Electronic Supplementary Material

Vacuum-assisted headspace-solid phase microextraction for

determining volatile free fatty acids and phenols. Investigations on the

effect of pressure on competitive adsorption phenomena in a

multicomponent system

María J. Trujillo-Rodríguez1, Verónica Pino*,1, Elefteria Psillakis*,2, Jared L.

Anderson3, Juan H. Ayala1, Evangelia Yiantzi2, Ana M. Afonso1

1Departamento de Química (Unidad Departamental de Química Analítica), Universidad de La Laguna (ULL), La Laguna (Tenerife), 38206 Spain

2Laboratory of Aquatic Chemistry, School of Environmental Engineering, Technical University of Crete (TUC), Polytecheioupolis, GR-73100 Chania-Crete, Greece

3Department of Chemistry, Iowa State University, Ames, Iowa 50011 USA

Table of Contents

Table ESM-1 page S2

Figure ESM-1 page S3

Figure ESM-2 pages S4-S5

Figure ESM-3 pages S6-S7

Figure ESM-4 pages S8-S9

Table ESM-1. Physicochemical properties of the group of FFAs and phenols studied. Data was obtained from SciFinder® Scholar.

Analyte Abbreviation MWa

(g·mol-1)Solubilityb)·103

(mg·L-1)dc

(g·cm-3)BPd

(ºC)VPe

(Pa)pKa

(25 ºC)Log

Kowf(KH

g)·107

(atm·m3·mol-

1)

Size (Å)

iso-butyric acid i-C4 88.11 49 0.950 152.0 217 4.85 0.541 9.7 4.29n-butyric acid n-C4 88.11 66 0.958 165.5 180 4.76 0.697 5.3 5.60iso-valeric acid i-C5 102.1 25 0.931 176.5 73.9 4.78 1.05 13 5.49n-valeric acid n-C5 102.1 19 0.939 186.0 60.3 4.78 1.21 4.5 6.97iso-hexanoic acid i-C6 116.2 11 0.939 200.5 17.5 4.78 1.56 17 6.73n-hexanoic acid n-C6 116.2 5.9 0.929 205.8 21.1 4.78 1.72 7.1 7.54guaiacol (2-methoxyphenol)

2-MOP 124.1 7.2 1.13 204.0 23.9 9.97 1.34 11 6.98

n-heptanoic acid n-C7 130.2 2.0 0.918 222.2 7.73 4.78 2.23 8.8 8.67phenol Ph 94.11 26 1.07 181.8 81.9 9.86 1.54 3.4 5.252-ethylphenol 2-EP 122.2 2.9 1.02 204.5 24.5 10.3 2.47 8.2 7.15eugenol (4-allyl-2-methoxyphenol)

4-Al-2-MOP

164.2 0.75 1.07 253.2 1.33 10.3 2.40 0.48 9.40

a molecular weightb water solubility at 25ºCc densityd boiling pointe vapor pressure at 25ºCf logarithm of the octanol-water partition coefficientg Henry’s law constant, predicted data generated using the US Environmental Protection Agency’s EPISuite, HENRYWIN v3.10; BOND METHOD

S2

Figure ESM-1 Analyte extraction efficiency, expressed as chromatographic peak area, obtained with (A) Vac-HSSPME and (B) regular HSSPME using the commercial and PIL-based SPME fibers. Other experimental conditions: 5 mL ultrapure water containing 25% (w/v) NaCl, 0.022 mmol·L-1 of each FFA and 1 mg·L-1 of each phenol; 30 min extraction time; 40 ºC sampling temperature; 400 rpm agitation rate; 6 min GC desorption time at 280 ºC.

S3

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i-C4 n-C4 i-C5 n-C5

i-C6 n-C6 2-MOP n-C7

Ph 2-EP 4-Al-2-MOP

Figure ESM-2. (A) Optimization of the HSSPME method using CAR/PDMS: Effect of the NaCl content (0–25%, w/w). Experimental conditions (n = 3): 5 mL ultrapure water, 0.022 mmol·L-1 of each FFA and 1 mg·L-1 of each phenol, extraction time of 40 min, extraction temperature of 45 ºC, extraction stirring of 400 rpm, desorption time of 6 min, desorption temperature of 280 ºC.

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i-C6 n-C6 2-MOP n-C7

Ph 2-EP 4-Al-2-MOP

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Figure ESM-2. (B) Optimization of the Vac-HSSPME method using CAR/PDMS: Effect of the NaCl content (0–25%, w/w). Experimental conditions (n = 3): air evacuation (7 mbar, 1.5 min), 5 mL ultrapure water, 0.022 mmol·L-1 of each FFA and 1 mg·L-1 of each phenol, extraction time of 40 min, extraction temperature of 45 ºC, extraction stirring of 400 rpm, desorption time of 6 min, desorption temperature of 280 ºC.

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i-C4n-C4

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i-C6 n-C6

Figure ESM-3. Desorption time profiles obtained (i) under reduced (Vac-HSSPME; filled symbols) and (ii) atmospheric (Regular HSSPME; open symbols) pressure conditions. Other experimental conditions (n = 3): CAR/PDMS fiber; 5 mL ultrapure water containing 25% (w/v) NaCl, 0.022 mmol·L-1 of each FFA and 1 mg·L-1 of each phenol; 40 min extraction time at 45 ºC; 400 rpm agitation rate; 280 ºC of desorption temperature.

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Ph 2-EP

4-Al-2-MOP

Figure ESM-3. (continued) Desorption time profiles obtained (i) under reduced (Vac-HSSPME; filled symbols) and (ii) atmospheric (Regular HSSPME; open symbols) pressure conditions. Other experimental conditions (n = 3): CAR/PDMS fiber; 5 mL ultrapure water containing 25% (w/v) NaCl, 0.022 mmol·L-1 of FFAs and 1 mg·L-1 of phenols; 40 min extraction time at 45 ºC; 400 rpm agitation rate; 280 ºC of desorption temperature.

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i-C4n-C4

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i-C6 n-C6

Figure ESM-4. Extraction time profiles obtained (i) under reduced (Vac-HSSPME; filled symbols) and (ii) atmospheric (Regular HSSPME; open symbols) pressure conditions. Other experimental conditions (n = 3): CAR/PDMS fiber; 5 mL ultrapure water containing 25% (w/v) NaCl, 0.022 mmol·L-1 of FFAs and 1 mg·L-1 of phenols; 45 ºC of extraction temperature; 400 rpm agitation rate; 6 min of desorption at 280 ºC.

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Ph 2-EP

4-Al-2-MOP

Figure ESM-4. (continued) Extraction time profiles obtained (i) under reduced (Vac-HSSPME; filled symbols) and (ii) atmospheric (Regular HSSPME; open symbols) pressure conditions. Other experimental conditions (n = 3): CAR/PDMS fiber; 5 mL ultrapure water containing 25% (w/v) NaCl, 0.022 mmol·L-1 of FFAs and 1 mg·L-1 of phenols; 45 ºC of extraction temperature; 400 rpm agitation rate; 6 min of desorption at 280 ºC.

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