This work was funded by SONATA, a joint project between the French Agence Nationale de la Recherche (ANR-13-IS08-0001) and the US National Science Foundation. Christine Baduel is funded by the French National Research Agency (ANR) through the ANR-16-ACHN-0026 project. The authors also warmly thank Marija Margu&#353;, Ana Cvite&#353;i&#263;, Sanja Frka Milosavljevi&#263; and Irena Ciglenecki, from Rudjer Boskovic Institute of Zagreb, Croatia for the help with the aerosol sampling at Marina Frapa, Rogoznica, Croatia.

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<li>Mustaffa, N., Latif, M., Ali, M., Khan, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Source+apportionment+of+surfactants+in+marine+aerosols+at+different+locations+along+the+Malacca+Straits%5BTitle%5D)+AND+%22Environ+Sci+Pollut+Res%22%5BJournal%5D)">Source apportionment of surfactants in marine aerosols at different locations along the Malacca Straits.</a> Environ Sci Pollut Res. 21, 6590-6602 (2014).</li>
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<li>Hummel, D. O. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aHummel%2C+DO+%22Handbook+of+Surfactant+Analysis%3A+Chemical%2C+Physico-chemical+and+Physical+Methods%22">Handbook of Surfactant Analysis: Chemical, Physico-chemical and Physical Methods</a>. , Wiley. 203(2000).</li>
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<li>Desai, J. D., Banat, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Microbial+production+of+surfactants+and+their+commercial+potential%5BTitle%5D)+AND+%22Microbiol.+Mol.+Biol.+R%22%5BJournal%5D)">Microbial production of surfactants and their commercial potential.</a> Microbiol. Mol. Biol. R. 61, 47-64 (1997).</li>
<li>Christofi, N., Ivshina, I. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Microbial+surfactants+and+their+use+in+field+studies+of+soil+remediation%5BTitle%5D)+AND+%22J.+Appl.+Microbiol%22%5BJournal%5D)">Microbial surfactants and their use in field studies of soil remediation.</a> J. Appl. Microbiol. 93, 915-929 (2002).</li>
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<li>Mircea, M., et al. <a target="_blank" href="http://www.atmos-chem-phys.net/5/3111/2005/">Importance of the organic aerosol fraction for modeling aerosol hygroscopic growth and activation: a case study in the Amazon Basin.</a> Atmos. Chem. Phys. 5, 3111-3126 (2005).</li>
<li>Varga, B., Kiss, G., Ganszky, I., Gelencsér, A., Krivácsy, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Isolation+of+water-soluble+organic+matter+from+atmospheric+aerosol%5BTitle%5D)+AND+%22Talanta%22%5BJournal%5D)">Isolation of water-soluble organic matter from atmospheric aerosol.</a> Talanta. 55, 561-572 (2001).</li>
<li>Kiss, G., Tombácz, E., Hansson, H. -C. <a target="_blank" href="http://link.springer.com/article/10.1007/s10874-005-5079-5">Surface Tension Effects of Humic-Like Substances in the Aqueous Extract of Tropospheric Fine Aerosol.</a> J Atmos Chem. 50, 279-294 (2005).</li>
<li>Salma, I., Ocskay, R., Varga, I., Maenhaut, W. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1029/2005JD007015/abstract">Surface tension of atmospheric humic-like substances in connection with relaxation, dilution, and solution pH.</a> J. Geophys. Res. 111, D23205(2006).</li>
<li>Taraniuk, I., Graber, E. R., Kostinski, A., Rudich, Y. <a target="_blank" href="http://www.phy.mtu.edu/~kostinsk/hulis_grl.pdf">Surfactant properties of atmospheric and model humic-like substances (HULIS).</a> Geophys. Res. Lett. 34, L16807(2007).</li>
<li>Morris, H. S., Grassian, V. H., Tivanski, A. V. <a target="_blank" href="http://pubs.rsc.org/en/content/articlelanding/sc/2015/c4sc03716b#!divAbstract">Humidity-dependent surface tension measurements of individual inorganic and organic submicrometre liquid particles.</a> Chemical Science. 6, 3242-3247 (2015).</li>
<li>Roslan, R. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Surfactants+in+the+sea-surface+microlayer+and+their+contribution+to+atmospheric+aerosols+around+coastal+areas+of+the+Malaysian+peninsula%5BTitle%5D)+AND+%22Mar.+Pollut.+Bull%22%5BJournal%5D)">Surfactants in the sea-surface microlayer and their contribution to atmospheric aerosols around coastal areas of the Malaysian peninsula.</a> Mar. Pollut. Bull. 60, 1584-1590 (2010).</li>
<li>Orlović-Leko, P., Kozarac, Z., Ćosović, B., Strmečki, S., Plavšić, M. <a target="_blank" href="http://link.springer.com/article/10.1007/s10874-011-9189-y">Characterization of atmospheric surfactants in the bulk precipitation by electrochemical tools.</a> J Atmos Chem. 66, 11-26 (2010).</li>
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</ol>

The authors have nothing to disclose.

In the protocol, all the critical steps have been detailed. They include the collection of the aerosols on filters, the extraction of surfactants from them (using a double extraction: a water extraction followed by a SPE extraction) and the analysis of the extracts (surface tension and concentration measurements).
For the whole method, a quality control has been made 1) by the application of the extraction and analysis method on blank filters (deviation &#60;5 mN m-1 compared with ultrapure water on the surface tension and absorbance under the detection limit for the colorimetric method), 2) by determining the extraction efficiency and their uncertainties including the reproducibility/repeatability, the % of extracted surfactants in a given range of concentration, 3) by checking the potential interferents on the colorimetric method, i.e. by checking that the method detects only the targeted type of surfactant (anionic, cationic and non-ionic) and do not see the others as fully detailed in references4,6) by checking potential interferents from the aerosol extracts (inorganic salts, small acids) on the colorimetric method as fully detailed in reference6.
To our knowledge, the extraction method for surfactants from atmospheric samples presented in this article is currently the most selective one in atmospheric chemistry. In particular it is much more selective than the simple water extractions performed in the past for the investigation of these compounds.11,23,24 The second extraction step is important as it has been shown to remove ionic components, such as inorganic salts and small organic acids, that are in large concentrations in the aerosol samples and interfere with the concentration measurements.6 This extraction method has also been shown to remove all the surfactants present in the samples, at the surface and in the bulk. The resulting extracts are thus concentrated enough to allow for accurate characterizations of these compounds.
However, in addition to surfactants, it is possible that other non-polar or mildly polar compounds are extracted from the atmospheric aerosols. For instance, &#34;Humic-like Substances&#34; (HULIS), that are usually extracted by similar methods25 and, depending on the sampling region, could be present in the extracts. These compounds are only mildly surfactant compared to the surfactants characterized in our samples,26,27,28 thus should not contribute significantly to the surface tension or CMC measured. However, they are polyacids and could interfere with the anionic concentration measurements. In the future, their contribution to the surfactant concentrations (i.e. whether or not they react with ethyl violet, the dye used to titrate anionic surfactants) will need to be determined. If their contribution is significant, extra steps could be added to the extraction method, to eliminate for instance all the compounds that are active in the UV-Vis or by fluorescence, which would include HULIS but not surfactants.
So far, no other method for the measurement of the surface tension of aerosols and of the surface tension curve for aerosol surfactants than the one presented in this manuscript is available. The hanging droplet technique is recommended for these measurements as it is the only one requiring sample volumes consistent with atmospheric samples. Optical techniques, measuring directly the surface tension on micron-size particles without any extraction, are being developed.10,20,29 So far, they are only applicable to laboratory-produced particles but could potentially someday be applied to atmospheric ones.
The colorimetric method presented in this work for the measurement of surfactant concentration has been applied previously to atmospheric aerosol samples11,13,14,30 but only to water extracts and not to double extracts, as in our method. This is an important difference as, as underlined above, the second extraction step removes compounds such as inorganic salts and small organic acids, which interfere with the concentration measurements.6
An electrochemical technique, initially developed for seawater and larger aqueous samples, has also been used to measure the concentration of surfactants in atmospheric aerosols.31,32 This method is relative, i.e. the surfactant concentrations obtained depend on the reference compounds chosen and assume that the detection sensitivity of all surfactants is identical. The detection limit reported for this technique is 0.02 mg L-1 when using tetra-octylphenolethoxylate as reference, thus 0.03 &#956;M, and comparable to the detection limit of about 0.05 &#956;M for anionic and cationic surfactants by the colorimetric method. But because of the uncertainties in the determination of the non-ionic and total surfactant concentrations with the colorimetric method, it would be interesting to compare both methods (inter-calibration).
A few points in the presented methods could be further improved.
Another dye than cobalt thiocyanate that would detect all non-ionic surfactants and wit the same sensitivity would be very useful and reduce the main source of uncertainties in the current concentration measurements.
The extraction efficiency for cationic surfactants, currently estimated to 20%, could also be improved, as these compounds are often at the detection limit in atmospheric samples. This could be done, for instance, by using a specific SPE column.
The extractions and titration conditions could be further improved. For instance, using in parallel three different SPE set-ups, each optimized for a class of surfactants, could improve the extraction efficiency, and improve the quality of the procedure (less contamination risks). The optimum sorbent density of the SPE cartridge for the sample mass to be analyzed could also been determined. The conditions for the titration reactions (pH, additives) could also be further optimized, to further improve the sensitivity of the concentration measurements, i.e. lower the detection limits.
Additional tests or steps could be added to the extraction protocol to exclude the non-surfactant compounds that might have been extracted. For instance, the potential presence of HULIS in the samples could be investigated by optical techniques (UV-Vis or fluorescence).
Further modifications, while not improving the quality of the analysis itself, would bring more information on atmospheric surfactants, such as applying the present method to different size-fractions (i.e. sub-populations) of the aerosol rather than on all the particles collected, as presented here. Other types of analyses could also be applied to the extracts such as, LC/HR MS, tandem MS, or NMR to determine the chemical structure of the surfactants or UV-Vis absorbance, fluorescence, or polarimetry, to indicate the presence of highly-conjugated or chiral compounds in the extracts.

Clouds are essential in the Earth&#39;s atmosphere, for the hydrology of most environments and ecosystems, and for the climate system. But some aspects of their formation mechanisms are still not understood, in particular the contributions of the chemical compounds present in the aerosol particles that act as condensation nuclei. Theory1 predicts that surface-active compounds, or surfactants, present in aerosol particles should strongly enhance cloud droplet formation by lowering their surface tension, thus their formation energy. But these effects have remained elusive to observation for decades and the role of surfactants on cloud formation is currently denied by a large part of the atmospheric community and ignored in all cloud investigations and atmospheric and climate models.
One reason for the lack of understanding of the role of aerosol surfactants in cloud formation has been the absence of method to isolate and characterize them. Unlike samples from other environments, the analysis of atmospheric samples faces recurring challenges2 such as very small sample volume and mass (here, typically between 10 and 100 &#956;g) and chemical complexity (mixtures of salts, minerals, and numerous organics). To overcome these challenges and improve the understanding of aerosol surfactants some methods have been recently developed by our group to 1) extract specifically these compounds from atmospheric aerosol samples, 2) determine their absolute concentrations in the aerosol phase and 3) determine their surface tension curves in water, including their Critical Micelle Concentration (CMC), the concentration at which the surfactants are saturated at the surface and start to form micelles in the bulk. The latest versions of these methods are presented in this paper.
Further improvements and other types of characterizations, that could be used in complement to those presented, will be discussed. Recent applications of these methods have already shown how such analyses can improve the understanding of the role of surfactants in cloud formation, by evidencing this role itself,3 determining the surfactant concentrations in atmospheric aerosols3,4,5,6 and mode of action in cloud droplet formation,3,6 evidencing their biogenic origin,3,4,7 and explaining their lack of observation by classical instruments.8,9,10

<table><tbody><tr><td>Quartz filters</td><td>Fioroni</td><td></td><td>for example &amp;Oslash; 47 mm or &amp;Oslash; 150 mm, Grammage 85 g/m&lt;sup&gt;2&lt;/sup&gt;</td></tr><tr><td>Aluminium foils or glass Petri dishes</td><td></td><td></td><td>baked in oven (773 K, 6&amp;nbsp;h)</td></tr><tr><td>Tweezers, scissors</td><td></td><td></td><td></td></tr><tr><td>Desiccator</td><td></td><td></td><td></td></tr><tr><td colspan="4">&lt;strong&gt;SPE (Solid Phase Extraction) set-up&lt;/strong&gt;</td></tr><tr><td>SPE vacuum manifold Ac-Elut</td><td>Varian&amp;nbsp;</td><td></td><td></td></tr><tr><td>Pump Laboxat</td><td>Knf LAB</td><td></td><td></td></tr><tr><td colspan="4">&lt;strong&gt;Nitrogen dryer set-up&lt;/strong&gt; (hand-made)</td></tr><tr><td>Compressed Nirogen 4.5 in bottle B50, 200 bar at 15 &amp;deg;C</td><td>Linde</td><td></td><td></td></tr><tr><td>Tensiometer</td><td>Dataphysics</td><td>OCA 15EC</td><td></td></tr><tr><td>Tensiometer Software</td><td></td><td>SCA software for OCA version 4-4.1</td><td></td></tr><tr><td>UV-Vis spectrometer</td><td>Agilent</td><td>8453</td><td></td></tr><tr><td>Stir-plates</td><td></td><td></td><td></td></tr><tr><td colspan="4">&lt;strong&gt;Glassware&lt;/strong&gt;</td></tr><tr><td>Glass Petri dishes</td><td></td><td></td><td>for the water extraction step</td></tr><tr><td>Beakers</td><td></td><td></td><td></td></tr><tr><td>15 mL, 30 mL, 60 mL glass bottles with corks</td><td></td><td></td><td></td></tr><tr><td>Tubes for SPE</td><td></td><td></td><td></td></tr><tr><td>Magnetic stirring bars</td><td></td><td></td><td></td></tr><tr><td>Ultrasound bath</td><td></td><td></td><td>for glassware washing</td></tr><tr><td>Micropipettes (0.5 - 5&amp;nbsp;mL, 0.100 - 1&amp;nbsp;mL, 10 - 100 &amp;mu;L)</td><td>Rainin Pipette-Life XLS</td><td></td><td></td></tr><tr><td colspan="4">&lt;strong&gt;Disposable small equipment&lt;/strong&gt;</td></tr><tr><td>Syringe filters 0.45 &amp;mu;m PVDF</td><td>Fisherbrand</td><td></td><td></td></tr><tr><td>SPE C18 cartridges Strata C18-E cartridges 500 mg / 3 mL&amp;nbsp;</td><td>Phenomenex</td><td></td><td></td></tr><tr><td>Plastic syringes</td><td></td><td></td><td></td></tr><tr><td>Needles</td><td></td><td></td><td></td></tr><tr><td>4 mL-vials</td><td></td><td></td><td></td></tr><tr><td>Pasteur glass pipettes</td><td></td><td></td><td></td></tr><tr><td>Micropipette tips</td><td></td><td></td><td></td></tr><tr><td colspan="4">&lt;strong&gt;Chemicals&lt;/strong&gt;</td></tr><tr><td>Sodium dodecyl sulfate (SDS) &amp;ge; 98.5% Bioreagent</td><td>Sigma- Aldrich</td><td>L3771</td><td></td></tr><tr><td>Dioctyl sulfosuccinate sodium salt (AOT) &amp;ge; 97%</td><td>Sigma- Aldrich</td><td>323586</td><td></td></tr><tr><td>Benzyltetradecyldimethylammonium (zephiramine)&amp;nbsp; &amp;ge; 99.0% anhydrous Fluka</td><td>Sigma- Aldrich</td><td>13401</td><td></td></tr><tr><td>Cetyltrimethylammonium chloride solution (CTAC) 25 wt% in H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma- Aldrich</td><td>292737</td><td></td></tr><tr><td>(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton X114) laboratory grade</td><td>Sigma- Aldrich</td><td>X114</td><td></td></tr><tr><td>Polyethylene glycol dodecyl ether (Brij35) Fluka Bio Chemika</td><td>Sigma- Aldrich</td><td>858366</td><td></td></tr><tr><td>L-&amp;alpha;-phosphatidylcholine from egg yolk type XVI-E lyophilized powder &amp;ge;&amp;nbsp;99%</td><td>Sigma- Aldrich</td><td>P3556</td><td></td></tr><tr><td>Surfactin from Bacillus subtilis &amp;ge; 98%</td><td>Sigma- Aldrich</td><td>S3523</td><td></td></tr><tr><td>R-95Dd rhamnolipid (95% dirhamnolipid, 5% monorhamnolipid)</td><td>Sigma- Aldrich</td><td>L510025</td><td></td></tr><tr><td>Ethyl violet cationic triarylmethane dye</td><td>Sigma- Aldrich</td><td>228842</td><td></td></tr><tr><td>Patent Blue VF dye content 50%</td><td>Sigma-Aldrich</td><td>198218</td><td></td></tr><tr><td>Ammonium thiocyanate &amp;ge; 99% puriss. p.a., ACS reagent</td><td>Sigma-Aldrich</td><td>31120</td><td></td></tr><tr><td>Cobalt(II) nitrate hexahydrate &amp;ge; 98% ACS reagent</td><td>Sigma-Aldrich</td><td>239267</td><td></td></tr><tr><td>Acetic anhydride &amp;ge; 99% ReagentPlus</td><td>Sigma-Aldrich</td><td>320102</td><td></td></tr><tr><td>Sodium acetate &amp;ge; 99.0% anhydrous Reagent Plus</td><td>Sigma-Aldrich</td><td>S8750</td><td></td></tr><tr><td>Ethylenediaminetetraacetic acid 99.4&amp;minus; 100.6% ACS reagent powder</td><td>Sigma-Aldrich</td><td>E9884</td><td></td></tr><tr><td>Sodium sulfate anhydrous &amp;ge; 99.0% granulated puriss. p.a. ACS reagent Fluka</td><td>Sigma-Aldrich</td><td>71960</td><td></td></tr><tr><td>Ethanol puriss. p.a. ACS Reagent reag. Ph. Eur. 96% (v/v)</td><td>Sigma-Aldrich</td><td>32294</td><td></td></tr><tr><td>Acetonitrile &amp;ge; 99.9% HiPerSolv CHROMANORM Reag. Ph. Eur. (European Pharmacopoeia Reagent) grade gradient for HPLC</td><td>VWR BDH Prolabo</td><td>20060.32</td><td>to be manipulated under hood</td></tr><tr><td>Chloroform 99% stable with 0.8&amp;minus;1% ethanol</td><td>Alfa Aesar</td><td>L13200-0F</td><td>to be manipulated under hood</td></tr><tr><td>Toluene &gt; 99%</td><td>Chimie Plus</td><td>24053</td><td>to be manipulated under hood</td></tr><tr><td>Denatured ethanol for washing</td><td></td><td></td><td></td></tr><tr><td>Ultra-Pure water</td><td>Ultrapure water system Purelab Classic, Elga</td><td></td><td></td></tr></tbody></table>

extraction and characterization of surfactants from atmospheric aerosols

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in the Earth&#39;s atmosphere, a central process in meteorology, hydrology, and for the climate system. But because specific extraction and characterization of these compounds have been lacking for decades, very little is known on their identity, properties, mode of action and origins, thus preventing the full understanding of cloud formation and its potential links with the Earth&#39;s ecosystems.
In this paper we present recently developed methods for 1) the targeted extraction of all the surfactants from atmospheric aerosol samples and for the determination of 2) their absolute concentrations in the aerosol phase and 3) their static surface tension curves in water, including their Critical Micelle Concentration (CMC). These methods have been validated with 9 references surfactants, including anionic, cationic and non-ionic ones. Examples of results are presented for surfactants found in fine aerosol particles (diameter &#60;1 &#956;m) collected at a coastal site in Croatia and suggestions for future improvements and other characterizations than those presented are discussed.

Note: Before being applied to atmospheric samples, all the protocols presented in this section have been tested with 9 reference surfactants and the surface tension curves, minimum surface tensions, and CMCs obtained were in excellent agreement with the literature.21,22
1. Concentrations
Fine aerosols (&#60;1 &#956;m in diameter, or &#34;PM1&#34;) samples were collected on Quartz fiber filters at the coastal site of Rogoznica, Croatia in February 2015. These samples were handled and extracted as described in Sections 2 and 3, respectively, of this manuscript. The concentrations for anionic, cationic and non-ionic surfactants and the total surfactant concentration in the aerosol sample volume, Csurf,p (M), were measured according to Section 4. The results are presented in Figure 1, and evidence the dominance of anionic and non-ionic surfactants among the surfactants measured.
2. Surface Tension of Sample and Surface Tension Curve for Extracted Surfactants
Combining surface tension measurements as described in Section 5, and the concentration measurements, resulted in absolute surface tension curves for the same samples, as shown in Figure 2. These curves indicate the surfactant concentration in the aerosol sample and the surface tension of these samples (&#34;&#963;min&#34;) and allow to determine graphically the CMC values (Figure 2).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/55622/55622fig1.jpg" /> 
Figure 1: Surfactant concentrations in fine aerosols (PM1) collected in Rogoznica, Croatia. Concentrations for anionic (in blue), cationic (in red), non-ionic surfactants (in green) and total surfactant concentration in the aerosol phase (sum of each surfactant concentrations), Csurf,p (M), measured with the colorimetric method in fine (&#60;1 &#956;m) atmospheric aerosols collected at the coastal site of Rogoznica, Croatia in February 2015. The results clearly show the dominance of anionic and non-ionic surfactants. <a href="http://cloudflare.jove.com/files/ftp_upload/55622/55622fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/55622/55622fig2.jpg" /> 
Figure 2: Typical surface tension curve and CMC for the surfactants in aerosols from Rogoznica, Croatia. Absolute surface tension curve for the surfactants in the sample of 03/02/2015 obtained by combining the surface tension and concentration measurements. The black dots represent the measured surface tension of the surfactant extract. The orange dot at the end of the curves represents the calculated concentration in the aerosol sample (step 4.4.6), and &#34;&#963;min&#34; its surface tension. The graphical determination of the CMC is illustrated. <a href="http://cloudflare.jove.com/files/ftp_upload/55622/55622fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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Extraction and Characterization of Surfactants from Atmospheric Aerosols

Methods are presented for the targeted extraction of surfactants present in atmospheric aerosols and the determination of their absolute concentrations and surface tension curves in water, including their Critical Micelle Concentration (CMC).

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in ...

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16.8K Views.  IRCELYON, F-69626.  Werkwijzen worden voor de gerichte extractie van oppervlakteactieve stoffen aanwezig in atmosferische aërosolen en bepaling van de absolute concentraties en oppervlaktespanning curven in water, met inbegrip van de kritische micelconcentratie (CMC). 

Video: Extraction and Characterization of Surfactants from Atmospheric Aerosols

Extraction and Analysis of Microbial Phospholipid Fatty Acids in Soils

Phospholipid fatty acids (PLFAs) are key components of microbial cell membranes. The analysis of PLFAs extracted from soils can provide information about the overall structure of terrestrial microbial communities. PLFA profiling has been extensively used in a range of ecosystems as a biological index of overall soil quality, and as a quantitative indicator of soil response to land management and other environmental stressors.
The standard method presented here outlines four key steps: 1. lipid extraction from soil samples with a single-phase chloroform mixture, 2. fractionation using solid phase extraction columns to isolate phospholipids from other extracted lipids, 3. methanolysis of phospholipids to produce fatty acid methyl esters (FAMEs), and 4. FAME analysis by capillary gas chromatography using a flame ionization detector (GC-FID). Two standards are used, including 1,2-dinonadecanoyl-sn-glycero-3-phosphocholine (PC(19:0/19:0)) to assess the overall recovery of the extraction method, and methyl decanoate (MeC10:0) as an internal standard (ISTD) for the GC analysis.

Phospholipid fatty acids provide information about the structure of soil microbial communities. We present methods for extraction from soil samples with a single-phase chloroform mixture, fractionation of extracted lipids using solid phase extraction columns, and methanolysis to produce fatty acid methyl esters, which are analyzed by capillary gas chromatography.

Phospholipid fatty acids (PLFAs) are key components of microbial cell membranes. The analysis of PLFAs extracted from soils can provide information about ...

Production and Measurement of Organic Particulate Matter in a Flow Tube Reactor

Organic particulate matter (PM) is increasingly recognized as important to the Earth's climate system as well as public health in urban regions, and the production of synthetic PM for laboratory studies have become a widespread necessity. Herein, experimental protocols demonstrate approaches to produce aerosolized organic PM by &#945;-pinene ozonolysis in a flow tube reactor. Methods are described for measuring the size distributions and morphology of the aerosol particles. The video demonstrates basic operations of the flow tube reactor and related instrumentation. The first part of the video shows the procedure for preparing gas-phase reactants, ozonolysis, and production of organic PM. The second part of the video shows the procedures for determining the properties of the produced particle population. The particle number-diameter distributions show different stages of particle growth, namely condensation, coagulation, or a combination of both, depending on reaction conditions. The particle morphology is characterized by an aerosol particle mass analyzer (APM) and a scanning electron microscope (SEM). The results confirm the existence of non-spherical particles that have grown from coagulation for specific reaction conditions. The experimental results also indicate that the flow tube reactor can be used to study the physical and chemical properties of organic PM for relatively high concentrations and short time frames.

This paper describes the operation procedure for the flow tube reactor and related data collection. It shows the protocols for setting the experiments, recording data and generating the number-diameter distribution as well as the particle mass information, which gives useful information about chemical and physical properties of the organic aerosols.

Organic particulate matter (PM) is increasingly recognized as important to the Earth's climate system as well as public health in urban regions, and the ...

Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to the gas phase, and efficiently transferred to a detection system. Fizzy extraction takes advantage of the effervescence phenomenon. First, a carrier gas (here, carbon dioxide) is dissolved in the sample by applying overpressure and stirring the sample. Second, the sample chamber is decompressed abruptly. Decompression leads to the formation of numerous carrier gas bubbles in the sample liquid. These bubbles assist the release of the dissolved analyte species from the liquid to the gas phase. The released analytes are immediately transferred to the atmospheric pressure chemical ionization interface of a triple quadrupole mass spectrometer. The ionizable analyte species give rise to mass spectrometric signals in the time domain. Because the release of the analyte species occurs over short periods of time (a few seconds), the temporal signals have high amplitudes and high signal-to-noise ratios. The amplitudes and areas of the temporal peaks can then be correlated with concentrations of the analytes in the liquid samples subjected to fizzy extraction, which enables quantitative analysis. The advantages of fizzy extraction include: simplicity, speed, and limited use of chemicals (solvents).

Fizzy extraction is a new laboratory technique for analysis of volatile and semivolatile compounds. A carrier gas is dissolved in the liquid sample by applying overpressure and stirring the sample. The sample chamber is then decompressed. The analyte species are liberated to the gas phase due to effervescence.

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to ...

Chemistry

Composition and Distribution Analysis of Bioaerosols Under Different Environmental Conditions

Variable microorganisms in particulate matter (PM) under different environmental conditions may have significant impacts on human health. In this study, we described a protocol for multiple analyses of the biological compositions in environmental PM. Five experiments are presented: (1) PM number monitoring by using a laser particle counter; (2) PM collection by using a cyclonic aerosol sampler; (3) PM collection by using a high-volume air sampler with filters; (4) culturable microbes collection by the Andersen six-stage sampler; and (5) detection of biological composition of environmental PM by bacterial 16SrDNA and fungal ITS region sequencing. We selected hazy days and a livestock farm as two typical examples of the application in this protocol. In this study, these two sampling methods, cyclonic aerosol sampler and filter sampler, showed different sampling efficiency. The cyclonic aerosol sampler performed much better in terms of collecting bacteria, while these two methods showed the same efficiency in collecting fungi. Filter samplers can work under low temperature conditions while cyclonic aerosol samplers have a sampling limitation for temperature. A solid impacting sampler, such as an Andersen six-stage sampler, can be used to sample bioaerosols directly into the culture medium, which increases the survival rate of culturable microorganisms. However, this method mainly relies on culture while more than 99% of microbes cannot be cultured. DNA extracted from the culturable bacteria collected by the Andersen six-stage sampler and samples collected by cyclonic aerosol sampler and filter sampler were detected by bacterial 16S rDNA and fungal ITS region sequencing.All the methods above may have wide application in many fields of study, such as environmental monitoring and airborne pathogen detection. From these results, we can conclude that these methods can be used under different conditions and may help other researchers further explore the health impacts of environmental bioaerosols.

Understanding the biological composition of environmental particulate matter is important for the study of its significant impacts on human health and disease spread. Here, we used three types of bioaerosol sampling methods and a biological analysis of airborne microbes to better explore airborne microbial communities under different environmental conditions.

Variable microorganisms in particulate matter (PM) under different environmental conditions may have significant impacts on human health. In this study, ...

Preparation of Hollow Polystyrene Particles and Microcapsules by Radical Polymerization of Janus Droplets Consisting of Hydrocarbon and Fluorocarbon Oils

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) and fluorocarbon oil (perfluoro-n-octane, PFO) in aqueous surfactant (sodium dodecylsulfate, SDS) solutions. Since fluorocarbon oils are immiscible with hydrocarbon oils, the two oils are separated. Emulsions are prepared by stirring styrene/PFO/aqueous SDS solution mixtures at 80 &#176;C. The type of emulsions and the morphology of droplets in the emulsions are observed by light microscope and scanning confocal fluorescence microscope. It is found that oil droplets with Janus-type morphologies consisting of mutually immiscible styrene and PFO are formed in aqueous SDS solutions. Polystyrene particles are fabricated by radical polymerization of the ternary mixtures of styrene/PFO/aqueous SDS solution at 80 &#176;C. The morphologies of the polystyrene are confirmed by scanning electron microscopy and scanning transmission electron microscopy observations. These observations show the preparation of hollow polystyrene particles with a single hole on the surface. To our knowledge, this method is a novel strategy using the immiscibility of hydrocarbon and fluorocarbon oils. The hollow particles can also be applied to the preparation of microcapsules.

A protocol for the fabrication of hollow polymer particles and microcapsules by radical polymerization using emulsions consisting of styrene, perfluoro-n-octane, and aqueous SDS (sodium dodecylsulfate) solution is presented.

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) ...

Enhanced Oil Recovery using a Combination of Biosurfactants

Biosurfactants are surface-active compounds capable of reducing the surface tension between two phases of different polarities. Biosurfactants have been emerging as promising alternatives to chemical surfactants due to less toxicity, high biodegradability, environmental compatibility and tolerance to extreme environmental conditions. Here, we illustrate the methods used for screening of microbes capable of producing biosurfactants. The biosurfactant producing microbes were identified using drop collapse, oil spreading, and emulsion index assays. Biosurfactant production was validated by determining the reduction in surface tension of the media due to growth of the microbial members. We also describe the methods involved in characterization and identification of biosurfactants. Thin layer chromatography of the extracted biosurfactant followed by differential staining of the plates was performed to determine the nature of the biosurfactant. LCMS, 1H NMR, and FT-IR were used to chemically identify the biosurfactant. We further illustrate the methods to evaluate the application of the combination of produced biosurfactants for enhancing residual oil recovery in a simulated sand pack column.

We illustrate the methods involved in screening and identification of the biosurfactant producing microbes. Methods for chromatographic characterization and chemical identification of the biosurfactants, determining the industrial applicability of the biosurfactant&#160;in enhancing residual oil recovery are also presented.

Biosurfactants are surface-active compounds capable of reducing the surface tension between two phases of different polarities. Biosurfactants have been ...

Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device

We introduce an approach to study the formation and growth of hydrates under the influence of nonionic surfactants. The experimental system includes a temperature regulator, visualization techniques, and inner pressure measurements. The temperature control system contains a low-cost, programmable temperature regulator made with solid-state Peltier components. Along with the temperature control system, we incorporated visualization techniques and internal pressure measurements to study hydrate formation and inhibition in the presence of nonionic surfactants. We studied the hydrate-inhibiting ability of nonionic surfactants (sorbitane monolaurate, sorbitane monooleate, PEG-PPG-PEG, and polyoxyethylenesorbitan tristearate) at low (i.e., 0.1 CMC), medium (i.e., CMC), and high (i.e., 10 CMC) concentrations. Two types of crystals were formed: planar and conical. Planar crystals were formed in plain water and low surfactant concentrations. Conical crystals were formed in high surfactant concentrations. The results of the study show that conical crystals are the most effective in terms of hydrate inhibition. Because conical crystals cannot grow past a certain size, the hydrate growth rate as a conical crystal is slower than the hydrate growth rate as planar crystal. Hence, surfactants that force hydrates to form conical crystals are the most efficient. The goal of the protocol is to provide a detailed description of an experimental system that is capable of investigating the cyclopentane hydrate crystallization process on the surface of a water droplet in the presence of surfactant molecules.

We present a protocol to study the formation of hydrates in the presence of nonionic surfactants on the interface of a water droplet submerged in cyclopentane. The protocol consists of building a low-cost, programmable, temperature regulator. The temperature control system is combined with visualization techniques and internal pressure measurements.

We introduce an approach to study the formation and growth of hydrates under the influence of nonionic surfactants. The experimental system includes a ...

Capturing Actively Produced Microbial Volatile Organic Compounds from Human-Associated Samples with Vacuum-Assisted Sorbent Extraction

Volatile organic compounds (VOCs) from biological samples have unknown origins. VOCs may originate from the host or different organisms from within the host&#39;s microbial community. To disentangle the origin of microbial VOCs, volatile headspace analysis of bacterial mono- and co-cultures of Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii, and stable isotope probing in biological samples of feces, saliva, sewage, and sputum were performed. Mono- and co-cultures were used to identify volatile production from individual bacterial species or in combination with stable isotope probing to identify the active metabolism of microbes from the biological samples.
Vacuum-assisted sorbent extraction (VASE) was employed to extract the VOCs. VASE is an easy-to-use, commercialized, solvent-free headspace extraction method for semi-volatile and volatile compounds. The lack of solvents and the near-vacuum conditions used during extraction make developing a method relatively easy and fast when compared to other extraction options such as tert-butylation and solid phase microextraction. The workflow described here was used to identify specific volatile signatures from mono- and co-cultures. Furthermore, analysis of the stable isotope probing of human associated biological samples identified VOCs that were either commonly or uniquely produced. This paper presents the general workflow and experimental considerations of VASE in conjunction with stable isotope probing of live microbial cultures.

This protocol describes the extraction of volatile organic compounds from a biological sample with the vacuum-assisted sorbent extraction method, gas chromatography coupled with mass spectrometry using the Entech Sample Preparation Rail, and data analysis. It also describes culture of biological samples and stable isotope probing.

Volatile organic compounds (VOCs) from biological samples have unknown origins. VOCs may originate from the host or different organisms from within the ...

Biochemistry

Solid-Liquid Extraction

Source: Laboratory of Dr. Jay Deiner &#8212; City University of New York
Extraction is a crucial step in most chemical analyses. It entails removing the analyte from its sample matrix and passing it into the phase required for spectroscopic or chromatographic identification and quantification. When the sample is a solid and the required phase for analysis is a liquid, the process is called solid-liquid extraction. A simple and broadly applicable form of solid-liquid extraction entails combining the solid with a solvent in which the analyte is soluble. Through agitation, the analyte partitions into the liquid phase, which may then be separated from the solid through filtration. The choice of solvent must be made based on the solubility of the target analyte, and on the balance of cost, safety, and environmental concerns.

Solid-Liquid Extraction: Principle, Procedure, Applications

Source: Laboratory of Dr. Jay Deiner &#8212; City University of New York
Extraction is a crucial step in most chemical analyses. It entails removing the ...

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Soxhlet Extraction of Lipid Biomarkers from Sediment

Source: Laboratory of Jeff Salacup&#160;- University of Massachusetts Amherst
Every lab needs standards that track the performance, accuracy, and precision of its instruments over time to ensure a measurement made today is the same as a measurement made a year from now (Figure 1). Because standards must test the performance of instruments over a long period of time, large volumes of the standards are often required. Many chemical standards can be purchased from retail scientific companies, like Sigma-Aldrich and Fisher. However, some compounds that occur in nature and that are relevant to paleoclimatic studies have not yet been isolated and purified for purchase. Therefore, these compounds need to be extracted from natural samples, and because of the large volumes of standards required, large volumes of sediment need to be extracted. The Accelerated Solvent Extraction (Dionex) and sonication extractions are not appropriate for the extraction of such large sediment volumes. In these circumstances, a Soxhlet extraction is used.
<img alt="Figure 1" src="/files/ftp_upload/10096/10096fig1.jpg" /> 
Figure 1. Schematic depicting how chemical standard tracks the performance of an instrument through time. The dashed line represents a 1:1 relationship between the accepted and measured (on the instrument) value of a variable. Each star is a weekly measurement of the chemical standard. Green stars represent standards that are accurate. Red stars reflect those that are not accurate indicating that the instrument requires corrective maintenance.

Extraction and Characterization of Surfactants from Atmospheric Aerosols

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