A Direct Weighing = Technique for Sampling

A = Direct Weighing=20 Technique for Sampling

Pressurized=20 Containers (Aerosol Cans)

1. =20 Remove spray nozzle and with an ice pick or = sharp=20 pointed item, carefully remove the inner spray valve. Use pliers or = clamp nozzle=20 in a vise to prevent injury to oneself. &n= bsp;. &n= bsp;=20

2. =20 Fit a length of small diameter tubing (teflon, = tygon,=20 stainless steel) into the inner spray valve opening. OR (and this is = probably the best=20 way): If, after removing nozzle, the can has a tube-like stem = attached, use a=20 piece of small diameter tubing that will fit snugly over the stem. = The tubing should be long = enough to reach=20 past the neck of the volumetric flask the sample will be dispensed into. = About 6 - 8 inches for 50 or = 100 ml=20 flasks and 8 - 12 inches for 500 or 1000 ml flasks. A disposable pipette tip = (Eppendorf,=20 etc.) may be used as an adaptor/connector for the tubing. See attached = photos.=20

3. =20 Assemble everything, refitting nozzle on can = with=20 pipette tip (if used) with tubing attached. Accurately weigh the can = with=20 attachments.

4. =20 Figure on what sample size is needed for the = analysis.=20 Roughly weigh and transfer that amount of plain water to a volumetric = flask the=20 size that will be used. Visually note how much liquid is in the flask. = This is a=20 visual reference as to how much sample needs to be dispensed to give the = weight=20 needed. If foaming is encountered, dispense/spray sample into a large = beaker and=20 rinse down with solvent to transfer to appropriate flask/contained = (volumetric=20 flask) for rest of analysis.

5. =20 Insert the tubing into the volumetric flask to = below the=20 neck. Carefully spray the can until a sufficient amount of sample has = been=20 dispensed that is similar to that in Step 4.

6. =20 Remove the tube and accurately re-weigh = everything. Be=20 careful to not drip any liquid from the tube before re-weighing as it = will=20 affect an accurate sample weight. The difference between the two = weighings is=20 the sample weight. Proceed with analyses. For additional sample weights, = repeat=20 Step 3 and Step 6.

Note: =20 As an approximate check on the sample(s) weights, the empty = volumetric=20 flask may be accurately weighed before and after dispensing/spraying the = sample=20 into it. This procedure is not accurate due to the volatiles released = from the=20 can during spraying.

Pic 1: = two=20 aerosol cans. Note, can = on left has=20 the nozzle inside top. Small black object was inside spray button and = removed=20 with ice pick. The = can on=20 right has a nozzle tip in can. =

Pic 2: = using=20 disposable pipette tips and tubing, direct sampling into volumetric = flask. Weigh can before and after = spray and=20 rinse tip and tubing with solvent into volumetric = flask.