Retention times collected

The basic operations in dust collection by any device are (1) separation of the gas-borne particles from the gas stream by deposition on a collecting surface (2) retention of the deposit on the surface and (3) removal of the deposit from the surface for recovery or disposal. The separation step requires (1) application of a force that produces a differential motion of a particle relative to the gas and (2) a gas retention time sufficient for the particle to migrate to the coUecting surface. The principal mechanisms of aerosol deposition that are apphed in dust collectors are (1) gravitational deposition, (2) flow-line interception, (3) inertial deposition, (4) diffusional deposition, and (5) electrostatic deposition. Thermal deposition is only a minor factor in practical dust-collectiou equipment because the thermophoretic force is small. Table 17-2 lists these six mechanisms and presents the characteristic... 

Preparative chromatography involves the collection of individual solutes as they are eluted from the column for further use, but does not necessarily entail the separation of large samples. Special columns can be designed and fabricated for preparative use, but for small samples the analytical column can often be overloaded for preparative purposes. Columns can be either volume overloaded or mass overloaded. Volume overload causes the peak to broaden, but the retention time of the front of the peak... 

The uniform growth of PCNTs generally requires the partial pressure of benzene to be as low as possible. Following a 1 h retention time, the chamber is cooled to room temperature and the H2 atmosphere is replaced by Ar. The product, deposited on the substrate is collected and then annealed at 2000-3000°C under Ar... 

In GC X GC, a sample is separated into a large number of small fractions and each of these is subsequently quantitatively transferred to a secondary column to be further separated. The second separation is very much faster than the first separation, so that the fractions can be narrow and the separation obtained on the first column can be maintained. The collection of the fractions from the first column is achieved by focusing, rather than by valve switching, and the entire sample reaches the detector. The consequence is a chromatogram, with a two-dimensional plane, rather than a one-dimensional axis, as the time domain. One dimension of this plane represents the retention time on the first column, while the second dimension represents the retention time on the second column. Every separated peak can be presented as a... 

The separation step requires (1) application of a force that produces a differential motion of the particles relative to the gas, and (2) sufficient gas-retention time for the particles to migrate to the collecting surface. Most dust-collections systems are comprised of a pneumatic-conveying system and some device that separates suspended particulate matter from the conveyed air stream. The more common systems use either filter media (e.g., fabric bags) or cyclonic separators to separate the particulate matter from air. 

The NMR spectrum is recorded during the chromatographic separation. Data are collected as in a 2D experiment, the two dimensions being the chemical shift and the retention time of the chromatogram. 

Since ProteinTrawler records the retention time of each protein mass, it is a simple endeavor to maintain chromatographic conditions, split the flow that exits the LC column with a small portion set to the mass spectrometer to monitor for assurance that there were no changes in the retention time that would hinder the pooling of fractions from multiple runs, and to facilitate the determination of which fractions contained the desired proteins. In our experimental setup, the flow was split after the column with 25% of the flow going to the mass spectrometer while the remaining diverted to an HP1100 fraction collector. The fraction collector was used to collect fractions at 1.0-minute intervals. 

In complex samples, when the range of elution times may not be known beforehand, there is the possibility of wraparound where components from the previous run are still eluting on the next second-dimension elution (Micyus et al., 2005). This situation is of concern and should be eliminated in the method development process for all but the most exploratory of work. This may require collecting fractions and injecting these fractions into the second-dimension column to determine the most retained compound retention time as part of the method development process. 

An accelerated retention window (ARW) starting from a certain proportion of organic (0A% acetonitrile) as the start of the gradient mobile phase composition was used to calculate preparative retention time on the basis of analytical retention time. The same procedure was used to adjust the retention times of all compounds to facilitate collection at the same predetermined retention time. This allowed set-up of a device for collecting any HPLC peaks that surpassed a certain threshold defined by UV or ELSD. 

Stock solutions of anthracyclines (1 mg/mL) were prepared in double distilled water and stored at 4°C in the dark. Standard working solutions were prepared by diluting stock solutions with double distilled water or 0.1 M phosphoric acid. Aliquots of blank human plasma (0.5 mL) were spiked with working solutions of anthracyclines, mixed with 0.5 mL of 0.2M dibasic sodium phosphate buffer (pH 8.4), extracted with 4 mL of chloroform 1-heptane (9 1 v/v) by shaking for 15 min and centrifuged at 4000 rpm for 10 min. The lower organic layer was re-extracted with 0.25 mL of 0.1M phosphoric acid. The upper aqueous layer was collected and assayed. The injection volume was 50 fiL. Retention times for daunorubicinol, daunorubicin, idarubicinol, idarubicin, doxorubicinol, doxorubicin, epirubicinol, and epirubicin were 6,7, 9.1, 8.0, 11.3, 5.1,6.4, 5.5, and 7.0 min, respectively. 

A standard stock solution of sirolimus was prepared in methanol. Controls and standard working solutions were prepared by spiking blank whole blood with the stock solution. Standards, controls, and patient whole blood (10 fi. ) were transferred to 1.5 mL polypropylene tubes, mixed with 40 fiL of 0.1M zinc sulfate solution, precipitated with 100 fiL of methanol containing the IS (2 fig/L), vor-texed vigorously for 5 sec, and centrifuged at 10,500 g for 5 min. Supernatants were collected and assayed. The injection volume was 20 fiL. The retention times of sirolimus and ascomycin were 0.93 and 0.89 min, respectively. The total run time was 2.5 min. Representative MRM chromatograms of a patient sample are shown in Figure 11.6. 

Extracts collected from reproductive females and boars contained on average more compounds than those from non-reproductive females (106, 125 and 61 respectively). There were a range of volatile compounds although there were many at a high molecular weight. A quantitative analysis of the compounds present in more than 50% of the animals per type revealed a high similarity between the compounds found in reproductive females and boars. Two major compounds of all extracts have a retention time of 8.45-8.51 (RI = 800) and 14.93-14.95 (RI = 992). 

---