Conventionally end-capped C₁₈ columns still have many residual silanol groups on the silica surface of stationary phase that can form ionic bonds with basic compounds. The resulting peak tailing makes accurate quantification of analytes difficult, especially in trace analyses. COSMOSIL 3C₁₈-EB with a better end-capping treatment offers improved peak shape and separation particularly for basic compounds.

Comparison 1 (Basic Compounds)

COSMOSIL 3C18-EB	Competitor A C18, 3 µm	Competitor B C18, 3 µm	Competitor C C18, 3 µm

Comparison 2 (Basic Compounds)

COSMOSIL 3C18-EB	Competitor A C18, 3 µm	Competitor B C18, 3 µm	Competitor C C18, 3 µm

Acidic or metal coordination compounds can also form bonds with residual silanol groups and metal impurities causing peak tailing. COSMOSIL 3C₁₈-EB with a better end-capping treatment and high purity silica gel offers improved peak shape and separation for acidic or metal coordination compounds.

Acidic Compounds

COSMOSIL 3C18-EB

Metal Coordination Compounds

COSMOSIL 3C18-EB

If you use insufficiently end-capped C₁₈ columns for basic compound analyses, you may need to spend much time adjusting mobile phase conditions. You may need

1. more than 3 or more organic solvents or buffers
2. ion-pair reagents or additives
3. buffers in different pH

In addition, the complexity of the mobile phase often is detrimental to reproducibility. COSMOSIL 3C₁₈-EB with a new end-capping treatment allows good peak shape and separation using simple mobile phase conditions.

Analysis with Simple Condition

Complicated Condition	Simple Condition
Methanol/ Acetonitrile/ 20mmol/l KH2PO4, 0.2%Triethylamine(pH3.0 with H3PO4) = 35/15/50(*)	Acetonitrile/ 20mmol/l Phosphate Buffer(pH2.5) = 30/70
(*): USP 38(1) Amlodipine and Benazepril Hydrochloride Capsules, Performance Tests

3C₁₈-EB has excellent synthesis reproducibility and column-to-column reproducibility, so it is applicable in routine analysis such as quality control of drugs.

Excellent Synthesis Reproducibility

COSMOSIL 3C18-EB

COSMOSIL 3C18-EB

COSMOSIL 3C₁₈-EB produces sharp peaks using ammonium acetate buffer in LC-MS.

Excellent Synthesis Reproducibility

Acetonitrile/ 20mmol/l Phosphate buffer(pH7.0) = 60/40	Acetonitrile/ 10mmol/l CH3COONH4 = 60/40

Excellent Synthesis Reproducibility

COSMOSIL 3C18-EB

Column size:	4.6 mm I.D. x 100 mm
Mobile phase:	A; Acetonitrile/ 36.7mmol/l Phosphate Buffer(pH7.6) = 10/90 B; Acetonitrile/ 36.7mmol/l Phosphate Buffer(pH7.6) = 80/20 B conc. 0→ 20%(0→ 10min), 20→ 100%(10→ 30min)
Flow rate:	1.0 ml/min
Temperature:	40°C
Detection:	UV 302 nm
Sample:	1. Omeprazole related compound A 0.001mg/ml 2. Omeprazole 0.001mg/ml
Inj. Vol:	20 µl
USP 37(3) Esomeprazole Magnesium Delayed-Release Capsules, Impurities