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L1 US Pharmacopoeia Columns

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Purospher® STAR RP-18 Endcapped (5 µm) HPLC Columns

Purospher® STAR RP-18 Endcapped (5 µm)MilliporeSigma offers a broad range of HPLC columns that are fully compliant with USP (United States Pharmacopoeia) specifications. L1 USP columns are described as octadecyl silane, chemically linked to porous silica or ceramic micro particles. Our high-quality L1 USP products deliver reliable, reproducible results – time after time. A perfect example is: Purospher® STAR RP-18 endcapped (5 µm).

Outstanding Stability and Flexibility

Purospher® STAR RP-18 endcapped HPLC columns are designed for universal use. They allow basic, neutral, and metal chelating compounds to be separated easily with simple mobile phases – without peak tailing. Based on 99.9999 % pure silica, the columns offer excellent peak symmetry, outstanding stability from pH 1.5 to 10.5 over a wide temperature range, and suitability for up to 100% aqueous mobile phases. Plus, they demonstrate best all-round retention characteristics, as proven by the Tanaka test. Thanks to this features, Purospher® STAR RP-18 endcapped HPLC columns allow high-throughput applications, and give you maximum flexibility in choosing the best chromatographic conditions for any separation.

Features and Benefits

  • Classified as L1 USP column
  • Highest purity silica (99.999%) for excellent peak symmetry
  • High separation efficiency
  • Reproducible results from run-to-run and batch-to-batch
  • Best all-round performance according to Tanaka
  • Outstanding pH stability from pH 1.5 to 10.5
  • No phase collapse when using highly aqueous mobile phases
  • Good suitability for LC-MS applications
  • Fast method development for complex samples


Suitable for 100% Aqueous Mobile Phases

Standard reversed phase columns, particularly RP-18 columns, often suffer from bonded phase collapse when used with highly aqueous mobile phases. Purospher® STAR RP-18 endcapped provides stable retention with excellent peak shapes, combined with the selectivity of a classical RP-18 phase – even in 100% aqueous conditions.

Surface Chemistry

The polymeric surface modification of Purospher® STAR RP-18 endcapped provides a virtually perfect coverage of the surface, thus preventing silanophilic interactions

Surface chemistry 

Column Comparison

Column Comparison

Chromatogram A shows the first separation of a test mixture with 1% acetic acid as mobile phase. Chromatogram B shows the same separation after 3 hours of continuous operation. Like no other column in its class, Purospher® STAR RP-18 endcapped shows identical results in chromatograms A and B. In contrast to competitive columns, Purospher® STAR RP-18 endcapped can be used as an “AQUA” RP-phase.

Stability at Higher Temperatures

Even at a higher temperature, the long-term stability test for efficiency and retention over 15,000 column volumes clearly demonstrates the excellent stability of Purospher® STAR RP-18 endcapped columns. The data and graphs from this endurance test show no significant changes in efficiency and retention.

Stability Test 

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