How to Prepare 6X DNA Loading Dye

6X concentrated gel loading dye for agarose gel electrophoresis

Components

ChemicalConcentration
Glycerol30% v/v
Bromophenol blue0.25% w/v
Xylene cyanol FF0.25% w/v
EDTA10 mM (pH 8)

Preparation Strategy

Method: stock_then_dilute

Reason: EDTA mass (0.29g) < 1g threshold; bromophenol blue and xylene cyanol masses are very small (<0.3g each). Stock approach ensures accuracy and avoids weighing errors.

Preparation Table

ComponentConc.AmountUnit
EDTA disodium salt dihydrate10 mM final1.0 mLmL
Glycerol30% v/v30.0mL
Bromophenol blue0.25% w/v250mg
Xylene cyanol FF0.25% w/v250mg
WaterBalanceto 100mL

Procedure

  1. 1Step 1: Prepare 1M EDTA stock (pH 8.0): Dissolve 2.92g EDTA disodium salt dihydrate in ~8mL water, adjust pH to 8.0 with NaOH pellets, bring to 10mL final volume
  2. 2Step 2: In a 100mL graduated cylinder, add 60mL nuclease-free water
  3. 3Step 3: Add 250mg bromophenol blue powder slowly while stirring vigorously to ensure complete dissolution
  4. 4Step 4: Add 250mg xylene cyanol FF powder and mix thoroughly until completely dissolved
  5. 5Step 5: Add 30.0mL glycerol and mix well
  6. 6Step 6: Add 1.0mL of 1M EDTA stock (pH 8.0) and mix
  7. 7Step 7: Adjust final volume to 100mL with nuclease-free water
  8. 8Step 8: Mix thoroughly by inversion until homogeneous
  9. 9Step 9: Check that solution is dark blue-purple color with no precipitate

pH Adjustment

pH should be ~8.0 from EDTA stock - do not require further adjustment. EDTA provides buffering capacity.

Sterilization

Filter through 0.22 μm syringe filter into sterile tubes. Do not autoclave as dyes may degrade and EDTA may precipitate.

Safety

Level 1 safety: Standard lab coat, safety glasses, nitrile gloves. Dyes can stain - avoid skin contact. Work in well-ventilated area when handling powders.

Storage

Store at 4°C in dark bottles or wrap in foil to protect from light. Aliquot into small volumes (1-5mL) to minimize freeze-thaw cycles. Stable for 1 year. Do not freeze as glycerol may crystallize.

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