## Appendix H. Data Quality

Table of Contents

1.1 Measurement Data Quality Objectives ..................................................................... 2

1.2 Quality Control and Assurance ................................................................................. 4

1.2.1 External Performance Audit for the API Section 211(b) Study ....................... 4

1.2.2 Laboratory Comparison and Ex ternal Performance Audits .............................. 4

1.2.3 Time-Integrated Methods .................................................................................. 5

1.2.4 Semi-Continuous Methods ................................................................................ 7

1.2.5 Continuous Methods ......................................................................................... 8

12 1.1 Measurement Data Quality Objectives

Data quality objectives, including measures of accuracy, precision, detection limit, time resolution, and known interferences, are su mmarized in Table H-1. For the two CO instruments and the PID, we use manufacturer ’s specifications for most data quality

parameters.

There are also some limitations that are not covered by the tabular summary. For the T-15 CO (electrochemical detector), we find that although the data system can collect data every 10 sec, the response of this in strument responds to rapid cha nges in concentration on a longer time frame. This may occur since CO must di ffuse across a membrane to be measured. The finite diffusion time means that rapid spikes in concentration may not achieve steady-state

values across the membrane and are thus not fully measured. Comparisons among CO methods are good over integration times greater than one minute. There were interferences from batteries (H 2 emissions) that were used to power in struments inside the van that showed up as a rising signal from the T-15 CO unit wh en the vehicle windows were closed. Under high-ventilation conditions in the vehicle or outdoors, no su ch interferences were observed. At high humidity near saturatio n we did observe high T-15 CO re adings that we suspect are due to the humidity.

The PID does not have an accuracy measure since this instrument reports the total ion signal,

which will differ with the dist ribution of compounds ionizable at 10.6 eV. However, since we find a good correlation of PID signal with BTEX as measured in the canisters, we feel this measurement provides a reasonable surrogate time series signal for these compounds. This instrument does respond to very high humid ity where there is condensation of water on the lamp and other areas of the electrometer that are exposed to air. In addition, we observed

some summer instances where th e PID readings increased inside the vehicle cabin under low ventilation conditions with no change in any ot her measurement. This may be a response to off-gassing of plasticizers in cabin materials that are mostly phthalate esters.InstrumentAccuracyPrecisionDet LimTime Res.ArtifactsSpecificationsSourceCO-T15+/- 1 ppm+/-0.05 ppm0.1 ppm10 secH2, very high humidityElectrochemical DetectorManufacturer literatureCO-NDIR0.50%+/-0.02 ppm0.04 ppm1 secNoneNDIRManufacturer literaturePIDNA10%1 ppb1 secPlasticizers, very highhumidity10.6 eV lamp PIDManufacturer literatureHCHO (a)<15%<5%1 ppb1 minNoneHantzch rxn/fluorescenceDRI Use/intercomparisonsMS-200<8%<5%1-3 ppbv1 minNoneMass spectrometerDRI Use/intercomparisonsSPME3-50%2-15%0.2 ppbvvariableNoneGC/FID & PIDDRI Use/intercomparisonsCanister<5%<3%0.05 ppbCvariableNoneGC/FIDDRI Use/intercomparisonsDNPH<5%<3%0.1 ppbvvariableNoneHPLC/Photodiode arrayDRI Use/intercomparisons(a) HCHO performance parameters based on Battelle instrument performance in the Reno pilot study.3Table H-1. Measurement data quality1.2 Quality Control and Assurance

1.2.1 External Performance Audit for the API Section 211(b) Study

A site visit to the mobile laboratory and all twelve mi croenvironment (ME) sampling sites in Atlanta, GA was conducted duri ng February 23-27, 2004, by the independent auditor, Christine Sexsmith, Sexsmith Consu lting Services, LLC. The auditor was on site at the mobile lab or in the sampling van and witnessed measurement in at least one of each of the 12 microenvironments sampled. A technical procedure inspection was conducted to verify that DRI personnel were following the approved exposure protocol and that no special circumstances occurred th at could affect the out come of the study. This audit was followed up by the DRI Organi c Analytical Laboratory audit in April 2005. The reports from these two audits are available from the API upon request.

1.2.2 Laboratory Comparison and External Performance Audits

The DRI Organic Analytical Laboratory ( OAL) participated in the International Hydrocarbon Intercomparison Experime nt, organized by National Center for Atmospheric Research (NCAR). The results of Tasks I, II, and III of this laboratory intercomparison have been published (Apel et al., 1994; 1999). Task I involved analysis of a two-component hydrocarbon mixture of known composition and unknown concentration prepared by NIST. The DRI results were within the acceptable range of ± 5% of the nominal values provided by NIST. In Task II the participating laboratories were asked to identify and quantify 16 component s present, in the ppb range, in a mixture prepared by NIST. The agreement between the DRI values and the NCAR values, as well as with nominal values provided by NIST, were within acceptable ranges ( ± 15%). Task III was more complex, involving th e analysis of 60 commonly observed hydrocarbons at low ppbv concentrations in a mixture prepared and analyzed by ScottMarrin, Inc., NCAR and U.S. EPA laboratory. The next tasks, IV and V, which were carried out in 1996 -1997, involved the analys is of ambient air samples in the ppbv and pptv concentration ranges, respectively. Th e DRI has successfully completed these tasks with agreement between the DRI values and the NCAR values for Tasks III – V within the acceptable range ( ± 10%).

In the summers of 1995 and 1996 the DRI OA L participated in the NARSTO-Northeast hydrocarbon intercomparison study, involving the analysis of two ambient air samples by participating laboratories. Participants incl uded Biospheric Research Corporation (BRC), State University of New York at Albany (S UNYA), EPA Region I, DRI, and eight of the

PAMS network labs in the northeastern U. S. The DRI laboratory performed best in comparison with all other participants (Fujit a et al., 1997). In the summer of 1997, the DRI OAL participated in the SCOS97-NARSTO performance audit and laboratory comparisons involving speciated non- methane hydrocarbons (NMHC), carbonyl compounds, halogenated compounds and biogen ic hydrocarbons (Fujita et al., 2003). Again, the agreement between DRI values and nominal values were within the acceptable range ( ± 10%).

4During the last six years, the DRI laboratory participated in non-methane hydrocarbon laboratory performance audits, organized by the Quality Assurance Section, Monitoring and Laboratory Division, CARB. The last intercompariso n studies, organized in 1999- 2002, involved the analysis of ambient air samp les by California district laboratories and the DRI OAL laboratory. The results of these intercomparison studies were always very

favorable for OAL.

1.2.3 Time-Integrated Methods

Sample Custody. For our quality assurance plan, a sample is considered in custody when it is received by the DRI Division of Atmosphe ric Sciences (DAS) receiving department from an official package courier. At this time it is logged into the general receiving department's logbook and the Organic Analytical Laboratory is notified of the package's arrival. A representative of the laboratory si gns for the package and returns with it to the laboratory where he opens it. The sample s are logged into the Organic Analytical Laboratory’s receiving logbook, th e chain-of-custody form is updated, and the samples are stored appropriately for the sample t ype. At this time any unusual situations (damaged shipping container, evidence of damage and/or tampering, etc.) are brought to the attention of the laboratory manager. If necessary, a re view will be initiated to determine if the damage compromised the integrity and/or quality of the sample.

Samples are stored in the Organic Analyt ical Laboratory, inside the DRI Northern Nevada Science Center (2215 Raggio Parkwa y, Reno, NV). The room is locked when not in use and the building has limited access (i.e., it is locked from 1730 to 0730 weekdays and all weekends to ensure access only to authorized personnel).

When a sample is analyzed, its identificati on number (sample number) is recorded both in the written log book for each inst rument and in the Laboratory Information Management System (LIMS) file created for that analys is. The sample number serves as a tracking number, as does the LIMS file its elf. Canisters will not be cleaned until each sample has passed initial validation.

Sampling Systems. The sampling equipment is leak-t ested and the electronic flow controllers are calibrated prior to the delivery to the field. The flow controllers are recalibrated after the program to determine if any significant change in the calibration has occurred. In addition, the flow controllers are checked at least weekly in the field with a Galibrator (an instrumented soap bubble flow meter). The average of the pre- and postsampling flow rates is used to determine the sample volume.

Sampling systems that have internal surfaces upstream of the collection media (e.g., canister sampler), must be cleaned and certi fied for cleanliness prior to sampling.

Sampling Media Prepara tion and Certification. Multibed adsorbent cartridges consisting of Tenax TA, Carbotrap (or Carboxen) and Carbosieve are used for ethanol sample collection. Prior to use, the Tenax-TA so lid adsorbent is cleaned by Soxhlet extraction with hexane/acetone mixture (4/1 v/v) overni ght, and dried in a vacuum oven at ~ 80 °C. The dry Tenax is packed into Pyrex glass t ubes together with Car botrap and Carbosieve and thermally conditioned for f our hours in an oven at 300 ° C under nitrogen purge. Approximately 10% of the precleaned cartridges are tested by GC/FID prior to sampling.

5After cleaning, the cartridges are sealed using clean Swagelok caps (brass) with graphite/Vespel ferrules, placed in metal contai ners with activated charcoal, and kept in a clean environment at room temperature until use.

The DNPH impregnated SiO2 cartridges are purch ased from Waters, Inc., in batches of 25. One cartridge from each batch is te sted for background contamination by the High Performance Liquid Chromatography (HPLC) method prior to sampling.

The canisters are cleaned by repeated evacuatio n and pressurization w ith humidified zero air, as described in the EPA document "Technical Assistance Document for Sampling and Analysis of Ozone Precursors" (Oct ober 1991, EPA/600-8-91/215 ). Six sequential cycles of evacuation to ~ 0.5 torr absolute pressure and pr essurization with ultra-highpurity (UHP) humid zero air to ~ 20 psig are used. The DRI procedure differs from the

EPA method in that canisters are heated to 140 °C during the vacuum cycle in the DRI procedure and more vacuum-pressure cycles ar e used. According to our experience and that of others (Rasmussen, 1992), heating is essential to achieve the desired canister cleanliness. Also, the canisters are maintained longer under vacuum, about one hour in the DRI method, as opposed to half of an hour in the EPA method.

At the end of the cleaning procedure, one canister out of twelve in a lot is filled with

humidified UHP zero air and analyzed by the gas chro matograph/flame ionization detection (GC/FID) method. The canisters are considered clean if the total non-methane organic compound (NMOC) concentration is le ss than 10 ppbC, and the concentration of any individual targeted compound is less than 0.2 ppbv. Canister cleaning and

certification are describe d in the DRI SOP1-701.4 .

Analytical Systems. Prior to analysis, all analytical systems (i.e., GC/ECD/FID, HPLC, GC/MS, and GC/IRD/MSD) are checked for clea nliness and are certified clean (less than 0.1 ppbv of targeted compound). Quality contro l in the laboratory includes instrument calibration for each batch of samples analyzed, re plicates of standards, and reanalysis of approximately 10% of the samples for es timation of analytic al precision, which historically has been be tter than 6%. In past programs, field blanks have come in at 0.5-1 ppb levels, based on the air volume of the sa mples. Coefficients of variation (CV)

calculated from observed differences be tween duplicate samples were less than 10%. The data quality in this program was within DRI’s historical range.

Standards and Materials. Each primary reference standard is traceable to an NIST Standard Reference Material (SRM). For canister hydrocarbon speci ation, we use NIST SRM 1805, which consists of 254 ppb of benzene in nitrogen.

Gas cylinders of helium, nitrogen, hydrogen, an d ultra zero air (all UHP grade) — from

the best sources available — are used fo r the GC/FID and GC/MSD. The current inventory of reference samples at DRI's Organic Analytical Laborat ory consists of over 250 single- and multi-component reference samples, and includes compounds of interest in this project.

Calibrations. The GC/FID, HPLC, and GC/MS sy stems are calibrated initially by multipoint calibration (i.e., three levels plus humid zero air), and regularly checked by a one-point calibration, using the appropriate NIST SRM or other standard. A day-to-day

6reproducibility of ±10% is acceptable for either standard. Control charts are used for assessing analytical system performance.

Samples that fall outside the calibration range are diluted until bracketed by the calibration curve. Instrument responses to calibration standards for each parameter are analyzed using a least squares linear re gression. The calibrati on must generate a correlation co-efficient (R 2 ) of 0.99 to be acceptable.

During the course of analysis, calibration standa rds are routinely analyzed to ensure that the instrument response has not changed. The criterion of an instrument response within 10% of the expected response is used by the analyst to determine whether the instrument

must be recalibrated.

Relative Accuracy and Precisi on of Sampling and Analysis. Accuracy involves the

closeness of a measurement to a reference va lue and reflects elemen ts of both bias and precision. Percent relative accuracy is calculated:

% Relative Accuracy = X - Y x 100

X

where:

Y = concentration of the targeted compound, as determined by the analytical instrument,

and

X = concentration of the targeted com pound in the NIST (or traceable) standard.

If the percent relative accuracy does not fa ll below 20%, the instru ment is recalibrated.

Precision is a measure of the repeatability of the results. The overall precision of sampling and analysis is determined by the analysis of collocated samples. These precision tests depend upon availa ble resources. Historically, we have performed collocated sampling of all samplers, of each t ype, that were deployed in the measurement program to establish equivalency and overall measurement precision prior to actual field sampling. Overall precision was within 20%.

Removal of Ozone and NOx Interferences. Since the carbonyl compound ambient measurement results are subject to various artif acts due to interaction with ozone, we use either a honeycomb O 3 denuder coated with sodium car bonate/sodium nitrite/glycerol mixture (method developed by Dr. Koutrakis from the Harvard School of Public Health), or a copper tube O 3 denuder coated with KI, as r ecommended by EPA Method TO-11a.

Since ambient NO 2 might react with 1,3 butadiene, we use a honeycomb NO 2 denuder coated with triethanolamine (a met hod also developed by Dr. Koutrakis).

1.2.4 Semi-Continuous Methods

For SPME fibers, blanks and calibration ch ecks were performed daily in order to determine the performance of the instrument and quality of the data. Fibers were kept in the injector port throughout the sample run in order to guarantee that the entire sample had been desorbed and to aid in conditioning of the fiber. In addition, fibers were

cleaned in a fiber conditioner at 300 ° C for at least one hour. The fiber conditioner

7consisted of a 304 SS container with 5 ports and a Watlow heater/tem perature controller capable of maintaining te mperatures in the 200-300 ° C range. A helium flow was maintained during fiber conditioning. One fiber per batch of 5 was checked for

cleanliness afte r conditioning.

Multi-level calibrations were done initially and throughoutthe summer field study. Liquid calibration was done by injecting 1 μ l of a liquid standard prepared in pentane with benzene, toluene, ethylbenzene, and xyl enes (BETX) at different concentrations (1, 5, 10, 20, 40, 50, and 100 ng/ μ l). Gas calibration was perf ormed with certificated

standards at different concentrations (20, 80, 100, 200, a nd 500 ppbv for each compound). Gas standards were stored in caniste rs and transferred to 1L Tedlar bags for static exposures of SPME fibers. Gas calib rations were performe d for different fiber exposure times.

SPME 75 μ m Carboxen-PDMS fibers were used w ith portable or manual samplers. When manual samplers were used, the tip of the ne edle was closed with a septum or Teflon tape. Fibers were kept after samp ling in sealed Mylar bags inside a cooler with dry ice. Storage stability tests showed that samples were preserved without any loss of analyte up to 5 hours (and reasonably preserved without subs tantial losses for as long as three days) when stored at dry ice temperature. In Atlanta, SPME samples were analyzed, on average, 10 hours after sampling, with a mi nimum of 1 hour and a maximum of 26 hours between sampling and analysis; 54% of the sa mples were analyzed before 10 hours of storage at dry ice temperature).

Detection limits for the BTEX com pounds were benzene 0.2 ppbv, toluene 0.3 ppbv, ethylbenzene 0.2 ppbv, m-p-xylene 0.2 ppbv, and o-xylene 0.2 ppbv. Precision was

evaluated in the laboratory by comparing repli cates and standards reproducibility. Two sets of replicates were placed side by side for 10 minutes inside solvent cabinets. Also, three replicates of 4 different standard c oncentrations were incl uded in the analysis. Replicates ranged from 2 to 15% error for a ll species. Accuracy was determined by daily calibration checks that varied within a rang e of 3-30% for benzene. When the relative accuracy did not fall within the 0-30% range for benzene, the GC was recalibrated.

The agreement between canis ter and SPME methods during the Atlanta field study was within 3-50%. For comparison, Li et al ., 2001, shows an agreement between SPME and a charcoal sampling method within a factor of two (100%), with a fiber repeatability of
20-30%, for 75 μ m Carboxen/PDMS.

1.2.5 Continuous Methods

The CO instruments were calibrated by standards purch ased from Scott Specialty and zero points were established by zero air purchas ed from Air Gas. Since both the T-15 and NDIR instruments have only zero and span controls, we used a span gas close to our expected concentrations, in this case 10 ppmv. For the T-15 CO instru ment, a cap is used

to flood the sensor with either zero or span gas. The cap is kept in place until a stable reading is obtained. For the NDIR, the gas was introduced through th e sample inlet line.

8Instruments were checked weekly and reca librated as needed. In general the CO instruments were very stable. The PID was calibrated with isobutene as a span gas as recommended by the manufacturer.

The MS-200 is calibrated by a standard containing pe ntane, isopentane, benzene, toluene, and o-xylene. This standard is mixed at DRI and tested against NIST traceable standards before being used in the field. Although the MS-200 is very stable once calibrated and essentially needs only zero checks before each run with the zero air cylinder carried with the instrument, calibration checks are made every few days to confirm instrument calibration. DRI purchased an Alpha Omega continuous HCHO instrument, the only commercially available instrument of its t ype, for use in the Atlanta field study. The instrument is, in theory, identical to the Battelle instrument that performed well in our Reno pilot study in February 2002. It uses the same reagents, the same reaction, and the same fluorescence basis for detection. However, there are engineering differences in the air/fluid interface, the pumping system, the mi xing of the reagents, the flow through the reactor, and the detectors. Although we have made a number changes to the instrument, it did not performed well in this study.

Precision evaluation of porta ble PID instruments. A series of tests were performed to evaluate the precision of the estimated VOC concentrations measured by the ppbRAE portable PID instruments. Although it is known that the concentrations recorded by these instruments vary with changes in the co mposition of the ambient VOC, making the accuracy of the instruments hard to quantif y, the precision can be evaluated by comparing the concentrations measured by two identical instruments sampling from the same source. This measure of precision is important if simultaneous measurements of VOC

concentration in two locati ons are to be compared.

In each test, both instruments were connected to the same in let using a stainless steel ‘T’ and tubing. After synchronizing th e internal clocks, data lo gging was started and a VOC source was introduced at varyi ng concentrations up to 10 ppm for a period of 20 to 45 minutes. The resulting 1-minute average co ncentrations from the two units were compared by linear regression to determine the level of correlation a nd bias. The test was repeated on 4 separate days over a 10-day pe riod. Zero checks and calibrations with 10 ppm isobutylene were made prior to the fi rst test and between the second and third.

In all tests, the correlation was high (R 2 = 0.97 or better) with a ze ro intercept. Slopes ranged from 0.79 to 1.45, indicating no consiste nt comparative bias. Since the average

concentration in most microenvironments is typically less than 100 ppb, we also evaluated the precision in this range. In two tests following the calibrations, the correlation was good (R 2 = 0.98)with the slope varying from 0.75 to 1.36. For two other tests, correlations were less (R 2 = 0.45 and 0.66) with slopes of 0.73 and 0.55. As earlier, the intercepts were zero. Overall, the test results suggest that instrument sensitivity varies, even with frequent calibration. Averag ed ambient data may have a precision of

about ± 35% or higher when comparing small numb ers of measurements or when at nearbackground concentrations.

9References:

Apel, E.C., J.G. Calvert and F.C. Fehsenfe ld (1994). “The Nonmethane Hydrocarbon Intercomparison Experiment ( NOMHICE): Tasks 1 and 2.” J. Geophys. Res ., 99: 16,651-16,664.

Apel, E.C., J.G. Calvert, T.M. Gilpin, F.C. Fehsenfeld, D.D. Parrish, W. A. Lonneman (1999). The Nonmethane Hydrocar bon Intercomparison Experiment (NOMHICE): Task 3. Journal of Geophysical Research , 104: 20,069-26,086

Fujita, E., Z. Lu, G. Harshfield, and B. Zielinska (1997). NARSTO-Northeast: Hydrocarbon and Carbonyl Measurement Audits for the 1995 Field Study. Final Report prepared for the Electric Power Research Institute, Palo Alto, CA, July

1997

Fujita, E., G. Harshfield, L. Sheetz (2003 ). Performance Audits and Laboratory Comparisons for SCOS97-NARSTO Measur ements of Speciated Volatile Organic Compounds. Atmos. Environ. 37, Supplement No. 2, S135-S147.

Li, K.; A. Santilli, M.; Goldthorp, S.; Whiticar , P.; and Lambert, M. F.; Solvent vapour monitoring in work space by solid phase mi croextraction. J. Hazard. Mater. 2001, 83, 83-91.

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