electrodes (94,97), micro acid digestion methods (98), and gas chromatography (99) suffer some limitations such as potential interferences, possibHity of contamination, and loss during analysis. More recendy neutron activation analysis, which is probably the most sensitive analytical technique for determining iodine, has also been used (100—102). 

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