FAQ
Q-1.When and why use chemically reactive silica? â–¾
Ans: Use chemically reactive silica when the surface must add selectivity, enable covalent immobilization of ligands/enzymes, or drive surface reactions.
Why use it: Functionalization (epoxy, aldehyde, silane, C18, thiol, amine) offers selective binding, stable immobilization, and tunable polarity for separations, catalysis, and biosensors.
Common applications: HPLC stationary phases; enzyme/antibody immobilization; heterogeneous catalysts; mesoporous drug carriers.
Quick checklist:
- Target size (small molecule vs protein)
- Reversible vs covalent capture
- Solvent and pH stability
- Required pore size/accessibility
Tell us the analyte or application and we’ll recommend a functional group and pore size.
Q-2.Why is particle size distribution important? â–¾
Ans: Particle size distribution (PSD) is the range and proportion of particle sizes (often D10/D50/D90 or volume/number distribution).
Performance: Controls flow, packing, compaction, dissolution rate, and functional properties of powders/suspensions.
Processing: Impacts mixing, milling, filtration, spray drying, coating; a narrower PSD often improves processability.
Product quality & consistency: Determines texture, stability, bioavailability, and batch-to-batch reproducibility.
Safety & regulation: Influences inhalation risk, environmental fate, and regulatory classification (especially nanoparticles).
Q-3.What does pore size mean? â–¾
Ans: Pore size is the diameter of internal voids in a porous material that can hold or transmit fluids, molecules, or particles.
Classification: Micropores < 2 nm; mesopores 2–50 nm; macropores > 50 nm.
Why it matters: Controls accessibility, transport, surface area, and selectivity in catalysis, separation, drug release, and filtration.
Reporting: Given in nm or µm; summarized by averages or a pore size distribution.
Examples: Large pores aid protein access; small pores increase surface area; membrane pore size sets filtration cutoffs.
Q-4.Parameters affecting chromatographic silica gel performance â–¾
Ans: Key parameters:
- Morphology (bead shape): packing uniformity, backpressure, mechanical stability
- Particle size / PSD (D10/D50/D90): efficiency, plate count, flow resistance
- Surface area & pore size: capacity, retention, accessibility
- Surface functionalisation: selectivity, peak shape, solvent/pH compatibility
- Pore volume / morphology: mass transfer, kinetics, peak broadening
Checklist: choose pore for analyte size; balance particle size for resolution vs backpressure; select chemistry for selectivity & stability.
Q-5.Why is alumina used in chromatography? â–¾
Ans: Alumina (Al₂O₃) is a high‑surface‑area adsorbent used as a stationary phase.
Why: Provides strong interactions and can separate compounds that perform poorly on silica, especially with acidic/basic/neutral forms.
Surface types: acidic, basic, neutral—chosen based on analyte behavior.
Applications: alcohols, hydrocarbons, steroids, alkaloids, natural pigments, and more.
Caution: basic alumina may induce side reactions for sensitive substrates—choose type/activity carefully.
Q-6.Is aluminium oxide polar or non‑polar? ▾
Ans: Aluminium oxide is polar due to surface hydroxyl (–OH) groups that form hydrogen bonds and dipole–dipole interactions.
- Polar compounds interact strongly → move slowly
- Non‑polar compounds interact weakly → move faster
Useful in adsorption chromatography (columns, TLC).
Q-7.Difference between aluminium oxide and silica gel â–¾
Nature: Aluminium Oxide – more basic; Silica Gel – slightly acidic
Adsorption strength: Alumina stronger; Silica milder
Suitability: Alumina for non‑acidic compounds; Silica for most organics
Stability: Alumina may decompose acid‑sensitive compounds; Silica more stable
Separation behavior: Alumina stronger interaction with polar compounds; Silica gentler conditions
Q-8.Applications of Silica Gel TLC Plates â–¾
- Identify compounds by Rf values
- Check purity of organic compounds
- Monitor reaction progress
- Separate mixture components
- Detect impurities in pharmaceuticals
- Analyze plant extracts and natural products
- Quality control in chemical/pharma
- Preliminary analysis before column chromatography
Silica gel TLC is simple, rapid, and cost‑effective for research, academic, and industrial labs.
Q-9.Why is silica gel used in TLC? â–¾
- Highly polar → effective separation by polarity
- Silanol (–OH) groups form hydrogen bonds
- Good adsorption capacity → clear separations
- Suitable for most organic compounds
- Chemically stable and cost‑effective
- Compatible with UV detection (e.g., F254)
Because of these properties, silica gel is the most widely used TLC stationary phase.
Q-10.How is Silica Gel HF used? â–¾
Ans: HF indicates: H – hardened layer (binder like CaSO₄), F – fluorescent indicator (typically 254 nm).
Usage in TLC:
- Stationary phase coated on TLC plates
- Sample spotted on the plate and developed in solvent
- Compounds separate based on polarity
- Spots visualized under UV; fluorescent background helps detection
Provides easy visualization and better mechanical strength.
