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Detection of Drugs with Cantilever-Enhanced Photoacoustic Spectroscopy

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  • Detection of Drugs With Cantilever-Enhanced Photoacoustic Spectroscopy

    Dr. Jaakko Lehtinen, Client Partner, Gasera Ltd. Pittcon 2017, 6.3.2017, 09:30 AM

    Gasera Ltd. Lemminkisenkatu 59, 20520 Turku, Finland

  • Projects overview

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    Two projects in FP7 program: CUSTOM and DOGGIES One project in H2020 program: IRON Some work is also done outside these projects

  • Photoacoustic effect was discovered in 1880 by Alexander Graham Bell

    This theoretical potential has not been reached, since conventional microphones have been used for sensing the pressure pulses

    Gaseras novel cantilever sensor technology allows the use of the full potential of the photoacoustic phenomena

    Photoacoustic spectroscopy is based on the absorption of light leading to the local warming of the absorbing volume element. The subsequent expansion of the volume element generates a pressure wave proportional to the absorbed energy, which can be detected via a pressure detector.

    Photoacoustic spectroscopy





    A typical setup of a conventional PAS system


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  • Key inventions Cantilever sensor

    Over 100 times greater physical movement can be achieved compared to conventional microphone membrane cantilever has very low string constant 1 N/m

    Highly linear response Optical readout system

    Contactless optical measurement based on laser interferometry

    Measures cantilever displacements smaller than picometer (10-12 m)

    Extremely wide dynamic measurement range

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  • Benefits of cantilever enhanced PAS

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    Absorption is measured directly in PAS which makes the measurement very accurate and free of drift -> stability and reliability, easy to use

    Cantilever sensor provides high sensitivity > below ppb detection limits Sensitivity is not dependent on the optical path length -> wide linear dynamic range, miniaturization,

    low sample volume Many different sources can be connected to one cell -> multi-gas capability Possibility to heat the sample cell -> suitable to wide range of process applications

  • CUSTOM-project

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    CUSTOM - Drugs And PreCUrsor Sensing By ComplemenTing Low COst Multiple Techniques. The project has started in 2010 and ended in 2013. The aim of the project is to is to build a portable device for drug precursor sensing from vapor phase based on the two orthogonal techniques, which are laser photoacoustic sensor and fluorescence optochip. Development of the cantilever enhanced photoacoustic detector combined with the widely tunable external cavity quantum cascade laser is introduced.

  • Example measurement with CW EC QCL - setup

    Example measurements were done with continuous wave external cavity quantum cascade laser (CW EC-QCL ) provided by Daylight Solutions.

    The wavenumber range was between 1020 cm-1 1100 cm-1. Example gases that were measured were: BMK and Safrole. The power of the laser at this wavenumber range was between 0 mW - 62 mW. The photoacoustic cell was Gasera PA201 detector (cell diameter 4 mm, length 100 mm). Amplitude modulation with mechanical chopper was done. FFT software was used for selecting amplitude from the modulation frequency (phase lock would give better

    results by order of 2)

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    Photoacoustic detector

    Beam path

  • Example measurement - BMK and Safrole

    The measurement was performed by modulating the amplitude mechanically by chopper and tuning the laser wavelength in 0.1 cm-1 steps from 1020 cm-1 to 1100 cm-1.

    Comparison to FTIR measurement was performed indicating a very good match between the line positions and spectrum details.

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    D3.8%Sensitivity%Evaluation%of%Different%Target%Molecules% CLASSIFIED)RESTRAINT)UE)

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    Figure 3. The IR spectra of several drug precursors. Courtesy of CUSTOM project.

    The sample of 100 ppm of phenylpropanone (BMK) was measured with a detection limit 2xRMS of 160 ppb (total response time about 60 s).

    Figure 4. PAS measurement of BMK and FTIR measurement in comparison.

    D3.8%Sensitivity%Evaluation%of%Different%Target%Molecules% CLASSIFIED)RESTRAINT)UE)

    ' ' ' ' ' ' '''''''''' '''''''''' ' ' Page' 11' of'20'


    The sample of 100 ppm of safrole was determined to have a detection limit of 24 ppb (total response time about 60 s)

    Figure 5. PAS measurement of Safrole with FTIR comparison measurement.

    Table 6. Sensitivity of PAS with EC-QCL to BMK and Safrole.

    BMK (100 ppm) Safrole (100 ppm)

    Wavenumber (cm-1) 1084.5 1059.0 Laser power (mW) 7.08 4.01

    Signal 0.069 0.538 Noise (2xRMS @ 1 s) 1.13eE-04 1.28E-04

    DL (ppm) 0.163 0.024

    5.4 Measurement of Acetylene

    Acetylene measurements were done with wavelength modulation technique, with a fiber coupled DFB laser. The fiber-coupled laser was a FITEL FRL15950 with center wavelength of 1530.1 nm with output power of 40 mW. The DFB diode laser can be used with small signal modulation i.e. wavelength modulation, thus there is no need for a mechanical chopper. The measurements were done with 100 ppm of acetylene and Ultra High Purity Nitrogen (5.0). The results are presented in the table below.

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    Funded by the European Commission under the FP7-Security programme

    Project started in 2012, ended in November 2015 The Consortium of 14 partners from 5 EU countries DOGGIES project aims at demonstrating: An operational movable stand-alone sensor for an efficient detection of hidden persons, drugs & explosives

    Orthogonal trace detection Mid-Infrared spectroscopy, based on photoacoustic detection (PAS) with widely tunable integrated MIR source i.e. MIRPAS

    Ion Mobility Spectrometry (IMS), with non-radioactive ionization source

    Using specific pre-concentrators and advanced software to provide reliable detection in real environments

    DOGGIES = Detection of Olfactory traces by orthoGonal Gas identification technologIES


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    Lab testing of the prototypes Headspace measurement of drugs and explosives with MIRPAS and commercially available EC-QCL. Measurements done at INPS, Lyon.

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    Lab testing of the prototypes

  • Multi-gas analysis with EC-QCL PAS Multi-gas analysis for air quality measurements Tuning range: 1000 1250 cm-1

    Resolution: 1 cm-1

    3 minutes response time ppb-level detection limits

    (1 26 ppb with analysis)

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    Photoacoustic spectroscopy

    Photoacoustic spectroscopy holds the promise of miniaturization without sacrificing the performance Compact scanning lasers enable multi-gas detection in portable form factor

  • Measurements with hair samples

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    A non-invasive drug-testing application Drugs enter hair via circulation A longer detection window of drugs in hair Occasional, random or constant abuse can be detected Drugs concentrate to the center of hair

    Benefits of photoacoustic spectroscopy: Measurement does not consume sample material

    No sample preparation needed Depth profiling

  • Detection of drugs in hair

    FTIR-PAS measurement without sample pre-processing

    Hair samples from cocaine overdose patients were measured (12 samples)

    Hair samples from a clean reference group were also measured (12 samples)

    20-30 mg sample material was used per measurement

    90 s measurement time Cocaine content was previously

    measured with MS to be between 1,5 and 38 ng/mg in different samples

  • - 16 -

    Detection of drugs in hair

    Principal component analysis was used in the spectral analysis

    Data processing: Selection of the wavelength ranges Normalization of the spectra by the

    area Second derivative Normalization of the single spectral


    Cocaine users could be separated based on their spectra

  • Micro-sample studies

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    Single hair fibers were also investigated Smallest measured fiber was only 0.5 mm long With single fibers, it is possible to study the time line of drug abuse Currently Society of Hair Testing recommends the use of more than 20 mg of hair material for reliable analysis

  • Solid phase drug measurement FTIR-PAS measurement of

    different drugs Study made in collaboration with

    Crime Lab of Finnish Police Forces

    No sample preparation Fast contactless measurement

  • FTIR-PAS measurement of cannabis

    Police wants to know the THC-level of the cannabis plant

    Different parts of the cannabis plant were measured Chemometry can be used to define the concentrations

    of the different compounds

  • Miniaturization

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    FTIR -> scanning EC-QCL Photoacoustic spectroscopy can be utilized in field use for solid samples as well