Resin Retention time

The methacrylic backbone structure makes the spherical Toyopearl particles rigid, which in turn allows linear pressure flow curves up to nearly 120 psi (<10 bar), as seen in Fig. 4.45. Toyopearl HW resins are highly resistant to chemical and microbial attack and are stable over a wide pH range (pH 2-12 for operation, and from pH 1 to 13 for routine cleaning and sanitization). Toyopearl HW resins are compatible with solvents such as methanol, ethanol, acetone, isopropanol, -propanol, and chloroform. Toyopearl HW media have been used with harsh denaturants such as guanidine chloride, sodium dodecyl sulfate, and urea with no loss of efficiency or resolution (40). Studies in which Toyopearl HW media were exposed to 50% trifluoroacetic acid at 40°C for 4 weeks revealed no change in the retention of various proteins. Similarly, the repeated exposure of Toyopearl HW-55S to 0.1 N NaOH did not change retention times or efficiencies for marker compounds (41). 

Immobilization by adsorption onto a surface such as activated carbon or to an ion-exchange resin gives a reversible and relatively weak bond, but this can be sufficient to increase the retention time in a flow system to acceptable levels. Recall Section 10.6 where it is shown that the residence time of an adsorbed species can be much larger than that of the mobile phase, in essence giving more time for catalysis. 

Silicone paints are formed by controlled hydrolysis and condensation of alkyl alkox-ysilanes, and may be encountered either alone or in formulations with other synthetic resins. The typical structural unit in the polymer chain is dimethyl siloxane, and pyrolysis of such resins takes place with random chain scission and the extended formation of stable cyclic fragments. In Figure 12.14 the pyrogram of a silicone resin is shown, with cyclic siloxane oligomers eluting at the shorter retention times, followed by the linear siloxane fragments. 

A high-performance liquid chromatographic method for nalidixic acid on a strong anion-exchange resin column has been reported, using a mobile phase of 0.01 M sodium tetraborate at pH 9.2 and 0.003 M sodium sulfate. The relative retention time for nalidixic acid in the system reported by Sondach and Koch was 0.86 with sulfanilic acid as the standard at... 

Hydraulic properties, of ion-exchange resins, 74 399 403 Hydraulic retention time (HRT), in biological waste treatment, 25 829 Hydraulic scales, 26 229-230 Hydraulic-settling classifiers, 22 275 Hydrazide(s), 70 504 73 573-576... 

In the pesticide industry, neutralization is provided prior to GAC and resin adsorption, pesticide hydrolysis, and biological treatment. The neutralization basin is sized on the basis of an average retention time of 6 minutes and 70 horsepower per million gallons for mixing requirements [7]. 

Stromberg, L. Minor components of Cannabis resin V. Mass spectrometric data and gas chromatographic retention times of cannabinoid components with retention times shorter than that of cannabidiol. J Chromatogr 1974 96 179. 

Eluent 2 is a lower ionic strength buffer and is used only to resolve DMA from interfering As (ill). With this eluent, MMA, p-APA, and As(V) have very long retention times and will accumulate on the column typing up active resin sites. Therefore the column must be flushed with Eluent 1 after 10-15 samples have been analyzed and the column reequilibrated for 1 hour with Eluent 2 before further analysis. The analysis of DMA and As (ill) can be performed at the rate of 10 samples per hour, and each chromatogram requires 3 minutes. 

The basis of the separation of amino acids by AAA lies in the interaction between acids - present in the elution buffer - and the stationary phase. This resin is made up of small sulfonated polystyrene particles. The negative charge of the sulfonic acid residues is counterbalanced by the Li+ -cations of the elution buffer. As the whole separation process takes place at a weakly acidic pH, the carboxylic acid residues are protonated and the interaction with the stationary phase of the column is achieved by the protonated (and thus positively charged) amino group(s) of the amino acids. The more basic the amino acid is, the stronger the interaction with the stationary phase and - consequently - the longer the retention time. So it is easily understood... 

Quality of the resin is the basis of good separation and reproducibility of the retention times. In this respect one is highly dependent upon the manufacturer of the instrument, who also supplies the column (and sometimes the resin). During the analysis, the resin is confronted with various buffers of increasing strength and temperature, a fierce regeneration step, and trace amounts of protein that cannot be... 

Note Ethyl acetate is a solvent impurity of ether. 900 mL of solvent/700 mL of resin was successively Soxhlet extracted for 24 h with CH3OH, CH3C=N, and ether. No compounds were identified in the ether fractions. A sample was injected directly into the GC-MS. Identifications are tentative no retention time data have yet been correlated. Identifications were completed by MS only. 

Table I. Retention Time Standard Deviations of Internal Alkane Standards of Composite XAD Resin Water Samples With and Without Cleanup...

In view of recent work by Neuberger and Wilson (33) pertaining to the relative acidities of various methyl glycosides as determined by retention times on a strongly basic ion-exchange resin (OH" form), the field-effect process may well be the operative mechanism. Neuberger and Wilson offer reasonable explanations for the acidities of these glycosides,... 

Among the other factors to be considered in the choice of separative conditions is temperature. Peak resolution and retention time (RT) depend greatly on this parameter an increase in temperature diminishes the viscosity of the mobile phase and of the sample, and a reduction of RT is observed in addition to an increase in the efficiency of the column. However, this effect is not always produced, nor for all supports some sulphonic ion-exchange resins show for analytes such as ethanol, the opposite effect. It is clear that thermostatization of the system must be very thorough so that repeatable results may be obtained. Very commonly used temperatures are those between 25°C and 70°C, values that must be adjusted each time depending on the complex of analytes to be separated. 

The determination of iodide in milk (2% milkfat) by ion chromatography coupled with pulsed amperometric detection on a silver electrode is an application that benefits from matrix elimination of fats. The pulsed amperometric waveform improves reproducibility by electrochemically cleaning the working electrode on each pulse. In addition, the fats are removed from the sample using a disposable cartridge containing a polymeric reversed phase resin (OnGuard II RP, Dionex Corp.). When 50 jal of 0.1 mg/1 iodide was added to 200 jal of prepared milk, the recovery was 100%. The iodide peak area and retention time RSDs were 1.4% and 0.4% respectively [28]. 

A more extensive study of mobilities of 3H- and 14C-labeled amino acids again found that amino acids labeled with 14C at Cl or C2 are retained on the column, relative to the unlabeled forms.135 Lysine is an exception. Tritiation at C3 also increases the retention time, but tritiation at C2 of glycine or at C4, C5, or C6 of lysine decreases it, and large decreases are seen with methionine tritium-labeled in the methyl and with tyrosine tritium-labeled at C3, 5. The 14C IEs can be attributed to a decrease of acidity, but the IEs of distant 3H may be due to hydrophobic interactions with the resin. A remarkable result is that intramolecular isotopic isomers (isotopomers) can be distinguished on the basis of their chromatographic mobilities. 

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