Fluorinated Bezoic Acids - publik.tuwien.ac.at · 1.19 16 2,3,4,5-‐Tetrafluorobenzoic acid...

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chrom+food forum 07 | 2017

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Chrysoula Kanakaki | Prof. Dr. Erwin Rosenberg

A tracer is a substance that is added to a fluid to indicate its flow path or pattern. Tracer tests were originally developed for tracking the movement of groundwater in the early 1900s. Their value for the petrochemical industry has only been realized in the mid-1950s [1].

In the petroleum industry, liquids are sometimes injected into oil or gas bearing formations for the purpose of enhancing the production of hydro-carbons. In order to find out where the injected solvents go, tracers can be added to the injected solvent. This is necessary since the subsurface flow in the reservoir is anisotropic, and the reservoirs usually exhibit a high degree of heterogeneity, making it difficult to predict flow patterns, espe-cially in reservoirs containing multiple injectors and producers. In that case, tagging solvents at each injection well with a different tracer and monitoring the tracers that appear at each producing well is an adequate strategy to identify the pertinent flow paths. Multiple tracers are therefore often used for interwell tracer tests in the petroleum industry [2].

A classification of substances used as chemical tracersTracers may generally be classified as passive or active. A passive or conservative tracer is a substance that blindly follows the fluid phase in which it is injected. An active tracer interacts with other fluids in the system or with the rock bed. The information obtained from tracer tests are tracer response curves that may be qualitatively and quantitatively evaluated to observe breakthrough and interwell communi-cation, or, if numerical simulations or data fitting procedures are used, to derive quantitative information on the flow behavior (e.g. velocity) in the reservoir (Figure 1).

Fluorinated Bezoic Acids as Conservative Tracers for the Petrochemical Industry

Fluorinated benzoic acids have received increasing attention as conservative tracers in petrochemical exploration

and geochemical investigations due to their favorable physico-chemical properties. This contribution discusses

various approaches to detect them in complex matrices at low ppb-levels.

When a chemical substance is used as a passive tracer in interwell tracer tests, it must fulfill the following criteria to a large extent:

• be detectable at very low concentrations

• be stable under reservoir conditions

• closely follow the phase in which it has been injected and have minimal partitioning into other phases

• exhibit no adsorption to rock material

• be environmentally benign

• be available at acceptable cost.

Substances that at least partially fulfill the above criteria are radioactive gas and water tracers, and chemical gas and water tracers, respectively. For the latter group of tracers, and with particular view to interwell tracer studies, the group of fluorinated benzoic acids has been proposed as suitable tracer substances [3].

Fluorinated benzoic acids are attractive water tracers as there are many isomers and congeners commercially available, although with a very signi-ficant difference in market price (Table 1). The advantage of using the individual representatives of this family of compounds is their relatively uniform range of physico-chemical properties with respect to pKa- and log P-values (Figure 2) and the fact that they can be determined by the same (chromatographic) method.

Analytical methods used for fluorinated benzoic acid tracersDue to the polar nature of the fluorinated benzoic acids, liquid chromato-graphic methods of determination are the evident choice and were among


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the first analytical methods used for this purpose [4]. In initial experiments, HPLC with UV detection was used. While this detection technique is suffici-ently sensitive to detect FBA tracer concentrations at low ppb concentra-tions in pure water samples such as groundwater, it is typically suffering from the interferences caused by other organic and particularly aromatic constituents or contaminants of the sample. For the use in petrochemical tracer studies, it was suggested to perform an extraction of interfering hydrocarbons with n-heptane; however, even this strategy could not re-move interferences to a sufficient extent.

HPLC-MS with single- or triple quadrupole mass spectrometric detection was therefore evaluated for the determination of FBAs in produced water from oilfield explorations. In selected ion- or selected reaction monitoring (SIM/SRM) mode, this technique was found both sufficiently selective and sensitive to determine FBAs in oil- or hydrocarbon containing aqueous matrices at the required low (one-digit) ppb level. Typical LC-MS parameters are [5]: Acquity UPLC BEH C18 column (150 mm × 2.1 mm × 1.7 μm) with matching precolumn. Gradient 0.05% acetic acid in both water and acetonitrile (ACN) mobile phases, starting with 13% ACN and increasing up to 80% ACN within 13 min. Flow rate 0.45 ml/min. Detection by MS/MS (triple quad) in MRM (multiple reaction monitoring) mode (Figure 3). As produced water samples cannot be injected directly due to the high salt load of the samples, a SPE step is required prior to the analysis. This step serves both for the desalination of samples [4] as well as for the preconcen-tration of the FBAs. More recently, the SPE step has been replaced by a faster ion exchange matrix removal procedure that uses ion exchangers for this purpose [6].

As an alternative to HPLC/MS-based methods, gas chromatography can also be used for the determination of FBAs. In this case, derivatisation of the compounds is mandatory to achieve good chromatographic peak shape and behavior. Derivatisation (esterification) of the FBAs can be achieved in various ways, such as by the reaction with diazomethane [7], silylation or the derivatisation with pentafluorobenzylbromide (PFB) as a most useful derivatisation scheme for the production of highly halogena-ted derivatives that can be detected in GC-NICI (negative ion chemical

Figure 1: Schematic of chemical tracer usage in an interwell experiment. The chemical tracer is added to the solvent injected into the reservoir and recovered from the produced water at the production well with a characteristic concentration/time profile.

Figure 2: Spider graph representing the acid dissociation constant (pKa) and the octanol/water partitioning coefficient log P of the different FBAs. The log P values were calculated with the ACD/ChemSketch software. FBA…fluorobenzoic acid; DFBA…difluorobenzoic acid; TFBA…trifluorobenzoic acid; TFMBA…fluorinated trifluoro-methyl benzoic acid.

Figure 3: HPLC/MS chromatogram of the separation of a standard solution of methylated FBAs (extracted ion traces from MRM).

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No. Compound Name Abbreviation CAS No. Market Price (US-‐$)

1 2-‐Fluorobenzoic acid 2-‐FBA [445-‐29-‐4] 0.17



4 2,3-‐Difluorobenzoic acid 2,3-‐DFBA [4519-‐39-‐5] 1.20






10 2,3,4-‐Trifluorobenzoic acid 2,3,4-‐TFBA [61079-‐72-‐9] 0.42






16 2,3,4,5-‐Tetrafluorobenzoic acid 2,3,4,5-‐Tetra-‐FBA [1201-‐31-‐6] 0.20

17 2,3,4,5,6-‐Pentafluorobenzoic acid Penta-‐FBA [602-‐94-‐8] 0.35

Authors | Contact

Chrysoula Kanakaki | Prof. Dr. Erwin Rosenberg Vienna University of TechnologyInstitute for Chemical Technologies and AnalyticsGetreidemarkt 9/164 AC | A-1060 Vienna www.cta.tuwien.ac.at

Figure 4: Gas chromatogram of the separation of methylated FBAs extracted from produced water from an oil well.

ionization) mode with excellent sensitivity [8]. Other derivatisation chemistries have also been used, such as the derivatisation with BF3-MeOH that again produces the methyl esters of the FBAs, or other methylating reagents [9]. Also for the GC/MS based methods, preconcentration is a must, otherwise the required low detection limits are not reached. A typical gas chromato-gram of derivatised FBAs extracted from produced water is shown in Figure 4.

ConclusionBoth gas- and liquid chromatographic methods show great potential for the determination of fluorobenzoic acid congeners used as conservative tracers in the petrochemical industry when used with MS- or MS/MS detec-tion (in the case of HPLC/MS/MS). Particularly the latter technique offers not only increased sensitivity, but is also more attractive from the practical point of view as it does not require derivatisation. While the GC-based method reaches detection limits (after pre-concentration) in the one-digit ppb range, the HPLC/MS/MS method clearly surpasses this sensitivity, being capable of detecting sub-ppb concentrations of the various FBAs.

AcknowledgementC.K. gratefully acknowledges the Fellowship issued to her by the OMV Exploration & Production AG that allowed her to perform this research.

[1] R.D. Hutchins, H.T. Dovan, B.B. Sandiford, Soc Petroleum Eng, Manuscript No. 21049-MS. DOI: 10.2118/21049-MS.

[2] C. Serres-Piole, A. Commarieu, H. Garraud, R. Lobinski, H. Preud'Homme, Energy Fuels 25 (2011) 4488-4496.

[3] R.S. Bowman, Soil Sci. Soc. Am. J. 48 (1984) 987-993.

[4] R.S. Bowman, J. Chromatogr. A 285 (1984) 467-477.

[5] P. Kubica, H. Garraud, J. Szpunar, R. Lobinski, J. Chromatogr. A, 1417 (2015) 30–40.

[6] P. Kubica, V. Vacchina, T. Wasilewski, S. Reynaud, J. Szpunar, R. Lobinski, Anal. Bioanal. Chem., 409 (2017) 871-879.

[7] C. U. Galdiga, T. Greibrokk, J. Chromatogr. A, 793 (1998) 297-306.

[8] C. Galdiga, T. Greibrokk, Fresenius J. Anal. Chem. 361 (1998) 797-802.

[9] K. Müller, A. Seubert, J. Chromatogr. A, 1260 (2012) 9-15.

Shimadzu has acquired AlsaChimShimadzu has joined forces with the France-based AlsaChim company, an independent contract research and development organization. AlsaChim specializes in stable isotope-labelled compounds, metabolites and phar-maceutical related substances, and analytical purposes. With immediate ef-fect, Shimadzu Europe has acquired AlsaChim by 100%. The brand name will be kept for the future complemented by the subtitle “a Shimadzu Group Company”.

The AlsaChim technology complements Shimadzu’s product and solution portfolio in the clinical market. AlsaChim is an established and well-known innovative company and provides standards and stable isotopes; particularly the latter are key differentiators for customers in the clinical and diagnostic fields. AlsaChim’s expertise and market-proven stable isotope

standards as reference material for application kits are value-adding line extensions to Shimadzu’s hard- and software. Through the acquisition of AlsaChim, Shimadzu also adds value to its European Innovation Center (EUIC), particularly for the clinical segments which is one of EUIC’s focus areas. This innovations-oriented Think Tank combines academic-scientific expertise from well-known European universities with Shimadzu’s cutting-edge technology to provide even more customer-focused service. “With AlsaChim, we have a strong partner in our organization who is able to finalize and validate new application kits and utilize the developments done by EUIC and transfer them into ready-to-use products”, said Dr. Bjoern-Thoralf Erxleben, Senior Manager Analytic Shimadzu Europa, based in Duisburg, Germany.www.shimadzu.eu

Tab. 1: Full names, abbreviations, CAS numbers, market prices (in US$) of the tracer substances.

Fluorinated Bezoic Acids - publik.tuwien.ac.at · 1.19 16 2,3,4,5-‐Tetrafluorobenzoic acid...

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