MAINTENANCE TIPS FOR USERS
lptOF THE MEINHARD® CONCENTRIC
GLASS NEBULIZER
1900 East Warner Avenue Suite J
Santa Ana, CA 92705 USA
Telephone: 800-634-6427
Fax: 949-250-3991
Email:
WWW: http:\\
© 2001 J. E. Meinhard Associates, Inc.
Your MEINHARD® nebulizer reflects the exacting standards in design and manufacturing that have ma
de it the choice of the industry worldwide. Properly maintained this nebulizer should yield stable performance indefinitely. However, failure to apply a few simple preventive measures can lead to obstructed gas and liquid passages in the nebulizer which can riously impair operation. We recommend that you follow the maintenance tips outlined here for long-lasting and trouble-free performance. We also include a diagnosis and treatment scheme [1] to help restore inoperative (but undamaged) nebulizers (e Figure 2 at end of booklet.). Refer to Figure 1 below for nebulizer configuration. We provide this information as a courtesy to our customers.
J E M EINHARD A SSOCIATES, I NC ASSUMES NO RESPONSIBILITY FOR ACCIDENTAL DAMAGE RESULTING FROM APPLICATION OF THE RECOVERY PROCEDURES.
老师英文Figure 1. MEINHARD® Nebulizer Configuration
PREVENTIVE MEASURES
Blockage in the nebulizer is caud generally by either particulate matter (from the sample or the carrier gas) or chemical deposits. It normally occurs in the nozzle where the flow passages are extremely small. Constriction is greatest in the annular gas channel between the tip of the capillary and the taper of the nozzle. In some nebulizer models this annular gap can be as small as 10-15 µm.
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Tip #1: Filter the carrier gas.
Install low-impedance in-line gas filters to prevent particles from being carried into the nebulizer and lodging in the gas annulus. This is especially important when polytetrafluoroethylene (PTFE-Teflon®) tape has been ud in the gas line plumbing. Shreds of this tape have been found wedged in the gas annulus and have resulted in drastic reductions in performance [2]. For the same reason, avoid using PTFE or other friable alants at the gas connection to the nebulizer.
Tip #2: Filter the sample.
The sample capillary is more tolerant of particulate matter than the gas annulus. In high sample uptake models especially, the capillary will carry visibly turbid suspensions. We suggest, however, that you filter or centrifuge the sample if the solids are not of analytical importance. Particulates and colloids of a polar nature such as silica, peptides, polyvalent metal hydroxides and others tend to build up on the (polar) glass and impede the fluid flow. In some instances, you can prevent deposition by adjusting the pH of the suspension away from its (presumed) isoelectric point.
济南槐荫教育网Tip #3: Rin your nebulizer.
It is especially important to rin the nebulizer before turning the gas off. Depending on the chemistry of your samples it may also be advisable to rin periodically throughout the testing. Solids may deposit in the nozzle as sample solvent evaporates, further constricting the flow passages and reducing the signal. Rinsing will minimize or eliminate the deposits. Gas flow through most nebulizer models creates a venturi suction at the capillary tip that can be ud to draw rin liquid through the capillary. Follow the testing of any salt solution promptly with a chemically compatible rin consisting only of volatiles. (This is not as necessary in flow injection analysis systems.)
A low-pH (acidic) sample should be followed by a low-pH rin; a high-pH sample by a high-pH rin; an organic sample by an appropriate solvent. Rin finally with pure water and/or isopropyl alcohol. Allow the nebulizer to dry before turning off the gas. Also make sure that the liquid feed is disconnected or arranged so as to prevent siphoning into the nebulizer while the gas is off.
英文美文Tip #4: Do NOT u ultrasonic cleaning.
Sympathetic vibrations may be t up in the capillary causing it to bounce against the inside of the nozzle and chip. Nebulizer performance can decline verely as a result.
RECOVERY METHODS
If you find that solids inside the nebulizer are interfering with performance, you generally can remove them by means of the steps outlined below. Full function usually can be recovered. This quence is diagrammed in Figure 2.
1. Preliminary Examination:
Dingage the nebulizer from its mounting and examine it under 20X or 30X magnification. If a particle appears to be wedged in one of the channels, go to Step 2. If solids are prent in the capillary but there is still a passage through them, go to Step 3. If solids have completely blocked the capillary, go to Step 6. If the nozzle is encrusted with crystalline deposits, go to Step 4. If no foreign matter can be en, go to Step 5. In all cas discontinue treatment when you have removed the obstruction.
NOTE: Rin the nebulizer after any treatment that introduces caustic or corrosive cleaning agents into the shell and/or capillary. Make sure that the final rin is with isopropyl alcohol to speed the drying process. Introduce a rinsing agent into the shell, either from the gas input or the nozzle (a squeeze bottle works well in both cas). Fill all areas previously expod to corrosive solutions. Att
ach pressurized gas to the side-arm to expel the liquid. Inject more rin solution into the liquid input while the gas is flowing and allow venturi suction to draw it through the capillary. Repeat the treatment if you think it necessary. Finally, dry the nebulizer completely.
NOTE: If you have an A-type nebulizer, avoid touching the capillary tip when injecting solutions into the shell from the nozzle. The capillary is flush with the nozzle surface. 2. Particles:
The operations are ranked in order of increasing aggressiveness. We recommend that you start with the gentlest. Some of the methods may take a little practice before they feel comfortable.
a. Tap the liquid input of the nebulizer gently against a wood surface (or surface
of comparable hardness) to jar the particle loo. This helps the particle to move in the direction of increasing inner diameter. Repeat the tapping as necessary to work the particle toward the appropriate exit orifice. Avoid extremely harsh tapping.在线英文签名
颜色英文
b. Apply compresd gas (15-30 psig) to the nozzle, forcing the gas backwards through the annulus and the capillary (backflushing). Make sure you hold the nebulizer curely during this operation. Tap or flick the shell soundly with your fingernail a few times. If this fails to dislodge the particle, clos
e off the liquid and gas input tubes with your fingertips. When the pressure builds up, "pop" a fingertip quickly off the appropriate orifice (if something is wedged in the gas annulus, "pop" your finger off the gas input; if in the capillary, off the liquid input). The sudden expansion of gas should help jar the particle loo in the direction of increasing inner diameter. Try to orient the nebulizer so that gravity assists you.
c. Force isopropyl alcohol backwards through the nozzle in an attempt to float the particle out through the larger gas and liquid input tubes. U a squeeze bottle or plastic dropper with a tip that will form a good al over the nebulizer nozzle. Then blow the alcohol through the input tubes using compresd gas, or blot onto lintless tissue (e.g., "Kimwipe").
八年级英语教学总结A variation of this procedure works best if (i) you know which passage the particle is in and (ii) your nebulizer is a type C or K with a recesd capillary. Inject 1/4" to 1/2" of solvent into the shell through the nozzle or the gas input tube. Clo off the nozzle with a fingertip. (Caution: U protection if the solvent is caustic.) Apply pressurized gas to the passage that does not contain the particle. Pressurized solvent will force its way out the other channel in the direction of increasing diameter, hopefully carrying the particle along with it.
d. If the particle still remains and you believe that it might be a shred of PTFE tape from the gas line, immer the nebulizer nozzle in hot water and apply gentle gas pressure to the side-arm. The hot water "relaxes" the polymer and allows it to be forced out of the nozzl
e.
gtte. To loon especially stubborn particles such as silica, u a solution of 3%-5% hydrofluoric acid (HF). (Caution: U appropriate protection and care when handling HF.) HF breaks the bonds between glass and other substances. Introduce the acid into the nozzle from a plastic dropper. Drain after 5-10 conds and rin with pure water and/or isopropyl alcohol. Examine the nebulizer under magnification. This process can be repeated veral times without significantly altering the performance of your nebulizer. However, longer soaks (e.g., 5 minutes) and higher HF concentrations will reduce the operating gas pressure. Dry the nebulizer thoroughly after the final treatment.runtime
f. If the particle still remains and is believed to be organic (e.
g., a cellulo fiber), go to Step 5.
g. If the particle is located in the capillary and still does not move, go to Step 7.
