Nine Elements That Challenge Handheld XRF Analyzers — But Are Easy for OES

Introduction

Handheld X-ray fluorescence (XRF) analyzers are

useful for many elemental measuring tasks across

numerous industries and applications. Advanced

models — such as the SPECTRO xSORT handheld

XRF spectrometer from SPECTRO Analytical

Instruments — produce fast, accurate results on

the spot, for sample identification, grade sorting,

and metals analysis involving elements from

magnesium to uranium. However, XRF technology

faces significant limitations for certain elements.

These constraints make it difficult or impossible

to get satisfactory performance from handheld

XRF in a number of applications.

A WHITE PAPER FROMSPECTRO ANALYTICAL INSTRUMENTS

This report highlights these challenging elements

— including carbon, sulfur, phosphorus,

aluminum, silicon, magnesium, lithium, beryllium,

and boron. It explains how they may instead be

routinely analyzed by mobile optical emission

spectrometry (OES) instruments.

Examples include the SPECTROTEST mobile arc/

spark OES metal analyzer and the SPECTROPORT

portable arc/spark OES metals analyzer. Each

can easily analyze the particularly challenging

elements that handheld XRF technology cannot.

When results matter

Carbon Due to difficulties with

elements lighter than

titanium (Ti; number 22

in the periodic table), handheld XRF

spectrometers lack the ability to determine

the carbon (C) content of a metal sample.

This makes these instruments unsuitable

for reliable analysis of some metal alloys,

including two common varieties of steel:

Carbon steels.

The amount of carbon present in a

sample is the chief factor available for

distinguishing between different low-

alloy steels (sometimes called carbon

steels). For applications from incoming/

outgoing inspection to repair, users

often must discern small differences in

elemental composition between grades.

When processing low-alloy steels for

use in engineering/construction of

structures, vessels, vehicles, or machines,

weldability becomes a key characteristic.

Steel alloys are weldable without special

measures when they contain up to about

0.2% carbon. However, after that point,

weldability decreases as carbon content

increases.

Chromium/nickel (CrNi) steels.

Requirements for certain stainless or

high-alloy steels demand precise analysis

of carbon as well. For example, Type 316

stainless steels are widely used in the

construction of petrochemical plants.

All 316 steel grades contain chromium;

however, their mechanical strength and

durability also depend on their carbon

content.

Again, a little carbon can go a long way.

Type 316 stainless steels contain up to

0.07% carbon, while 316L stainless steels

— remember, the “L” designates “low

carbon” — contain a maximum of 0.03%

carbon.

So a small absolute difference of a few

hundred parts per million (ppm) is enough

to give these alloys clearly different

intergranular corrosion behaviors. Welded

seams formed in low-carbon 316L are

more durable than in the higher-carbon

alloy.

Unlike handheld XRF instruments, high-

quality mobile or portable metal analyzers

such as SPECTROTEST or SPECTROPORT

can easily differentiate these alloys on the

spot.

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Sulfur and Phosphorus Sulfur (S) and phosphorus

(P) are two other elements

whose measurement

is often critical to

accurate metals analysis.

Unfortunately, both are so-

called light elements that are challenging

for handheld XRF.

So, for example, XRF analyzers can only

identify metal grades with quite high sulfur

values — such as Type 303 steel, which

contains a minimum of 0.15% sulfur.

By contrast, Type 304 or 316 chrome-nickel

steels have a maximum of 0.03% sulfur.

Such low concentrations cannot be reliably

detected by handheld XRF analyzers. Their

limits of detection (LODs) are usually too

high to determine critical in-spec and

out-of-spec levels in CrNi steels —

typically less than 0.03% sulfur.

Similar problems arise with

low concentrations of

phosphorus. The necessary

measurements are

likely to be at or near

a handheld XRF

analyzer’s basic

limits of precision.

They may also be

thrown off by the

impact of surface

preparation anomalies

in any given sample.

Result: unreliable

measurements.

Aluminum, Silicon, and Magnesium XRF technology also

encounters problems

when trying to measure

aluminum (Al), silicon

(Si), and magnesium (Mg)

elements in metals. Again,

the cause is inherently

high LODs. Handheld XRF

analyzers may often be able

to identify these elements at lower levels.

But especially at levels below 0.1%, they

typically cannot reliably analyze them.

For example, in many aluminum-based

metal samples, magnesium measurement

becomes critical. An advanced handheld

XRF analyzer such as SPECTRO xSORT is

able to detect magnesium concentrations

that let it differentiate among samples

of 2000 or 6000 series aluminum alloys.

But no handheld XRF instrument can

differentiate unalloyed or low-alloy

1000 series samples by magnesium.

Nor can it easily deal with poor sample

surfaces in alloys with aluminum, silicon,

or magnesium. Solution: the superior

analytical headroom of an OES analyzer.

Lithium The lightest metal, lithium

(Li) is frequently found in

aluminum-based alloys.

Up to a point, adding lithium decreases

weight without affecting strength. So

alloys such as the 8090 series, with

2.2% to 2.7% lithium, are widely used in

aerospace manufacturing, for example,

where accurate analysis is required in

incoming and outgoing inspection.

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Also, in metals recycling, it’s vital to

separate out lithium-bearing alloys.

Lithium reduces the ductility of standard

aluminum alloys with which it might be

intermixed. More than 5 ppm lithium

content can cause difficulties in casting a

recycled aluminum alloy.

Problem: handheld XRF instruments can’t

detect lithium at all.

Fortunately, an OES analyzer such

as SPECTROTEST can. In the 5 ppm

example above, SPECTROTEST easily

detects such levels and can help ensure

the correct recycling process.

Beryllium Copper/beryllium (CuBe)

alloys typically contain

0.4% to 2% beryllium in

combination with cobalt (Co), chromium

(Cr), or silicon (Si). They may be

shaped into semifinished bars, rods,

etc., for further processing; or used in

valve seat rings or machine inserts, in

nonarcing tools (for potentially explosive

environments), and as die material for

brass castings.

Awareness of beryllium content is also a

safety measure. Beryllium is among the

chemical elements most toxic to humans.

So repair shops, for instance, must

carefully identify any beryllium content in

a copper piece undergoing grinding, so

that precautions can be taken to prevent

exposure via skin or lungs.

Unfortunately, beryllium is yet

another element that’s impossible to

measure effectively with handheld XRF

spectrometers.

Boron The basic effect of

alloying with boron

(B) is to enhance the

hardenability of low-alloy steels. For

example, the presence of boron is key

to distinguishing 13MnCrB5 from non-

boron-bearing 16MnCr5 steel.

Boron also helps high-speed blade steels

improve cutting performance. Analysis

can be critical for users such as repair

shops, which must determine the exact

components of tool steels to effect

repairs.

In austenitic steels, low concentrations

of boron (up to 0.01%) improve the

high-temperature strength of the

finished alloy. These steels are used as

construction steels, and for screws and

fasteners.

Once again, though, it’s not possible to

analyze boron effectively with handheld

XRF technology.

SPECTRO xSORT

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XRF Alternatives: OES Analyzers All the elements mentioned in this

report present significant challenges

to measurement by handheld XRF

analyzers. In several cases, handheld XRF

techniques simply can’t detect them at

all. (See Table 1 below.)

Fortunately, recent advances in

technology have created a new

generation of high-capability, mobile

and portable OES metal analyzers. They

can quickly and precisely measure these

challenging elements, or supply fast alloy

sorting based on elemental content — on

the dock or at the line.

For example, the SPECTROTEST mobile

arc/spark OES spectrometer is the

flagship of SPECTRO’s field-deployable

metals analyzers. It provides rapid,

accurate results in a mobile device —

bringing laboratory-quality analysis of

these challenging elements and more,

right to the work site.

Perhaps even more

impressively, the new

SPECTROPORT portable

arc/spark OES metals

analyzer combines many

of SPECTROTEST’s

advantages with the

ease of a handheld. It

delivers effortless on-

the-spot, point-and-

shoot performance in a

smaller, lighter, affordable

package.

Both these instruments provide superior

analytical performance and high

sample throughput. They can precisely

measure every challenging element

mentioned here. That includes carbon,

sulfur, phosphorus, aluminum, silicon,

magnesium, lithium, beryllium, boron,

and more.

Both, SPECTROTEST and SPECTROPORT

can perform accurate and comprehensive

analysis of elements, traces, and

impurities, even at low concentration

levels. And their greater OES analytical

headroom lets them handle most

sample anomalies such as poor

sample surfaces, which can mislead

handheld XRF instruments into incorrect

measurements.

In many applications where XRF

technology just can’t deliver adequate

performance, these mobile OES solutions

have become the spectrometers of

choice.

Standard handheld XRF analyzer

SPECTROPORT portable OES analyzer

SPECTROTEST mobile OES analyzer

Carbon no excellent excellent

Sulfur limited excellent excellent

Phosphorus limited excellent excellent

Aluminum limited very good excellent

Silicon limited very good excellent

Magnesium limited very good excellent

Lithium no good excellent

Beryllium no very good excellent

Boron no excellent excellent

SPECTROTEST

SPECTROPORT

Selecting an OES mobile or portable metal analyzer

High-quality, field-deployable OES metal analyzers

tackle tasks that handheld analyzers just can’t han-

dle, because they can measure carbon content with

good precision. And compared to laboratory mod-

els, they offer much of the functionality with all the

convenience of on-the-spot analysis. However, not all

instruments in this class are created equal. Look for an

analyzer with the following features:

Tested and proven. You may find the best success

with technology that’s validated by wide use. If so,

consider a market leader in this analyzer category.

Easy calibration. Some devices demand frequent

recalibration. By contrast, the iCAL logic system in

SPECTROTEST and SPECTROPORT takes a single

sample and only 5 minutes for standardization.

Wide wavelength range. Since materials, specifica-

tions, or applications may change, look for an analyzer

that covers all the elements needing analysis — today

or tomorrow.

Ease of use. Look for large, simple, easily read

displays, and the ability to customize the interface to

your operators’ knowledge and needs.

Large metals database. Prepackaged methods for

selected materials make for simple setup and use. Favor

devices that can easily accommodate new alloys or

materials, and that offer the ability to identify virtually any

common commercial metal alloy — based on a built-in

comprehensive library.

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IntroductionCarbonSulfur and PhosphorusAluminum, Silicon, and MagnesiumLithiumBerylliumBoronXRF Alternatives: OES AnalyzersSelecting an OES mobile or portable metal analyzerContact Us