Maintenance and use of glassware

Considering the diversity, wide application and different shapes of glassware and the special dedicated glassware used in the assay laboratories of different specialities, it is difficult to classify all the glassware in details. Generally, the glassware and glass products used in the laboratories are classified to the following 8 types in accordance with general international standards:

(1) Conveying and trapping devices, such as glass adapters, ports, valves, plugs, pipes and rods, etc.

(2) Vessels, such as dishes, bottles, beakers, flasks, basins and test tubes, etc.

(3) Basic operating instrument and devices, such as those used for absorbing, drying, distillation, condensation, separation, evaporation, extraction, gas generation, chromatography, liquid separating, mixing, breaking, centrifugation, filtration, purification, burning and burning analysis.

(4) Measuring instrument, such as measuring instrument, measuring devices, droppers, pipettes and injectors for flow rate, specific gravity, pressure, temperature and surface tension.

(5) Physical measuring instrument, such as glass instrument used for test of colour, optical density, electrical parameter, phase change, radioactivity, molecular weight, viscosity and particle size.

(6) Glass instrument for test of chemical elements and compounds, such as instrument used for arsenic, CO₂, element analysis, radical analysis, metallic elements, sulphur, halogen and moisture test.

(7) Material test instrument, such as instrument used for atmosphere, explosives, gases, metals and minerals, mineral oils, construction materials and water quality measurement.

(8) Analytical instrument for food, medicine and biology, such as analytical instrument for food analysis, blood analysis, microculture, microscope accessory, serum and vaccine test, and urine test.

Use of glassware

When the maximum accuracy is required, the glassware shall be operated at the same conditions as those upon calibration, and the calibration value of division error shall be used. The measuring devices shall be cleaned before use. If the deviation from the indicated capacity is found during calibration, suitable correction shall be made.

(I) Volumetric flask

When the volumetric flask is used to prepare the water solution, it does not need drying after it is cleaned with distilled water. Recommended dilution method of water solution: add the matter to be dissolved into a suitable amount of water; when necessary, the flask can be heated and shaken properly to dissolve that matter; next, add more water to raise the liquid level to centimetres below the mark. Fit the flask plug, and rinse the flask with cleaning water till the liquid level is 1 cm below the mark; then open the flask plug, and keep the flask still for 2 min for the liquid at the flask neck to flow down; next, when the solution reaches the room temperature, refit the flask plug, and wait for a while; finally, fill some water along the flask neck from a point within 1 cm below the mark, and make the lowest point of curved liquid level above the mark. Refit the flask plug, shake the flask and put the flask upside down to make the solution homogeneous and ready for use.  

(II) Measuring cylinder and cup

After the measuring cylinder or cup is cleaned and dried, first fill the liquid to be measured into the cylinder or cup to millimetres above the nominal mark or required mark, and then use the pipette to remove the surplus liquid.

(III) Pipette

1. Output pipette

The pipette shall be first cleaned with distilled water, and then rinsed with the liquid to be measured.

The pipette shall remove the liquid till the liquid level is millimetres above the zero mark or required mark.

2. Input pipette

The pipettes shall be cleaned with distilled water, and then dried or rinsed with the liquid to be measured for 3 times. The pipette shall remove the liquid till the liquid level is millimetres above the zero mark or required mark. To ensure the correct input volume, the pipette shall be operated by the method mentioned in the definition of capacity.

Heating of glassware

(1) The glassware that can be heated directly includes test tube, glass rod, crucible and evaporating dish, etc.

(2) The glassware that can be heated with asbestos mesh, and not be heated directly with alcohol burner includes beaker, flask (round-bottom flask and flat-bottom flask), distillation flask (round-bottom distillation flask and flat-bottom distillation flask) and conical flask.

(3) The glassware that cannot be heated during use, but without heating, can be used for chemical reaction includes Kipp’s apparatus, gas bottle, watch glass and drying tube, etc.

(4) The glassware that cannot be heated during use, or used for chemical reaction includes rubber-head dropper, separating funnel, long-neck funnel, water sink, measuring cylinder, acid burette, basic burette, dryer, reagent bottle, dropping bottle and condensing tube.

Source: Performance Calibration and Maintenance Manual of Food Microorganism Detection Instrument and Equipment