Name: Fluorescent Paper Strips for the Detection of Diesel Adulteration with Smartphone Read-out (Video) | JoVE Journal
Uploaded: 2018-11-09T12:30:00.000+00:00
Duration: 7 min 10 s
Description: Learn to detect diesel adulteration with kerosene using fluorescent paper strips and smartphone readout. This rapid method provides qualitative results in under one minute without specialized equipment.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

The authors would like to acknowledge the BAM for funding through the focus area Analytical Sciences: https://www.bam.de/Navigation/EN/Topics/Analytical-Sciences/Rapid-Oil-Test/rapid-oil-test.html.

1. Fluorescent Dyes (Figure 1A)
<ol>
	<li>Purchase commercially available 4-DNS and 4-DNS-OH. 
	Note: 4-DNS-COOH is not commercially available and is prepared from 4-DNS-OH as described hereafter.</li>
	<li>Place 50 mg (0.16 mmol) of 2-[ethyl[4-[2-(4-nitrophenyl)ethenyl]phenyl]amino]ethanol, 2 mg (0.016 mmol) of 4-dimethylaminopyridine and 19.2 mg (0.192 mmol) of succinic anhydride in a 10 mL round bottom flask.</li>
	<li>Dissolve the reagents in 2 mL of dry dichloromethane under argon atmosphere.</li>
	<li>Add 11.6 &#181;L (0.08 mmol) of triethylamine and let the mixture react for 20 h.</li>
	<li>Monitor the reaction by thin layer chromatography until quantitative conversion of the starting materials (Rf = 0.61) into the product (Rf = 0.27) is indicated (hexane/EtOAc, 4/6, v/v)</li>
	<li>Add 2 mL of water to the mixture before acidification to pH 2 with acetic acid (approx. 10 &#181;L).</li>
	<li>Extract the mixture by performing two successive liquid-liquid extractions, with 10 mL of dichloromethane each time.</li>
	<li>Wash once the reunited organic phases with 10 mL of saturated NaCl (&#62; 359 g L&#8211;1).</li>
	<li>Dry the organic phases by adding Na2SO4 powder until some fine drying agent powder remains visible.</li>
	<li>Purify the crude product by flash silica column chromatography with petroleum ether:ethylacetate 1:9 as the eluent. 
	Note: The yield achieved were 49 mg (74%) of the desired product.</li>
	<li>Perform 1H NMR analysis of the purified product in DMSO-d6 to validate the structure (&#948; 8.17 (d, J = 8.8 Hz, 2H), 7.75 (d, J = 8.8 Hz, 2H), 7.49 (d, J = 8.8 Hz, 2H), 7.41 (d, J = 16.3 Hz, 1H), 7.10 (d, J = 16.3 Hz, 1H), 6.75 (d, J = 8.9 Hz, 2H), 4.18 (t, J = 6.0 Hz, 2H), 3.58 (t, J = 6.0 Hz, 2H), 3.43 (q, J = 7.0 Hz, 2H), 2.50 &#8211; 2.45 (m, 4H), 1.10 (t, J = 7.0 Hz, 3H) ppm).</li>
	<li>Perform 13C NMR analysis of the purified product in DMSO-d6 to validate the structure (&#948; 173.36, 172.20, 147.99, 145.23, 145.13, 133.89, 128.76, 126.30, 124.03, 123.67, 120.95, 111.58, 61.52, 48.05, 44.57, 28.73, 28.63, 12.00 ppm).</li>
	<li>Perform high resolution mass spectrometry with positive electro spray ionization of the purified product, corresponding to the calculated value (C22H25N2O6 [M+H]+: 413.1707) m/z ratio of 413.1713.</li>
</ol>
2. Synthesis of the Reference Dye
Note: The synthetic procedure of 8-(phenyl)-1,3,5,7-tetramethyl-2,6-diethyl-4,4-difluoro-4 bora-3a,4a-diaza-s-indacene was adopted from Coskun et al.18.
<ol>
	<li>Purify the crude product by column chromatography on silica with toluene as eluent. 
	Note: The yield achieved were 441 mg (29 %) of bright reddish crystals.</li>
	<li>Perform 1H NMR analysis of the pure product at 600 MHz in DMSO-d6 to validate the structure (&#948; 0.98 (t, 6H, J = 7.6 Hz), 1.27 (s, 6H), 2.29 (q, 4H, J = 7.6 Hz), 2.53 (s, 6H), 7.27-7.29 (m, 2H), 7.46-7.48 (m, 3H) ppm).</li>
	<li>Perform high resolution mass spectrometry with positive electro spray ionization of the purified product, corresponding to the calculated value (C23H28BF2N2 [M+H]+: 381.2314) m/z ratio of 381.2267.</li>
</ol>
3. TEST STRIP FABRICATION, METHOD 1.
<ol>
	<li>Prepare 1 mM solutions of the reference dye and dyes 4-DNS, 4-DNS-OH and 4-DNS-COOH in toluene.</li>
	<li>Cut cellulose strips of 30 &#215; 5 mm from filter paper.</li>
	<li>Place approximately 50 of those strips (611 mg) in a sealable 5 mL vial together with 4.5 mL of the desired dye solution from step 3.1.</li>
	<li>Shake the strips inside the vial with a vertical rotator for 20 min at 30 rpm.</li>
	<li>Pour the toluene solution out of the vial, and immediately fill with 4 mL of cyclohexane and rotate for 1 min at 30 rpm to wash off excess dyes.</li>
	<li>Repeat the washing operation from Step 3.5 three times.</li>
	<li>Dry the obtained test strips on a filter paper for 10 min in air at room temperature.</li>
</ol>
4. Test Strip Fabrication, Method 2.
<ol>
	<li>Amination of the paper strips.
	<ol>
		<li>Cut cellulose strips of 30 &#215; 5 mm from filter paper.</li>
		<li>Under a fume hood, place approximately 20 of those strips (308 mg) in a flask containing 40 mL of toluene.</li>
		<li>Add 960 &#181;L of 3-aminopropyltriethoxysilane (APTES) in the flask and stir the mixture for 24 h at 80 &#176;C.</li>
		<li>Remove the strips from the flask and wash thoroughly with 50 mL of ethanol.</li>
		<li>Dry the strips for 2 h at 50 &#176;C.</li>
	</ol>
	</li>
	<li>Grafting of the dye.
	<ol>
		<li>Under a fume hood, dissolve 5 mg of 4-DNS-COOH (13 &#181;mol) in 10 mL of dry dichloromethane under argon atmosphere in a 25 mL flask.</li>
		<li>Add N,N&#39;-dicyclohexylcarbodiimide (DCC, 3.3 mg, 16 &#181;mol) and allow the carboxylic acid to be activated for 15 min.</li>
		<li>Add triethylamine (2.2 &#181;L, 16 &#181;mol) and 18 aminated paper strips (278 mg).</li>
		<li>Stir the mixture for additional 2 h.</li>
		<li>Remove the strips from the solution and wash with 25 mL of dichloromethane and 25 mL of ethanol.</li>
	</ol>
	</li>
</ol>
5. Sample Pre-Treatment.
<ol>
	<li>Laboratory treatment
	<ol>
		<li>Place 10 mL of a fresh diesel/kerosene blend in a 25 mL vial.</li>
		<li>Suspend 10 wt% of active charcoal in the blend.</li>
		<li>Stir the vial for 1 h, centrifuge (400 x g, 10 min) and filter to remove the charcoal.</li>
	</ol>
	</li>
	<li>On-site treatment
	<ol>
		<li>Purchase circular activated carbon loaded filters of 47 mm diameter.</li>
		<li>Place four of the filters in a 47 mm stainless steel in-line filter holder.</li>
		<li>Flush 5 mL of a fresh diesel/kerosene blend through the filters with a standard 10 mL syringe; approximately 2 mL of polycyclic aromatic hydrocarbon-free solution was obtained.</li>
	</ol>
	</li>
</ol>
6. Smartphone Reader Implementation
Note: An Android based smartphone with a centered front camera was used as the core of the smartphone measurement system. All the necessary optical elements and 3D-printed accessory were custom-made for this device. However, any other smartphone with a CMOS (Complementary Metal Oxide Semiconductor) camera can be used.19,20
<ol>
	<li>Purchase a standard 5 mm epoxy LED at 460 nm, a 100 &#937; resistor and a USB on-the-go (OTG) cable with an ON/OFF switch and a micro USB port.</li>
	<li>Cut the USB cable on the opposite of the OTG side to isolate the red wire powering +5 V (up to 300 mA) and the black wire corresponding to the ground.</li>
	<li>Cut the black wire of the USB cable and solder the 100 &#937; resistor on the back of the switch. Solder the LED anode to the +5V red wire and the LED cathode to the ground black wire.</li>
	<li>Purchase a diffuser and two filters for the LED and the camera, typically a short pass filter for the excitation channel (LED) and a band pass filter for the emission collection (camera).</li>
	<li>3D-print a smartphone case that fits on the smartphone and integrates the different optical parts consisting of a black chamber (20 x 30 x 40 mm)21 as described in Figure 2.</li>
	<li>3D-print a strip holder as described in Figure 2 to hold a reference and a test strip.</li>
	<li>Implement the excitation channel by placing the LED, the diffuser and the filter to illuminate the paper strips at an angle of 60&#176;.</li>
	<li>Implement the reading channel by placing the filter in front of the smartphone CMOS camera.</li>
	<li>Insert the test strip holder containing the strips to start a measurement.</li>
</ol>
7. Sample Analysis Using the Smartphone-Based Detector
Note: Analyses were carried out by running a Java app(lication) for Android that finally displayed the adulteration level on the screen. Without the app, pictures can be taken, exported to a computer and analyzed with a standard image analysis software.
<ol>
	<li>Select the adequate calibration file, here diesel/kerosene, from the software memory by clicking on the Menu button in the upper-right corner of the software window.</li>
	<li>Dip the test strip into the diesel sample for a couple of seconds by holding the test strip with tweezers.</li>
	<li>Remove excess fuel by simple patting with a drying paper.</li>
	<li>Place the test strip inside the strip holder besides the reference strip and introduce the holder into the smartphone case. 
	Note: An image of the strips&#8217; fluorescence is then immediately displayed on the smartphone&#8217;s screen.</li>
	<li>Press the SHOOT button to record the fluorescence intensities of test and reference strips. 
	Note: The degree of adulteration is immediately calculated by the internal algorithm and displayed on the screen.</li>
</ol>

<ol><li>Mattheou, L., Zannikos, F., Schinas, P., Karavalakis, G., Karonis, D., Stournas, S. <a target="_blank" href="https://www.researchgate.net/publication/258518426_Impact_of_using_adulterated_automotive_diesel_on_the_exhaust_emissions_of_a_stationary_diesel_engine">Impact of Using Adulterated Automotive Diesel on the Exhaust Emissions of a Stationary Diesel Engine.</a> Global NEST Journal. 8 (3), 291-296 (2006).</li>
<li>Gawande, A. P., Kaware, J. P. <a target="_blank" href="http://www.tsijournals.com/abstract/fuel-adulteration-consequences-in-india--a-review-11609.html">Fuel Adulteration Consequences in India : A Review.</a> Scientific Reviews and Chemical Communications. 3 (3), 161-171 (2013).</li>
<li>Lam, N. L., Smith, K. R., Gauthier, A., Bates, M. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Kerosene%3A+A+Review+of+Household+Uses+and+their+Hazards+in+Low-+and+Middle-Income+Countries%5BTitle%5D)+AND+%22Journal+of+Toxicology+and+Environmental+Health%2C+Part+B%22%5BJournal%5D)">Kerosene: A Review of Household Uses and their Hazards in Low- and Middle-Income Countries.</a> Journal of Toxicology and Environmental Health, Part B. 15 (6), 396-432 (2012).</li>
<li>Chandrappa, R., Chandra Kulshrestha, U. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aChandrappa%2C+R+%22Sustainable+Air+Pollution+Management%3A+Theory+and+Practice%22">Sustainable Air Pollution Management: Theory and Practice</a>. , Springer International Publishing. 305-323 (2016).</li>
<li>Felix, V. J., Udaykiran, P. A., Ganesan, K. <a target="_blank" href="http://www.indjst.org/index.php/indjst/article/viewFile/59076/46230">Fuel Adulteration Detection System.</a> Indian Journal of Science and Technology. 8, 90-95 (2015).</li>
<li>Meira, M., et al. <a target="_blank" href="https://www.researchgate.net/publication/277348556_Determination_of_Adulterants_in_Diesel_by_Integration_of_LED_Fluorescence_Spectra">Determination of Adulterants in Diesel by Integration of LED Fluorescence Spectra.</a> Journal of the Brazilian Chemical Society. 26 (7), 1351-1356 (2015).</li>
<li>Klingbeil, A. E., Jeffries, J. B., Hanson, R. K. <a target="_blank" href="https://www.sciencedirect.com/science/article/pii/S0016236108002585">Temperature- and composition-dependent mid-infrared absorption spectrum of gas-phase gasoline: Model and measurements.</a> Fuel. 87 (17-18), 3600-3609 (2008).</li>
<li>Gupta, A., Sharma, R. K. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aGupta%2C+A+%22Air+Pollution%22">Air Pollution</a>. Villanyi, V. , InTech. (2010).</li>
<li>Gruber, J., Lippi, R., Li, R. W. C., Benvenho, A. R. V. <a target="_blank" href="https://www.researchgate.net/publication/221910033_Analytical_Methods_for_Determining_Automotive_Fuel_Composition">Analytical Methods for Determining Automotive Fuel Composition.</a> New Trends and Developments in Automotive System Engineering. 13, 13-28 (2011).</li>
<li>Park, D. H., Hong, J., Park, I. S., Lee, C. W., Kim, J. M. <a target="_blank" href="https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201400779">A Colorimetric Hydrocarbon Sensor Employing a Swelling-Induced Mechanochromic Polydiacetylene.</a> Advanced Functional Materials. 24 (33), 5186-5193 (2014).</li>
<li>Haidekker, M. A., Theodorakis, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ratiometric+mechanosensitive+fluorescent+dyes%3A+Design+and+applications%5BTitle%5D)+AND+%22Journal+of+Materials+Chemistry+C%22%5BJournal%5D)">Ratiometric mechanosensitive fluorescent dyes: Design and applications.</a> Journal of Materials Chemistry C. 4 (14), 2707-2718 (2016).</li>
<li>Uzhinov, B. M., Ivanov, V. L., Melnikov, M. Y. <a target="_blank" href="http://iopscience.iop.org/article/10.1070/RC2011v080n12ABEH004246">Molecular rotors as luminescence sensors of local viscosity and viscous flow in solutions and organized systems.</a> Russian Chemical Reviews. 80 (12), 1179-1190 (2011).</li>
<li>Grabowski, Z. R., Rotkiewicz, K., Rettig, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Structural+Changes+Accompanying+Intramolecular+Electron+Transfer%3A+Focus+on+Twisted+Intramolecular+Charge-Transfer+States+and+Structures%5BTitle%5D)+AND+%22Chemical+Reviews%22%5BJournal%5D)">Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures.</a> Chemical Reviews. 103 (10), 3899-4032 (2003).</li>
<li><a target="_blank" href="https://www.astm.org/DATABASE.CART/HISTORICAL/D975-16A.htm">ASTM D975 - 16a, Standard Specification for Diesel Fuel Oils</a>. , ASTM International. (2016).</li>
<li>Colucci, J. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aColucci%2C+J+%22Future+Automotive+Fuels+%E2%80%A2+Prospects+%E2%80%A2+Performance+%E2%80%A2+Perspective%22">Future Automotive Fuels • Prospects • Performance • Perspective</a>. , Springer US. (1977).</li>
<li>Lackner, M., Winter, F., Agarwal, A. K. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aLackner%2C+M+%22Gaseous+and+Liquid+Fuels%22">Gaseous and Liquid Fuels</a>. 3, WILEY-VCH Verlag GmbH & Co. (2010).</li>
<li>Gotor, R., Tiebe, C., Schlischka, J., Bell, J., Rurack, K. <a target="_blank" href="https://pubs.acs.org/doi/abs/10.1021/acs.energyfuels.7b01538">Detection of Adulterated Diesel Using Fluorescent Test Strips and Smartphone Readout.</a> Energy & Fuels. 31 (11), 11594-11600 (2017).</li>
<li>Coskun, A., Akkaya, E. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ion+Sensing+Coupled+to+Resonance+Energy+Transfer%3A+A+Highly+Selective+and+Sensitive+Ratiometric+Fluorescent+Chemosensor+for+Ag%28I%29+by+a+Modular+Approach%5BTitle%5D)+AND+%22Journal+of+the+American+Chemical+Society%22%5BJournal%5D)">Ion Sensing Coupled to Resonance Energy Transfer: A Highly Selective and Sensitive Ratiometric Fluorescent Chemosensor for Ag(I) by a Modular Approach.</a> Journal of the American Chemical Society. 127 (30), 10464-10465 (2005).</li>
<li>Chang, B. Y. <a target="_blank" href="http://koreascience.or.kr/article/ArticleFullRecord.jsp?cn=JCGMCS_2012_v33n2_549">Smartphone-based Chemistry Instrumentation: Digitization of Colorimetric Measurements.</a> Bulletin of the Korean Chemical Society. 33 (2), 549-552 (2012).</li>
<li>Roda, A., et al. <a target="_blank" href="https://www.sciencedirect.com/science/article/pii/S0165993615301060">Smartphone-based biosensors: A critical review and perspectives.</a> TrAC Trends in Analytical Chemistry. 79, 317-325 (2016).</li>
<li>McCracken, K. E., Yoon, J. -Y. <a target="_blank" href="http://pubs.rsc.org/en/content/articlelanding/2016/ay/c6ay01575a">Recent approaches for optical smartphone sensing in resource-limited settings: a brief review.</a> Analytical Methods. 8 (36), 6591-6601 (2016).</li>
</ol>

The authors have nothing to disclose.

A fluorescent probe, based on a molecular rotor dye that is sensitive to viscosities in the range of those measured for diesel and its different blends with kerosene, was used to obtain simple and efficient test strips for the detection of diesel fuel adulteration. The emission intensity of 4-DNS at 550 nm in various diesel/kerosene blends correlates with a reduction in viscosity when the proportion of kerosene increases. At a temperature of 24 &#176;C, a nonlinear fluorescence quenching of up to 55% was observed for up ...

Fuel adulteration is a serious problem in many different parts of the world, simply due to the enormous relevance of fuel as an energy source. Running engines on adulterated fuel reduces their performance, leads to earlier engine failure and entails environmental pollution1. Increased SOx emissions occur if diesel is adulterated with kerosene that usually contains a higher amount of sulfur2,3. Although the problem exists for decades, sustainable fuel management that uncovers such criminal activity at its point of origin is still rare, because simple and reliable tests for fuel adulteration are largely lacking4. Despite substantial progress in laboratory-based mineral oil analysis in the past decades5,6,7, approaches to on-site measurements are still scarce. Various methods for the use outside of the laboratory have recently been devised, using fiber optics8, field-effect transistors9 or mechano-chromic materials10. Although they overcome some of the drawbacks of conventional methods, robust, user-friendly and portable methods are still lacking largely. Fluorescent viscosity probes based on molecular rotors are an interesting alternative11,12, because mineral oils are comprised of a great variety of hydrocarbons that differ in chain length and cyclicity, being often reflected in different viscosities. Because fuels are complex mixtures without specific lead compounds to act as tracers, the measurement of the change of a macroscopic property like viscosity or polarity seems very promising. The latter can be addressed by fluorescent molecular rotors for which the fluorescence quantum yields depend on environmental viscosity. After photoexcitation, deactivation commonly involves a twisted intramolecular charge transfer (TICT) state, the population of which is determined by the viscosity of its surrounding microenvironment13. Highly viscous solvents hinder molecular rotors to adopt a TICT state, entailing bright emission. In low-viscous solvents, the rotor can much better access the TICT state, accelerating non-radiative decay and thus quenched fluorescence. The addition of kerosene, with a viscosity of 1.64 mm2&#8729;s-1 at 27 &#176;C, to diesel, with respective viscosities of 1.3-2.4, 1.9-4.1, 2.0-4.5 or 5.5-24.0 mm2&#8729;s -1 at 40 &#176;C for grades 1D, 2D, EN 950 and 4D14,15,16, reduces the kinematic viscosity of the mixture and potentially leads to a proportional quenching of the fluorescence of a molecular rotor probe. The family of 4-dimethylamino-4-nitrostilbenes (4-DNS) seemed most promising to us because of their strong fluorescence variation over a kinematic viscosity range of 0.74-70.6 mm2&#8729;s -1. This range matches well with the known values of kerosene and diesel.
We therefore explored the ability of 4DNS, 2-[ethyl[4-[2-(4-nitrophenyl)ethenyl]phenyl]amino]ethanol (4DNSOH) and (E)-4-(2-(ethyl(4-(4-nitrostyryl)phenyl)amino)ethoxy)-4-oxobutanoic acid (4DNSCOOH) to indicate the viscosity of diesel-kerosene mixtures through their fluorescence, depending on intramolecular rotation and finally yielding a rapid test for diesel adulteration with kerosene. The disposable test is easy to use, precise, reliable, cost-effective and dimensionally small. The adsorption of the probes onto the filter paper as a solid support was investigated and the analysis was accomplished with an embedded smartphone-based fluorescence reader. Today, ubiquitously available smartphones are equipped with high-quality cameras, rendering the detection of optical changes such as color and fluorescence straightforward, and paving the way for powerful on-site analyses. We demonstrate here that the measurement of the emission of fluorescent probes adsorbed on paper strips with a smartphone can be used for fraud detection on combustion fuels in a reliable manner17.

<table><tbody><tr><td>4-dimethylamino-4-nitrostilbene (CAS Number: 2844-15-7)</td><td>Sigma-Aldrich</td><td>39255</td><td>4-DNS Dye</td></tr><tr><td>2-[ethyl[4-[2-(4-nitrophenyl)ethenyl]phenyl]amino]ethanol (CAS Number: 122258-56-4)</td><td>Sigma-Aldrich</td><td>518565</td><td>4-DNS-OH Dye</td></tr><tr><td>Whatman&amp;nbsp;qualitative filter paper, Grade 1</td><td>Sigma-Aldrich</td><td>Z274852</td><td>Test strips support</td></tr><tr><td>Whatman&amp;nbsp;application specific filter, activated carbon loaded paper, Grade 72</td><td>Sigma-Aldrich</td><td>WHA1872047</td><td>Fuel pre-treatment filters</td></tr><tr><td>Pall reusable in-line filter holders stainless steel, diam. 47&amp;nbsp;mm</td><td>Sigma-Aldrich</td><td>Z268453&amp;nbsp;</td><td>Holder pre-treatment filters</td></tr><tr><td>(3-Aminopropyl)triethoxysilane</td><td>Sigma-Aldrich</td><td>919-30-2</td><td>APTES</td></tr><tr><td>4-(Dimethylamino)pyridine</td><td>Sigma-Aldrich</td><td>1122-58-3</td><td>DMAP</td></tr><tr><td>Succinic anhydride</td><td>Sigma-Aldrich</td><td>108-30-5</td><td></td></tr><tr><td>Triethylamine</td><td>Sigma-Aldrich</td><td>121-44-8</td><td>Et&lt;sub&gt;3&lt;/sub&gt;N</td></tr><tr><td>&lt;em&gt;N,N&#039;&lt;/em&gt;-dicyclohexylcarbodiimide&amp;nbsp;</td><td>Sigma-Aldrich</td><td>538-75-0</td><td>DCC</td></tr><tr><td>Stuart Tube Rotators</td><td>Cole-Parmer</td><td>SB3</td><td>Rotator</td></tr><tr><td>FreeCAD</td><td>freecadweb.org</td><td>-</td><td>Freeware - 3D design</td></tr><tr><td>Ultimaker Cura</td><td>Ultimaker</td><td>-</td><td>Freeware - 3D printing</td></tr><tr><td>Android Studio</td><td>Google</td><td>-</td><td>Freeware - App programming</td></tr><tr><td>Renkforce SuperSoft OTG-Mirror Micro-USB Cable 0,15 m</td><td>Conrad.de</td><td>1359890&amp;nbsp;- 62</td><td>Smartphone setup electronic part</td></tr><tr><td>Black Cord Switch 1 x Off / On</td><td>Conrad.de</td><td>1371835&amp;nbsp;- 62</td><td>Smartphone setup electronic part</td></tr><tr><td>Carbon Film Resistor 100 &amp;Omega;</td><td>Conrad.de</td><td>1417639&amp;nbsp;- 62</td><td>Smartphone setup electronic part</td></tr><tr><td>492 nm blocking edge BrightLine&amp;nbsp;short-pass filter</td><td>Semrock</td><td>FF01-492/SP-25</td><td>Filter excitation</td></tr><tr><td>550/49&amp;nbsp;nm BrightLine single-band bandpass filter</td><td>Semrock</td><td>FF01-550/49-25</td><td>Filter emission</td></tr><tr><td>&amp;Oslash;1/2&quot; Unmounted N-BK7 Ground Glass Diffuser, 220 Grit</td><td>Thorlabs</td><td>DG05-220</td><td>Diffuser excitation</td></tr><tr><td>LED 465 nm, 9 cd, 20 mA, &amp;plusmn;15&amp;deg;, 5 mm clear epoxy</td><td>Roithner</td><td>RLS-B465</td><td>LED excitation</td></tr></tbody></table>

fluorescent paper strips for the detection of diesel adulteration with smartphone read-out

Fluorescent Paper Strips for the Detection of Diesel Adulteration with Smartphone Read-out

Three fluorescent molecular rotors of 4-dimethylamino-4-nitrostilbene (4-DNS) were investigated for their potential use as viscosity probes to indicate the content of kerosene in diesel/kerosene blends, a wide-spread activity to adulterate fuel. In solvents with low viscosity, the dyes rapidly deactivate via a so-called twisted intramolecular charge transfer state, efficiently quenching the fluorescence. Measurements of diesel/kerosene blends revealed a good linear correlation between the decrease in fluorescence and the increase of the fraction of the less viscous kerosene in diesel/kerosene blends. Immobilization of the hydroxy derivative 4-DNS-OH in cellulose paper yielded test strips that preserve the fluorescent indicator&#39;s behavior. Combination of the strips with a reader based on a smartphone and a controlling app allowed to create a simple field test. The method can reliably detect the presence of kerosene in diesel from 7 to 100%, outperforming present standard methods for diesel adulteration.

The three structures of the two commercial dyes 4-DNS and 4-DNS-OH and the synthesized dye 4-DNS-COOH contain a stilbene core element substituted with a donor (-NR2) and an acceptor (-NO2) group at both ends, the central double bond constituting the hinge of the so called 'molecular rotor' (Figure 1A). The structures differ in amino group substitution pattern with short alkyl groups for 4-DNS, two slightly longer groups including an alco...

Here, we present a protocol to detect the adulteration of diesel with kerosene using test strips coated with a fluorescent viscosity probe together with a smartphone-based analysis system.

Three fluorescent molecular rotors of 4-dimethylamino-4-nitrostilbene (4-DNS) were investigated for their potential use as viscosity probes to indicate ...

fluorescent-paper-strips-for-detection-diesel-adulteration-with

Research

JoVE Journal

Environment

Droplet-based microfluidic platforms are promising candidates for high throughput experimentation since they are able to generate picoliter, self-compartmentalized vessels inexpensively at kHz rates. Through integration with fast, sensitive and high resolution fluorescence spectroscopic methods, the large amounts of information generated within these systems can be efficiently extracted, harnessed and utilized.

Fluorescence detection methods for microfluidic droplet platforms

We review our recent results on the integration of fluorescent microscopy and imaging flow cytometry tools on a cell-phone using compact and cost-effective opto-fluidic attachments. These cell-phone based micro-analysis devices might be useful for cytometric analysis, such as performing various cell counting tasks as well as for high-throughput screening of e.g., water samples in resource limited settings.

Wide-field Fluorescent Microscopy and Fluorescent Imaging Flow Cytometry on a Cell-phone

Cross-conjugated cruciform fluorophores based on 1,4-distyryl-2,5-bis(arylethynyl)benzene and benzobisoxazole nuclei can be used to qualitatively identify diverse Lewis acidic and Lewis basic analytes. This method relies on the differences in emission colors of the cruciforms that are observed upon analyte addition. Structurally closely related species can be distinguished from each other.

Qualitative Identification of Carboxylic Acids, Boronic Acids, and Amines Using Cruciform Fluorophores

A protocol involving integrated concentration, enrichment, and end-point colorimetric detection of foodborne pathogens in large volumes of agricultural water is presented here.  Water is filtered through Modified Moore Swabs (MMS), enriched with selective or non-selective media, and detection is performed using paper-based analytical devices (µPAD) imbedded with bacterial-indicative colorimetric substrates.

Colorimetric Paper-based Detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from Large Volumes of Agricultural Water

The study demonstrates the growth of iridium oxide-reduced graphene oxide (IrO2-RGO) nanohybrid thin films on irregular and rough screen-printed carbon substrate through a green electrochemical synthesis, and their implementation as a pH sensor with a patterned paper-fluidic platform.

Iridium Oxide-reduced Graphene Oxide Nanohybrid Thin Film Modified Screen-printed Electrodes as Disposable Electrochemical Paper Microfluidic pH Sensors

Multicolor fluorescence detection in droplet microfluidics typically involves bulky and complex epifluorescence microscope-based detection systems. Here we describe a compact and modular multicolor detection scheme that utilizes an array of optical fibers to temporally encode multicolor data collected by a single photodetector.

Multicolor Fluorescence Detection for Droplet Microfluidics Using Optical Fibers

Dipstick urinalysis is a quick and affordable method of assessing one’s personal state of health. We present a method to perform accurate, low-cost dipstick urinalysis that removes the primary sources of error associated with traditional dip-and-wipe protocols and is simple enough to be performed by lay users at home.

Low-Cost, Volume-Controlled Dipstick Urinalysis for Home-Testing

Addressing urgent dengue diagnostic needs, here we introduce a smartphone app-integrated Dengue NS1 Paper-based Analytical Device (DEN-NS1-PAD) for quantifying Dengue NS1 antigen concentration in clinical serum/blood samples. This innovation enhances dengue management by aiding clinical decision-making in various healthcare settings, even resource-limited ones.

Portable Paper-Based Immunoassay Combined with Smartphone Application for Colorimetric and Quantitative Detection of Dengue NS1 Antigen

This protocol describes a CRISPR-Cas-mediated, multianalyte synthetic urine biomarker test that enables point-of-care cancer diagnostics through the ex vivo analysis of tumor-associated protease activities.

CRISPR-Cas-mediated Multianalyte Synthetic Urine Biomarker Test for Portable Diagnostics

Here, we describe a protocol for the preparation of quantum dot nanobeads (QDNB) and the detection of disease biomarkers using QDNB-based lateral flow immunoassay strips. The test results can be qualitatively assessed under UV light illumination and quantitatively measured using a fluorescent strip reader within 15 min.

Fluorescent Lateral Flow Immunoassay Based on Quantum Dots Nanobeads

This work has discussed the protocol for designing and developing an E-Eye-Enable POCT device to detect Fe, Cr, As, and F in environmental samples, biological samples, and food and beverages. Nearly 2000 samples have been tested, and the results accord with the gold-standard technique.

TD-DFT Guided Advanced E-Eye Sensing Technique for On-site Quantification of Fe, Cr, F, and As in the Environmental, Biological, and Food Samples

Learn to detect diesel adulteration with kerosene using fluorescent paper strips and smartphone readout. This rapid method provides qualitative results in under one minute without specialized equipment.

Fluorescent Paper Strips for the Detection of Diesel Adulteration with Smartphone Read-out

Explore More Videos