# Performance Specification XX: Performance Specifications for a Quantitative Reference Aerosol Generator

June 9, 2005



# DRAFT

Submitted to: The Environmental Protection Agency Research Triangle Park, NC

Prepared by: Cooper Environmental Services, LLC 10180 SW Nimbus Blvd Suite J6 Portland, Oregon 97223

# Performance Specification XX: Performance Specifications for a Quantitative Reference Aerosol Generator

June 9, 2005



# DRAFT

Submitted to: The Environmental Protection Agency Research Triangle Park, NC

Prepared by: C. A. Yanca, D.C. Barth, J.A. Cooper, B.E. Johnsen, M.P. Nakanishi, K.A. Petterson,

Cooper Environmental Services 10180 SW Nimbus Blvd Suite J6 Portland, Oregon 97223

# Performance Specification XX: Performance Specifications for a Quantitative Reference Aerosol Generator

Prepared by:___________________________________ Date:_________ Catherine A. Yanca, Environmental Scientist Reviewed by: ___________________________________ Date:_________ Krag A. Petterson, Environmental Scientist Reviewed by: ___________________________________ Date:_________ Bruce E. Johnson, QA Manger Approved by: ___________________________________ Date:________ John A. Cooper, DirectorPerformance Specifications for a QRAG: V1.0 Page i of iii 

### Executive Summary This performance specification de scribes the criteria that a Qu antitative Reference Aerosol Generator (QRAG) must meet to be consid ered valid for EPA compliance and/or other regulatory applications. A QR AG should be capable of generating an aerosol containing an analyte whose concentration is traceable to the National Institute of Standards and Technology (NIST) or other equiva lent reference. It quantitatively combines solids and/or liquids with a carrier gas to form a stab le flow of aerosol with known reference concentration. Before it can be used with regulatory applications, it must be certified according to the requirements of PS-XX. To be certified, you are required to do the following on an annual basis:

• You must ensure that all key components of the QRAG and the analyte standard are process traceable to NIST or ot her equivalent reference.

• You must test the stability of the QRAG, which is measured by the percent relative standard deviation (PRSD) over a 12-hour te st period. The PRSD must be less than 5%.

• You must determine the concentration of the QRAG’s generated aerosol with a reference method that measures the concen tration of the emissions over the proposed applicable concentration range. The ge nerated aerosol conc entration and the reference method measured concentration must have a correlation coefficient ( r) greater than 0.95, a slope e qual to 1.00 ± 0.15, and an intercept less than 1/10 th of the applicable regulated concentration.Performance Specifications for a QRAG: V1.0 Page ii of iii 

### Table of Contents Executive Summary.............................................................................................................. ... i List of Symbols ................................................................................................................ .......iii 1.0 Using PS-XX................................................................................................................ ... 1 1.1 What is the purpose and applicability of Performance Specification XX? ............... 1 1.2 What is PS-XX?......................................................................................................... 1 1.3 What special definiti ons apply to PS-XX? ................................................................ 2 2.0 Interferences, Safety, a nd Equipment Requirements................................................. 3 2.1 Are there any potential in terferences for my QRAG? ............................................... 3 2.2 What do I need to know to ensure the safety of persons using PS-XX? ................... 3 2.3 What equipment and supplies do I need? .................................................................. 3 2.4 What reagents and standards do I need?.................................................................... 4 3.0 Performance Evaluation and Documentation Procedures......................................... 5 3.1 What pre-test performance evaluation procedures do I follow?................................ 5 3.2 How do I monitor and document my QRAG’s performance?................................... 5 3.3 What concentration range must my linearity tests span?........................................... 5 4.0 Performance Criteria and Calculations....................................................................... 6 4.1 What performance criteria must my QRAG meet? ................................................... 6 4.2 What calculations and data analyses are required?.................................................... 6 5.0 Other Requirements and Information......................................................................... 9 5.1 What quality control and assurance procedures are required by PS-XX?................. 9 5.2 What standardization procedures must I use?............................................................ 9 5.3 What pollution prevention procedures must I follow? .............................................. 9 5.4 What waste management pro cedures are required by PS-XX? ................................. 9 5.5 What references apply to PS-XX?............................................................................. 9Performance Specifications for a QRAG: V1.0 Page iii of iii 

### List of Symbols

0 b = The y intercept

1 b = Slope PRSD = Percent relative standard de viation (given as a percent)

r = The correlation coefficient SD = Standard deviation

x = Data set for the QRAG generated aerosol concentrations

i x = Value of the i th data point for variable x

x = Average of the values in data set x y = Data set for the reference method aerosol concentrations

i y = Value of the i th data point for variable y
y = Average of the set of values of variable yPerformance Specifications for a QRAG: V1.0 Page 1 of 9 

### 1.0 Using PS-XX
1.1 What is the purpose and applicability of Performance Specification XX? The purpose of Performance Specification XX (PS-XX) is to establish the initial performance requirements for evaluating the acceptability of a quantitative reference aerosol generator (QRAG) prior to using the aerosol it genera tes as a reference for compliance or other regulatory applications. Such applications ma y include, (1) instrument, method or procedure calibration, (2) evaluation or certification for in itial acceptance, and (3) continuing quality assurance audits or other applications.
1.1.1 Application PS-XX applies to you if you will be using a QRAG to validate an instrument, method or procedure that will be used in a co mpliance or other regulatory application.
1.1.2 Compliance You must comply with PS-XX prior to us ing any equipment that depends on the QRAG for calibration and/or validation.
1.1.3 Other Data All components of the QRAG must be certified as NIST-traceable or equivalent; you must obtain the necessary documents of NIST or equivalent certif ication before using the QRAG.
1.2 What is PS-XX? This performance specification describes the criteria that a QRAG must meet to be considered valid for use in a compliance or othe r regulatory application. It should be capable of generating an aerosol of known analyte concentration. A QRAG combines solids and/or liquids with a carrier gas to form an aerosol stream with a NIST-tra ceable or equivalent analyte concentration that is stable over extended periods.
1.2.1 Basic Requirements

You must have your QRAG certified according to the requirements of PS-XX before its aerosol emissions can be used in a co mpliance or other regulatory application. To be certified, you are required to do th e following on an annual basis:

• You must ensure that all key compon ents of the QRAG and standards are process traceable to NI ST (Subsection 4.1.1).

• You must test the stability of the QR AG, which is measured by the percent relative standard deviation (PRSD) of a 12-hour test run. The PRSD must be less than 5% (Subsection 4.1.2).Performance Specifications for a QRAG: V1.0 Page 2 of 9 • You must determine the concentration of the QRAG’s generated aerosol with a reference method over a range of concentrations that exceeds the range over which it will be used (Subsection 3.3). The generated aerosol concentration and the reference method measured c oncentration must have a correlation coefficient ( r) greater than 0.95, a slope equa l to 1.00 ± 0.15, and an intercept less than 1/10 th of the applicable regulated or compliance concentration (Subsection 4.1.3).
1.3 What special definitions apply to PS-XX? Aerosol: A suspension of solids and/ or liquids in a gas. Analyte: A species (element, metal, etc.) of interest in an analytical method. Analytically NIST Traceable Parameter: A parameter whose value is traceable to NIST through a measurement that is NIST traceable 1

. Applicable Concentration Range: The range of concentrations over which a QRAG must be able to produce an aerosol of NIST-traceable or equivalent analyte concentration to be used for a given application. Certified Concentration Range: The range of concentrations for which the QRAG is certified. Key Component: A piece of equipment or instrument that measures any parameter used to determine the generated aerosol concentration. Linearity: The degree to which two parameters are linearly related as determined by the value of the slope and correlation coefficien t of a least squares regression analysis. NIST: The National Institute of Standa rds and Technology, Gaithersburg, MD. Particulate: A particle of solid or liquid matter. Process NIST Traceable : A parameter whose value is traceable to NIST through a procedure, the steps of which are each NIST traceable 1

. Quantitative Reference Aerosol Generator (QRAG): An aerosol generator which emits an aerosol of known analyte concentration that is NIST or equivalent traceable. Sampling System: A collection of integrated component s designed to collect a portion of an aerosol that accurately represents an analyte concentration. Stability: Percent relative standard de viation of a value measured over an extended period of time. Standard: Something established by authority, cust om, or agreement for use as a rule or basis for comparison in measurement.Performance Specifications for a QRAG: V1.0 Page 3 of 9 Standard deviation : A parameter that indicates the way in which a probability function or a probability density function is cente red around its mean and that is equal to the square root of the moment in which the deviation from the mean is squared. Traceability: A property of a result of a measuremen t or the value of a standard whereby it can be related to stated references, usually na tional or international standards, through an unbroken chain of comparisons al l having stated uncertainties 2

. Traceability to NIST: A documented procedure by which a measured response is related to a standard with an accuracy defined by and certified by the National Institute of Standards Technology (NIST). Transport/Interface Component: That portion of a test arrangement that connects a QRAG to the point where the aerosol will be evaluated. Uncertainty: An indication of the degree of reli ability of a value usually expressed statistically (probability) as a multiple of the standard deviation of a set of measurements. Unless otherwise stated, the uncertainty in a mean value of a series of measurements will be the standard deviation. In the case of values based on calculations, th e uncertainty in the value is equal to the propagated uncertainty ba sed on the uncertainties in the parameters used in the calculations.



### 2.0 Interferences, Safety, and Equipment Requirements
2.1 Are there any potential in terferences for my QRAG? There are no interferences in this procedure.
2.2 What do I need to know to ensure the safety of persons using PS-XX? People using PS-XX procedures may be exposed to hazardous materials, operations, and equipment. This performance specification ma y not address all of the safety problems associated with its use. It is your responsibil ity to establish appropria te safety and health practices and determine the appl icability of regulatory limitati ons prior to performing these procedures. You must consu lt your QRAG manual and adhere to its specific safety precautions.
2.3 What equipment and supplies do I need? Your QRAG must be able to continuously emit an aerosol of predictable concentration. You should select a QRAG and a transport system that is appropriate for your specific application. The PS-XX requires that you include, at minimum, the equipment described in subsections 2.3.1-2.3.2.Performance Specifications for a QRAG: V1.0 Page 4 of 9 2.3.1 The QRAG System A QRAG consists of the follo wing five major components:

• Analyte Control: This component quantitatively transports the analyte and/or analyte containing carrier to the point of aerosolization, controls the conditions within which it is delivered, and determines the rate at which it is delivered.

• Gas Control: This component quan titatively transports the aerosolizing and/or carrier gas to the point of aerosolization, controls the conditions within which it is delivered, and determines the rate at which it is delivered

• Aerosolization: This component combines the analyte and/or analyte carrier with the aerosolizing gas to form a part iculate and gas mixture or aerosol under quantitatively controlled conditions.

• Particulate Size Separator: This component separates small particulates more likely to have high transport efficiency from larger particles. The separator quantitatively recycles the large particul ates that are removed from the aerosol and controls the conditions under wh ich this process takes place.

• Total Flow Control: This component controls the to tal flow rate of the aerosol emerging from the particulate size se parator component and controls the conditions under which the final QRAG aerosol is emitted.
2.3.2 Reference Measurement System For the purpose of certifying the QRAG emissions, you must use either an EPA method or an approved alternative or c onditional method. It must be capable of measuring the concentration of analyte in the QRAG emissions over the certified concentration range and test period with an accuracy and precision adequate to evaluate the accuracy and precision of the candidate QRAG.
2.4 What reagents and standards do I need?
2.4.1 Analyte Standard The QRAG generates an aerosol with NIST-t raceable or equivalent accuracy based on the accuracy of the analyte-containing sta ndard. An adequate supply of standard required by a test plan should be prepared prior to testing. The primary requirements of these standards are that (1) the accuracy of the analyte concentrations be NISTtraceable (2) the standards be stable over the period of their use.
2.4.2 Gas

You must select a gas to use for creating th e analyte aerosol. The chosen gas must not react with the analyte or with any com ponent in the aerosol that would generate either analyte or analyte interferants.Performance Specifications for a QRAG: V1.0 Page 5 of 9 

### 3.0 Performance Evaluation and Documentation Procedures
3.1 What pre-test performance evalu ation procedures do I follow?
3.1.1 Installation

You must install your QRAG according to the manufacturer’s written instructions and in a manner that allots an appropriate am ount of space for the QRAG to be connected to the reference method measurement system.
3.1.2 Operation

You must operate yourQRAG according to the manufact urer’s written instructions and specifications.
3.2 How do I monitor and document my QRAG’s performance? You must monitor you QRAG’s performance accord ing to the instructions written by the manufacturer, with special atte ntion given to safety precautio ns. You must also document the QRAG’s performance in accordance with the manufacturer’s instructions.
3.3 What concentration range must my linearity tests span? To satisfy the linearity criteria, your tests must span the full applicable concentration range by meeting the following requirements:

• 25% of the data points must be within th e upper 66% of the applicable concentration range

• 35% of the data points must be between 33% and 66% of the applicable concentration range.

• 15% of the data points must be within bounds of the lower 33% of the applicable concentration range You must run linearity tests at a minimum of 4 different c oncentrations, including a blank. You must ensure that aerosol concentrations requ ired for testing are within (1) the detectable concentration range of the equipment to be calibrated or evaluate d and (2) the QRAG’s minimum and maximum limits as de termined by the manufacturer. M inimum of 12 data pointsPerformance Specifications for a QRAG: V1.0 Page 6 of 9 

### 4.0 Performance Criteria and Calculations
4.1 What performance criteria must my QRAG meet? Your QRAG must meet the following performa nce criteria to be certified as a quantitative reference aerosol generator. You must demonstrate that your QRAG meets these criteria on an annual basis at a minimum.
4.1.1 NIST-Traceability

You must ensure that the generated aero sol concentration of the QRAG is process traceable to NIST or equivalent. This process traceability is established by confirming the traceability of the QRAG’s parameters 1,2 . You must obtain documentation demonstrating that the QRAG’ s key components have NIST-traceable or equivalent certification and that the certification is current. Bu t changes, bumps needs to be validated before use. Dan is c oncerned that in this early stages of use, there is significant room for developing l eaks and other problems between when it was last certified and when it might be used. He feels for a while we need to demonstrate that it is working prior to its use. This isn’t too much of a problem if we use the XFM to certify it prior to use. E. G. install the QRAG and start generating an aerosol. Then collect a XFM sample or seri es of samples and fedx them back to the lab for analysis.
4.1.2 Stability Criteria

You must determine the percent relative st andard deviation (PRSD) of the analyte concentration in the QRAG aerosol over a 12- hour tests period. The PRSD must be less than 5% (see also Section 4.2.3). Specify minimum # of measurements need instructions on how to do the tests a nd how many data points do we need.
4.1.3 Linearity Criteria

You must demonstrate that a linear relationship exists between the QRAG generated aerosol analyte concentration and the reference method meas ured concentration. This relationship must meet the following criteria (see also Section 4.2.4):

• The correlation coefficient ( r) must be greater than 0.95.

• The slope must be equal to 1.00 ± 0.15%.

• The intercept must be less than 1/10 th the applicable compliance or other regulated concentration. Dan was somewhat confused with this section and how it related to bias, etc.
4.2 What calculations and da ta analyses are required?
4.2.1 Arithmetic Mean
Calculate the arithmetic mean of a data set as follows.Performance Specifications for a QRAG: V1.0 Page 7 of 9 

# ∑ = i x n 1 x Equation 1

Where:

x = Arithmetic mean

n = Number of data points

x i = Value of each data point
4.2.2 Standard Deviation

1 n ) x x ( SD 2 i

− ∑

− = Equation 2

Where: SD = Standard deviation

x = Arithmetic mean

n = Number of data points

x i = Value of each data point
4.2.3 Stability To measure the stability of your QRAG, you must conduct a 12-hour test run using a reference or other EPA approved method to measure the analyte c oncentration in the emitted aerosol. You must take a minimum of 6 measurements during this time period. Calculate the PRSD using the following equation:



### % 100 * x SD PRSD ⎟ ⎠ ⎞ ⎜ ⎝ ⎛

= Equation 3

Where: PRSD = Percent relative standard deviation SD = Standard deviation

x = Arithmetic mean
4.2.4 Linearity To determine the linearity of your QRAG, you must measure the c oncentration of its aerosol emissions with the reference or other EPA approved method over the applicable concentration range (Section 3.3). You must test the QRAG at the8 following aerosol concentrations at a minimum: one concentration must be at or above the upper end of the concentr ation range, two concentratio ns must be between this concentration and a blank, and one test mu st be a blank. You must calculate the QRAG’s generated aerosol concentration usi ng equations defined by the manufacturer. You must determine the slope, correlation co efficient, and the intercept using a least squares linear regression of the aerosol con centration as measured by the reference or other EPA approved method and the QRAG re ference aerosol analyte concentration. The relationship must be in the form of a straight line as follows:

0 1 b x b y +

= Equation 4
Where: y = reference method measured aerosol concentrations

x = predicted generated aerosol concentrations

0 b = y intercept

1 b = slope To calculate the slope, b 1 : 

## ( ) ( ) ( ) 

## ∑ ∑

− − − = 2 i 1 i 1 x x y y x x b Equation 5

Where:

i x = value of the i th data point for data set x

x = average of the values in data set x

i y = value of the i th data point for set of data y
y = average of the values in data set y To calculate the intercept, b 0:
x b y b 1

0 −

= Equation 6 In addition to determining the slope and in tercept of the linear relationship, you must calculate the correlation coefficient, r , according to the following equation: 

## ( ) ( ) ( ) ( ) 

## ∑ ∑ ∑

− − − − = y y x x y y x x r
1 i 1 i Equation 7Performance Specifications for a QRAG: V1.0 Page 9 of 9 4.2.5 Uncertainty It is also recommended that you report the uncertainty of the QRAG’s generated aerosol concentration. This uncertainty should be de termined using standard propagation of error techniques 3 relevant to the parameters used to ca lculate aerosol analyt e concentration. The uncertainty values for the parameters are those listed as certified uncertainties by the manufacturers of the key components and/or NI ST or equivalent. This procedure should be consistent with those used by NIST 4,5 ,6

. How is this used? Is it confusing? A distinction needs to be made between propagated uncertainty, measured error and how each is used and for example type of illustrations. Do we need a sample calculation or a discussion of how this uncertainty is calcula ted? Should we make the analogy with the uncertainty associated with a cal gas?



### 5.0 Other Requirements and Information
5.1 What quality control and assurance procedures are required by PS-XX? You must ensure that the QRAG components are NIST-traceable after installation and before using the generated reference aerosol in a complia nce or other regulated application. You must obtain valid NIST certifications for all key components and standards as well as document all equipment calibrations with NIST standards. You must also ensure that the QRAG is functioning according the manufacturer’s spec ifications prior to aerosol generation
5.2 What standardization procedures must I use? The QRAG generated aerosol anal yte concentration is based on parameters such as solution concentration, gas flow, rate of solution mass loss, and rate of vapor loss. You must document and demonstrate that each of the parameters affecting the final concentration of aerosol emissions is process traceable to a NIST standard and certification of the standard is current.
5.3 What pollution prevention procedures must I follow? The excess aerosol generated by the QRAG should be trapped in a filt er and disposed of according to appropriate regulations. Unused hazardous supplies should also be disposed of according to regulation.
5.4 What waste management procedur es are required by PS-XX? Any hazardous materials used should be handled accord ing to their Material Safety Data Sheets.
5.5 What references apply to PS-XX? 1. Scott Specialty Gases. Scott Gas Mixt ures Data: Gas and Li quid Mixture Basics. Plumsteadville, PA: Scott Specialty Gases; 2004.Performance Specifications for a QRAG: V1.0 Page 10 of 9 2. Bureau International des Poids et Mesure s, International Elec trotechnical Commission, International Federation of Clinical Chemis try and Laboratory Medicine, International Organization for Standardizati on, International Uni on of Pure and Applied Chemistry International Union of Pure and Applied P hysics, International Organization of Legal Metrology [BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML]. International Vocabulary of Basic and General Terms in Metrology (VIM). Geneva, Switzerland: BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML; 1993. Av ailable from: ISO, Geneva, Switzerland; ISBN 92-67-01075-1. 3. McClave, J.T., F.H. Dietrich, II, and T. Si ncich. Statistics, 7th Ed. Upper Saddle River, NJ: Prentice Hall; 1997. 4. Scace, G.E. and J.T. Hodges. Uncertainty of the NIST Low Frost-Point Humidity Generator. Gaithersburg, MD: National Inst itute of Standards and Technology; 2004.
5. American National Standards Institute/Na tional Conference of Standards Laboratories [ANSI/NCSL]

. U.S. Guide to the Expression of Uncertainty in Measurement

. Washington, D.C: ANSI/NCSL; 1997. Available from: NCSL In ternational, Washington, D.C; Z540-2-1996. 6. Taylor, B.N. and C.E. Kuyatt. Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results. Gaithersbur g, MD: National Institute of Standards and Technology [NIST]; 1994. Available from : NIST, Gaithersburg, MD; TN 1297.