COSMOSIL C₁₈-PREP

The large particle size C₁₈ bulk materials are widely used for lab- to process-scale purifications. COSMOSIL offers three different particle sizes of C₁₈ packing materials.

Particle Size, Flow Rate, and Theoretical Plate Number

Because reversed phase chromatography employs eluents of high viscosity such as methanol and water, the flow rate is lower than that of normal phase chromatography, which uses solvents of low viscosity such as hexane and ethyl acetate. In general, higher theoretical plate numbers can be obtained with lower flow rates.

graph of flow rate vs. methanol percent

Figure 1. Concentration of methanol vs. flow rate
Column: 10 mm I.D. x 180 mm bed height (gravitational liquid flow)

graph of number of theoretical plates vs. flow rate

Figure 2. Flow rate vs. theoretical plate number
Column: 20 mm I.D. x 300 mm

Application Data

Vitamin E

chromatogram of tocopherol and tocopherol acetate

Natural Compounds

chromatogram of baicalein and wogonin

Basic Compounds

chromatogram of quinoline, naphthalene, and N,N-diethylaniline

Polar Compounds

chromatogram of theobromine, theophylline, and caffeine

Antifungals

chromatogram of econazole and miconazole

Coumarin

chromatogram of coumarin and 3,4-dihydrocoumarin

Packing Material by Column Size

Column size and required amount of C₁₈-PREP packing material:

Column I.D. (mm)	Bed height (mm)	Column volume (ml)	Amount of C18-PREP (g)
8	300	15	9
8	500	25	15
10	300	25	15
10	500	40	25
20	300	95	55
20	500	160	95
30	300	210	125
30	500	350	220
50	300	560	350
50	500	980	600

Packing method

Use a standard open glass column, close the stopcock, pack a small amount of absorbent cotton in the bottom of the column and add solvent to approximately 1/3 of the column length.
Add a thin layer (5 mm) of sea sand to the surface of the absorbent cotton.
Prepare a slurry solution of the packing material (30% w/v) with solvent right before packing. (Make sure to prepare enough slurry solution to form a column bed sufficient to separate the compounds of interest.)
Simultaneously open the stopcock and add the slurry solution to the column to form the column bed.
After packing the column, wash the newly packed column bed with 5-10 column volumes of solvent. Allow the bed to stabilize overnight in solvent.
Add a thin layer (5 mm) of sea sand to the top of the bed in order to prevent disturbance of the top of the column bed during sample or solvent addition.

Reference list

COSMOSIL C18-PREP reference list

Ordering information

COSMOSIL C₁₈-PREP

Product Name	PKG size	Product No.
COSMOSIL 50C18-PREP Replacement for discontinued 40 µm gel
	100 g	12065-84
	500 g	12065-55
	1 kg	12065-71
COSMOSIL 75C18-PREP
	100 g	12061-24
	500 g	12061-95
	1 kg	12061-11
COSMOSIL 140C18-PREP
	100 g	12063-04
	500 g	12063-75
	1 kg	12063-91