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 External Performance Audits.............................. 4 

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

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

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

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1.1 Measurement Data Quality Objectives 

Data quality objectives, including measures of accuracy, precision, detection limit, time 

resolution, and known interferences, are summarized 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 instrument responds to rapid changes in concentration on a longer

time frame. This may occur since CO must diffuse 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 (H2 emissions) that were used to power instruments inside the van that showed 

up as a rising signal from the T-15 CO unit when the vehicle windows were closed. Under 

high-ventilation conditions in the vehicle or outdoors, no such interferences were observed. 

At high humidity near saturation we did observe high T-15 CO readings 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 distribution 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 humidity 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 the PID readings increased inside the vehicle cabin under low 

ventilation conditions with no change in any other measurement. This may be a response to 

off-gassing of plasticizers in cabin materials that are mostly phthalate esters. 
Instrument Accuracy Precision Det Lim Time Res. Artifacts Specifications 

CO-T15 +/- 1 ppm +/-0.05 ppm 0.1 ppm 10 sec H2, very high humidity Electrochemical Detector 

CO-NDIR 0.50% +/-0.02 ppm 0.04 ppm 1 sec None NDIR 

PID NA 10% 1 ppb 1 sec Plasticizers, very high 

humidity 

10.6 eV lamp PID 

HCHO (a) <15% <5% 1 ppb 1 min None Hantzch rxn/fluorescence 

MS-200 <8% <5% 1-3 ppbv 1 min None Mass spectrometer 

SPME 3-50% 2-15% 0.2 ppbv variable None GC/FID & PID 

Canister <5% <3% 0.05 ppbC variable None GC/FID 

DNPH <5% <3% 0.1 ppbv variable None HPLC/Photodiode array 

(a) HCHO performance parameters based on Battelle instrument performance in the Reno pilot study. Table H-1. Measurement data quality 
1.2 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 microenvironment (ME) sampling 

sites in Atlanta, GA was conducted during February 23-27, 2004, by the independent 

auditor, Christine Sexsmith, Sexsmith Consulting 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 that could affect the outcome of the study. 

This audit was followed up by the DRI Organic 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 Experiment, 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 components 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 the 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 analysis of ambient air samples in the ppbv and 

pptv concentration ranges, respectively. The 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 OAL participated in the NARSTO-Northeast 

hydrocarbon intercomparison study, involving the analysis of two ambient air samples by 

participating laboratories. Participants included Biospheric Research Corporation (BRC), 

State University of New York at Albany (SUNYA), 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 (Fujita 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 biogenic hydrocarbons (Fujita et al., 2003). 

Again, the agreement between DRI values and nominal values were within the acceptable 

range (± 10%). 

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During 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 intercomparison studies, organized in 1999-

2002, involved the analysis of ambient air samples 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 Atmospheric 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 signs for the package and returns with it to the 

laboratory where he opens it. The samples are logged into the Organic Analytical 

Laboratory’s receiving logbook, the chain-of-custody form is updated, and the samples 

are stored appropriately for the sample type. 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 review will be initiated to 

determine if the damage compromised the integrity and/or quality of the sample. 

Samples are stored in the Organic Analytical Laboratory, inside the DRI Northern 

Nevada Science Center (2215 Raggio Parkway, 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 identification number (sample number) is recorded both in 

the written log book for each instrument and in the Laboratory Information Management 

System (LIMS) file created for that analysis. The sample number serves as a tracking 

number, as does the LIMS file itself. Canisters will not be cleaned until each sample has 

passed initial validation. 

Sampling Systems. The sampling equipment is leak-tested 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 certified for cleanliness prior to sampling. 

Sampling Media Preparation 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 solid adsorbent is cleaned by Soxhlet extraction 

with hexane/acetone mixture (4/1 v/v) overnight, and dried in a vacuum oven at ~ 80 °C. 

The dry Tenax is packed into Pyrex glass tubes together with Carbotrap and Carbosieve 

and thermally conditioned for four hours in an oven at 300 °C under nitrogen purge. 

Approximately 10% of the precleaned cartridges are tested by GC/FID prior to sampling. 

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After cleaning, the cartridges are sealed using clean Swagelok caps (brass) with 

graphite/Vespel ferrules, placed in metal containers with activated charcoal, and kept in a 

clean environment at room temperature until use. 

The DNPH impregnated SiO2 cartridges are purchased from Waters, Inc., in batches of 

25. One cartridge from each batch is tested for background contamination by the High 

Performance Liquid Chromatography (HPLC) method prior to sampling. 

The canisters are cleaned by repeated evacuation and pressurization with humidified zero 

air, as described in the EPA document "Technical Assistance Document for Sampling 

and Analysis of Ozone Precursors" (October 1991, EPA/600-8-91/215). Six sequential 

cycles of evacuation to ~ 0.5 torr absolute pressure and pressurization 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 are 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 chromatograph/flame ionization 

detection (GC/FID) method. The canisters are considered clean if the total non-methane 

organic compound (NMOC) concentration is less than 10 ppbC, and the concentration of 

any individual targeted compound is less than 0.2 ppbv. Canister cleaning and 

certification are described 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 cleanliness and are certified clean (less than 

0.1 ppbv of targeted compound). Quality control in the laboratory includes instrument 

calibration for each batch of samples analyzed, replicates of standards, and reanalysis of 

approximately 10% of the samples for estimation of analytical precision, which 

historically has been better than 6%. In past programs, field blanks have come in at 0.5-1 

ppb levels, based on the air volume of the samples. Coefficients of variation (CV) 

calculated from observed differences between 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 speciation, we use NIST 

SRM 1805, which consists of 254 ppb of benzene in nitrogen. 

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

the best sources available — are used for the GC/FID and GC/MSD. The current 

inventory of reference samples at DRI's Organic Analytical Laboratory 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 systems 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 

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reproducibility 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 regression. The calibration must generate a 

correlation co-efficient (R2

) of 0.99 to be acceptable. 

During the course of analysis, calibration standards 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 Precision of Sampling and Analysis. Accuracy involves the 

closeness of a measurement to a reference value and reflects elements 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 compound in the NIST (or traceable) standard. 

If the percent relative accuracy does not fall below 20%, the instrument 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 available resources. Historically, we have performed 

collocated sampling of all samplers, of each type, 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 artifacts due to interaction with ozone, we use 

either a honeycomb O3 denuder coated with sodium carbonate/sodium nitrite/glycerol 

mixture (method developed by Dr. Koutrakis from the Harvard School of Public Health), 

or a copper tube O3 denuder coated with KI, as recommended by EPA Method TO-11a. 

Since ambient NO2 might react with 1,3 butadiene, we use a honeycomb NO2 denuder 

coated with triethanolamine (a method also developed by Dr. Koutrakis). 

1.2.4 Semi-Continuous Methods 

For SPME fibers, blanks and calibration checks 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 

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consisted of a 304 SS container with 5 ports and a Watlow heater/temperature controller 

capable of maintaining temperatures in the 200-300 °C range. A helium flow was 

maintained during fiber conditioning. One fiber per batch of 5 was checked for 

cleanliness after conditioning. 

Multi-level calibrations were done initially and throughout the summer field study. 

Liquid calibration was done by injecting 1 μl of a liquid standard prepared in pentane 

with benzene, toluene, ethylbenzene, and xylenes (BETX) at different concentrations (1, 

5, 10, 20, 40, 50, and 100 ng/μl). Gas calibration was performed with certificated 

standards at different concentrations (20, 80, 100, 200, and 500 ppbv for each 

compound). Gas standards were stored in canisters and transferred to 1L Tedlar bags for 

static exposures of SPME fibers. Gas calibrations were performed for different fiber 

exposure times. 

SPME 75 μm Carboxen-PDMS fibers were used with portable or manual samplers. When 

manual samplers were used, the tip of the needle was closed with a septum or Teflon 

tape. Fibers were kept after sampling 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 substantial 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 minimum of 1 hour and a maximum of 26 hours 

between sampling and analysis; 54% of the samples were analyzed before 10 hours of 

storage at dry ice temperature). 

Detection limits for the BTEX compounds 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 replicates 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 concentrations were included in the analysis. 

Replicates ranged from 2 to 15% error for all species. Accuracy was determined by daily 

calibration checks that varied within a range 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 canister 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 μm Carboxen/PDMS. 

1.2.5 Continuous Methods 

The CO instruments were calibrated by standards purchased from Scott Specialty and 

zero points were established by zero air purchased 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 instrument, 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 the sample inlet line. 

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Instruments were checked weekly and recalibrated 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 pentane, 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 type, 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 mixing 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 portable 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 composition of the ambient VOC, making the 

accuracy of the instruments hard to quantify, 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 locations are to be compared. 

In each test, both instruments were connected to the same inlet using a stainless steel ‘T’ 

and tubing. After synchronizing the internal clocks, data logging was started and a VOC 

source was introduced at varying concentrations up to 10 ppm for a period of 20 to 45 

minutes. The resulting 1-minute average concentrations from the two units were 

compared by linear regression to determine the level of correlation and bias. The test was 

repeated on 4 separate days over a 10-day period. Zero checks and calibrations with 10 

ppm isobutylene were made prior to the first test and between the second and third. 

In all tests, the correlation was high (R2 = 0.97 or better) with a zero intercept. Slopes 

ranged from 0.79 to 1.45, indicating no consistent 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 (R2

 = 0.98)with the slope varying from 0.75 to 1.36. For two other 

tests, correlations were less (R2 = 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. Averaged ambient data may have a precision of 

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

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References: 

Apel, E.C., J.G. Calvert and F.C. Fehsenfeld (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 Hydrocarbon 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 Measurements 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 microextraction. J. Hazard. Mater. 2001, 

83, 83-91. 

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