Long-term column stability

Jungbauer, A., Lettner, H. P., Guerrier, L., and Boschetti, E. (1974). Chemical sanitization in process chromatography. Part 2 In situ treatment of packed columns and long-term stability of resins. Bio-Pharm. 7, 37-42. 

The CdS nanoparticles were autocapped by the fungal proteins, which were responsible for imparting them high stability. The colloidal solution of as-prepared CdS nanoparticles was extremely stable with no evidence for aggregation even after 10 months of continuously running the column. The long-term stability of the as-prepared CdS... 

FIGURE 7.15 Long-term stability of Fractogel EMD BioSEC (S) after long-term treatment with sodium hydroxide. The chromatography of standard proteins (for conditions, see Fig. 7.2A) was carried out after various times of exposure to I M sodium hydroxide solution and reequilibration of the column with the buffer. 

Cool on-column >250 pm column (i.d.) 1 ppm (FID) Reduced thermal degradation and discrimination Wide range of analyte concentrations High sample capacity (LVI) Autosamplers Direct quantification Excellent precision Control of operational conditions (initial oven temperature) Optimisation required Not applicable for polar solvents Column contamination by dirty matrices Poor long term stability... 

Increasing the molecular weight of a copolymer containing 5% methyl acrylate (MA) from 100,000 to 1,000,000 daltons had little effect on silica stabilization effectiveness (see Table IX). Increasing the methyl acrylate content from 5% to 30% had also little effect on silica fines stabilization effectiveness. Acidizing substantially reduced the effectiveness of this class of copolymer. Results for the injection of 10,000 pore volumes of water indicated that silica fines elution from the test column was substantially reduced on a long-term basis. 

The application of HPLC in routine environments, like pharmaceutical, food, or environmental analysis and particularly quality assurance, makes not only great demands on the robnstness of HPLC hardware, comprising pumps, column thermostats, and detection units, bnt in addition to the column reproducibility. Column reproducibility can be investigated at different levels of complexity Run-to-run reproducibility compares consecutive chromatographic runs, whereas long-term stability describes the column variance over several hundreds of injections. Column-to-column (batch-to-batch) reproducibility finally explores the match of independently fabricated chromatographic columns. Column characteristics that are routinely consulted for the determination of the robustness are retention, selectivity, column efficiency, and peak symmetry. 

Chromatographic Resolution. To optimize column-coating conditions and operating parameters glass capillary columns coated with various silicone-based stationary phases were tested with difficult-to-separate groups of PAH standards and Complex samples. The SE5 -coated columns performed excellently with respect to separation efficiency, column bleed and long-term stability. Other observers have had similar results with this... 

Column adsorbants, specifications and eluent solutions are discussed in determining generator performance for yield, breakthrough, and stability for long term use. Some examples of clinical applications in positron emission tomography are presented. 

The LTQ-Orbitrap has resolution and mass accuracy performance close to that of the LTQ-FTICR. As shown in Table 5.3 (column 4), LTQ-Orbitrap accurate mass measurements, using external calibration, for a set of 30 pharmaceutical compounds resulted in less than 2.3 ppm error. The data were acquired with a 4-min, 1-mL/min-flow-rate, positive-mode LC-ESI-MS method where all measurements were performed within 5h from mass calibration. Mass accuracies below 2-3 ppm, and often below 1 ppm, can be routinely achieved in both the positive- and negative-ion mode (Table 5.3, columns 4 and 5). The long-term mass stability of the LTQ-Orbitrap is not as consistent as observed for the LTQ-FTICR-MS, and the Orbitrap requires more frequent mass calibration however, mass calibration is a routine procedure that can be accomplished within 5-10 min. Figure 5.7 displays a 70-h (external calibration) mass accuracy plot for three negative ions collected with a LTQ-Orbitrap where the observed accuracy is 2.5 ppm or better with little mass drift for each ion. Overall, for routine accurate mass measurements on the Orbitrap, once-a-week calibration (for the desired polarity) is required however, considering the ease of the process, more frequent external calibration is not a burden. 

Various workers [23-32] have studied the application of high performance liquid chromatography to the determination of PAHs in water samples. Hagenmaier et al. [31] used a reversed phase high-pressure liquid chromatography procedure for the determination of trace amounts of polycyclic aromatic hydrocarbons in water. Different column packing materials were tested, in conjunction with non polar stationary phases of various polarities, for separation efficiency, detection limits and long-term stability. The method was suitable for concentrations as low as 2ng L 1 in a IL sample. Compounds... 

Long-term column stability (pH and temperature) and batch-to-batch reproducibility are probably the most important quality characteristics to be considered in column selection in the pharmaceutical industry. Nevertheless,... 

With a proper choice of mobile phase (aqueous or nonaqueous), many commercially columns are available for SEC of PVP and VP-based copolymers. Mobile-phase modifiers (such as methanol, salt, and buffer) are normally required to eliminate interactions with columns. A single linear or mixed-bed column has been found to provide good separation of PVP and VP-based copolymers with a molecular weight range of from a few thousands to several millions. In general, the aqueous SEC system has better long-term stability and provides better separation than the nonaqueous SEC system, especially at the low-molecular-weight end. Hydroxylated methyl-methacrylate-type columns and water-methanol mobile phase (50 ... 

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