Disposability, capillary column

Methods have been described for determining chlorinated aliphatic hydrocarbons in soil and chemical waste disposal site samples. The latter method involves a simple hexane extraction and temperature programmed gas chromatographic analysis using electron capture detection and high resolution glass capillary columns. Combined gas chromatography-mass spectrometry was used to confirm the presence of the chlorocarbons in the samples [4],... 

Due to the rapidly growing importance of capillary columns in bioanalytical applications, special attention will now be devoted to sampling techniques associated with capillary GC. Small samples are typical for this type of chromatography and, consequently, a direct introduction of such samples is an apparent technological problem. In most biochemically interesting applications (typically, trace analysis problems), there is no general discrepancy between the demands of such analysis and the performance and sensitivity of capillary separation techniques. However, the manipulation of samples presents difficulties, as reliable methods for measurement, disposal, and introduction of nanoliter volumes are not readily available. Ironically, in many capillary GC applications, the solvent serves only as a sample vehicle we... 

Figure 5.18 Steps in preparation and use of elution column used for fraction collecting (a) Pasteur-type disposable pipette (23 cm length) (b) Pipette modified and ready for elution (c) Capillary column before evaporation (d) Capillary column after evaporation Reproduced from McCoy and Fiebig, Analytical Chemistry, ACS [111]...

Our method for the quantitative analysis of lAA consists of four major steps 1) extraction, 2) prepurification, 3) HPLC, and 4) GC-MS. The major time-consuming steps are the purification steps prior to GC-MS. The traditional prepurification [1, 11] has involved solvent partitioning steps and, in some protocols, open column liquid chromatography. Use of high resolution bonded phase capillary GC columns has allowed increased sensitivity at the mass spectral step, and the use of 3 and 5 /xm HPLC packings has made it reasonable to use shorter columns, thus reducing the time required for HPLC. The improvement in recovery afforded by the shorter HPLC columns and the improved sensitivity of capillary GC-MS suggested to us that it was possible to scale down the sample size to a level that made practical the use of Sep-Pak-Mko disposable mini-columns for sample preparation [2, 6, 7]. 

Water is evaporated and trapped from aqueous or moist samples as well. Most of which is disposed of by the dry purge step, particularly when using Tenax adsorption traps with low water retention. Residual moisture can still be transferred to the GC column during the desorption step (Madden and Lehan, 1991). As the resolution of highly volatile substances on capillary columns would be impaired and the detection by the mass spectrometer would be affected, additional devices are used to remove water. In particular, where the P T technique is used with ECD or MS as detectors, reliable water removal is necessary. Different technical solutions working automated during the desorption phase are in use with the P8dT instruments of different manufacturers. 

Miniaturized columns have provided a decisive advantage in speed. Uracil, phenol, and benzyl alcohol were separated in 20 seconds by CEC in an 18 mm column with a propyl reversed phase.29 A19 cm electrophoretic channel was etched into a glass wafer, filled with a y-cyclodextrin buffer, and used to resolve chiral amino acids from a meteorite in 4 minutes.30 A 6 cm channel equipped with a syringe pump to automate sample derivatization was used to separate amino acids modified with fluorescein isothiocyanate.31 Nanovials have been used to perform tryptic digests on the 15 nL scale for subsequent separation on capillary Electrophoresis.32 A microcolumn has also been used to generate fractions representing time-points of digestion from a 40 pL sample.33 A disposable nanoelectrospray emitter has been... 

The sample solutions injected into an ion chromatographic system must be free of particulate matter to avoid plugging of the capillary connecting tubing and the frits at the head of the analytical column. Even samples that appear to be clear may contain unsuspected fine particles. It is more or less standard procedure to filter sample solutions prior to their injection. Disposable membrane filters with a pore diameter of... 

Disposable steel needles used widely in medical practice for drawing of blood samples cannot be used for sampling blood intended for trace metal analysis. Contamination of blood samples by such needles can exceed the actual level of chromium in the sample by a factor of 100-1000. In case liquid chromatography (LC) is used for separation of species, the system inherent contamination has to be taken in account, when using high-performance liquid chromatography (HPLC) equipment (pumps, valves, columns, capillaries) made from stainless steel. 

Owing to the rising cost of solvent disposal, CE is becoming a more attractive method for extract analysis. The method makes it easy to separate ionizable substances using minimal amounts of solvents. On-column detection removes the coupling problems, and the separation power is comparable to that obtained in capillary gas chromatography. If alkaloids have to be analyzed, this method is currently the most suitable. 

LC-DAD, IT-SPME-capillary LC-DAD and IT-SPME-LC with a monolithic column-FLD. Such methods are clearly advantageous over a classical procedure based on SPE with disposable cartridges for a number of reasons (i) the minimum off-line sample manipulation, as the samples only needed to be filtered (ii) the rapidity, as on-line analyte enrichment is accomplished in a few min, (Hi) the minimum consumption of extractive phases, as the extractive columns used (a Cis packed microcolumn or a segment of a capillary GC coliunn) can be reutilized for several hundred samples and (iv) the total elimination of organic solvents in sample preparation. 

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