Transcription of IDEMA STANDARDS
1 IDEMA STANDARDS . Microcontamination Document No. M11-99. Page 1of 6. General Outgas Test Procedure by Dynamic Headspace Analysis Description Purpose This document describes a general procedure for dynamic headspace analysis. This procedure can be applied to quantitatively and qualitatively measure the material purged from the space inside a chamber that contains disc drive piece parts and or sub- assemblies. The test is not designed to sample all of the material that could outgas from a particular part at a given temperature, but, rather to provide a snapshot of the outgassing performance of a material under certain conditions that may be duplicated so as to make it possible for multiple laboratories to obtain similar results on similar materials when performing this test.
2 Scope This procedure describes the use of GC-MS as a detection method. Two methods for quantification are described. One method is semi-quantitative and utilizes an external hexadecane standard and applies a common response factor (of the hexadecane) to a number of compounds. The other method described is a quantitative method and utilizes a calibration curve that is compound specific. Both methods are most applicable for detecting organic compounds in the approximately C10 to C25 range. In general, compounds smaller than C10 could be too volatile to be trapped on the specified sorbents with the specified flow rate. Also compounds above C25 may not desorb completely under the parameters specified. In such cases where the goal is to measure compounds outside these ranges method modifications may be made based on experimental evidence of good recovery of surrogates and guidelines described in the NIOSH Guidelines for Method Development, 4th Edition, August 1994.
3 Limitations of Application Because the method takes only a snapshot of the material that is emitted from a part in a given time, the results of these tests can be misleading if the proper development work was not done to characterize a material's outgassing behavior. Multiple dynamic outgassing tests, using various conditions (time, temperature ) would need to be carried out to fully characterize the outgassing behavior of a material or part. Referenced Documents ASTM D 5116 - 90 Standard Guide for Small-Scale Environmental Chamber Determinations of Organic Emissions from Indoor Materials Guidelines for Sample Chamber. (This is a valuable reference for background reading and definition of terms. It is referred to in Section ). IDEMA STANDARDS .
4 Microcontamination Document No. M11-99. Page 2of 6. Statistics for Analytical Chemistry, Miller and Miller, 3rd Edition, 1993 (A. useful reference for definitions and terms used in this procedure.). NIOSH Manual of Analytical Methods (NMAM) 4th Edition, August 1994, Introduction Sections A - E (This is a valuable reference for the definition of terms and also offers guidance for method development in Sections D and E). Equipment and Materials Required Permanent Equipment Sample Chamber (The chamber should be made of a material that does not interfere with the recovery of analytes (ie. inert), large enough to house the part(s). being tested and leak proof. The chamber should also allow for the intake and exit of the extraction gas and provisions for adequate mixing of the gas should be taken).
5 Sorbent Tubes, filled with CarbotrapTM B and C or equivalent. Temperature Controlled Heating Apparatus Flowmeter, recommend Humonics Veri-Flow 500 or equivalent, calibrated Hydrocarbon trap for purification of carrier gases. Regulator, dual stage, 0 - 30 psi Stainless steel tubing, 1/8 inch Insulation, glass fiber Gas Chromatograph equipped with Mass Spectrometer Desorption System GC-Column, Fused Silica Coated w/ poly (5%-diphenyl-95%- dimethylsiloxane) to .25 micron film thickness, length of 10 to 35 meters, of mm or demonstrated equivalent Flow Controller Thermocouple, calibrated Expendable Equipment Chemicals Nitrogen Gas, pure or better Internal STANDARDS , n-decane preferred, or hexadecane as alternate Sorbent Helium Gas, pure or better Carrier Solvent for STANDARDS , acetone recommended STANDARDS Sample Collection and Analysis Sample Preparation Preparation of Assemblies and Mechanical Piece Parts IDEMA STANDARDS .
6 Microcontamination Document No. M11-99. Page 3of 6. Take care not to contaminate the test parts. Prepare a method blank at the same time as the sample and run the method blank in the same set of runs. Sample Collection Pack the adsorption tubes with the appropriate type and amount of sorbent. The sorbent should not extend into regions of the tube that are not heated. The sorbent should be chosen so that it adsorbs the compound(s) of interest and also desorbs the compound(s) of interest at reasonable desorption temperatures. Care must be taken that the sorbent design has the appropriate breakthrough volume (refer to NIOSH Manual of Analytical Methods Section E (Development and Evaluation of Methods) for the compounds of interest.)
7 Condition the adsorption tubes by heating them 10 to 50 degrees Celsius above the sample desorption temperature, while purging with a gas (ie. nitrogen). This would 350 to 390 degrees Celsius. Prepare the sample and place the sample in the sample chamber ( ). Install the adsorption tube. Use a calibrated flow rate meter and a flow controller to set the flow to 50. ml/minute. Take measurement at exit of adsorption tube. Heat chamber to 85 degrees Celsius or 120 degrees Celsius (depending on whether the high temperature or low temperature method is applied). Note: Verify the time vs. temperature of a model sample with a thermocouple mounted to the part. Record the temperature of the sample chamber vs. time Remove the adsorption tube after three hours.
8 Operating Conditions for the Thermal Desorption Unit and GC-MS. Consult Instrument Operation Manual Apply general good chromatography practices so as to avoid co-elution of target compounds and obtain proper peak shapes Program desorber to desorb tube at a temperature greater than or equal to 340. degrees Celsius for a time greater than 4 minutes at a flow rate greater than or equal to 10 ml per minute. These parameters can be modified if the desired performance targets are achieved. Tune the mass spectrometer so at least one of the abundance ratios of the PFTBA peaks 219 or 264 relative to the 69 peak falls into the following ranges: Ion from PFTBA Mass Spec Calibration Relative Abundance to ion 69 (%). Standard Mass 219 30 - 70.
9 Mass 264 5 - 20. Quantitative Analysis IDEMA STANDARDS . Microcontamination Document No. M11-99. Page 4of 6. Load internal standard into all tubes by adding a five microliter amount of a dilute solution of standard into the front end (the end first contacting the incoming gas during sampling) of the sampling tube. The sampling tube should contain the same type and amount of adsorbents that will be used for the sampling. Make a solution at 200 nanograms per microliter so that a five microliter injection of the solution into the tube will yield 1000 nanograms of standard. Immediately after a standard has been injected into a sorbent tube, run clean ( or better) nitrogen into the tube by connecting a nitrogen output into the side of tube closest to where the standard was added (front of tube) at 100.
10 Ml per minute for 5 minutes. The direction of gas flow is from the front of the tube to the back so that the standard is carried into the tube. Store each tube at below 0 degrees Celsius until ready to analyze. Do not let tubes stand for more than 24 hours at room temperature prior to analysis. Calibration Procedure for Quantitative Analysis Prepare STANDARDS for each target compound. Create calibration curves for each analyte using the extracted ion response from the desorption of the standard solutions off of tubes. Apply and desorb the tubes in the same way as described for the hexadecane standard. Calibration curve levels should include the range being measured. Calculations Calculating Values for Semi-Quantitative Analyses Record the total ion counts for each target compound.