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During NIR 2019 conference, Gold Coast, Australia, a presentation upon a critical review of instrumentation and applications of handheld spectrometers was delivered during the plenary session held on Thursday morning, 19 September. Following the conference presentation, a vivid discussion flared up among the audience that equally involved academic scholars, industry representatives, as well as professionals who carry out every day in-the-field applications. Various aspects were raised connected with the emerged new generation of near-infrared instrumentation, with many individuals expressing their point-of-view on the merits and pitfalls of the miniaturized spectrometers. This vigorous dispute and exchange of impressions indicated that the community remains concerned about the applicability of such devices. That concern reflects the still relatively shallowly explored miniaturization versus performance factor, which can only be dismissed by focused feasibility studies with comparative analyses carried out on scientific-grade benchtop spectrometers. It is the aim of the present manuscript to summarize the discussed scientific content and to share the developed point-of-view with addition of our remarks.
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Original Article
Handheld near-infrared spectrometers:
Where are we heading?
Krzysztof B Be
, Justyna Grabska
, Heinz W Siesler
Christian W Huck
During NIR 2019 conference, Gold Coast, Australia, a presentation upon a critical review of instrumentation and applications
of handheld spectrometers was delivered during the plenary session held on Thursday morning, 19 September. Following
the conference presentation, a vivid discussion flared up among the audience that equally involved academic scholars,
industry representatives, as well as professionals who carry out every day in-the-field applications. Various aspects were
raised connected with the emerged new generation of near-infrared instrumentation, with many individuals expressing
their point-of-view on the merits and pitfalls of the miniaturized spectrometers. This vigorous dispute and exchange of
impressions indicated that the community remains concerned about the applicability of such devices. That concern reflects
the still relatively shallowly explored miniaturization versus performance factor, which can only be dismissed by focused
feasibility studies with comparative analyses carried out on scientific-grade benchtop spectrometers. It is the aim of the
present manuscript to summarize the discussed scientific content and to share the developed point-of-view with addition of
our remarks.
Handheld, portable, near-infrared instrumentation, application, evaluation, miniaturization versus performance
It is commonly accepted to divide the fieldable spec-
trometers (i.e. deployable in-the-field, in contrast to
benchtop instrumentation, that is only applicable in a
laboratory setting) into transportable (e.g. deployable
on field while mounted in a car), portable in ‘suitcase’
format (>4 kg of total equipment weight) and hand-
held (<1 kg) ones.
These criteria suit the broadly
understood spectroscopy and spectrometry, including
e.g. elemental (atomic) techniques such as X-ray fluo-
rescence or laser-induced breakdown spectroscopy,
and even mass spectrometry (MS) or nuclear magnetic
resonance. When considering purely this sole factor,
NIR spectroscopy enjoys a fair advantage over several
other techniques in its compact technology. The most
recent years have brought ultra-miniaturized NIR
spectrometers to reality; such devices are either USB
powered or have own built-in battery, weigh less than
50 g and can be operated by an application installed on
a smartphone. The progress in miniaturization is
accompanied by software development aimed at ease
of use and suitability for operation by a non-expert
consumer community. Qualitative differences in the
level of sensor miniaturization achieved over the past
few decades in different fields of spectroscopy and
spectrometry are demonstrated in Figure 1.
While some other physicochemical methods of anal-
ysis reached similarly impressive levels of miniaturiza-
tion (e.g. fluorescence), NIR spectroscopy still offers
superior chemical specificity and applicability to a
broad range of sample types.
Searching for ‘portable near-infrared spectroscopy’
in ISI Web of Science database (https://apps.webof results in 239 publications since 2005
with increasing tendency (Figure 2(a)). The total
number of citations since 2005 is 2512 and from the
graph depicted in Figure 2(b) the highly increasing
number on a yearly basis can be deduced. From this
statistics, it is obvious that portable NIR spectroscopy
is an efficient and popular analytical chemistry tech-
nique. Current technological progress enables new
advance in miniaturization and there is no doubt that
Institute of Analytical Chemistry and Radiochemistry, CCB – Center for
Chemistry and Biomedicine, Innsbruck, Austria
Department of Physical Chemistry, University of Duisburg-Essen, Essen,
Corresponding author:
Christian W Huck, Institute of Analytical Chemistry and Radiochemistry,
CCB – Center for Chemistry and Biomedicine, Innrain 80/82, Innsbruck
6020, Austria.
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Figure 1. Various level of transportability of spectrometers. (a) Car-transportable GC–MS and long-path reflective FT-IR instrumentation,
(b) portable tunable diode-laser absorption spectroscopy (TDLAS) sensor mounted on a height-adjustable tripod, (c) Agilent 4300
Handheld FT-IR spectrometer and (d) miniaturized USB-powered NIR spectrometer Viavi MicroNIR Pro ES 1700. Source: Panel (a)
reproduced from Eckenrode
with permission under Elsevier Open Access license. Panel (b) reproduced from Zhang et al.
under CC-BY
4.0 license. Panel (c) reproduced from Hutengs et al.
under CC-BY 4.0 license.
Figure 2. Number of (a) publications and (b) citations of ‘portable near-infrared spectroscopy’ since 2005 according to Web of Knowledge
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handheld NIR spectrometers belong to the next gener-
ation of analytical instrumentation. More and more
they are suitable to become a technology of choice
not only in industry but also in everyday life
There are several fields of application, which strong-
ly depend on maturing miniaturized spectroscopy as a
robust analytical tool – one of such fields is the agro-
food sector. European Commission stresses the prime
importance of food analysis for the public safety.
2015, the European Union opened a challenge on
‘health, demographic chance and wellbeing’ to reward
solutions, intended for the general public, that allow to
analyse and secure food quality including allergen rec-
ognition. Thus, in 2017 at the CeBIT Exhibition in
Hannover, Germany, three companies were awarded
and shared 1 million e: 800,000 efor the winner,
Spectral Engines (Spectral Engines Oy, Helsinki,
Finland), and 100,000 e, each, for the two runners-
up, SCiO (Consumer Physics, Tel Aviv, Israel) and
Tellspec (Tellspec Inc., Toronto, Canada). These
three instruments have in common that they are (i)
cheap, (ii) portable, (iii) handheld, (iv) applicable to
fulfil the requested aim and (v) rely on internet-of-
things and cloud computing to enable communication
and to facilitate their use. At this point, it must be
noted that these companies are not the only ones at
the market, which will be discussed later.
It is a natural course to promote new technologies
capable of improving everyone’s life. Miniaturized
NIRS is one of the first methods of analytical chemis-
try that reached out to the level of ordinary consumers.
There is of course a great and unique potential in such
a trend. However, it becomes apparent that some
attempts to take shortcuts appeared. The community
gathered at the International NIR 2019 conference has
become well aware of the hazard resulting from rapidly
increasing use of NIR sensors in general public, which
we will outline at the end of this article. However, first
it is necessary to summarize the essentials of portable
NIR spectroscopy, the instrumental basis and the
applicability of the latest generation of handheld NIR
spectrometers. Only on such background, the major
point of the community’s concern can be expressed
The principles of the technology leading to
miniaturized NIR spectroscopy
Best strategy for discussing the design of handheld
NIR spectrometers is to divide up the optical spectrum
by detector technology.
In the silicon detector region, we have low cost 1D
and 2D array sensors, and therefore multichannel
techniques are dominating. Complementary metal–
oxide–semiconductor (CMOS) technology has been
gaining steadily on charge-coupled device, mainly
driven by developments in smartphones and cameras,
with CMOS requiring lower power consumption.
wavelengths longer than approximately 1050 nm,
indium–gallium–arsenide (InGaAs) detectors dominate
and have substituted both Germanium (Ge) and lead
salt detectors (lead sulphide (PbS) and lead selenide
(PbSe)), with lead salt single point detectors being
still available on the market. For miniaturized NIR
spectrometers, cost and power consumption are
major drivers. Therefore, single element detectors are
preferred showing the disadvantage of being noisier
than standard InGaAs (1700 nm cut-off) and require
Wavelength selectors
Micro-electro-mechanical systems (MEMSs; if com-
bined with micro-optics then referred to as micro-
opto-electro-mechanical systems, i.e. optical MEMS
or MOEMS) enable constructing micro-scaled complex
mechanical devices directly in-silicon using various
techniques established in semiconductor industry for
chip manufacturing. MEMS-based spectrometers
have been proposed almost 20 years ago, including
Fourier transform (FT) spectrometers. In the case of
the latter, the key component is a resonantly driven
micro-mirror, suspended on two long springs, and
driven by interlocking comb-structured electrodes.
About a decade ago, it was expected that MEMS spec-
trometers would be rapidly commercialized, but this
fact did not become true.
A key issue in this context
is the size of the optics and the ability of an MEMS
comb actuator to drive the moving mirror. The com-
mercially successful handheld FT-IR spectrometer
from Thermo Fisher Scientific uses a voice-coil and
piston-bearing scheme, with a 1.2 cm diameter
moving mirror, which is essentially a scaled-down ver-
sion of conventional laboratory interferometers.
Compared to mid-IR, NIR sources are brighter and
detectors have a higher specific detectivity D*, so that
the issue of mirror size is mitigated in NIR instruments.
Between 2017 and 2020, NeoSpectra, the commercial
arm of Si-Ware Systems, has launched several MEMS
FT-NIR sensors/scanners that are based on the same
optical principle (the first and the latest product are
shown in Figure 3(e)).
A Hadamard spectrometer is a multiplex device that
observes more than one wavelength at a time using one
or two masks instead of slits. This spectrometer offers
both a Jacquinot and a multiplex advantage. In a single
mask design spectrometer, light passes from the source
through a sample and onto the entrance slit of a spec-
trograph; it is dispersed by a grating. Then, the encod-
ing mask selects 50% of the resolution elements and
passes that light onto a single element detector. A typ-
ical mask is an array of zeros and ones. The position of
the zeros and ones on the mask changes and the detec-
tor is read out for each of these positions. Typically,
c et al. 3
the mask uses a cyclic S-matrix sequence, in which each
row is obtained by shifting the previous row one posi-
tion to the left. At the end of data collection, a simple
matrix transform recovers the spectrum from the col-
lected data. A handheld NIR spectrometer, using an
MEMS chip as the Hadamard encoding device, has
been commercially available since 2007 (Figure 3(a)).
The Hadamard mask is a programmable MEMS dif-
fraction grating, originally developed as key element in
a programmable correlation spectrometer for remote
detection and is included in a spectrometer for
NASA to determine water content on the surface of
the moon.
Almost 20 years ago, the use of a digital light pro-
jector as a Hadamard mask was described. Texas
Instruments’ DLP is probably the most common
MEMS device. Texas instruments offers two NIR
engines: DLP NIRscan and DLP NIRscan Nano, as
evaluation modules (EVMs) (Figure 3(c)). To achieve a
micro-scaled programmable Hadamard mask, the DLP
devices use MEMS-based digital micromirror device
(DMD), while Thermo Fischer design microPHAZIR
employs MEMS piano-like diffraction grating in its
implementation of the Hadamard principle.
Application of Hadamard transformation enables con-
structing compact cost-effective spectrometers with a
single-pixel photodetector operating at any wave-
length. An MEMS-driven moving mask is used to
encode the light intensity at its imaging slit, which is
then collected by a single-pixel detector. Afterwards,
the spectrum is obtained through an inverse
Hadamard transform.
Fabry–Perot interferometers are playing a dominant
role as a wavelength separation technique since about
Figure 3. Principles of wavelengths selectors built into different handheld NIR spectrometers: (a) MEMS Hadamard mask – microPHAZIR,
Thermo Fisher Scientific, Waltham, USA; (b) LVF –MicroNIR Pro ES 1700, VIAVI, Santa Rosa, USA; (c) MEMS DMD – implementation
of DLP NIRscan module, Texas Instruments, Dallas, USA; (d) MEMS Fabry–Perot interferometer – NIRONE Sensor S, Spectral Engines,
Helsinki, Finland; (e) MEMS Michelson interferometer – NeoSpectra, Si-Ware, Cairo, Egypt; (f) MEMS Michelson interferometer with
a large mirror – nanoFTIR NIR, SouthNest Technology, Hefei, China. ADC: analog-to-digital converter; InGaAs: indium–gallium–arsenide;
MEMS: micro-electro-mechanical system.
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25 years. A Fabry–Perot filter consists of two mirrors,
either plane or curved, facing each other and separated
by a distance d. There are two basic versions: an inter-
ferometer, where d is variable, and an etalon, where d is
fixed. The condition for constructive interference with a
Fabry–Perot interferometer is that the light forms a
standing wave between the two mirrors, in which case
the optical distance between the two mirrors must equal
an integral number of half wavelengths of the incident
light. A Fabry–Perot interferometer may be also imple-
mented through MEMS-technology, e.g. as it is used in
NIRONE Sensor S device. Thus, MEMS technology
enables to implement as a fully programmable optical
filter in the form of a micro-scale module.
Linear variable filters (LVFs) are optical bandpass
filters that have been wedged in one direction; the
thickness of the coating is not constant across the fil-
ters. The transmitted wavelength varies linearly across
the filter. A LVF can be thought of as a scanning
Fabry–Perot filter which scans the position across the
filter. The typical range is one octave. Ocean Optics
mid-infrared spectrometer has a nine-reflection ATR
interface and covers the wavenumber range 1818–
909 cm
at 75 cm
resolution, with a nominal S/N
ratio of 300:1. For NIR spectroscopy, the LVF tech-
nology is of interest for the following reasons: It is low
cost, very compact, rugged, satisfying spectral resolu-
tion for real applications, and low power consumption.
For example, VIAVI has a line of handheld and pro-
cess spectrometers based on LVF and InGaAs array
(Figure 3(b)).
In the silicon detector region, a number of filter tech-
nologies compete: LVFs and mosaic, patterned, and dis-
crete filters. Consumer Physics released a spectroscopic
product called SCiO, with dimensions of 67.7 mm
40.2 mm 18.8 mm and weight of 35 g. It consists of a
43 photodiode array, with optical filters over the indi-
vidual pixels. The device has only 12 resolution elements
resulting in a rather poor spectral resolution of ca. 28 nm
across its working spectral region of 740–1070nm
(13,514–9346 cm
). The absorption properties of numer-
ous samples in the visible/short-wave NIR should also be
considered as a limiting factor here. It becomes apparent
that this design accepted a number of compromises in
order to achieve its compact factor and low cost.
The instrumental development continues, and
almost every year new concepts and products are intro-
duced to the market of miniaturized NIRS. Some of
the engineering principles are being refined as well. As
a good example serves here the concept of Michelson
interferometer implemented in MEMS technology. The
difficulties with maintaining stable operation of the
MEMS elements and the optical throughput could
have been challenged recently. This technology was
introduced as the final products in NIRONE sensors
from Spectral Engines and nanoFTIR NIR spectrom-
eter from SouthNest Technology. The latter is one of
the most recent miniaturized NIR sensors; it imple-
ments an MEMS Michelson interferometer with a
large mirror (in relation to MEMS chip) in order to
improve the light output. This device operates over the
entire NIR wavelength region (12,500–3846 cm
800–2600 nm), which stands in contrast to most other
handheld spectrometers including the earlier MEMS-
based portable NIR sensors (Table 1). According to
the information provided by the vendor, in addition
to a very broad working spectral region, the sensor
offers higher (although still inferior to benchtops) spec-
tral resolution of 6 nm at 1600nm, high SNR and rapid
scanning, while being far more compact (143 mm
49 mm 28 mm dimensions and 220 g weight) than
early MEMS spectrometers. However, how these
Table 1. Spectral regions and spectral resolution in which the discussed handheld NIR spectrometers operate.
Spectral resolution
Spectral resolution
(at wavelength)
(nm)(nm) (cm
microPHAZIR (Thermo Fisher Scientific) 1596–2396 6267–4173 11
MicroNIR Pro ES 1700 (VIAVI) 908–1676 11,013–5967 12.5 (at 1000)
25 (at 2000)
SCiO (Consumer Physics) 740–1070 13,514–9346 Unknown
NIRscan (Texas Instruments) 900–1700 11,111–5882 10
NIRONE Sensors (Spectral Engines) 1100–1350 9091–7407 12–16
1350–1650 7407–6061 13–17
1550–1950 6452–5128 15–21
1750–2150 5714–4651 16–22
2000–2450 5000–4082 18–28
NeoSpectra (Si-Ware Systems) 1350–2500 7407–4000 16 (at 1550)
nanoFTIR NIR (SouthNest Technology) 800–2600 12,500–3846 2.5 (at 1000)
6 (at 1600)
13 (at 2400)
NIR: near-infrared.
‘At wavelength’ parameter listed if available in the data-sheet provided by the vendor.
SCiO presents to the operator interpolated spectra with 1 nm data-spacing, but the real resolution is considerably lower.
Depending on the sensor implementation/factory configuration.
c et al. 5
promising data-sheet entries translate into the
real-world analytical performance remains to be eval-
uated through peer-reviewed research.
Application and in-depth evaluation of
performance characteristics of portable
NIR spectrometers
The contemporary benchtop spectrometers implement
a long-matured technology and over the past decades
those devices converged almost to a generic FT-NIR
design differing mostly by subtle nuances, at least from
the application point-of-view. In sharp contrast, vari-
ous technology concepts have been implemented into
portable NIR instrumentation in its vigorous develop-
ment over the last 10 years, as briefly outlined in the
‘The principles of the technology leading to miniatur-
ized NIR spectroscopy’ section. Through adoption of
innovative approaches and overcoming engineering
challenges, various handheld NIR sensors have been
brought into the market. However, the progressing
miniaturization unavoidably influenced the working
characteristics (e.g. sensitivity and S/N, spectral
region, spectral resolution) and the resulting analytical
performance of such spectrometers in relation to the
benchtop ones. Furthermore, the vendors often took
upon completely different engineering directions
when designing their portable instruments. Therefore,
several research groups recognized the need for per-
forming comprehensive research studies aimed at
establishing the applicability limits of handheld NIR
spectroscopy. As a good example, Hoffman et al.
explored the transferability of spectral sets, as well as
qualitative and quantitative calibrations that have been
developed thereof, between NIR spectroscopy in
benchtop and portable scenario. Miniaturized spec-
trometers demonstrate a particular potential for the
analysis of natural products outside laboratories. In
2017, for instance, Kirchler et al.
investigated the fea-
sibility of using portable NIRS to determine the con-
tent of the anti-oxidative active ingredients (rosmarinic
acid and closely related polyphenols) in medicinal
plants. They compared the working characteristics
and the final analytical performance of two handheld
spectrometers exemplifying distinctly different design
philosophies and levels of miniaturization. The study
was based on the comparison with a reference bench-
top NIR spectrometer (high-performance Bu
Figure 4. Identification performance of different types of handheld NIR spectrometers for the recycling of polymer commodities. Top row:
3D score plots of the PCA calibration. Bottom row: fit of test samples () into calibration plots. PE: polyethylene; PET: polyethylene
terephthalate; PP: polypropylene; PS: polystyrene; PVC: polyvinyl chloride. Reproduced from Ref. 11.
6NIR news 0(0)
NIRFlex N-500) and supported by exhaustive
data-analytical tools, including hetero-correlated 2D
plots that highlighted the differences between the
NIR spectra measured on the three spectrometers.
Further exploration of the potential of miniaturized
NIR sensors in quantitative assessment of the antioxi-
dant capacity of natural-borne products was demon-
strated by Wiedemair and Huck.
In that case, the total
of three different miniaturized NIR devices was evalu-
ated towards their performance in assessing gluten-free
grains. Performance comparisons of different handheld
near-infrared spectrometers have been performed in
the demanding scenario of quantitative analysis of a
pharmaceutical formulation as well, e.g. by Yan and
However, the discussed problem is essential in var-
ious other fields of research and analysis. Yan and
studied the identification performance of dif-
ferent types of handheld NIR spectrometers for the
recycling of polymer commodities, including polyeth-
ylene (PE), polypropylene, polyethylene terephthalate,
polyvinyl chloride (PVC) and polystyrene. Four differ-
ent handheld spectrometers based on different mono-
chromator principles were investigated: Si-Ware
systems, Spectral Engines NR 2.0 W; DLP NIRscan
Nano EVM, and Viavi MicroNIR Pro ES 1700. The
investigation clearly demonstrated that the spectra of
the most common polymer commodities provide suit-
able analytical measurement parameters for the correct
classification of unknown test samples. Upon perform-
ing principal component analysis (PCA), all polymer
classes could be sufficiently separated, excepting PE
and PVC measured by the Spectral Engines NR
2.0W spectrometer (Figure 4).
Wiedemair et al.
have tested the performance of
SCiO in comparison with Bu
¨chi NIRFLex N-500 for
the analysis of protein content in millet samples and
the fat content in cheese samples. As can be deduced
from Tables 2 and 3 they found that the analytical
performance of portable devices may considerably
vary between different scenarios. Although clearly infe-
rior in the former analytical problem (Table 2), in the
determination of fat content in cheese (Table 3), the
inexpensive SCiO sensor delivered the performance,
evaluated by statistical values, comparable to the
high-performing benchtop instrument. Several other
examples may be mentioned that clearly demonstrate
the interest that portable NIRS attracts for a variety of
applications, e.g. identification/authentication of tex-
tiles as a measure against counterfeit.
This gives pros-
pects for future evolution of applications of
miniaturized NIRS. However, the scientific and profes-
sional community understands that the performance
evaluation of miniaturized spectrometers in different
scenarios needs to remain a continuously explored
direction, as new devices keep appearing on the
The conclusions from the community discussion
at NIR 2019 concerning portable NIRS
The continuous instrumental developments and appli-
cations observed over the last few years have launched
NIR spectroscopy into a new era of on-site and in-the-
field analysis. Generally, popularization of handheld
instruments brings a reasonable prospect for enabling
truly wide scale applications and high volume NIR
spectroscopic analyses in a wide spectrum of scenarios.
Seen through these lenses, a major transformation is
occurring that brings this tool closer to general public
in everyday use. Vendors have succeeded in consider-
ably reducing manufacturing costs of handheld NIR
Table 2. Performance of benchtop versus ultra-portable NIR spectrometer in millet analysis. Parameters of the established PLS-R models
for protein content (7–14% w/w in this sample set).
Spectrometer State of the grains PCs R
(CV) RMSECV (mg GAE/g) R
(TV) RMSEP (mg GAE/g)
NIRFlex N-500 Intact 4 0.953 0.365 0.940 0.467
Milled 6 0.985 0.223 0.920 0.479
SCiO Intact 5 0.876 0.601 0.814 0.806
Milled 5 0.8240 0.743 0.782 0.840
CV: cross-validated regressions; GAE: gallic acid equivalents; NIR: near-infrared; PC: principal component; PLS-R: Partial Least Squares Regression;
RMSECV: Root Mean Square Error of Cross Validation; RMSEP: Root Mean Square Error of Prediction; TV: test set-validated regressions.
Table 3. Performance of benchtop versus ultra-portable NIR spectrometer in cheese analysis. Parameters of the established PLS-R models
for fat content (9–36% w/w in this sample set).
Spectrometer State of the grains PCs R
(CV) RMSECV (mg GAE/g) R
(TV) RMSEP (mg GAE/g)
NIRFlex N-500 Intact 2 0.9726 1.5711 0.9431 1.8964
Grated 2 0.9930 0.7845 0.9913 0.7676
SCiO Intact 2 0.9801 1.2466 0.9838 1.1874
Grated 2 0.9838 1.0527 0.9940 0.8194
CV: cross-validated regressions; GAE: gallic acid equivalents; NIR: near-infrared; PC: principal component; PLS-R: Partial Least Squares Regression;
RMSECV: Root Mean Square Error of Cross Validation; RMSEP: Root Mean Square Error of Prediction; TV: test set-validated regressions.
c et al. 7
spectrometers and made great efforts to make these
instruments suitable for everyday life applications by
a non-expert user community. However, caution
should be applied with the instruments advertised by
The major gathering of the global NIR community
in Gold Coast, Australia in 2019 reflected that aware-
ness. The primary concern expressed by the experts in
the field was the following: miniaturized equipment still
requires comprehensive validation studies performed in
well-equipped laboratories. The need for closer coop-
eration between the vendors and these laboratories
would be beneficial for the adoption of new
Opportune conditions of the contemporary market
promote overly optimistic and aggressive marketing
strategies, which may bring the opposite effect. At
some point, the customers are likely to attempt to use
NIR spectroscopy in unrealistic scenarios and fail
therein. The resulting crisis of public trust in this tech-
nology may severely harm sales, and thus future devel-
opment. Such scheme can, however, be avoided if a
close cooperation between the vendor companies and
research laboratories is maintained. This summarizes
the ‘take home message’ from the NIRS community,
as resulted from the discussion upon the current state
and future path of miniaturized spectrometers at NIR
2019 conference (Gold Coast, Australia).
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
The author(s) disclosed receipt of the following financial sup-
port for the research, authorship, and/or publication of this
article: This work was funded by the Austrian Science Fund
(FWF): M2729-N28.
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8NIR news 0(0)
... In recent years, novel technology led to the introduction of affordable miniaturized NIR spectrometers that can be easily operated by non-experts and offered as portable or handheld devices [44,45]. A number of competing engineering solutions exist in this area, for example, instruments based on a digital micromirror device (DMD) ( Figure 3A). ...
... In recent years, the use of portable or handheld NIR spectrometers has become increasingly popular for the analysis of food products [44,45,343]. These instruments offer a convenient and cost-effective alternative to traditional benchtop spectrometers, as they can be used in the field or on the production line for rapid, non-destructive analysis. ...
... Miniaturized sensors have varying designs and multiple competing engineering solutions exist in this area, factors which introduce differences in their applicability and performance profiles in different analytical scenarios [44,45]. This topic attracts considerable attention also in the context of apple analysis, and several studies have been conducted to compare the performance and accuracy of portable NIR devices and their applicability potential in various setups. ...
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Spectroscopic methods deliver a valuable non-destructive analytical tool that provides simultaneous qualitative and quantitative characterization of various samples. Apples belong to the world's most consumed crops and with the current challenges of climate change and human impacts on the environment, maintaining high-quality apple production has become critical. This review comprehensively analyzes the application of spectroscopy in near-infrared (NIR) and visible (Vis) regions, which not only show particular potential in evaluating the quality parameters of apples but also in optimizing their production and supply routines. This includes the assessment of the external and internal characteristics such as color, size, shape, surface defects, soluble solids content (SSC), total titratable acidity (TA), firmness, starch pattern index (SPI), total dry matter concentration (DM), and nutritional value. The review also summarizes various techniques and approaches used in Vis/NIR studies of apples, such as authenticity, origin, identification, adulteration, and quality control. Optical sensors and associated methods offer a wide suite of solutions readily addressing the main needs of the industry in practical routines as well, e.g., efficient sorting and grading of apples based on sweetness and other quality parameters, facilitating quality control throughout the production and supply chain. This review also evaluates ongoing development trends in the application of handheld and portable instruments operating in the Vis/NIR and NIR spectral regions for apple quality control. The use of these technologies can enhance apple crop quality, maintain competitiveness, and meet the demands of consumers, making them a crucial topic in the apple industry. The focal point of this review is placed on the literature published in the last five years, with the exceptions of seminal works that have played a critical role in shaping the field or representative studies that highlight the progress made in specific areas.
... Handheld MicroNIR spectrometer devices are available for various NIR spectroscopy applications [18][19][20] and have been used for grain sorghum evaluation. Kosmowsky and Worku [21] investigated the suitability of a miniaturized NIR spectrometer for cultivar identification of barley, chickpea, and sorghum. ...
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Near infrared (NIR) spectroscopy is widely used for evaluating quality traits of cereal grains. For evaluating protein content of intact sorghum grains, parallel NIR calibrations were developed using an established benchtop instrumentation (Perten DA-7250) as a baseline to test the efficacy of an adaptive handheld instrument (VIAVI MicroNIR OnSite-W). Spectra were collected from 59 grain samples using both instruments at the same time. Cross-validated calibration models were validated with 33 test samples. The selected calibration model for DA-7250 with a coefficient of determination (R 2) = 0.98 and a root mean square error of cross validation (RMSECV) = 0.41% predicted the protein content of a test set with R 2 = 0.94, root mean square error of prediction (RMSEP) = 0.52% with a ratio of performance to deviation (RPD) of 4.13. The selected model for the MicroNIR with R 2 = 0.95 and RMSECV = 0.62% predicted the protein content of the test set with R 2 = 0.87, RMSEP = 0.76% with an RPD of 2.74. In comparison, the performance of the DA-7250 was better than the MicroNIR, however, the performance of the MicroNIR was also acceptable for screening intact sorghum grain protein levels. Therefore, the MicroNIR instrument may be used as a potential tool for screening sorghum samples where benchtop instruments are not appropriate such as for screening samples in the field or as a less expensive option compared with benchtop instruments.
... IUP certainly offers a promising alternative to direct infrared imaging, but it is important to address the potential barriers to practical implementation, and a literature is emerging that tackles issues of size, stability, and speed [29][30][31], with compact near-and mid-IR technologies already seeing use in environmental and agricultural arXiv:2307.06225v1 [quant-ph] 12 Jul 2023 studies [32,33]. ...
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Infrared (IR) imaging is invaluable across many scientific disciplines, from material analysis to diagnostic medicine. However, applications are often limited by detector cost, resolution and sensitivity, noise caused by the thermal IR background, and the cost, portability and tunability of infrared sources. Here, we describe a compact, portable, and low-cost system that is able to image objects at IR wavelengths without an IR source or IR detector. This imaging with undetected photons (IUP) approach uses quantum interference and correlations between entangled photon pairs to transfer image information from the IR to the visible, where it can be detected with a standard silicon camera. We also demonstrate a rapid analysis approach to acquire both phase and transmission image information. These developments provide an important step towards making IUP a commercially viable technique.
... The benefit of utilizing this filtometer therefore lies in reducing processing time costs by having a real-time DPM quantification, as well as the ability to miniaturize infrared sampling, which will also help timely decision making to reduce worker exposure. Although nearinfrared spectrometers have been miniaturized to an extent commensurate with a belt wearable device [12], this has yet to be achieved for mid-infrared spectrometers where information related to OC and EC is found. ...
Conference Paper
Diesel particulate matter (DPM) is a common and well-known health hazard in the mining environment. The current approved method for monitoring both the organic and elemental carbon (OC, EC) portions of DPM is a laboratory method with a turnaround time of approximately one week. In order to evaluate exposure levels and take corrective action before overexposures occur, a portable real-time device capable of quantifying both OC and EC is needed. To that end, researchers from the National Institute for Occupational Safety and Health (NIOSH) designed and tested a device based on narrow bandpass optical filters that is capable of targeting infrared absorbance bands associated with DPM. Five optical bandpass filters were chosen based on previous work quantifying DPM using Fourier-transform infrared (FT-IR) spectrometry. The resulting device, referred to as a filtometer, is optimized to exclusively determine DPM and could serve as a cost-effective, field-portable alternative to laboratory-grade FT-IR analysis and instrumentation. The performance of the filtometer was investigated by calibrating FT-IR data from DPM (dependent variable) to the filtometer spectra (predictor variables) using a partial least-squares (PLS) and ordinary least squares (OLS) approach. The square of the correlation coefficient and root-mean-square error of cross validation measures were used to assess individual model performance.
... The SCiO (740-1070 nm) uses a LED light source and consists of a 4 × 3 photodiode array, with optical filters over the individual pixels. It has only 12 resolution elements resulting in a spectral resolution of approximately 28 nm (Beć et al., 2020). ...
... These tools are particularly suitable for the use on the farm and in the field, even by non-specialised personnel, also thanks to the development of easy-to-use software. Alongside the hardware evolutions, cloud applications for the management of predictive models and spectra have been developed, allowing to obtain the predicted data in real time [7]. ...
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A mild solar drying process on melon slices was carried out. During the whole process, Near InfraRed (NIR) spectra (900–1700 nm) were collected continuously in reflectance mode using a portable spectrometer (Viavi Solutions). Samplings were performed for the determination of weight, moisture content (MC), water activity (aw) and colour. Partial least square (PLS) regressions showed good prediction ability for MC, aw and colour parameters: MC: R²CV = 0.99; RMSECV = 2.49%; aw: R²CV = 0.97; RMSECV = 0.03; a*: R²CV = 0.91; RMSECV = 1.13; b*: R²CV = 0.86; RMSECV = 2.49; C*: R²CV = 0.87; RMSECV = 2.52; total colour difference: R²CV = 0.85; RMSECV = 1.77; Browning Index: R²CV = 0.86; RMSECV = 11.00. Ratio Performance in Deviation values higher than 3 for MC and aw models allowed their use for the estimation of such parameters’ pattern along the process, providing satisfactory predictions. These preliminary data suggested the potential applicability of NIR spectroscopy in monitoring the dehydration process.
... 3 Current important ultrafast technology applications in the NIR region are in food chemistry, 4 medical and pharmaceutics NIR spectroscopy. 2,5 For all these applications, cost-effective NIR sensors, higher sensitivity, and hand-held devices [6][7][8] are required. The most common sensor material in the region between 1100 and 1700 nm is Indium Gallium Arsenide (InGaAs). ...
We present a Silicon-based Charge-Coupled Device (Si-CCD) sensor applied as a cost-effective spectrometer for femtosecond pulse characterization in the Near Infrared region in two different configurations: two-Fourier and Czerny-Turner setups. To test the spectrometer's performance, a femtosecond Optical Parametric Oscillator with a tuning range between 1100 and 1700 nm and a femtosecond Erbium-Doped Fiber Amplifier at 1582 nm were employed. The nonlinear spectrometer operation is based on the Two-Photon Absorption effect generated in the Si-CCD sensor. The achieved spectrometer resolution was 0.6 ± 0.1 nm with a threshold peak intensity of 2×106Wcm2. An analysis of the nonlinear response as a function of the wavelength, the response saturation, and the criteria to prevent it are also presented.
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Compact near-infrared (NIR) spectrophotometers are low-cost instruments that enable a rapid, non-destructive and environmentally friendly measurement of soil organic carbon (SOC). However, the several aspects, such as soil sample preparation...
Fused deposition modelling (FDM) is one of the most researched 3D printing technologies that holds great potential for low-cost manufacturing of personalised medicine. To achieve real-time release, timely quality control is a major challenge for applying 3D printing technologies as a point-of-care (PoC) manufacturing approach. This work proposes the use of a low-cost and compact near-infrared (NIR) spectroscopy modality as a process analytical technology (PAT) to monitor a critical quality attribute (drug content) during and after FDM 3D printing process. 3D printed caffeine tablets were used to manifest the feasibility of the NIR model as a quantitative analytical procedure and dose verification method. Caffeine tablets (0-40% w/w) were fabricated using polyvinyl alcohol and FDM 3D printing. The predictive performance of the NIR model was demonstrated in linearity (correlation coefficient, R2) and accuracy (root mean square error of prediction, RMSEP). The actual drug content values were determined using the reference high-performance liquid chromatography (HPLC) method. The model of full-completion caffeine tablets demonstrated linearity (R2 = 0.985) and accuracy (RMSEP =1.4%), indicated to be an alternative dose quantitation method for 3D printed products. The ability of the models to assess caffeine contents during the 3D printing process could not be accurately achieved using the model built with complete tablets. Instead, by building a predictive model for each completion stage of 20%, 40%, 60% and 80%, the model of different completion caffeine tablets displayed linearity (R2 of 0.991, 0.99, 0.987, and 0.983) and accuracy (RMSEP of 2.22%, 1.65%, 1.41%, 0.83%), respectively. Overall, this study demonstrated the feasibility of a low NIR model as a non-destructive, low-cost, compact, and rapid analysis dose verification method enabling the real-time release to facilitate 3D printing medicine production in the clinic.
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We present field deployment results of a portable optical absorption spectrometer for localization and quantification of fugitive methane (CH4) emissions. Our near-infrared sensor targets the 2ν3 R(4) CH4 transition at 6057.1 cm−1 (1651 nm) via line-scanned tunable diode-laser absorption spectroscopy (TDLAS), with Allan deviation analysis yielding a normalized 2.0 ppmv∙Hz−1/2 sensitivity (4.5 × 10−6 Hz−1/2 noise-equivalent absorption) over 5 cm open-path length. Controlled CH4 leak experiments are performed at the METEC CSU engineering facility, where concurrent deployment of our TDLAS and a customized volatile organic compound (VOC) sensor demonstrates good linear correlation (R2 = 0.74) over high-flow (>60 SCFH) CH4 releases spanning 4.4 h. In conjunction with simultaneous wind velocity measurements, the leak angle-of-arrival (AOA) is ascertained via correlation of CH4 concentration and wind angle, demonstrating the efficacy of single-sensor line-of-sight (LOS) determination of leak sources. Source magnitude estimation based on a Gaussian plume model is demonstrated, with good correspondence (R2 = 0.74) between calculated and measured release rates.
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The performance of a newly developed pocket-sized near-infrared (NIR) spectrometer was investigated by analysing 46 cheese samples for their water and fat content, and comparing results with a benchtop NIR device. Additionally, the automated data analysis of the pocket-sized spectrometer and its cloud-based data analysis software, designed for laypeople, was put to the test by comparing performances to a highly sophisticated multivariate data analysis software. All developed partial least squares regression (PLS-R) models yield a coefficient of determination (R2) of over 0.9, indicating high correlation between spectra and reference data for both spectrometers and all data analysis routes taken. In general, the analysis of grated cheese yields better results than whole pieces of cheese. Additionally, the ratios of performance to deviation (RPDs) and standard errors of prediction (SEPs) suggest that the performance of the pocket-sized spectrometer is comparable to the benchtop device. Small improvements are observable, when using sophisticated data analysis software, instead of automated tools.
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Mid-infrared (MIR) spectroscopy has received widespread interest as a method to complement traditional soil analysis. Recently available portable MIR spectrometers additionally offer potential for on-site applications, given sufficient spectral data quality. We therefore tested the performance of the Agilent 4300 Handheld FTIR (DRIFT spectra) in comparison to a Bruker Tensor 27 bench-top instrument in terms of (i) spectral quality and measurement noise quantified by wavelet analysis; (ii) accuracy of partial least squares (PLS) calibrations for soil organic carbon (SOC), total nitrogen (N), pH, clay and sand content with a repeated cross-validation analysis; and (iii) key spectral regions for these soil properties identified with a Monte Carlo spectral variable selection approach. Measurements and multivariate calibrations with the handheld device were as good as or slightly better than Bruker equipped with a DRIFT accessory, but not as accurate as with directional hemispherical reflectance (DHR) data collected with an integrating sphere. Variations in noise did not markedly affect the accuracy of multivariate PLS calibrations. Identified key spectral regions for PLS calibrations provided a good match between Agilent and Bruker DHR data, especially for SOC and N. Our findings suggest that portable FTIR instruments are a viable alternative for MIR measurements in the laboratory and offer great potential for on-site applications.
A set of 42 millet (panicum miliaceum L.) samples was investigated for its protein content using standard Kjeldahl analysis and near-infrared spectroscopy. The performance of three handheld spectrometers was compared to a benchtop instrument. The used spectrometers operate in different regions of the NIR, which gives interesting insights into the applicability of each region. Additionally, semi-automated, consumer-oriented multivariate data analysis was compared to sophisticated data evaluation. The performance of the near-infrared instruments was compared using important statistical parameters of the established cross- and test set validated partial least squares regression (PLS-R) models. Milled and intact samples were analysed, in order to further evaluate the importance of homogeneity. The results showed that the benchtop spectrometer is capable of accurately analysing protein content of millet grains, with root mean square error (RMSEP) values for milled and intact grains of approximately 0.5%. Two PLS-R models of handheld instruments also yielded good results for milled grains with RMSEP values of about 0.6%. The semi-automated multivariate data analysis showed some drawbacks compared to standard data processing software. For intact grains, however, similar results could be achieved.
Until very recently, handheld spectrometers were the domain of major analytical and security instrument companies, with turnkey analyzers using spectroscopic techniques from X-ray fluorescence (XRF) for elemental analysis (metals), to Raman, mid-infrared, and near-infrared (NIR) for molecular analysis (mostly organics). However, the past few years have seen rapid changes in this landscape with the introduction of handheld laser-induced breakdown spectroscopy (LIBS), smartphone spectroscopy focusing on medical diagnostics for low-resource areas, commercial engines that a variety of companies can build up into products, hyphenated or dual technology instruments, low-cost visible-shortwave NIR instruments selling directly to the public, and, most recently, portable hyperspectral imaging instruments. Successful handheld instruments are designed to give answers to non-scientist operators; therefore, their developers have put extensive resources into reliable identification algorithms, spectroscopic libraries or databases, and qualitative and quantitative calibrations. As spectroscopic instruments become smaller and lower cost, “engines” have emerged, leading to the possibility of being incorporated in consumer devices and smart appliances, part of the Internet of Things (IOT). This review outlines the technologies used in portable spectroscopy, discusses their applications, both qualitative and quantitative, and how instrument developers and vendors have approached giving actionable answers to non-scientists. It outlines concerns on crowdsourced data, especially for heterogeneous samples, and finally looks towards the future in areas like IOT, emerging technologies for instruments, and portable hyphenated and hyperspectral instruments.
Textiles are extremely important materials for everyday life with a broad range of applications and properties. Due to the large variations in quality on the one hand and the increasing quality awareness and price consciousness of customers on the other hand, the availability of a simple tool for a rapid test of the correct identity of the purchased textile article would be a significant progress in customer protection. Miniaturization of near infrared spectrometers has advanced to the point where handheld instruments could provide reliable and affordable means to serve this purpose. One objective of the present communication was to scrutinize the identification and discrimination performance for textile materials for four real-handheld (<200 g) near infrared spectrometers based on different monochromator principles. The second focus was to show that in the near future these handheld instruments can be used by a non-expert user community to protect themselves against fraud in textile purchase situations. For this purpose, diffuse reflection spectra of 72 textile samples of synthetic and natural origin were measured. While in simple situations, test samples can readily be authenticated by visual inspection of their near infrared spectra only, for a more comprehensive identification of unknown samples principal component analysis in combination with soft independent modeling of class analogies was applied. In the present work, this approach provided a suitable analytical tool for the correct assignment of the investigated different types of textile materials. Moreover, the evaluation of the mean Euclidian distances in the principal component analysis score plots derived from the near infrared spectra of the textile classes under investigation allowed to compare the identification performance and discrimination capability of the different handheld instruments.
Notwithstanding the first developments of miniaturized vibrational spectrometers more than a decade ago, only recently real handheld near-infrared (NIR) spectrometers (<200 g) became commercially available at significantly reduced costs compared to other portable systems. While on the one hand this development was driven by the consumer request for every-day-life applications by non-experts, on the manufacturer side it was supported by the availability and potential of new technologies such as micro-electromechanical systems (MEMS). In the present communication calibration spectra of a solid pharmaceutical formulation consisting of two excipients and three active ingredients, acetylsalicylic acid (ASA), ascorbic acid (ASC) and caffeine (CAF), have been measured with four handheld NIR spectrometers based on different monochromator principles and have subsequently been used to develop partial least squares (PLS) models for the quantitative determination of the active ingredients. Taking into account the instrumental and spectral peculiarities of the four instruments and the three analytes, respectively, the detailed analysis of the calibration parameters and the prediction accuracy for a test sample set then allowed to compare the performance of the different spectrometers for the analytical problem under investigation.
The performance of three portable NIR spectrometers was compared by analysing the total antioxidant capacity (TAC) of different species of gluten-free grains. TAC is often used to evaluate the quality of foods and was determined using Folin-Ciocalteu measurements and used as reference data for establishing PLS-R models with NIR data. NIRS enables fast and non-invasive measurements. The microPhazir RX and the MicroNIR 2200 are broadly used in chemical and pharmaceutical industries, whereas SCiO is a pocket-sized, consumer-oriented spectrometer. The devices work in different regions of the NIR spectrum and their performances was compared using statistical parameters. 77 samples were measured and analysed using the software The Unscrambler X, as well as SCiO-Lab. All models established were cross- and test set validated. The multivariate data processing using The Unscrambler X yielded similar results as SCiO-Lab. The best model was established for non-milled samples measured with the MicroNIR 2200 and analysed using The Unscrambler X.
For sustainable utilization of raw materials and environmental protection, the recycling of the most common polymers—polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS)—is an extremely important issue. In the present communication, the discrimination performance of the above polymer commodities based on their near-infrared (NIR) spectra measured with four real handheld (<200 g) spectrometers based on different monochromator principles were investigated. From a total of 43 polymer samples, the diffuse reflection spectra were measured with the handheld instruments. After the original spectra were pretreated by second derivative and standard normal variate (SNV), principal component analysis (PCA) was applied and unknown samples were tested by soft independent modeling of class analogies (SIMCA). The results show that the five polymer commodities cluster in the score plots of their first three principal components (PCs) and, furthermore, samples in calibration and test sets can be correctly identified by SICMA. Thus, it was concluded that on the basis of the NIR spectra measured with the handheld spectrometers the SIMCA analysis provides a suitable analytical tool for the correct assignment of the type of polymer. Because the mean distance between clusters in the score plot reflects the discrimination capability for each polymer pair the variation of this parameter for the spectra measured with the different handheld spectrometers was used to rank the identification performance of the five polymer commodities.