How new spectrometer technologies substantially cut operating costs

Introduction

Inductively coupled plasma optical emission spectrometry (ICP-OES) is routinely used for elemental analysis by professionals in environ-mental, industrial, and academic laboratories worldwide. This fundamental spectroscopy technology analyzes everything from soil and sludge to water and wastewater, plus various industrial process materials. It helps ensure that governmental regulations are met, assists in environmental cleanup efforts, and supports industrial research and processes.

In evaluating which ICP-OES instrument to select for a given set of tasks, two differing emphases emerge. Many independent laboratories — especially those specializing in environmental contract work — naturally require an adequate level of performance, but in addition prioritize sensitivity and speed. Their prime concern: choosing an instrument that can maintain the

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highest possible number of tests per shift. By contrast, other operations — including many industrial research laboratories — prioritize stability and analytical precision.

However, both groups agree on the importance of a common concern: controlling costs. This can be difficult, since most ICP-OES instruments presently on the market incur a variety of opera-tional and maintenance expenses, both obvious and hidden, that dramatically increase their total cost of ownership.

Fortunately, some newer enhancements to traditional spectrometer technologies reduce or eliminate these expenses. This report explores how engineering innovations can significantly reduce costs — enabling substantial savings while improving performance.

The trouble with traditional ICP-OES instruments

Many users report that several specific

technical features of most spectrometers

can cause considerable trouble

and expense.

In older instruments, these may require

inordinate spending on maintenance

and repairs. (Naturally, such problems

are magnified by subsequent down-

time, which itself further depresses the

bottom line.)

Even in newer spectrometers, if they’re

based on traditional technology, problems

may be persistent — and expensive. The

troubles can often be traced to inherent

weaknesses in the instruments’ design,

such as the ones discussed below.

The price of purging

Conventional ICP-OES instruments rely

on at least one costly consumable: a

constant supply of purge gas.

Certain often-analyzed elements

(including most or all nonmetals)

require measurements below 200

nanometers (nm) in the advanced UV

range. Unfortunately, conventional

designs are open to the environment,

so atmospheric air is present in their

optical paths. And lines below 180 nm

are strongly absorbed by the molecular

oxygen and water in that air.

So such instruments must purge air by

replacing it with argon or nitrogen gas.

2

Again unfortunately, purging sufficient

air from the optical path can take up to

2 hours after startup. Most laboratories

can’t afford to lose that much produc-

tivity. So to maintain system integrity,

they must fill and purge gas continually

— even when the system is not analyz-

ing samples. This “standby purging”

often consumes 1 liter (L) of expensive

gas per minute. Result: up to several

thousand dollars in purge gas waste and

expense each year.

Finally, this constant-fill/purge design

increases the chance that impurities in

the gas may contaminate components of

the optical system — requiring additional

pricey repairs.

The cost of cooling

Not surprisingly, plasmas generate quite

a bit of heat. To deal with this, traditional

ICP-OES systems require users to add

on an external cooling system.

Typically a water-based chiller, this

expensive, complicated component can

represent a significant headache. It may

well generate the largest volume of user

complaints about conventional spec-

trometer designs.

It adds unwelcome complexity to the

overall system. It’s often prone to inter-

nal leaks, which can cause the failure of

expensive instrument components such

as the plasma RF generator or load coil.

It can require frequent maintenance, and

serve as a disproportionate source of

system downtime.

Few such cooling systems outlast their

spectrometers. In fact, chillers often re-

quire early (and expensive) replacement.

Direct expenses may comprise the great-

est headaches of all. A hefty addition

to the spectrometer’s initial base price,

the separate chiller purchase may total

as much as $5,000. And energy costs

for this power-hungry component boost

utility bills for the life of the instrument.

The expense of instability and lower sensitivity

Its optical system is the heart of any

ICP-OES instrument. Conventional optics

still used in the majority of spectrome-

ters today utilize diffraction gratings of

the echelle type. (French for “ladder,” this

describes a particular grating pattern.)

Echelle-based instruments provide

adequate performance in varying

analytical situations. However, in a

number of not-uncommon applications,

echelle-based systems struggle and

fail to provide the levels of

performance necessary.

First, the way an echelle-based spec-

trometer processes spectral lines makes

it susceptible to interference when spec-

tra for certain elements present them-

selves too close together. Stray light

from reflections caused by the system’s

multiple optical components (see more

on this topic below) increases back-

ground radiation and affects sensitivity.

This stray light interference means that

echelle technology makes it harder to

3

satisfactorily analyze very line-rich ma-

trices, such as those encountered with

metals or some organics.

A second disadvantage is the echelle

systems’ strongly wavelength-dependent

resolution. They exhibit higher resolution

in the 200 nm range, but lower resolu-

tion above 300 nm. This makes working

with those line-rich metal matrices even

more challenging, and may require extra

processing — which adds even more

time, trouble, and expense.

For example, a user trying to utilize a

spectrometer with conventional optics

to analyze a sample of high-aluminum

soil finds it difficult to accurately mea-

sure the sample’s parts per billion levels

of lead. In an echelle-based system, the

lead analytical line at 220.3 nm is influ-

enced by the aluminum analytical line at

220.4 nm. A clever optical design allows

the use of the less influenced lead line at

168 nm.

In a third design shortcoming, optical

systems in all conventional echelle-

based ICP-OES spectrometers utilize

four to eight reflective/transmission

components (mirrors, prisms, cross-

dispersers, etc.). However, light

transmission is decreased at each

reflection/transmission. Most systems

have enhancements to try to com-

pensate for these losses, but they still

lose significant percentages of light —

enough in some cases to substantially

degrade sensitivity.

The problem becomes acute in the UV/

VUV spectral range below 190 nm,

leading to lower sensitivities for cer-

tain wavelengths and their respective

elements (aluminum at about 167 nm,

lead at 168, phosphorous at 177, sulfur

at 180, and so on).

Another challenge: echelle system

optics’ openness to the environment

requires expensive fill/purge gas supply

to replace ambient air, as already noted.

But it also negatively impacts measure-

ment stability. Any pressure change

in the ambient atmosphere is echoed

within the optical system, changing

the diffraction index of the optic atmo-

sphere. This leads to wavelength drift,

which may negatively influence recovery

of accurate results.

Finally, the limitations of echelle optics

may disadvantage a user’s selection

of plasma viewing options when pur-

chasing a spectrometer. Traditional

radial-view systems often can’t handle

trace concentration levels of a signifi-

cant number of elements. So the user

may be forced (instead, or also) to buy

higher-sensitivity axial or even dual-view

systems, even though these suffer from

lower stability and matrix compatibility,

while their added complexities demand

extra maintenance, cleaning, and cost.

4

It all adds up

Traditional spectrometers also suffer

from a few other problems.

Generators often aren’t powerful

enough to deliver the higher levels

of performance routinely needed in

real-world laboratories. For example, in

analytical situations requiring high plas-

ma loads, conventional spectrometers

can struggle (or fail) if challenged to

supply sufficient power when suddenly

switching matrices with different types

of samples. So sample throughput may

be effectively reduced.

These spectrometers’ overly complex

software and operational routines can

also require excessively long (and thus

expensive) learning curves and training.

Such delays can have a significantly

negative impact on laboratory or in-

dustrial process productivity. Also, the

design deficiencies noted above — and

others — can all appreciably increase

the chance of expensive errors.

When added up, all these hidden main-

tenance and operational expenses

can easily triple a user’s real cost

of ownership.

New designs and substantial savings

Fortunately, innovative engineering

improvements have eliminated these high-

priced spectroscopy headaches. Certain

systems can surpass conventional designs

to deliver consistent, rapid — and consid-

erably less expensive — results, day in

and day out.

Example: the SPECTROBLUE ICP-OES

analyzer from SPECTRO Analytical Instru-

ments. This powerful spectrometer contin-

ually sets new benchmarks for simplified

operation, low maintenance, and assured

affordability. Users report that its innova-

tive engineering overcomes the problems

detailed above, enabling the achievement

of high throughput — yet with drastically

lower costs of operation.

5

Eliminating purge gas consumption

The instrument’s innovative technology

improves on conventional spectrometer

design. A unique sealed optical system

abolishes the necessity for constant purg-

ing of argon or nitrogen. That means no

gas consumables cost or purging delays.

Instead, the system is permanently

argon-filled, recirculating gas through a

small purifier cartridge good for 2 years of

life. The user can start and stop the instru-

ment at will. So the spectrometer achieves

highly stable analytical results and excel-

lent low UV performance, right from the

beginning of a shift, without purge waiting

or delays at startup.

With an estimated 600 cubic meters of

purge gas saved per year, at current prices

a user of this technology may save $3800

annually in gas consumption alone.

OPI-AIR Interface

12 CCDs

PurifyingCartridgeUV-Plus

Na

Li

K

Grating3600 gr/mm165 - 285 nm

Grating1800 gr/mm285 - 470 nm

Avoiding external cooling

Improved spectrometer technology

eliminates the need to buy, install, pow-

er, and maintain a separate, external,

water-based cooling system.

Instead, the SPECTROBLUE analyzer

comes from a line of the only spectrom-

eters currently available that integrate in-

novative, patented air-cooled technology.

Simple in conception, this approach

generates inherently less need than

conventional designs for maintenance or

downtime. It saves the higher continuing

energy costs of water-based chillers. It

eliminates leaks and corrosion. It’s proven

less prone to breakdown. And it avoids

the need for expensive early replacement.

Attaining strong sensitivity and stability

In numerous analytical situations, in-

novations in optical technology affect

performance measures such as sensitiv-

ity and stability, which can also impact

operational costs.

6

Example: SPECTRO analyzer models such

as SPECTROBLUE utilize a unique optics

approach known as Optimized Rowland

Circle Alignment (ORCA polychroma-

tor) technology. (Here “Circle” describes

an optical arrangement with a concave

grating, optimized to limit the loss of light

during diffraction.)

Echelle optical systems utilizing charge-

coupled device/charge injection device

(CCD/CID) technologies were developed in

the 1990s, using two-dimensional sen-

sors as their foundation. By contrast, the

ORCA polychromator technique takes full

advantage of linear array detectors. This

spectrometer’s ORCA polychromator-based

optical system employs 15 linear CCD de-

tectors mounted into 2 hollow-section cast

shells to cover the wavelength range from

165 to 770 nm. It enables simultaneous cap-

ture of a sample’s complete spectrum with-

in 4 seconds. Prime ORCA polychromator

characteristics: sensitivity across a broader

spectral range, and excellent long-term

stability due to factors such as the absence

of any optics purging needs.

As mentioned earlier, the question of which

spectrometer type to buy can also be influ-

enced by the quality of a choice’s optics.

For example, in many industrial applica-

tions, users routinely encounter high con-

centrations of target elements. For this kind

of work, users often choose a higher-preci-

sion, lower-sensitivity radial-view model.

However, if these users sometimes

also encounter samples with trace-

level concentrations, their conventional

echelle-based radial-view system may

well prove inadequate. They must instead

choose a higher-sensitivity axial-view mod-

el. (Note that axial-based instruments bal-

ance their improved sensitivity with lower

precision, lower stability, and lower matrix

compatibility, while their greater complexi-

ty demands more maintenance and incurs

higher operating costs.) Or depending

on anticipated usage, they may select a

dual-view instrument that can provide both

capabilities. Either alternative means more

expense.

SPECTROBLUE may relieve the user

from having to make that choice. ORCA

polychromator-enabled optics gives it

unusually low detection limits that let even

its radial-view version handle many trace

analysis applications with sufficient sensi-

tivity (in addition to radial view’s inherent

high precision).

In all three SPECTROBLUE versions —

axial, radial, or twin-interface models

— ORCA polychromator optics create a

direct, high-luminance optical path that

limits light loss and “stray light” while max-

imizing spectral separation and information

throughput. These and other engineering

innovations improve sensitivity and stabili-

ty, allow the system to more easily process

line-rich spectra, boost measurement accu-

racy, and reduce expensive rework.

7

Achieving even more advantages

Innovative spectrometer technologies offer

other attractive benefits.

A robust generator design provides ample

power reserves, so it can handle extreme

plasma loads, and adapt to quickly changing

demands. Suppose the instrument is run-

ning a set of wastewater samples containing

roughly similar levels of organic materials.

If a sample suddenly appears that shows

much higher organics levels — causing a

higher plasma load — the system can han-

dle the change and make the measurement

without troublesome or costly delays.

The example system (SPECTROBLUE) also

uses a proprietary technology to enable

one-sample wavelength normalization. This

capability may be especially advantageous

for a large organization with many sites. It

can run the same methods on this same

model of analyzer at different locations —

using the same setup, without the need for

redundant local method development —

and get directly comparable results, with-

out costly delays. Larger operations can

standardize on a single model for uniform

results plus inventory cost savings.

Finally, innovative designs with less overall

instrument complexity result in easier,

less expensive installation, operation, and

maintenance. For just one instance, the

SPECTROBLUE approach is designed to

allow simple access and maintenance of

the introduction system. Software is intui-

tive and easy to learn. Overall, easy learn-

ing curves reduce training time and costs.

This is especially important where labora-

tories experience high operator turnover.

Conclusion

Traditional spectrometers bear the burden of a number of inherent problems in their

design. With more recent, more innovative technologies applied to improve ICP-OES

performance and usability in models such as SPECTROBLUE, users discover that many

headaches — and hefty costs — have been engineered out of the system.

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