Accurately weigh an authentic Reference Substance for each analyte into a measured volume of chromatography-grade Desorption Solvent (typically benzene-free, gas chromatography grade carbon disulfide which may have 3% benzyl alcohol or butyl alcohol) to make a Stock Standard Solution equivalent to of 1.0 mg of analyte per ml of Desorption Solvent. A Stock Standard may contain up to seven(7) Standard Analytes provided they do not co-elute in the chromatography systems being used. Date Stock Standards, store under refrigeration, and make fresh monthly. Dilute the Stock Standard Solution at least weekly using Internal Standard Solution to make 3-5 Working Standards in the range 0.01-10 ug per ml of Desorption Solvent. Date Working Standards, store under refrigeration, and make fresh weekly.
INTERNAL STANDARD SOLUTION
Accurately weigh pure (99+%) cyclohexane and n-decane to make a solution of 1-10 ug of each internal standard substance (accurately measured) per ml of Desorption Solvent.
Remove each Monitor to be tested from the Return Container. Using lab spatula as a pry, un-snap the white Sampling Grid from the clear plastic Wafer Tray exposing the carbon Sampling Wafer. Transfer the carbon Sampling Wafer to weighing paper which has been creased in the middle, then, grasp the Wafer through the weighing paper, break it in two along the score mark, and pour the pieces of carbon wafer into a 7 ml glass vial.
Immediately pipette 2.0 ml of Internal Standard Solution and cap the vial with inert, gas-tight closure. Agitate the vial continuously for one hour using an orbital shaker or equivalent. Reserve for gas chromatographic analysis.
At least weekly, remove a Monitor from the same manufacturing Lot as those being analyzed which has not been exposed. Process the unexposed "BLANK" Monitor exactly as the Sample Preparations (above) and subtract any Peak Area response at the retention time of interest from the value obtained from the Sample Preparation. Report any significant BLANK values to Quality Assurance group along with the Lot number of the Monitor analyzed.
QUALITY CONTROL SAMPLES
At least weekly, run Analyte Standards for all Analytes analyzed during the week and determine whether Analyte Standard responses fall within the Calibration Parameters specified for that Analyte and stored in the Computer. Investigate and resolve deviations or discrepancies of Standards from the known Calibration Parameters.
At least monthly, submit spiked Monitors for Lab Analysis by this method along with regular samples received from outside the laboratory. Report results for these Monitors in the normal manner. The Analyte Concentration reported should fall within 2 standard deviations of the known, spiked concentration submitted for 90% of QC Samples submitted and all samples should fall within 3 standard deviations of the known concentration spiked on the Monitor. Investigate and resolve any deviations or discrepancies.
CAPILLARY GAS CHROMATOGRAPHY(GC) ANALYSIS
Inject an aliquot of the Sample Preparation from each Monitor to be analyzed into a Gas Chromatrography System using the following conditions.
GC Columns dual) - RT-1(*)(Column A); RT-Volatiles(*)(Column B)
Column Size - 0.20 or 0.32 mm capillary x 50 meter
Injection Mode - Split (typical 10:1)
Injector/Detector Temp - 225oC
Column Temp - Hold 3 min 35oC; 30oC per min to 220oC; Hold 3 min
Injection Volume - 1.0 microliter (nominal)
(*) Restek Corp, Bellefonte, Pennsylvania
Concomitantly, inject measured aliquots of a BLANK Preparation and three Standard Preparations in the range of interest (i.e. which bracket the concentrations of the Sample Preparations).
Acquire analytical data into a computer system in which chromatography data handling software (ChromPerfect, Palo Alto, California) has been installed. Using the software, compare the peak area ratio for analyte vs internal standard normalized for concentration from each Sample Preparation to the best-fit Calibration Curve obtained from BLANK and Standard Preparations and compute the Analyte Concentration in the Sample Preparation.
Calculate Exposure Level from Analyte Concentration as follows.
EXPOSURE LEVEL= 1000(C)(S)(R)
(ppm) (DE)(M)(SR)(T) where
C = Analyte Concentration (mcg/ml)
S = Volume of Solvent (ml)
R = Molar Volume @ 22oC (24.1 l/mole)
DE = De-Sorption Efficiency
(fraction of extraction) for 2.0 ml CS2
M = Analyte Molecular Wt (g/mole)
SR = Monitor Sampling Rate (ml/min)
T = Sampling Time (min)
If temperature during sampling was outside the range, 10-36oC (50-97oF), apply compensation as follows.
EXPOSURE LEVEL(ppm) = [EXPOSURE LEVEL (ppm)]x (295/Tave)1/2
Tave = Average actual temperature during sampling in oK
[ NOTE: oK = oC + 273o ]