Comparing glass and plastic for an organic solvent

Acetone in a polystyrene tube is a short experiment with a bad ending. The tube softens, the volume changes, and the liquid is no longer only the solvent you added. This application note is how to choose glass or a named plastic for an organic solvent in ordinary research preparation. The glass side of that choice is choosing laboratory glassware. The plastic side, when the liquid is aqueous, is when to use plastic tubes, tips and plates.

A concrete solvent, a concrete vessel

Take a common research sequence. You need a stated concentration of a standard in acetonitrile, acetone, chloroform, hexane or DMSO. The concentration is a number other calculations will use, so the make-up belongs in a volumetric flask. The flask is glass, almost always borosilicate, read at the reference temperature printed on it. NIST metrology practice is the background for that mark. You rinse the flask with the solvent, you do not rinse it with a detergent you then fail to remove, and you stopper it with a closure the solvent will not destroy during the mix.

Storage is the second vessel. A borosilicate bottle with a liner the chart allows, often a fluoropolymer liner, keeps the stock. A polystyrene bottle or a clear assay plate is the wrong store. Polystyrene's application is aqueous clarity. Ketones and chlorinated solvents attack it. A polycarbonate centrifuge tube may look robust and still crack under solvent stress. Polypropylene might accept a brief contact or a particular alcohol and refuse another solvent. The only general rule is the manufacturer chart for that product, at the temperature and contact time you will actually use.

DMSO deserves a specific caution because it dissolves many organics and also carries solutes through skin and through materials people treat casually. Compatibility and personal exposure are both institutional chemical-hygiene questions. This page does not list a safe DMSO container beyond "read the chart and the safety data for your use".

What glass does not forgive

Glass is the default, not the universal solvent vessel. Hydrofluoric acid attacks silica. Strong alkali etches glass with time and heat. Neither belongs in a volumetric flask as a storage plan. ASTM E438 tells you the glass family. It does not list every chemical. A solvent that is fine in borosilicate can still attack the cap, the glue in a label, a plastic pour ring, or a pipette bulb. The wetted list is the whole list.

Soda-lime glass is still glass, and it still beats polystyrene for many organics, and it remains a poor choice if the solvent will be warmed or the bottle autoclaved. Specify borosilicate when heat is in the method. Cold solvent in an intact soda-lime bottle can be acceptable. Do not let that acceptance creep into the hot plate.

Plastic that can be right

Plastic is right when the chart says the resin tolerates that solvent for that duty, and when glass is the greater practical hazard, for example a teaching context where breakage dominates and the solvent is one the plastic maker names. High-density polyethylene has accepted uses with some aqueous-organic mixtures and is a bad guess for aggressive solvents. PTFE and some other fluoropolymers are the resistant class for liners, sleeves and some tubing. A PTFE liner in an incompatible cap body still leaves the thread and any uncovered surface to the solvent if the liner is only a disc on the top.

Filter plates, solid-phase tips and chromatography tubes add their own wetted polymers and sorbents. A column body that survives the solvent does not mean the frit does. The assigned hardware in a purification setup can be several resins at once. Read them separately.

Branch points in a real extraction

If the organic phase is going into a tube you cannot identify, stop and identify it. A cloudy wall means the transfer has already leached something. Move the liquid to glass if it is safe to do so under your chemical rules, and do not use the affected tube for the aqueous phase either. If a volumetric flask's stopper seizes after solvent work, do not force it. A PTFE sleeve or a stopper the method allows is the prevention. A seized stopper is a glassblower or a retirement, not a wrench.

If the assay downstream is enzymatic, solvent carry-over in a plastic well can inhibit the enzyme and look like a biological result. Evaporate and exchange into the assay buffer in a vessel the solvent tolerated. The plate colour and the resin only matter after the solvent is gone.

If you have a chart entry that allows polypropylene for that solvent at room temperature for a short time, you may use it for that stated duty and not for weekend storage in a warm cabinet. Write the time limit into the method so the next person does not extend it.

Safety

Organic solvents are a flammability and toxicity problem. This note does not choose your hood, your bonding and grounding, or your waste stream. Biological material suspended in a solvent is still a biosafety question under your rules, with the WHO laboratory biosafety manual and the CDC BMBL as background only. Research preparation, not a clinical formulation method. Do not store solvent in a food container or an unmarked wash bottle because the glassware shelf was empty.

Heat in storage

A solvent bottle in a warm store, or in a vehicle, sits above the temperature many casual chart readings assume. Vapour pressure rises, caps weep, and marginal plastics soften. Specify glass and a liner for stocks that will see that room. Leave headspace. Do not fill to the brim and then carry the bottle up a hot stairwell. A power cut that stops a flammable cabinet's ventilation is a facilities event. It is not solved by transferring the solvent into polystyrene trays to "reduce glass risk".

What the enquiry should contain

The solvent or solvent family, the duty (make-up, storage, brief transfer, centrifugation), glass type and flask class if a concentration will be declared, cap or liner material, any plastic the chart has already allowed, and the quantity. Keep glass and plastic as separate lines. Browse laboratory glassware and volumetric glassware, and use the laboratory plasticware catalogue only for pieces the chart supports. Send the specification through the quote request.