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Spherical Silica Sorbent for Consistent Results

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Merck:/Freestyle/LE-Lab-Essentials/Chromatography/LE-LiChrospher-120x196-3600.jpgLiChrospher® is a reliable and versatile spherical silica sorbent, which is traditionally produced and available with different modifications. The polar modified phases LiChrospher® CN, LiChrospher® NH2 and LiChrospher® DIOL, as well as LiChrospher® SI with no modification are best for normal phase analytical HPLC. Furthermore, LiChrospher® PAH is highly efficient and selective for the separation of PAH compounds, as is LiChrospher® WP 300 RP-18 for the separation of peptides and low molecular weight proteins.

LiChrospher® packing materials are available as Hibar® RT columns and as LiChroCART® cartridges in different lengths and with different internal diameters (10 mm, 4.6 mm, 3 mm, and 2 mm). LiChroCART® 3 mm i.d. and 2 mm i.d. narrow bore cartridges for HPLC save costs by reducing solvent consumption. They enable the handling of very small quantities while achieving increased sensitivity as well as resolution. LiChroCART® cartridges 4.6 mm i.d., 3 mm i.d., and 2 mm i.d. are compatible with manu-CART® “4” NT. This enables faster and more flexible method adaptation to smaller bore columns. LiChroCART® cartridges 10 mm i.d. should be used with manu-CART® “10”-II.


LiChrospher® packing materials

Certified Reproducibility of HPLC Separations

The heart of each HPLC system is the column where the separation of sample components takes place. Due to the chemical properties of silica, HPLC columns are subject to wear. This could be from the irreversible adsorption of injected samples and sample matrix, or from mechanical and chemical instabilities of the stationary phase. Column wear can result in altered selectivities, "ghost peaks", diminished separation efficiency or excessively elevated back pressures. Hence, HPLC columns must be continuously replaced. To avoid problems, the new column should be of the same type and have the same properties as the preceding one. The certified reproducibility of HPLC columns prevents extensive method revision as well as additional costs.

Separation Performance, Selectivity and Capacity

Reproducibility is the most important property of an HPLC column, independent of the respective production batch. All columns of the same type should be reproducible and therefore comparable in terms of separation performance, selectivity and retention behavior. In its determination, a characteristic substance test mixture is subjected to chromatography under buffered elution conditions. The resulting chromatographic parameters, such as k-values, separation factors and the minimum number of theoretical plates, are fixed.

  • Retention factor k (previously designated as ‘capacity factor k´) of a neutral compound means: the defined hydrophobic character of the stationary phase.
  • Separation factors (i.e. relative retention times, previously designated as selectivity) bring about a defined order of elution and defined peak distance from batch to batch and cartridge to cartridge.
  • Minimum number of theoretical plates (N) under buffered (not ideal) chromatographic conditions ensures separation performance.

Certified Reproducibility to Avoid Additional Costs in Method Evaluation

The evaluation of quality control methods for certain products, such as in pharmaceutical applications, constitutes a considerable cost factor. Once established, an analytical method is used in expensive registration procedures for many years (10 or more). In this context, the selection of the HPLC column is an important criterion. Thanks to stringent quality controls, Merck’s HPLC columns offer certified reproducibility, thus avoiding extensive method revision and unnecessary costs. The column certificate places the highest demands on process control during the batch-to-batch production of column materials. This ensures constant HPLC column quality over many years.

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