ThermoFisher The wortd leader

SCIENTIFIC In selVing science

March 15,2011 

Anne M. Northup 

Commissioner 

U.S. Consumer Product Safety Commission 

4330 East West Highway 

Bethesda, MD 20814 

Dear Commissioner Northup: 

Before I address your questions, let me first say that we very much appreciated the opportunity to 

testify before the Commission, and, at the same time, feel privileged for being called upon to 

share our expertise. 

Question 1. 

Please explain the scope o.[testing that can be performed with a single trigger pull 0.[a 

hand held XRF machine. In particular, please describe: (1) the size ofthe area that can 

be tested; and (2) whether and to what extent a single trigger pull can test the lead 

content ofmultiple substances, such as two adjacent surface coatings with different 

characteristics (i.e., color, materials, etc.), a multilayered item (i.e., one or more coatings 

on a substrate or multilayered substrates), or two adjacent parts ofa composite object, 

each 0.[ which are comprised ofa different material. 

The first question relates to the way a handheld x-ray fluorescence (HHXRF) instrument operates. 

To clarify some terms, let me note here that we define a "single trigger pull" as the execution of a 

single, complete measurement cycle culminating in a display of analytical results. The XRF 

analyzer operates on the principle of x-ray fluorescence, meaning that its built-in source of x-rays 

excites the characteristic x-rays of chemical clements present in the sample. Thcsc, in turn, arc 

detected and converted to an electric signal by a detector, typically a "silicon drift detector." The 

electric signal carries information about the type and the intensity of the detected characteristic xrays, which is then converted by electronics and analytical software into concentrations of 

chemical elements that make up the sample. 

For this process to work consistently from one sample to another, the sample must be "presented" 

to the instrument in a repeatable manner, or, as we call it, at a fixed geometry of measurement. 

This is accomplished by designing the "nose" of the instrument with a t1at plate and a defined 

aperture in it against which the sample is placed for measurement. It is through this aperture that 

the instrument excites and measures the characteristic x-rays of clements present in the sample. 

Therefore, the area that can be tested by a handheld XRF analyzer is typically delineated by the 

size and shape of the aperture. In the case of Thermo Scientific Niton handheld XRF analyzers, 

the aperture is a circle of approximately 9 mm in diameter, which is smaller than its physical 

diameter of 10.8 mm. This difference is because the beam from the x -ray tube is deliberately 

collimated to a slightly smaller diameter than that of the aperture so that during testing it only 

Thermo Nilan Analyzers LLC 900 Middlesex Tumpike BW.,.;ca, MA 01821 +1 978670·7460 ph WlNw,thennoscienlific,comfnlton 


Bu;ld;ng 8 USA +1 978215-6121 fa. 

ThermoFisher 

SCIENTIFIC 

penetrates and excites the sample and not a plate supporting it. Thus the area being tested is 

slightly less than 1cm2

. 

The instrument itself is calibrated for quantitative analysis under a fundamental assumption of a 

homogeneous, infinitely thick uniform sample. It is, therefore, critical to make every effort thal 

the portion of the object targeted for analysis is homogeneous and completely covers the 

measuring aperture. Only in this way will the results be representative of the actual 

concentrations of elements. Real objects, as we know, are made of many different substances. 

When testing them we should make sure that only one substance is placed within the instrument 

measuring aperture because the characteristic x-rays of a given element are the same regardless of 

where the element is located. In other words, the characteristic x-rays of lead within paint are 

indistinguishable from the characteristic x-rays oflead embedded in a substrate over which the 

paint is applied. Therefore, we can see that if the substances are not tested separately, then the 

results might be inaccurate, representing some kind of an average which would not refleet the true 

concentration ofthe element in any of the substances. 

For example, let us assume we have a toy truck made ofmetal and various colored plastic parts 

and that our task is to test this toy for lead content. In such a case, we should test separately each 

individually distinguishable material/part by selecting a test area on each that is large enough to 

cover the measuring aperture of the instrument, Le., we must not test an area which would contain 

different substances side by side. In some instances this may prove difficult when, for example, 

we need to measure the lead content of a small metallic part such as a rivet holding together two 

plastic components. The size of the rivet is much smaller than the measuring aperture of the 

instrument. Consequently, when attempting to test the rivet, we would not be able to avoid 

interference from x-rays generated in the plastic parts. The way around this is to collimate the 

exciting beam from the x-ray tube to a much smaller diameter, thereby generating x-rays only in 

the rivet and not in the parts it holds together. Some handheld analyzers are equipped with an 

additional, small diameter collimator that can be selected by the user when necessary. Thermo 

Scientific Niton XRF analyzers are equipped with this option, called a "small spot," which allows 

analysis of objects as small as 3 mm in diameter. By using the "small spot" collimator separately 

on the rivet and on the plastics, the user can analyze both materials for lead and obtain 

meaningful results. 

Similar requirements apply when analyzing layered materials. That is, both the coating and 

substrate must be tested separately for lead or any other element. For example, if the coating is 

applied as paint over a substrate, first the paint layer should be tested for lead, followed by testing 

the substrate for lead, but on its unpainted section. Ifthe substrate does not contain lead, then the 

test performed on the painted fragment of the substrate will reflect the correct amount of lead in 

paint. On the other hand, if the substrate does contain lead, then the measurement oflead in paint 

obtained on the painted section ofsubstrate will most likely be inflated. If the paint does not 

contain lead but the substrate does, the measurement of lead in the substrate could show a result 

that is lower than the actual concentration of lead in the substmte because sil:,'Oai (x-rays) from 

lead in the substrate may be attenuated by the layer of paint. Small painted surfaces, such as an 

eye of a doll or a toy duck, should be tested using a collimated x-ray beam such as the "smaIJ 

spot" mentioned earlier. 

W\NW thermo.ccm/rilton 
ThermoFisher 

SCIENTIFIC 

In sununary, in order for measurements to be as meaningful as possible, we should always make 

sure that each test, i.e., each "single trigger pull," is performed on a single type of materiaL Even 

the different colors of the same material (as often is the case with plastics) should be tested 

individually. 

Question 2. 

Does the cost ofa single HHXRF trigger pull vary depending upon the number of 

elements analyzed during the single measurement? 

The cost ofa single trigger pull is the same regardless ofthe number of elements analyzed. With 

a single trigger pull, the analyzer can measure many elements, in practice anywhere from I to 25 

or even 30. This is because the XRF method, while totally nondestructive, is simultaneously 

multi-elemental. This means that in a single measurement cycle, that is a "single trigger pull," the 

instrument acquires an x-ray spectrum that contains information from many, if not all, elements, 

in the tested object. This is both a curse and a blessing. A blessing because in one "shot" we can 

have complete information about the tested material. A curse because the elements present in the 

tested object mutually affect the others' x-rays, and therefore make their interpretation more 

difficult. In other words, to analyze for even one element, we need to measure other elements 

present in the material as well. For example, when used to measure lead in paint, a ThemlO 

Scientific Niton HHXRF analyzer reports the results for lead only, but it monitors signals from 

more than 10 other elements that may potentially interfere with the lead signaL 

I hope my explanations have helped to shed some light on the issues raised in your questions. 

Should you need clarification or have other questions, please do not hesitate to contact me. 

Respectfully, 

Stanislaw Piorek, Ph.D. 

Director, Applied Research 

Thermo Scientific Niton Analyzers 

Thermo Fisher Scientific 

900 Middlesex Turnpike, Building 8 

Billerica, MA 01821 USA 

Tel +1 978-215-1327 


Mobile: 1-978-761-3784 


stan.piorek@thenno.com 

www.lhermo.CCJn/f))tOf) 
Hammond. Rocky 

From: Fellin, Mark 

Sent: Friday, April 01, 2011 9:28 AM 

To: Hammond, Rocky 

Subject: FW: Questions 

Attachments: Letter response to Comm. Northup as e-mailed on March 16 2011.pdf 

Importance: High 

From: Piorek, Stanislaw [mailto:stan.piorek@thermofisher,com] 

Sent: Wednesday, March 16, 2011 3:21 PM 

To: Fellin, Mark 

Subject: RE: Questions 

Importance: High 

Dear Mark, 

Attached is my response to Comm. Northup's questions. The original hard copy is ill the mail. 

Please, pass my regards to the Commissioner, 

Stan 

Stanislaw Piorek, PtlD. 

Director, Applied Research 

Thermo Scientific NITON Analyzers 

Thermo Fisher Scientific 

900 Middlesex Turnpike, Building 8 

Billerica, MA 01821 USA 

Tel +1 978-215-1327 

Mobile: 1-978-761-3784 

Fax +1 978·670·7430 

stan.piorek@thermofisher.com 

From: Fellin, Mark [mailto:MFellin@cpsc.gov] 

Sent: Monday, February 28, 2011 1:37 PM 

To: Piorek, Stanislaw 

Subject: RE: Address 

Dr. Piorek, 

/\ttilched you will find Comm. Northup's follow-up questions for the record. i will also be sending you a h:ml copy Ii) 1 

your records. Please let me know if you have any questions. Thanks! 

Mark 

From: Plorek, Stanislaw [mailto:stan.piorek@thermofisher.com] 

Sent: Thursday, February 24, 2011 11;19 AM 

To: Fellin, Mark 

Subject: RE: Address 

1 
Hello Mark, 

I will be more than happy to answer any questions Commissioner Northup may have, 

My address is below, unless you are asking for a private one? 

Stan 

Stanislaw Piorek. Ph,D 

Director, Applied Research 

Thermo Scientific NITON Analyzers 

Thermo Fisher Scientific 

900 Middlesex Turnpike, Building 8 

Billerica, MA 01821 USA 

Tel +1978-215-1327 

Mobile: 1w 978-761 w 3784 

Fax +1 978-670-7430 

stan, piorek@thermofisheLcom 

www.thermo.com/niton 

From: Fellin, Mark [mailto:MFellin@cpsc.gov] 

Sent: Thursday, February 24, 2011 9:38 AM 

To: Piorek, Stanislaw 

Subject: Address 

Good Morning Stan, 

Could you please give me your address when you get a chance? Comm. Northup has some follow-up questions from 

your testimony on 100ppm. Thanks for your help! 

Mark 5. Fellin 

Office of Commissioner Anne M. Northup 

Consumer Product Safety Commission 

(301) 504-7780 

http://www.safetvandcommonsense.blogspot.com/ 

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