Objective. Achieve a single‑run separation of cocaine together with its very polar metabolite ecgonine and other, less‑polar metabolites (e.g., benzoylecgonine, ethylmethyl ecgonine), using Cogent TYPE‑C™ silica columns and LC‑MS/MS‑compatible mobile phases. 

Recommended Strategy

1. Primary column for the full panel:
   Cogent Diamond Hydride™ (TYPE‑C silica hydride) operated in Aqueous Normal Phase (ANP).

   • Rationale: ANP provides strong retention for highly polar, ionizable species like ecgonine, while still accommodating compounds with hydrophobic character. In practice, tertiary amine–containing analytes (e.g., cocaine) retain well under ANP conditions on Diamond Hydride™, enabling a unified method window.

2. Alternate / complementary column for alkaloids:
   Cogent Phenyl Hydride™ (TYPE‑C phenyl‑modified silica) in RP‑like conditions.

   • Rationale: Phenyl Hydride™ often produces excellent peak shapes for alkaloids; however, ecgonine may not retain sufficiently in RP, so it is better covered by the Diamond Hydride™ ANP method. Phenyl Hydride™ can be a strong complementary option when the focus is primarily on the less‑polar alkaloids.

Bottom line: For a single‑method solution that captures ecgonine + cocaine + less‑polar metabolites, start with Diamond Hydride™ under ANP. Consider Phenyl Hydride™ if you later want an RP‑oriented, alkaloid‑focused method. 

Mobile‑Phase & Additive Guidance (LC‑MS Compatible)

• Begin with 0.1% formic acid as the sole additive in both aqueous and organic channels (e.g., A = water + 0.1% FA, B = acetonitrile + 0.1% FA). This improves peak symmetry for basic analytes and preserves MS compatibility. 
• Use an ANP gradient on Diamond Hydride™ (start at high %B with acetonitrile, then reduce %B to increase aqueous content). This approach enhances retention of very polar metabolites (e.g., ecgonine) while eluting less‑polar species in an orderly fashion. 

Why ANP Works Here

• Polar/ionizable metabolites (e.g., ecgonine) are retained strongly under ANP because the mobile phase is rich in organic (ACN) with controlled water; increasing water decreases ANP retention, enabling gradient elution.
• Cocaine (tertiary amine) also shows good ANP retention on Diamond Hydride™, allowing it to be analyzed with its polar metabolites in a single run.

Method Development Tips

1. Starting gradient (on Diamond Hydride™, ANP):

   • %B (ACN + 0.1% FA) high (e.g., 85–95%) → step/linear to ~40–60% over 5–10 min → re‑equilibrate at high %B.
   • Tune slope to push ecgonine off with adequate resolution while maintaining reasonable analysis time. (Exact conditions are application‑dependent; this is a development starting point.) 

2. Injection solvent:

   • Favor high‑organic (≥70% ACN) sample diluent for ANP to avoid early band‑broadening and to sharpen early‑eluting polar peaks. (General ANP best practice consistent with the referenced guidance set.)

3. pH & buffers:

   • With 0.1% formic acid, pH typically remains within the supported range for TYPE‑C silica and is LC‑MS friendly; avoid non‑volatile buffers that can suppress MS signal. 

4. Alternate selectivity (Phenyl Hydride™):

   • If you need extra selectivity for aromatic alkaloids or to refine resolution among the less‑polar metabolites, evaluate Phenyl Hydride™ under RP‑like conditions (higher aqueous). Keep in mind that ecgonine may require the ANP method on Diamond Hydride™ for reliable retention. 

Notes & Practical Considerations

• Prior application experience indicates tertiary amines (e.g., clopidogrel as an analogy) retain effectively on Diamond Hydride™ in ANP—supporting the expectation that cocaine will also behave well in this mode. 
• If your lab uses both alkaloid screens and targeted polar metabolite assays, consider keeping both columns in the toolkit: Diamond Hydride™ (ANP) for the full‑polarity panel including ecgonine, and Phenyl Hydride™ (RP) when you want alternate selectivity on the alkaloid sub‑set.​