Dear Joyanto, only way is flotation in flotation machine for example type Ankara. It separates light fraction over the mesh. Archaeological sediments are easier, because charcoal fragments are large. Pedoanthracological sediments produce very fragmented pieces. Then separation under binocular microscope is necessary.

Floatation will often collect more organic particles than charcoal alone. You can also remove carbonates (using HCl) and silicates (using HF), then pick the charcoal pieces in a watery solution by sucking them up. Pending the size of your charcoal particles you can take a glass pipette attached to flexible tubing leading to your mouth and use underpressure of your respiratory system to suck up the particles. For tiny particles you can draw a micropipette from a glass rod, and connect this with flexible tubing to a micro-injector (which can serve also as a sucking device). If you mount the micro-pipette to a 3D micro-manipulator you have full control of your motions and can handle really tiny particles in the order of tens of microns.

Modern 14C dating can handle 30 micrograms of carbon so the amount of carbon needed is manageable. Be careful though that you don't let your samples standing around at room temperature since microbes may attack the OM in them. Also consider extracting and carefully dry your charcoal. Charcoal is good in absorbing small organic molecules.

I work with archaeological and palaeo-landslides sediment samples which contain sediments comprised of silt/sands/rocks and have submitted many charcoal samples for AMS dating. Floatation in water does not always work since the charcoal will be coated in silt. I use a processing technique to concentrate charcoal from the silt/sand/rock fraction. Dependent upon the sample volume, I place ~500 ml in a 2L beaker with a handle. Using a water spray hose, I swirl the contents by spraying along the interior walls of the beaker to create a vortex of organic (charcoal) material. I immediately decant the swirled organics onto nested sieves (0.85 and 0.425mm mesh opening). This is repeated many times to fully obtain all of the charcoal pieces. This wet concentrate of charcoal is then picked under a microscope using stainless steel forceps. For very small charcoal fragments, I use a glass micropipette fitted with a bulb for suction. Since some mineral grains exist in the charcoal concentrate, I clear the grains away from the charcoal (under a microscope) and then suction the charcoal by clamping the bulb (no air in the bulb) and slowly pipette charcoal pieces releasing the bulb slowly. Should there be too much water (after pipetting) the charcoal into a smaller, separate glass petri dish, you can pipette the water off for quick drying of the charcoal.

Dr. Ursula Thanheiser of Dakhleh Oasis Project and her assistant developed an electrostatic separator for use on dry sediments. Consult with Ursula, University of Vienna. [email protected]