Choosing the Right TLC Plate: Selection Guide
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TLC plates come in various forms and sizes to suit different needs. Here are the key factors to consider when selecting a TLC plate:
Adsorbent Material
The adsorbent layer is usually silica gel but can also include aluminum oxide, Florisil, or modified silica like reversed-phase layers (C8, C18), amino, or cyano. Your choice depends on the compound you’re separating. Check past methods to guide your selection - it saves time and effort.
Plate Backing
Most plates have a glass backing for durability and compatibility with solvents. Flexible backing like aluminum is easier to cut for smaller sizes. Glass plates can also come pre-scored for convenience. The table below compare the glass and aluminum backings for TLC plates.
Properties | Glass | Aluminum |
|---|---|---|
Appearance | Rigid and transparent | Flexible and opaque |
Susceptible to breakage | Yes | No |
Temperature stability | High | High |
Weight and shelf space | High | Low |
Can be cut with scissors | No | Yes |
Binder stability in water | Depends on the plate type | Limited |
Resistance against solvents | High | High |
Resistance against mineral acids and conc. ammonia | High | Low |
Layer Thickness
Thicker layers allow for sample recovery using scrapers or suction tools.
- 100 - 200 μm: for high-performance HPTLC with better resolution
- 200 - 250 μm: standard for analytical TLC plates
- 500 - 2,000 μm: for preparative TLC to separate larger samples
Feature | Classical TLC | HPTLC | Preparative TLC |
|---|---|---|---|
Application | General-purpose analytical separations | High-resolution separations for small samples | Separation and recovery of large sample quantities |
Available backing | Aluminum & Glass | Glass | Glass |
Cost | Cost-effective | Higher due to precision manufacturing | Higher due to large-scale applications |
Layer thickness | 200 μm (aluminum), 250 μm (glass) | 100 - 200 μm | 500 - 2000 μm |
Resolution | Moderate | High | Low to moderate |
Sample Size | Small | Very Small | Large |
Sensitivity | Standard | Higher sensitivity due to thinner layers | Lower sensitivity due to thicker layers |
Special features | Pre-adsorbent zones, fluorescent indicators | Narrow particle size distribution, high uniformity | Thick layers for sample recovery |
Plate Size
Choose a size based on the number of samples and separation distance needed. Common sizes are:
- Large size 20 x 20 cm: most popular size and cost-effective.
- Smaller sizes: 10 × 10 cm, 5 × 10 cm, or 2.5 x 7.5 cm: are great for method development or fewer samples.
Plate Type
SepaFlash™ TLC plates are available with three (3) binder types, tailored for different applications:
Scored Plate
Glass plates can be pre-scored for easy division into smaller pieces. A single plate can be spotted and split for development in different solvents or developed first, then divided for testing with various visualization techniques.
- 20 x 20 cm scored have three (3) score marks 5 cm apart (can be snapped to produce four (4) 5 x 20 cm plates).
- 10 x 20 cm scored have seven (7) score marks 2.5 cm apart (can be snapped to produce eight (8) 2.5 x 10 cm plates).
Preadsorbent Zone
The non-reactive layer at the bottom of the plate compresses the sample into a narrow band before separation, enabling larger sample application, enhancing resolution, and allowing for less precise sample placement.
Channeled Plate
Channeled plates have individual sample lanes separated by gaps in the adsorbent. These plates have 9 mm wide adsorbent tracks which are separated by 1 mm wide channels (total of 19 channels) where the adsorbent layer has been removed. This design prevents cross-contamination, making them ideal for precise analyses or legal documentation.
Fluorescent Indicator
Plates with a fluorescent indicator glow under UV light, enabling visualization of compounds that are invisible to the naked eye. This method preserves your compounds, making it ideal for preparative TLC.
- UV254 (most popular): show dark spots where compounds absorb light at 254 nm.
- UV366: may be needed for samples that fluoresce or require spraying with reagents for visibility.
Binder Type
SepaFlash™ TLC plates are available with three (3) binder types, tailored for different applications:
Soft Layer (Gypsum Binder)
Calcium sulfate hemihydrate (CaSO₄•1/2 H₂O), or gypsum, provides strong adhesion to the glass backing and cohesive particle layers. These plates are compatible with sulfuric acid charring and organic solvents but are not recommended for systems with over 20 % water due to gypsum’s aqueous solubility. For higher water tolerance, hard layer plates are ideal.
Hard Layer (Organic Binder)
An organic binder enhances durability, making these plates highly abrasion-resistant and compatible with solvents containing up to 80 % water. The hard layer surface is easy to write on, providing added convenience. This binder supports faster separations (25 - 30 % faster than standard plates) and yields compact, well-resolved spots. It is ideal for most visualization methods but is not recommended for vigorous stains like potassium permanganate (KMnO₄) and p-anisaldehyde.
Hard Layer (Inorganic Binder)
These water-resistant plates are compatible with aqueous solvents, offering superior handling and sample application compared to gypsum binder plates. Their durable surface allows writing with a soft pencil. Hard layer plates with inorganic binders are ideal for applications requiring vigorous stains or avoiding organic binder interactions.
These binder options ensure versatility and reliable performance across diverse TLC applications.
