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# ThermoFisher In selVing science SCIENTIFIC

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 saythat we very much appreciated the opportunity to testify beforethe 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 beperformed with a single triggerpull 0.[

### a hand heldXRFmachine. In particular, please describe: (1) 

### the size of the area that can be tested; and (2) 

### whether and to what extent a single triggerpull can test the lead content of multiple substances, such as two adjacentsurface coatings with different characteristics (i.e., color, materials, etc.), a multilayered item (i.e., one ormore coatings on asubstrate ormultilayeredsubstrates), ortwo adjacentparts of a composite object, each 0.[

### which are comprisedof a different material. The first question relates to the way a handheld x-ray fluorescence (HHXRF) instrument operates. To clarify some terms, let me note herethat we define a "singletrigger pull" as the execution ofa single, complete measurement cycle culminating in a display ofanalytical results. TheXRF analyzer operates on theprinciple ofx-ray fluorescence, meaning that its built-in source ofx-rays excites thecharacteristic x-rays ofchemical 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 ofthe detected characteristic xrays, which is then convertedby 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 ofmeasurement. This is accomplished by designing the "nose" ofthe 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 ofclements present 

### in the sample. Therefore, the area that can be tested by a handheld XRF analyzer is typically delineated by the size and shapeofthe aperture. In the case ofThermo Scientific Nitonhandheld XRF analyzers, the aperture is a circle ofapproximately 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 ofthe 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

. Theinstrument itselfis calibrated for quantitative analysis under a fundamental assumption ofa homogeneous, infinitely thick uniform sample. It is, therefore, critical to make every effort thal theportion oftheobject targeted for analysis is homogeneous and completely covers the measuring aperture. Only in this way will theresults berepresentative ofthe actual concentrations ofelements. Real objects, as weknow, aremade ofmany different substances. Whentesting them we should make surethat only one substance is placed within the instrument measuring aperture becausethe characteristic x-rays ofa given element arethe sameregardless of wheretheelement is located. In other words, the characteristic x-rays oflead within paint are indistinguishable from the characteristic x-rays ofleadembedded in a substrate over which the paint is applied. Therefore, wecan see that ifthe substances are not tested separately, then the results mightbeinaccurate, representing somekind ofan average which would not refleet the true concentration ofthe element in any ofthe 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 ofthe 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 measurethe lead content ofa small metallic part such as a rivet holding together two plastic components. The size ofthe rivet is much smaller than the measuring aperture ofthe instrument. Consequently, when attemptingto test therivet, we would not be ableto avoid interference from x-rays generated in theplastic parts. The way around this is to collimate the exciting beamfrom the x-raytubeto a much smaller diameter, thereby generating x-rays only in therivet 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 ofobjects as small as 3 mm in diameter. By using the "small spot" collimator separately on the rivet and on the plastics, theuser can analyzeboth materials for lead and obtain meaningful results. Similar requirements apply when analyzing layered materials. That is, both the coating and substratemust be tested separately for lead or any other element. For example, ifthe coating is applied as paint over a substrate, first thepaint layer should betested for lead, followed bytesting the substrate for lead, but on its unpainted section. Ifthe substrate does not contain lead, then the test performed on the painted fragment ofthe substratewill reflect the correct amount oflead in paint. On the other hand, ifthe substrate does contain lead, then the measurement oflead in paint obtainedon the painted section ofsubstrate will most likely be inflated. Ifthepaint does not contain lead but the substrate does, the measurement oflead in the substrate could show a result that is lower than the actual concentration oflead in the substmtebecause sil:,'Oai (x-rays) from lead in the substrate may be attenuatedbythe layer ofpaint. Small painted surfaces, such as an eye ofa doll or a toy duck, should be tested using a collimated x-raybeam such as the "smaIJ spot" mentioned earlier.

W\NW thermo.ccm/rilton

### Thermo

### Fisher SCIENTIFIC

In sununary, in order for measurements to beas meaningful as possible, we should always make surethat each test, i.e., each "single trigger pull," 

### is performed on a single type ofmateriaL Even the different colors ofthe same material (as often is the casewith plastics) should be tested individually. 

### Question 2. Does the costof a single HHXRFtriggerpull vary depending upon the number of elements analyzed during the single measurement? Thecost ofa singletrigger pull is the sameregardless ofthe number ofelements analyzed. With a singletrigger pull, the analyzer can measuremanyelements, in practice anywhere from 

### I to 

### 25 or even 30. This is becausetheXRF method, while totally nondestructive, is simultaneously multi-elemental. This means that in a single measurement cycle, that is a "single triggerpull," the instrument acquires an x-ray spectrum that contains information from many, ifnot all, elements, in thetested object. This is both a curse and a blessing. A blessing because in one "shot" we can have completeinformation about the tested material. A cursebecausethe elements present in the tested object mutuallyaffect the others' x-rays, andtherefore make their interpretation more difficult. In otherwords, to analyzefor evenoneelement, weneed to measure other elements present in the material as well. Forexample, 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 maypotentiallyinterfere with the lead signaL I hope my explanations havehelped to shed some light on the 

### issues raised 

### in your questions. Should you need clarification or have other questions, please do not hesitate to contactme. 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 ifyou 

### 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 1Hello 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: 1 w978-761 w3784 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 ofCommissioner Anne M. Northup Consumer Product Safety Commission (301) 504-7780 http://www.safetvandcommonsense.blogspot.com/



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