- 500 ml funnel with PTFE key stopcock
- Made from high-quality 3.3 borosilicate glass
- Includes interchangeable polypropylene stopper
- 29/32 socket size
- Low temperature gradient – can withstand high temperatures and thermal shocks*
- Superior chemical durability
- Compliance with IS 1575.
- Cylindrical shape
OVERVIEW:
The GWSI 500 ml Graduated Dropping Funnel with PTFE Stopcock and Socket is a semi-micro addition tool built for the smallest reaction scales where reagent volumes are measured in single milliliters, and zero contamination tolerance is the standard. Formed from premium borosilicate 3.3 glass, it delivers high thermal shock resistance and complete chemical inertness in a format compact enough for micro-reactor and semi-micro distillation assemblies. The conventional PTFE plug stopcock offers smooth, grease-free flow adjustment, while the interchangeable ground joint socket provides a vapor-tight connection that holds reliably under reflux and reduced-pressure conditions.
HISTORY:
Semi-micro dropping funnels with PTFE valves emerged in the 1990s as a convergence of two trends — the microscale chemistry movement’s push to reduce solvent waste and the analytical community’s growing demand for contamination-free sample handling. Researchers working with expensive isotopically labeled compounds, rare natural product isolates, and radiolabeled tracers simply could not afford to lose material to oversized glassware or risk background interference from stopcock grease. The 500 ml PTFE plug funnel answered both needs: right sized for sub-10 ml additions, chemically inert across the full reagent spectrum, and light enough to mount on the most compact semi-micro stands.
APPLICATIONS:
– Pharmaceutical discovery labs — microliter-precision addition of high-value building blocks during fragment-based screening
– Biotech molecular biology labs— controlled delivery of restriction enzymes and ligation reagents in small-volume protocols
– Industrial flavor and fragrance labs — dropwise dosing of concentrated essential oils and aroma chemicals during micro-formulation
– University microscale organic labs— green chemistry practicals using catalytic reagent quantities and minimal solvent volumes
– College biochemistry labs— enzyme kinetics assays requiring timed substrate pulses into cuvette-scale reactions
– School advanced science streams — safe, low-waste demonstrations of reaction rates, equilibrium shifts, and limiting reagent concepts
– Research institutes — radiolabeling, stable isotope dilution, and trace-level catalysis screening where every microliter counts
– Educational institutes — training students on semi-micro-PTFE valve technique, contamination control, and responsible chemical stewardship
MANUFACTURING PROCESS:
GWSI fabricates each 500 ml PTFE stopcock dropping funnel by melting high-purity borosilicate 3.3 glass at over 1,600 °C, then shaping the miniature reservoir through master hand-blowing for fine wall control and the narrow-graduated stem via automated precision molding for repeatable volumetric accuracy. The PTFE stopcock barrel is precision-bored into the miniature glass stem at tight tolerances suited to this reduced scale, and the socket joint is formed using ceramic glass fusing for exact taper conformity. The completed piece then enters a controlled annealing lehr cycle to relieve all internal thermal stress and ensure dimensional permanence.
TESTING PROCESS:
Each funnel begins with a meticulous manual inspection under magnification — technicians verify wall uniformity, miniature PTFE plug seating and rotation, joint taper accuracy, and fine graduation legibility at the 500 ml scale. A Polariscope polarization stress test then confirms zero residual strain across the body, stem, and stopcock barrel; any birefringence pattern leads to immediate rejection. Volumetric accuracy is checked on the basis of ISO and DIN standards using manual or automatic testing machines, and NABL gravimetric calibration certifies the graduation scale to its declared Class A or Class B tolerance.
PRINTING PROCESS:
Ultra-fine graduation lines and small-format volume numerals are applied through precision screening with glass enamels — high-resolution ceramic inks engineered for crisp marking on miniature borosilicate surfaces. The funnels are then fired in high-temperature kilns where the ceramic layer sinters and permanently fuses into the glass matrix, producing scale markings that remain sharp and legible through years of aggressive solvent exposure, acid washing, and autoclave sterilization.
PACKAGING PROCESS :
Every funnel passes through a final cosmetic sorting station where inspectors reject any unit with surface imperfections, wall irregularities, joint defects, or PTFE plug blemishes. The miniature PTFE stopcock plug is then backed off to its open position to relieve O-ring compression during storage and transit. Approved funnels are individually wrapped in shock-absorbing bubble wrap, nested in custom-fit cardboard inserts, and packed in heavy-duty double-wall corrugated export boxes for safe domestic and international shipment.
MAINTENANCE & SAFETY :
– No grease — the PTFE plug is designed for clean, dry operation; even a trace of grease at this scale can block the narrow bore or contaminate microliter-level additions.
– Rinse immediately after use with warm deionized water, then wash with a mild non-ionic detergent; use a fine-tipped micro-brush to clear the miniature stopcock bore.
– Autoclave at 121 °C with the PTFE plug removed from the barrel to extend O-ring life; this autoclavable lab glass maintains full dimensional accuracy through repeated sterilization cycles.
– Store with the stopcock open and a small paper slip between the plug and barrel to prevent any surface adhesion during prolonged storage.
– Inspect the PTFE plug and O-ring under magnification before each use — wear patterns at semi-micro scale can be subtle but still compromise drop-rate precision.
– Handle with extra care — the thinner wall sections of 500 ml semi-micro glassware are more susceptible to chipping at the stem tip, joint rim, and stopcock barrel if knocked against hard surfaces.
Manufactured by GWSI Glass Lab — Ambala, Haryana, India (The Science City)