nonanoic Acid from Disposable Latex Gloves - ACS Publications

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Concentrations, Stability and Isolation of the Furan Fatty Acid 9-(3-Methyl-5Pentylfuran-2-yl)-Nonanoic Acid (9M5) from Disposable Latex Gloves Marco Müller, Melanie Hogg, Kerstin Ulms, and Walter Vetter J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b02444 • Publication Date (Web): 18 Aug 2017 Downloaded from http://pubs.acs.org on September 1, 2017

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Journal of Agricultural and Food Chemistry

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Concentrations, Stability and Isolation of the Furan Fatty Acid 9-(3-Methyl-5-

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Pentylfuran-2-yl)-Nonanoic Acid (9M5) from Disposable Latex Gloves

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Marco Müller, Melanie Hogg, Kerstin Ulms and Walter Vetter*

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University of Hohenheim, Institute of Food Chemistry, Department of Food Chemistry

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(170b), D-70593 Stuttgart, Germany

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* Corresponding author

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Phone: +49 711 459 24016

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Fax: +49 711 459 24377

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Email: [email protected]

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ABSTRACT

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Because of their antioxidant properties, furan fatty acids (furan-FA) are valuable

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minor compounds with a widespread occurrence in all living matter. Unfortunately, pure

19

standards are not readily available, as they usually contribute only 1% to the lipid fraction. A

20

known exception of this is the milky fluid of Hevea brasiliensis, commonly known as latex,

21

in which the furan-FA 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid (9M5) contributes with

22

about 90% to the triacylglycerides. In this study, we investigated the content of 9M5 in 30

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different disposable latex gloves, which ranged from 0.7 to 8.2 mg/g glove. The light

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degradability of 9M5 in latex gloves was investigated and different amounts of 9M5 in

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disposable latex gloves were attributed to varying exposure time to light. Additionally, over

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100 mg of the methyl or ethyl ester of 9M5 (purity >98%) could be extracted from disposable

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latex gloves, employing cold extraction and silver ion chromatography. With this method,

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standards for the quantitation of furan-FA are obtained easily and rapidly in all laboratories.

29 30

KEYWORDS

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Furan fatty acids, disposable latex gloves, 9M5, Hevea brasiliensis, GC/MS


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INTRODUCTION

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Furan fatty acids (furan-FA) are a group of naturally occurring fatty acids which are

34

characterized by a furan ring in the center of the molecule. The furan moiety is substituted

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with a straight-chain (usually 9, 11 or 13 carbons) saturated acid in α-position and a short

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alkyl chain (usually 3 or 5 carbons) in α'-position (Figure 1).1 A typical example for furan-FA

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is 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid (9M5), 1, which is substituted with one

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methyl group at the β-position (M). Other naturally occurring furan-FA possess two methyl

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groups at the β- and β'-positions (D), while furan-FA without methyl groups (F) are rarely

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found in nature.2

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Furan-FA are de novo synthesized by various plants and bacteria and can be

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incorporated into the lipids of animals.1,3 Hence, they are found widespread in all living

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matter, albeit at low concentrations.1,3–6 Because of their high radical scavenging activity,

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they are potent antioxidants.7,8 Due to this property they are thought to protect

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polyunsaturated fatty acids (PUFA) from oxidative stress and support them in their beneficial

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effects on the prevention of cardiovascular diseases.1

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Furan-FA are easily transformed into volatile compounds by exposure to light which

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were found to cause off-flavor in spinach,9 soybean oil10 as well as dried herbs and

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vegetables.11 In addition, the potential furan-FA metabolite 3-carboxy-4-methyl-5-propyl-2-

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furanpropionic acid, 2, was found to be significantly high in blood plasma of patients with

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type 2 diabetes.12,13 2 was also found to enhance type 2 diabetes by hampering the insulin

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biosynthesis in β-cells.14 However, high amounts of fish in the diet only moderately increased

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the plasma concentration of 2 and it could not be linked to harmful glucose metabolism.13

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To gain further knowledge of the biological function of furan-FA, pure standards are

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needed to perform tests concerning their biological activity. Unfortunately, isolation of furan-

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FA from natural sources is non-economic because they usually contribute less than 1% to the 3 ACS Paragon Plus Environment


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total fatty acids of plant and animal lipids.1,2,15 Hitherto, the only relevant exception is the

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milky fluid of Hevea brasiliensis, commonly known as latex. About 90% of the fatty acid

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pattern of latex originated from the furan-FA 9M5, 1.16,17 Recently, isolation of pure 9M5, 1,

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from liquid centrifuged latex was achieved by countercurrent chromatography (CCC).17 This

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isolate is suited for the use as an analytical standard in furan-FA analysis15,18,19 and may also

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serve as substrate for in vitro investigations of the relevance of furan-FA. However, the

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isolation procedure is not only time consuming,17 but also CCC instruments and the milky

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latex fluid are not readily available to all researchers interested in such studies.17

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The goal of this study was to select a more convenient source and isolation procedure

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for 9M5, 1, For this purpose, we studied its occurrence in disposable latex gloves, i.e. one

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readily available industrial product made from latex. Disposable latex gloves are widely

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distributed in medical and chemical laboratories, and samples from different producers were

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screened for the presence of 9M5, 1, and possibly other furan-FA. We also studied the

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stability of 9M5, 1, when disposable latex gloves were removed from the (light-protecting)

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packaging and exposed to daylight. Finally, we present an easy and fast method for the

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isolation of methyl and ethyl esters of 9M5, 1, from disposable latex gloves.

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MATERIALS AND METHODS

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Organic solvents and chemicals. Methanol (>99.8%) and n-hexane (>95%) were

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from VWR Chemicals (Darmstadt, Germany), while ethanol, diethyl ether (both distilled

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before use) and sulfuric acid were from Carl Roth (Karlsruhe, Germany). Silica gel 60 and

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silver nitrate were from Sigma Aldrich (Taufkirchen, Germany). Sodium chloride and the

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fatty acids palmitic acid (16:0; >98.5%), stearic acid (18:0; >98.5%), oleic acid (18:1∆9;

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>99%), linoleic acid (18:2∆9,12; 99%) and nonadecanoic acid (19:0; >99%) were from Fluka

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Chemicals (Taufkirchen, Germany). Myristic acid (14:0; >99%) was from Merck Chemicals


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(Darmstadt, Germany). A standard of 9M5, 1, was previously isolated from centrifuged latex

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with CCC in our laboratory.17

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Samples and standards. At least one disposable latex glove from 30 different

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products was obtained from 14 producers (Table 1). The quantitation standard 19:0 (ISTD-1)

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was prepared at a concentration of 10.1 mg/mL in n-hexane/diethyl ether (1:1, v/v). For the

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second internal standard (14:0-EE, ISTD-2), 10 mg 14:0 were transesterified as described by

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Wendlinger et al.15 with 2 mL ethanol containing sulfuric acid (1 vol%) instead of methanol.

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The resulting ISTD-2 (14:0-EE, c = 5.61 mg/mL) was transferred into an amber 1.5 mL screw

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cap vial and stored at -20 °C.

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Gas chromatography with flame ionization detector (GC/FID) or mass

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spectrometry (GC/MS). Samples were measured on an Autosystem XL GC/FID instrument

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(Perkin Elmer, Rodgau, Germany) which was equipped with a 25 m x 0.53 mm i.d., 0.5 µm

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DB 23-Megabore (50% cyanopropyl, 50% dimethyl polysiloxane) column (Agilent,

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Waldbronn, Germany). Measurements were carried out with N2 (5.0) as carrier gas (constant

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pressure, 15 kPa). Injections (1 µL) in split mode (split ratio 1:4.7, flow rate: 20 mL/min)

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were performed at 205 °C. The GC oven program started for 1 min at 60 °C. Then the

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temperature was first raised to 190 °C with a ramp of 20 °C/min and then to 220 °C with 4

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°C/min. The final temperature of 230 °C was reached with another ramp of 20 °C/min and

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held for 10 min.

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GC/MS measurements were performed on a 6890/5973N GC/MS system (Agilent

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Technologies, Santa Clara, CA), equipped with a 30 m x 0.25 mm i.d., 0.25 µm HP-5MS

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(95% methyl, 5% phenyl polysiloxane) column (Agilent, Waldbronn, Germany) as recently

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described (system 1).20 All measurements in full scan mode (m/z 60 - 600) were done with the

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following oven program: The initial temperature of 60 °C was held for 1 min and was then

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raised to 180 °C with a ramp of 13 °C/min and further increased to 250 °C with 3 °C/min. The

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final temperature of 300 °C was reached with a ramp of 20 °C/min and held for 5 min, 5 ACS Paragon Plus Environment


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resulting in a total run time of 41.06 min. For measurements in selected ion monitoring (SIM)

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mode characteristic ions were divided into time windows according to Wendlinger et al.15

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Response factors of fatty acid methyl esters (FAME) were also measured on another

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6890/5973 GC/MS system equipped with a cool on-column inlet (Hewlett-Packard/Agilent,

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Waldbronn, Germany) and a 15 m x 0.25 mm i.d., 0.1 µm Rtx-1 (100% dimethyl

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polysiloxane) column (Restek, Bellefonte, PA) as recently described (system 2).20 All

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measurements were performed in full scan mode (m/z 30 – 600). Additionally, response

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factors were measured on a 5890 Series II GC/FID instrument (Hewlett Packard) equipped

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with a 60 m Rtx 2330 column (biscyanopropyl cyanopropylphenyl polysiloxane, 0.25 mm

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internal diameter, 0.1 µm film thickness) (Restek, Bellefonte, PA). Injections of 1 µL in split

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mode (1:10) were done with a Hewlett-Packard 7673 autosampler.

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Liquid extraction and determination of the fat content. Initial tests confirmed that

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the extraction efficiency of 9M5, 1, with 25 mL n-hexane was >90%, which was considered

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appropriate. Hence, disposable latex gloves were cut into pieces of ~1 cm2 and 1.5 g of these

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pieces (~30% of one glove) were supplemented with 25 mL n-hexane and extracted by

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ultrasonication for 5 min. The hexane extract was filtered and the residue on the filter was

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washed twice with 5 mL n-hexane. The combined hexane phases were condensed to ~2 mL

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with a rotary evaporator and transferred into a 10 mL volumetric flask. The volume was

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adjusted to 10 mL with n-hexane. A 1 mL aliquot of this extract was used for gravimetric

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determination of the (lipid) extract content, performed in a pre-weighed 1.5 mL screw cap vial

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once the solvent was removed by a gentle stream of air at 40 °C. Due to logistic reasons, air

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had to be used in this experiment instead of nitrogen. Because 9M5, 1, is sensitive to

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oxidation, the variation of the sample weight under the chosen experimental conditions was

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investigated in additional tests (Figure S1, Supporting Information).

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Formation of methyl esters. Between 3 and 8 mL latex extract (corresponding with

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~10 mg extract content) were placed in a 10 mL vial and 50 µL ISTD-1 (19:0) was added. 6 ACS Paragon Plus Environment

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The solvent was removed by a gentle stream of nitrogen at 40 °C and the sample was

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transesterified as previously described.15 In short, 2 mL methanol containing 1 vol% sulfuric

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acid was added, heated to 80 °C and extracted with 2 mL n-hexane. About 1 mL of the

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resulting FAME solution was transferred into an amber 1.5 mL screw cap vial and stored at -

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20 °C until analysis by GC/FID or GC/MS.

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Determination of the GC/FID response factor of 9M5-ME. The GC/FID response

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of FAMEs in the transesterified sample was found to be nearly the same for all conventional

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fatty acids.21 The response factor of 9M5-ME was determined with a solution containing

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methyl esters of palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1∆9), linoleic acid

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(18:2∆9,12) and 9M5, 1, all at the same concentration of 2 mg/mL. This solution was

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measured three times on two different GC/FID systems each and on GC/MS system 2

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operated in full scan mode.

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Quantitation and quality control. Before GC/FID measurements all FAME solutions

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of purified samples were spiked with 25 µL of ISTD-2 (14:0-EE) which was used to level out

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differences in the injection volume. The peak area of 9M5-ME was additionally corrected by

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its GC/FID response factor. A blank sample containing both internal standards ISTD-1 and

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ISTD-2 was measured every day and the recovery of ISTD-1 (19:0) was generally >95%.

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Therefore, the content of 9M5, 1, in the sample was quantified by means of ISTD-1. All peaks

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in GC/FID chromatograms were verified by means of authentic standards. In addition, the

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lipid extracts of eight samples #9, #10, #12, #13, #20, #22, #28 and #29 (Table 1) were

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measured on GC/MS system 1.

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Exposure of 1 (9M5, 1) to sunlight behind a window (inside). Five gloves from two

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different producers each #13 and #30 (Table 1) were selected and one glove of each producer

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was extracted as shown above and measured by GC/FID. The remaining four gloves from

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each producer (eight total) were exposed to light by placing them on a windowsill inside the



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laboratory, facing north (August 2016). Over the course of four days (including night- and

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daytime), every 24 h one glove from each producer was removed and analyzed.

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Silver ion mini-column chromatography. FAMEs obtained from the latex extracts

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were subjected to silver ion mini-column chromatography according to Wendlinger et al.15 In

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short, ~450 mg silica gel containing 20% silver nitrate deactivated with 1% water was placed

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into a Pasteur pipette whose conical exit was packed with glass wool. The column was

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conditioned with ~5 mL n-hexane. Then the lipid extract (obtained from 2.5 g disposable

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latex glove sample) was placed on the column and fractionated with three solvents. Fraction

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(i) was collected with 15 mL n-hexane/diethyl ether (99.5:0.5, v/v), fraction (ii) was eluted

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with 15 mL n-hexane/diethyl ether (97:3, v/v) and fraction (iii) with 15 mL n-hexane/diethyl

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ether (80:20, v/v). The solvents of all fractions were then removed by a gentle stream of

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nitrogen and adjusted to exactly 1 mL with n-hexane. All fractions were measured on GC/MS

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system 1.

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Isolation of 9M5, 1, from latex gloves. About 50 g disposable latex gloves (sample

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#30) (Table 1) were cut into pieces of ~1 cm² and placed in an amber 1 L-glass bottle. After

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the addition of 800 mL n-hexane, extraction was performed by ultrasonication (5 min). The

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extract was filtered and the residue was washed twice with 50 mL n-hexane. The solvent was

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removed and the residue was taken up in 50 mL methanol containing 1 vol% sulfuric acid (or

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ethanol for the extraction of 9M5-EE). The solution was refluxed for 2 h at 80 °C. Then 30

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mL water and 30 mL saturated NaCl solution were added and fatty acid methyl (ethyl) esters

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were extracted 3x with 50 mL n-hexane. The solvent was removed by a rotary evaporator at

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40 °C and 230 mbar and the residue taken up in 1 mL n-hexane. Column chromatography as

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described before was performed on a large scale. About 5 g silica gel containing 20% silver

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nitrate deactivated with 1% water was placed in a glass column (inner diameter ~1 cm) and

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fractionation was done by eluting the sample with 70 mL n-hexane/diethyl ether (99.5:0.5,


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v/v) (fraction 1), 50 mL n-hexane/diethyl ether (97:3, v/v) (fraction 2) and 50 mL n-

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hexane/diethyl ether (80:20, v/v) (fraction 3).

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Statistical analysis. After verifying normal distribution with the Anderson-Darling-

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test (p > 0.05), all results were analyzed using univariate ANOVA tests (α = 0.05) as

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integrated in Excel and statistical significance was assumed for p > 0.05. Statistical outliers

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were detected with the David-Hartley-Pearson-test (α = 0.05) and not considered for ANOVA

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tests. Correlation of the lipid extract and the amount of 9M5, 1, in disposable latex gloves was

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calculated with the Pearson correlation coefficient (PCC) in Excel.

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RESULTS AND DISCUSSION

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Peak identification in latex gloves. The hexane extracts of disposable latex gloves

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consisted of 0.6-1.6% of the initial sample weight (mean value: 1.1%) (Table 1). In either

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case, 9M5, 1, was detected as prominent peak in all samples. In addition to 9M5, 1, the fatty

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acid pattern of the samples was characterized by 18:2∆9,12; 18:0; 18:1∆9; 16:0; 18:3∆9,12,15

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and 20:0 as their methyl esters (Figure 2A), which was verified by GC/MS analysis (Figure

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2B) of eight arbitrarily selected samples #9, #10, #12, #13, #20, #22, #28 and #29 (Table 1).

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FAMEs were identified by means of the correct retention time and the molecular ions relative

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to authentic external reference standards. Specifically, m/z 270 (16:0-ME), m/z 292 (18:3n-3-

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ME), m/z 294 (18:2n-6-ME), m/z 296 (18:1n-9-ME), m/z 298 (18:0-ME) and m/z 326 (20:0-

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ME). Likewise, 9M5-ME was identified by GC/MS data including the characteristic

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molecular ion at m/z 322, the McLafferty ion at m/z 109, and the base peak at m/z 165).2

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Additional GC/MS measurements in SIM mode (Figure 3A) allowed to identify traces of the

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furan-FA 9M3, 3, 9D5, 4, and 11M5, 5, in two samples #9 and #22 (Table 1) by means of

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their characteristic MS molecular ion, McLafferty ion, and base peak (Figures 3B-D).2

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Unfortunately, the producer country of the disposable latex gloves was only listed on four



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samples, but the two samples which featured the minor furan-FA were both produced in

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Malaysia.

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Amount of 9M5, 1, in disposable latex gloves. Surprisingly, the GC/FID response of

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9M5-ME (injected in the same concentration of 2 mg/mL) was considerably lower than those

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of conventional FAMEs (Figure 4). GC/FID measurements on two instruments showed that

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the response factor of 9M5-ME was only 40% of the response of conventional FAMEs (16:0-

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ME, 18:0-ME, 18:1∆9-ME, 18:2∆9,12-ME), which had very similar GC/FID response factors

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(all >85% compared to 16:0). Standard deviations for the calculated response factor for 9M5-

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ME were 0.05,

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ANOVA) was observed for the ratio of 18:2∆9,12 to 18:0 within samples of producers A (p =

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0.068), B (p = 0.12), C (p = 0.33) and D/E (p = 0.08), for the ratio of 18:2∆9,12 to 18:1∆9 in

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samples of producer C (p = 0.16) and for gloves of single producers (p = 0.17) as well as for

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the ratio of 18:2∆9,12 to 16:0 for producer B (p = 0.69) and for gloves of single producers (p

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= 0.06). Although no general statistical significance was found, the data strongly indicated

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that the content of 9M5, 1, in the disposable latex gloves was lower and more variable than in

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fresh liquid latex.16,17,22

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Processing of crude latex and/or storage could reduce the content of 9M5, 1, but not

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the content of the more stable conventional fatty acids. For instance, Englert et al.17 noted that

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9M5, 1, was instable at pH 12 (~30% transformed in 12 h). Thus, partial post-harvest

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transformation of 9M5, 1, at pH 10 in technical (stabilized) liquid latex could not be excluded.

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Liengprayoon et al.23 noted that some lipids (saturated and unsaturated fatty acids) are

255

retained in the dry rubber and varied shares of them may have an effect on the plasticizing

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properties of the product. Hence, 9M5, 1, could have an effect on the product quality of latex.

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Next to the pH value, the crucial processes could be varying exposure of 9M5, 1, to light.

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Further investigations were therefore carried out to study the stability of 9M5, 1, in disposable

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latex gloves when exposed to natural sunlight. 11 ACS Paragon Plus Environment


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Exposure of disposable latex gloves to light. The stability of 9M5, 1, in disposable latex

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gloves when exposed to daylight inside a room behind a window for 1-4 days (24-96 h) was

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studied with two types of samples in which 9M5, 1, initially contributed with 68% (sample

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#30) (Table 1) and 53% to the total fatty acids (sample #13) (Table 1). The contribution of

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9M5, 1, to the total fatty acids decreased every 24 h (Figure 6). Due to the changing

265

meteorological conditions during the exposure time (Table S1, Supporting Information) a

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kinetic evaluation was not possible. For instance, higher decomposition rates in the first 24

267

hours (28% and 23%, respectively) (Figures 6A and 6B) were likely due to the higher light

268

intensity on day 1. Nevertheless, our data verifies the sensitivity of 9M5, 1, when exposed to

269

light. Varied exposure to light during production and storage of the disposable latex gloves

270

could also partly explain the varying contribution of 9M5, 1, to the fatty acids in individual

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samples, which was lower than in the raw material (~90%).16,17,22

272

Additional peaks were not detected in the GC/FID chromatograms of the extracts after

273

exposure to sunlight. Thus, degradation products of 9M5, 1, may either be volatile as

274

suggested previously9,10 for other furan-FA and/or polar compounds that were not extracted or

275

accessible to GC analysis.

276

Isolation of 9M5-ME by silver ion chromatography. Separation of other FAMEs

277

from 9M5-ME in the extract of 2.5 g disposable latex gloves from sample #30 (Table 1) was

278

achieved with silver ion chromatography. Fraction 1 contained the methyl esters of saturated

279

fatty acids (16:0-ME, 18:0-ME and 20:0-ME) (Figure 7A), whereas the methyl esters of

280

unsaturated fatty acids (18:1∆9-ME and 18:2∆9,12-ME, 18:3∆9,12,15-ME) eluted into

281

fraction 3 (Figure 7C). Hence, 9M5-ME in fraction 2 could be obtained with a purity of ~98%

282

(Figure 7B). The yield was ~5 mg (~97% from the calculated content of 9M5, 1, of 5.1 mg in

283

2.5 g disposable latex gloves, Table 1).

284

Functionality of the method was confirmed by the extraction of 50 g disposable latex

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gloves from sample #30 (Table 1) (corresponding with ~12 gloves) which provided 101 mg 12 ACS Paragon Plus Environment

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9M5-ME after column chromatography. The yield was still very high (99% of the calculated

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content of 9M5, 1, vs. 97% in the analytical batch) and the purity was ~99%.

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Furan-FA analysis is currently hampered by the lack of authentic reference standards

289

for quantitation and method verification.24 Recently, we suggested the use of the ethyl ester of

290

9M5 (9M5-EE) as internal standard for the quantitative analysis of furan-FA in fish and butter

291

samples.2,15,18 This standard can easily be prepared when transesterification is performed with

292

ethanol instead of methanol. In this way, 82.1 mg 9M5-EE (purity ~99%) were obtained from

293

50 g latex from sample #30 (Table 1).

294

The presented data shows that disposable latex gloves contain high amounts of 9M5,

295

1, which can easily be extracted with n-hexane. For quality assurance reasons, disposable

296

latex gloves should not be used during analyses on furan-FA. Yet, the simple extraction and

297

isolation protocol described in this study allows access to sufficient amounts of 9M5-ME and

298

9M5-EE in high purity which can be used as internal standard for furan-FA quantitation. Only

299

5 mg 9M5-EE extracted and isolated from 2.5 g disposable latex gloves will be enough for the

300

use as internal standard in ~5,000 quantitative analyses on fatty acids.

301 302

AUTHOR INFORMATION

303

Corresponding Author

304

* (W.V.) E-mail: [email protected] Phone: +49 711 459 24016. Fax +49 711

305

459 309 24377.

306

Funding

307

No funding was obtained for performing this study.

308

Notes

309

The authors declare no competing interests.

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ABBREVIATIONS USED. 9M5, 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid; 16:0,

312

palmitic acid; 18:0, stearic acid; 18:1∆9, oleic acid; 18:2∆9,12, linoleic acid; 18:3∆9,12,15, α-

313

linoleic acid; 20:0, arachidic acid; furan-FA, furan fatty acid; FAME, fatty acid methyl ester;

314

ISTD, internal standard; SIM, selected ion monitoring;

315

316

SUPPORTING INFORMATION. Response factors of stearic acid (18:0), oleic acid

317

(18:1∆9), linoleic acid (18:2∆9,12) and the furan fatty acid 9-(3-methyl-5-pentylfuran-2-yl)-

318

nonanoic acid (9M5), 1, compared to palmitic acid (16:0) measured on two different GC/FID

319

systems and weight reduction of the lipid extract of disposable latex gloves when evaporated

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with air over the period of 10 minutes in two samples. This material is available free of charge

321

via the Internet at http://pubs.acs.org.

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REFERENCES

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(1)

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acids responsible for the cardioprotective effects of a fish diet? Lipids, 2005, 40, 755–771

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(2)

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Determination of furan fatty acids in food samples. J. Am. Oil Chem. Soc., 2012, 89,1501–

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1508

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(3)

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marine bacterium, Shewanella putrefaciens. Biochim. Biophys. Acta, Lipids Lipid Metab.,

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1997, 1346, 253–260

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Shirasaka, N.; Nishi, K.; Shimizu, S. Biosynthesis of furan fatty acids (F-acids) by a

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common occurrence of furan fatty acids in plants. Lipids, 1989, 24, 296–298

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fatty acids (F-acids). Lipids, 1988, 23, 1032–1036

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occuring furan fatty acids. Biol. Pharm. Bull., 1996, 19, 1607–1610

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Technol. 2013, 25, 7–10



381

CAPTIONS TO FIGURES

382

Figure 1. Chemical structures of (9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid (9M5)), 1,

383

(3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid), 2, (9-(3-methyl-5-propylfuran-2-yl)-

384

nonanoic (9M3)), 3, (9-(3,4-dimethyl-5-pentylfuran-2-yl)-nonanoic acid (9D5)), 4, and (11-

385

(3-methyl-5-pentylfuran-2-yl)-undecanoic acid (11M5)), 5.

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386 387

Figure 2. Extract of (A) the GC/FID chromatogram and (B) the GC/MS chromatogram

388

(system 1) of the lipid extract from disposable latex gloves, #28 (Table 1). All fatty acids

389

were measured as methyl esters.

390 391

Figure 3. Extract of (A) GC/MS-SIM chromatogram (system 1) and (B-D) mass spectra of

392

the furan fatty acids (9-(3-methyl-5-propylfuran-2-yl)-nonanoic (9M3)), 3, (9-(3,4-dimethyl-

393

5-pentylfuran-2-yl)-nonanoic acid (9D5)), 4, and (11-(3-methyl-5-pentylfuran-2-yl)-

394

undecanoic acid (11M5), 5, detected in disposable latex gloves from Malaysia, #9 and #22

395

(Table 1).

396 397

Figure 4. GC/FID chromatogram of a standard mix containing methyl esters of palmitic acid

398

(16:0), stearic acid (18:0), oleic acid (18:1∆9), linoleic acid (18:2∆9,12) and 9-(3-methyl-5-

399

pentylfuran-2-yl)-nonanoic acid (9M5), 1, in the same concentration (c = 2 mg/mL).

400 401

Figure 5. Share of fatty acids stearic acid (18:0), oleic acid (18:1∆9) and palmitic acid (16:0)

402

compared to linoleic acid (18:2∆9,12) in disposable latex gloves from different producers.

403

Producers D and E and those with only one sample (single gloves) were summed up in one

404

group each. 18 ACS Paragon Plus Environment

Page 19 of 28


405 406

Figure 6. Percentage contribution of 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid (9M5), 1,

407

to the total fatty acids in disposable latex gloves exposed to daylight from (A) samples #30

408

and (B) #13 (Table 1) at different time points.

409 410

Figure 7. GC/MS chromatograms (system 1) in full scan mode after silver ion mini

411

chromatography of (A) fraction 1, (B) fraction 2 and (C) fraction 3 of the lipid extract of

412

disposable latex gloves, #30 (Table 1).



Page 20 of 28

Table 1: Share of Lipid Extract per Glove, Contribution of (9-(3-methyl-5-pentylfuran-2-yl)nonanoic acid (9M5)), 1, of the Total Fatty Acids, and Amount of 9M5 in 30 Different Disposable Latex Gloves from 14 Different Producers.

Number

Product

1 A1 2 A2 3 A3 4 A4 5 A5 6 A6 7 A7 8 A8 9 B1 10 B2 11 B3 12 B4 13 B5 14 C1 15 C2 16 C3 17 C4 18 D1 19 D2 20 E1 21 E2 22 F1 23 G1 24 H1 25 I1 26 J1 27 K1 28 L1 29 M1 30 N1 Mean/Median:

Share of lipid extract per glove [%]

Contribution of 9M5 to the total fatty acids [%]

Amount of 9M5 [mg/g glove]

1.4 1.3 1.2 1.2 0.8 0.6 1.6 1.2 1.6 1.2 1.0 1.0 0.9 1.5 1.4 1.1 0.9 0.9 0.9 1.1 0.9 1.6 1.5 1.2 1.2 1.0 1.0 0.9 0.8 0.8 1.1/1.1

67.2 67.2 65.4 58.1 52.3 57.4 51.9 37.9 57.6 74.7 39.4 70.3 52.8 54.9 87.0 47.3 54.7 85.1 66.9 68.2 68.4 59.2 68.7 76.0 60.5 58.3 57.3 56.1 53.0 67.9 61.4/58.8

2.6 2.5 1.9 1.6 0.8 1.1 2.0 0.7 2.9 3.2 0.6 2.9 0.8 2.0 8.2 1.0 1.5 4.4 1.8 2.0 1.7 3.8 2.8 3.8 1.6 2.0 1.7 2.2 1.1 2.1 2.2/2.0


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Figure 1

′ ′

9

1

M

5

2

3

4

5



Page 22 of 28

Figure 2


Page 23 of 28


Figure 3 Irel

9M5 (1)

A

9M3 (3) 9D5 (4) 18.0

Irel

19.0

20.0

21.0

22.0

23.0

11M5 (5) 24.0

25.0

137

9M3 (3)

[min]

B

294 109

100

Irel

180

140

260

220

300

9D5 (4)

m/z

C 179

123

100

Irel

336

140

11M5 (5)

180

220

260

165

m/z

D

109

100

300

350

140

180

220

260

300

340

380

m/z



Page 24 of 28

Figure 4


Page 25 of 28


share of fatty acid compared to 18:2 9,12 [%]

Figure 5 100 120

18:0 18:1∆9 18:1 16:0

80

60

40

20

0 A

B

C

D/E

single gloves

different producers



Page 26 of 28

Figure 6

Contribution of 9M5 to total fatty acids [%]

80

60

A 68

49

40

40 34 20

22

0 0

24

48 hours in daylight [h]

72

96

Contribution of 9M5 to total fatty acids [%]

80

B

60 53 40 41 36 31

28

72

96

20

0 0

24

48 hours in daylight [h]


Page 27 of 28


Figure 7 Irel

Fraction 1

A

18:0

16:0

20:0 14.0 Irel

18.0

20.0

Fraction 2

14.0 Irel

16.0

22.0

24.0

B

9M5

16.0

Fraction 3

18.0

20.0

22.0

[min]

24.0

[min]

C

18:2∆9,12

18:1∆9

18:3∆9,12,15 14.0

16.0

18.0

20.0

22.0

24.0

[min]



Page 28 of 28

TABLE OF CONTENTS GRAPHIC


nonanoic Acid from Disposable Latex Gloves - ACS Publications

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