Reproducibility improvement

Other matters to consider in column choice are column length, column diameter, and particle size. Column efficiency (theoretical plate count) is determined by a ratio of column length to particle size. A shorter column with the same particle size may give a shorter run time but at a loss of resolution. A shorter column with a smaller particle size with a lower flow rate may give a similar resolution in a shorter time. Retention time reproducibility improves in systems where column temperature can be controlled, especially in cases where ambient room temperature varies. 

Reproducibility. Reproducibility is a third factor that depends primarily on recovery. As a general rule, reproducibility improves as recovery increases. For the majority of compounds for which the recovery is greater than 40%, the reproducibility will be on the order of 2 - 8% relative standard deviation (RSD). This number is strongly affected by column resolution, however, since many foods samples tend to give complicated chromatograms. As the recovery drops below 40% the reproducibility rapidly deteriorates. For very volatile compounds, the purge efficiency... 

SPE is an attractive sample-preparation technique for these reasons very selective extracts can be obtained (reducing the potential for ionization suppression from matrix materials) wide variety of sample matrices accepted analytes can be concentrated high recoveries with good reproducibility improved throughput via parallel processing low solvent volumes suitable for full automation and no emulsion Ibnnation as seen with LLE. In addition, so many product formats and chemistry choices are available that nearly all extraction requirements can be met. 

Poor reproducibility (improving with conunercial equipment)... 

It has been well documented that most artificial materials, whether hydrophilic, hydrophobic, made electroconductive by the dispersion of conductive particles in it, smooth, rough or heparinized, were covered with protein immediately following implantation into the cardiovascular system (1,2). Regardless of this protein coating, some of the materials had higher thromboresistance than others. Many theories have been proposed to explain these thrombo-resistant properties, but a definitive answer to these questions would be premature at this time. We have also found that not every protein surface shows thromboresistance however, when the protein surface was treated with an aldehyde or heat. It resulted in a reproducibly improved thromboresistant surface. 

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