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  Phenyl-Hexyl ColumnCare & Use Sheet 

HALO DescriptionHALO Phenyl-Hexyl is a high-speed, high-performanceliquid chromatography column based on a new fused core

particle design. The fused core particle provides a thinporous shell of high-purity silica surrounding a solidsilica core. This particle design exhibits very highcolumn efficiency due to the shallow diffusion paths inthe 0.5-micron thick porous shell and the small overallparticle size of 2.7-microns. The bonded, endcapped,dimethylphenylhexyl stationary phase of HALO Phenyl-Hexyl provides a stable, reversed phase packing withenhanced π-π  and mild steric interactions due to therelatively long-chain hexyl linkage to the base silica.HALO Phenyl-Hexyl can be used for basic, acidic, orneutral compounds with alternate selectivity from C18.

Column CharacteristicsFigure 1 shows a sample Quality Control testchromatogram for a 4.6 mm x 100 mm column. A printedreport including the actual test chromatogram andperformance results is enclosed with every column.The fused core particle has a surface area of ~ 150 m2 /gand an average pore size of 90Å. The fused core particlesare 30% to 50% heavier than commercially availabletotally porous particles due to the density of the solidcores. Therefore, the effective surface area per column issimilar to columns packed with totally porous particles

having surface areas in the 225-300 m2

 /g range.

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Time, minutes

FIGURE 1 - Phenyl-Hexyl QC Chromatogram

Test Conditions:

Column: 4.6 x 100 mm HALO Phenyl-Hexyl

Mobile Phase: 60/40 ACN/H2O

Flow: 1.8 ml/min

Temperature: Ambient (~24ºC)

Detection: UV at 254 nm

Sample Volume: 1 µL

Peaks:

1) uracil 30 µg/ml

2) phenol 500 µg/ml

3) 4-chloro-nitrobenzene

  120 µg/ml

4) naphthalene 200 µg/ml

 

Operation Guidelines•  The direction of flow is marked on the column label.•  Reversed flow may be used to attempt removal of

inlet pluggage or contamination.•  A new column contains a mixture of acetonitrile and

water. Initial care should be taken to avoid mobilephases that are immiscible with this mixture.

•  Water and all common organic solvents arecompatible with HALO Phenyl-Hexyl columns.

•  Halo Phenyl-Hexyl columns are best used attemperatures below 60ºC for maximum column life.

•  Mobile phase pH for HALO Phenyl-Hexyl columnsis best maintained in the range of pH = 2 to 9 formaximum column stability.

•  HALO Phenyl-Hexyl columns are stable tooperating pressures up to 600 bar (9000 psi).

Column CareTo maximize column life, ensure that samples andmobile phases are particle-free. The use of guardcolumns or an in-line filter with 0.5-micron porosity

between the sample injector and the column is highlyrecommended. The 2-micron porosity frits on HALOPhenyl-Hexyl columns are less subject to pluggage thanare the 0.5-micron frits typically used with other small-particle columns. Should the operating pressure of thecolumn suddenly increase beyond normal levels,reversing the flow direction of the column may beattempted to remove debris on the inlet frit.To remove strongly retained materials from the column,flush the column in the reverse direction with verystrong solvents such as 100% of the organic componentof the mobile phase in use. A mixture (95/5 v/v) of

dichloromethane and methanol is often effective at thistask. Extreme cases may require the use of very strongsolvents such as dimethylformamide (DMF) ordimethylsulfoxide (DMSO).

Column StorageLong-term storage of silica-based, reversed-phasecolumns is best in 100% acetonitrile. Columns may besafely stored for short periods (up to 3 or 4 days) in mostcommon mobile phases. However, when using buffers,it is best to protect both the column and the HPLCequipment to remove the salts by flushing the column

with the same mobile phase without the buffer (e.g.,when using 60/40 ACN/buffer, flush the column with60/40 ACN/H2O) to eliminate any danger fromcorrosion from the salts while providing rapid re-equilibration of the column with the original mobilephase.Before storing the column, the end-fittings should betightly sealed with the end-plugs that came with thecolumn to prevent the packing from drying.

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Safety•  HPLC columns are for laboratory use only. Not

for drug, household, or other use.

•  Users of HPLC columns should be aware of thetoxicity or flammability of the mobile phases chosenfor use with the columns. Precautions should be takento avoid contact and leaks. 

•  HPLC columns should be used in well-ventilatedenvironments to minimize concentration of solvent

fumes.

ApplicationsThe HALO Phenyl-Hexyl columns are best utilized withmobile phases that are mixtures of methanol and water oracetonitrile and water. Higher levels of the organicsolvent component will typically reduce the retention ofthe sample compounds. Using elevated temperatures(e.g., 40 – 60 ºC) will reduce the viscosity of the mobilephase and allow the use of faster flowrates and lowercolumn pressure for high sample throughput. Gradient-elution techniques using 5 -10% organic component asthe initial mobile phase and increasing to 100% organiccomponent as the final mobile phase often can effectseparations of complex sample mixtures in minimal time.Ionizable compounds, such as acids and bases, aregenerally best separated with mobile phases buffered atpH of 2 to 3. The use of 20-50 mM buffers is alwaysrecommended for optimum results and long-term stabilitywhen separating ionizable compounds. Additionalinformation on solvent selection and separationtechniques can be found in Chapters Six, Seven, andEight, Practical HPLC Method Development, SecondEdition, L.R. Snyder, J.L. Glajch, and J.J. Kirkland, (JohnWiley & Sons, 1997).

HALO Phenyl-Hexyl columns will have similar retentionto C8 phases but different selectivity for somecompounds compared to alkane phases. Many aromaticcompounds interact more strongly with the phenyl phasecompared to C18/C8.

Guidelines for Low-Volume ColumnsHigh performance columns with small internal volumes(shorter lengths, internal diameters < 3 mm) are being

increasingly used for high speed separations, especiallywith specialty detection systems such as massspectrometers. These low-volume columns generatepeaks having considerably less volume than those elutingfrom columns of larger dimensions (e.g., 4.6 mm x 150mm). The efficiency of separations performed in low-volume columns is highly dependent on the HPLC

system having components designed to minimize bandspreading. All low-volume columns perform best whenused with proper attention to the following factors:•  Detector – Flow cells should be of low-volume

design (preferably < 2µl).•  Detector – To properly sense and integrate the often

very fast peaks that elute from low-volume columns,the detector response time should be set to the

fastest level (~ 0.1 second) and the integrationsoftware should sample the detector signal at least20 points per second.

•  Injector – The injection system should be of a low-volume design (e.g., Rheodyne Model 8125). Auto-samplers will often cause band-spreading with low-volume columns but may be used for conveniencewith the expectation of some loss in columnefficiency.

•  Connecting Tubing – The shortest possible lengthsof connecting tubing with narrow internal diameters(at most 0.005-inch, 0.12 mm ID) should be used to

connect the column to the injector and the detectorcell. The tubing must have flat ends and shouldbottom out inside all fittings. Zero-dead-volumefittings should always be used where required.

•  Peak Retention – As retention is increased, thevolume of a peak increases, decreasing the effectson band spreading caused by components of theinstrument.

•  Sample Solvent – For isocratic separations, thesample should be dissolved in the mobile phase or ina solvent that is weaker (less polar) than the mobilephase. For gradient separations, the sample should

be dissolved in the initial mobile phase or in asolvent substantially weaker than the final mobilephase.

•  Injection Volume – For isocratic separations, thevolume of sample injected should be kept as smallas possible (typically 2 µl or less). Sample volumesare less critical for gradient separations, , especiallyif the sample is dissolved in a weak solvent.

Ordering InformationFor ordering information or for technical support on thisproduct, in the U.S. call 1-800-441-7508 For

information in other countries go to the website:www.advanced-materials-tech.com