Sterilization

Glassware Preparation for Use

Selection

Grade A glassware needs no testing. Grade B is satisfactory

for most routine work. Others should be heat resistant,

have a low coefficient of expansion

and be free from

soluble metals and free alkali; in addition, they should be

mechanically strong.

Cleaning Glassware

New: Look for cracks if any. Soak in 2% HCl for overnight to

neutralize any alkali present. Wash in running water. Boil

in synthetic detergent for 30 minutes, rinse in tap water

and finally in distilled water.

Used glassware should be rinsed immediately after use.

Boil in a detergent for 30 minutes and clean thoroughly with

a brush, rinse in tap water and finally in distilled water. Dry

them in the oven with temperature not exceeding 80°C.

Dichromate Cleaning Solution

Dissolve 25 g potassium dichromate in 25 mL of water. Add

50 mL concentrated sulfuric acid (slowly, always add acid

to water and not (vice-versa), cool, store it in a stoppered

bottle; discard when it starts turning green.

Petri Dishes

* Autoclave to remove infected material

* Wash in soapy water

* Rinse in running water, let dry

* Rinse in methylated spirit, let dry

* Sterilize in hot air oven.

Pipettes

*Soak in chromic acid solution overnight

* Wash in running water

* Rinse in distilled water

* Dry on suction pump using methylated spirit, or ether,

or methylated acetone

* To sterilize—plug mouth piece with nonabsorbent

cotton wool, wrap in kraft paper and hot air sterilize

(160°C for 1 hour).

Test Tube

* Autoclave to remove infected material

* Boil in detergent solution for 30 minutes

* Clean witsh a brush

* Rinse in running water, rinse in distilled water and place

   them in a wire basket upside down and dry in an oven

* Cotton plug them and sterilize in the hot air oven.

Pasteur Pipettes

* Soak in 3% lysol for 1 hour

* Wash as before (as for test tubes).

Screw-capped Bottles

* Wash the liners separately

* Dry quickly to avoid corrosion

* Sterilize metal caps and their bottles in hot air oven

* Rubber liners—autoclaved.

Glass Slides

New

* Boil in a detergent for 30 minutes

* Place in dichromate for overnight

* Wash in running water

* Keep in methylated spirit

* For using, take them out with a forceps and hold them

only by the edges.

Used

* As for used glassware.

Infected Slides

* Should be autoclaved and then cleaned as mentioned

earlier (never use slides used for examining

acid fast

bacilli for the same purpose).

Infected Glassware

Contaminated material—may be disposed in paper or

cardboard wrappers and incinerated.

Autoclave the glassware that has been contaminated.

Having autoclaved, wash and prepare in the usual way.

Syringes

Complete bacterial sterility can be achieved either by

sterilizing them in the hot air oven or in an autoclave.

Keep injection syringes separate

from blood withdrawing

syringes. Fresh syringes (sterilized) should be used

for withdrawing blood for each patient. Before reusing

them, clean them properly and then sterilize them.

Needles used should be sharp and not with blunted

ends.

Choice of Syringes and Needles

All glass syringes are preferred over glass and metal ones.

Preferably keep size 5 mL or more syringes for withdrawing

blood. Needles should be of size equal to or less than 21

(SWG). A needle with a smaller diameter would cause lysis

of blood when used for blood withdrawing. Withdrawing

needles should be at least an inch long.

New Syringes

These are washed in the usual way. Dried with acetone.

Wrap the plunger and the barrel in a paper and sterilize in

hot air oven.

Used Syringes

Immediately after use, wash them thoroughly with cold

water (hot water will coagulate

proteins and will make

the syringes

difficult to clean). Clean them thoroughly in

a detergent, brush the barrel properly, rinse in tap water

and then in distilled water. Rinse in acetone and let dry.

Sterilize in hot air oven as mentioned above.

Infected Syringes

These should be washed at first with cold 2% lysol solution

and then clean as above. Syringes infected with highly

virulent material should at first be autoclaved. The syringes

should be placed in the cold oven and be heated at 160°C

for 90 minutes. Syringes not used for 3 months should be

resterilized before use.

Glass Barrel and Metal Plunger Syringes

The only precaution to be taken here is that metal corrosion

should be avoided and the barrel and the plunger should

be sterilized separately

(kept in a wrapper) by autoclaving

them.

Needles

* Should first be rinsed in cold water

* Clean the mounts with a cotton-wool swab

* Wash again, rinse in acetone

*Pass a stylet through the hole to remove any plugs if

present

(It is important to discard all needles with blunted

tips,

a hand lens can be used to examine needle tips)

* Serum hepatitis and HIV can be transmitted through

using imperfectly cleaned and sterilized needles

* The needle should be sterilized in hot air oven.

Disinfection of Syringes by Boiling

In an emergency, syringes can be effectively sterilized by

boiling them in distilled water for at least 5 minutes after

having cleaned them in the usual way.

Disposable Sterile Syringes

This is the world and time of disposables. In the interest

of the patient every laboratory should ideally use disposable

syringes only.

As far as possible use disposable, sterilized plasticware

instead of glassware.