Analysis of Ochratoxin A in Wine by High-Resolution UHPLC-MS

A method for determination of ochratoxin A (OTA) in wines using a new-solid phase extraction clean-up procedure followed with ultra performance liquid chromatography (UHPLC)-Orbitrap MS based on two scan events (full-scan Fourier transform mass spectrometer [FTMS] and higher energy-induced collision dissociation[HCD] data-dependent MS/MS) in positive ionization mode has been developed. The limit of detection (LOD) was estimated at 0.46 μg l^?1 for white wine, 0.53 and 0.54 μg l^?1 for rosé and red wines, respectively. The limit of quantification (LOQ) was estimated at 1.57 μg l^?1 in white wine, 1.77 and 1.81 μg l^?1 in rosé and red wines. Recovery experiments were carried out with spiked samples at three concentration levels (2, 5 and 10 μg l^?1). The OTA recoveries in spiked white wine samples varied from 69.6 % to 99.8 %, while the recoveries for rosé and red wine samples were in the range of 63.0–110.2 % and 63.6–103.2 %, respectively. Finally, based on the results, it is concluded that the combination of C18 cartridge with conventional particle packed columns and UHPLC LTQ-Orbitrap XL is an appropriate procedure for OTA analysis in wines.     

RP-HPLC-DAD Determination of Phenolics in Industrial Apple Pomace

Processing of apple fruits for juice/cider production generates large volume of pomace at industrial scale. This biomass (cell wall material and pulp tissues) is rich in array of nutrients, especially dietary fiber and polyphenols. Apple fruits confront various processing conditions at industrial level, influencing the biochemical composition of generated pomace, including its phenolic profile. In present study, a simple, fast and reproducible reversed-phase high-performance liquid chromatography method using diode array detector was developed and validated for separation of different phenolics present in industrial apple pomace. The present method showed reliable and reproducible intraday (0.2–4.0 % RSD) and interday (3.7–8.1 % RSD) precision with limits of detection and quantification values in range of 0.14–0.58 and 0.48–1.95 μg ml^?1, respectively, for all the phenolics. Different solvent-mediated extraction of dried pomace powder was also performed to evaluate its total antioxidant potential using standard spectrophotometric assays. The major phenolics found in industrial apple pomace extracts were quercetin (1.4–10.3 μg mg^?1), phloretin (1.1–9.3 μg mg^?1) and phloridzin (0.62–2.0 μg mg^?1).     

Screening method for identification of adulterate and fake tequilas by using UV–VIS spectroscopy and chemometrics

Based on UV–VIS spectroscopy and chemometric techniques, a screening method is presented with which the studied brands of white and rested tequila can be differentiated among them and on the other hand, adulterate and fake tequilas can be distinguished from the corresponding genuine brands. Eighty bottles of tequila (39 white type and 41 rested type) were studied and purchased at liquor stores; special care was taken to get different batches. Through the use of support vector machine (SVM), principal component analysis (PCA) and linear discriminant analysis (LDA) the studied tequilas were differentiated and classified into 8 sets: 4 sets of white and 4 of rested tequilas; each set corresponded to a specific tequila brand. Seven additional samples with similar labeling than the 80 samples were used to validate the method and it was found that each sample was located within the ellipse of confidence of the corresponding tequila brand. Furthermore, 14 adulterated samples were generated from 2 bottles of tequila, one white and one rested, and they could be distinguishable from the genuine tequila, i.e., they were outside of the corresponding ellipse of confidence. In addition, the screening method here presented was employed to analyze rested tequilas that were purchased on the street market, i.e., fake tequilas, with the same label than 3 of the used brands in this work. These samples were discriminated from the corresponding genuine tequila brand. The results suggested that the reported method could play an important role when a quick, trustworthy and feasible result on site is needed since the test of the spirit takes minutes, affording robustness, reliability and in addition, a skilled worker is not required necessarily to apply the method.     

Application of Ionic Liquid-Based Ultrasound-Assisted Extraction of Five Phenolic Compounds from Fig (<Emphasis Type="Italic">Ficus carica</Emphasis> L.) for HPLC-UV

Ionic liquid-based ultrasonic-assisted extraction (IL-UAE) was successfully developed to extract the known phenolics gallic acid, chlorogenic acid, rutin, psoralen, and bergapten present in the leaves, pulps, and peels of Ficus carica L. In this work, the proposed method was evaluated in comparison with regular ultrasonic-assisted extraction in which methanol was the extractant and exhibited higher efficiency. Moreover, ionic liquids with different cations were investigated and 1-butyl-3-methylimidazole hexafluorophosphate solution was selected as the optimal extractant at concentration of 1.0 mol L^?1. The corresponding extraction parameters including extraction solvent, the concentration of [BMIM][PF₆], solid–liquid ratio (g mL^?1), ultrasonic extraction time, and extraction temperature were optimized. The phenolics were then determined by high-performance liquid chromatography (HPLC). Under the optimized conditions, the content of gallic acid, chlorogenic acid, rutin, psoralen, and bergapten in leaves, pulps, and peels of F. carica L. was 12.67–37.16, 14.75–90.07, 107.91–222.37, 2.59–67.83, and 1.99–20.21 μg/0.1 g, respectively. This study suggests that IL-UAE is a rapid, simple, and green preparation technique.     

Determination of Free Amino Acids in Coated Foods by GC–MS: Optimization of the Extraction Procedure by Using Statistical Design

The development and validation of an extraction procedure for quantification of free amino acids in coated products by MTBSTFA derivatization and GC–MS detection is described. The extraction method entailed the sample homogenization with hydrochloric acid (HCl) by stirring at 40 °C followed by two centrifugation steps. The optimum combination of the extraction variables was achieved by response surface methodology. HCl concentration and volume and stirring time influenced free amino acid extraction yield. The selected optimal extraction conditions were 5 g of sample mixed to 7.5 ml of 0.1 N HCl and stirred during 90 min. Consistency between predicted and experimental values as well as in the quality parameters was observed. The calibration curves were linear within the range 5–100 μg ml^?1 with correlation coefficient values (R ² ) higher than 0.99. Detection and quantification limits of the analytical procedure ranged from 2.10^?5 to 18.10^?2 μg μl^?1 and from 8.10^?5 to 60.10^?2 μg μl^?1, respectively. Precision was 0.20–12.59 % for run-to-run and 3.38–17.60 % for day-to-day. The accuracy is between 82.99 and 115.77 %. Nineteen amino acids were analyzed in frozen-thawed and deep-fried coated products from different origin, with cysteine being the most relevant.     

Selective Determination of Selenium in Garlic, Mushroom and Water Samples by Chemically Modified Mesoporous Silica Solid Phase Coupled with ICP-OES

A selective sorbent for solid phase extraction (SPE), based on a chemically modified mesoporous silica (SBA-15), followed by inductively coupled plasma-optical emission spectrometry was used for extraction, preconcentration, and determination of selenium in water and food samples. The main parameters of SPE including pH, amount of mesoporous (solid phase), concentration of the eluent (desorption solvent), and equilibrium time were optimized by using a fractional central composite design (f-CCD). The optimum conditions were found to be 3.2 for pH, 21 mg for amount of the mesoporous, 1 mol l^?1 for eluent concentration, and 9 min for equilibrium time. Under the optimal conditions, the limit of detection (LOD) was 2.56 μg l^?1. The linear dynamic range (LDR) was 5–1,000 μg l^?1 with determination coefficient (R ²) of 0.999. Relative standard deviation (C?=?400 μg l^?1, n?=?5) was 3.84 %. The enrichment factor was 20. The maximum sorption capacity of the modified SBA-15 was 15 mg g^?1. The sorbent presented good stability, reusability, high adsorption capacity, and fast rate of equilibrium for sorption/desorption of selenium (IV) ions.     

A simple and efficient ultrasonic-assisted extraction procedure combined with UV-Vis spectrophotometry for the pre-concentration and determination of folic acid (vitamin B9) in various sample matrices

A simple and efficient ultrasonic-assisted extraction (UAE) procedure has been proposed for the pre-concentration of (2S)-2-[(4-{[(2-amino-4-hydroxypteridin-yl)methyl]amino}phenyl)formamido]pentanedioic acid (folic acid) in vegetables, pharmaceuticals and foods prior to determination at 540 nm using UV-Vis spectrophotometry. The method is based on hydrophobic ternary complex formation of folic acid with silver ions in the presence of cetyltrimethylammonium bromide (CTAB) as a sensitivity enhancer counter ion at pH 7.0, and then extraction into a micellar phase of polyethylene glycol monoalkyl ether (Genapol X-080). The impacts on the extraction efficiency and complex formation of analytical parameters such as sample pH, concentration of silver, concentration of surfactants and extraction time, ultrasonic time and sample volume, were investigated and optimised in detail. The matrix effect on the pre-concentration and determination of folic acid was investigated, and it was observed that the proposed method was highly selective against possible matrix co-extractives. Under optimised conditions, a good linear relationship between the analytical signal and folic acid concentration was obtained in the range of 0.6–180 μg l^?1 with a detection limit of 0.19 μg l^?1 and quantification limit of 0.63 μg l^?1. The applicability was evaluated using samples fortified at different concentration levels, and recoveries higher than 94.1% were obtained. The precision as the percent relative standard deviation (RSD%) was in range of 2.5–3.8% (10 and 40 μg l^?1, n = 5). The proposed method was validated by analysis of two standard reference materials (SRMs) and various real samples, and satisfactory results were obtained.     

Molecularly Imprinted Nanosilica Solid-Phase Extraction for Bisphenol A in Fish Samples

This paper reports a method using molecularly imprinted nanosilica as the solid-phase extraction sorbent to extract bisphenol A (BPA) from fish samples. The selective extraction efficiency of BPA from its structure-analogous by molecularly imprinted solid-phase extraction (MISPE) was compared with commercial C18 SPE column. The reproducibility of MISPE and optimal flow rate of sample were studied. There was a linear correlation in the concentration range of 0.7–114.1 μg l^?1 of BPA (r?=?0.997). The limit of detection (LOD) based on three times ratio of signal to noise was 0.11 μg l^?1. Under optimal conditions, the proposed method was applied to the analysis of BPA in fish samples. The amount of BPA in bream was 4.00 μg kg^?1, and both concentrations of BPA in crucian and weever were below the LOD. The recoveries of BPA standard solution spiked with fish samples were in the range of 92.56–102.3 % with the relative standard deviation less than 10 %.     

Qualitative and quantitative research of propyl lactate in brewed alcoholic beverages

Recently, propyl lactate has been firstly detected in Chinese Baijiu (Chinese liquor) as one of the odor-active components. In this study, the contents of propyl lactate in other different brewed alcoholic beverages were investigated, including wine, soju, sake, vodka, rum, tequila, whisky and beer, and analyzed by solid-phase microextraction and liquid–liquid extraction coupled with gas chromatography-mass spectrometry, determined by internal standard method followed by GC-MS with selective ion monitoring. The analyses indicated that propyl lactate was present in beer and tequila samples, while not detected in other brewed alcoholic beverages. The results showed that among the 40 beer samples from 11 different countries, 36 of them contained propyl lactate at concentrations in the range of 0.23–51.71 µg L^?1. In addition, all of six tequila samples contained propyl lactate at concentrations in the range of 0.77–12.14 mg L^?1, and the odor activity values (OAVs) of propyl lactate were greater than 1 in all of the tequila samples. These findings indicated that propyl lactate was widely distributed in beer and tequila; it was also an odor-active component of tequila according to OAVs.     

Application of Dispersive Liquid–Liquid Micro-extraction Using Mean Centering of Ratio Spectra Method for Trace Determination of Mercury in Food and Environmental Samples

In the present study, dispersive liquid–liquid micro-extraction has been applied for trace extraction and determination of mercury (Hg) ions in environmental samples. The mean centering of ratio spectra method was used to optimize the experimental parameters affecting the extraction of Hg. The factors influencing the extraction procedure such as type and volume of extracting and disperser solvent, concentration of chelating reagent, pH, salt effect, and centrifuge time were investigated and optimized. Under the optimized conditions, the limit of detection of the method was 0.15 μg l^?1 and enrichment factor was 39. The calibration curve was linear in the range of 0.5–100 μg l^?1 with a correlation of determination (R ²) of 0.998. The relative standard deviation for determination of 40 μg l^?1 of Hg(II) was 2.6 % (n?=?5). The proposed method was applied for the determination of Hg in pine leaf, sea and river fish, sand, and water samples as indicators of environmental pollution and cigarette with satisfactory analytical results. In comparison with other methods, the proposed method is very simple, easy, rapid, and sensitive for determination of Hg at trace levels in complex matrices.     

Betalain and Phenolic Compositions,Antioxidant Activity of Tunisian Red Beet (Beta vulgaris L. conditiva) Roots and Stems Extracts

In the present study, betalains content, phenolic composition, and antioxidant activity of different parts of red beet (Beta vulgaris L. conditiva) (i.e., roots and stems) were compared. Crude extract of root showed the highest betalain content with a maximum of 53 ± 4 mg betanin eq and 46 ± 3 mg vulgaxantin I eq g^?1 of extract stems showed higher total phenolic concentration than roots, ranging between 2.0 ± 0.4 and 14.6 ± 0.5 mg gallic acid eq^?1 of extract. Chemical composition was analyzed using LC-MS. Betalains (vulgaxanthin I, betanin, and isobetanin) and phenolics (gallic acid, ferulic acid, chlorogenic acid, caffeic acid, vanillic acid, syringic acid, ellagic acid myricetin, quercetin, rutin, kampferol) were identified in roots and stems. Betalain extract obtained from roots showed higher antioxidant activity than extract obtained from stems.     

Large-Volume Sample Staking of Rice Polyphenols Prior to Their Determination by Non-aqueous Capillary Electrophoresis

A rapid non-aqueous capillary electrophoretic (NACE) method for the separation of (?)-epicatechin (EPI), (+)-catechin (?CAT), kaempferol (KAE), quercetin (QUR), naringanin (NAR), ferulic acid (FA), and p-coumaric acid (p-CA) has been developed and applied to the determination of these compounds in different rice varieties. All seven compounds were separated on capillary of 50 μm?×?68 cm (60-cm effective length) using 20 mmol L^?1 borate buffer of pH 9.0 and 5 % acetonitrile in methanol. Large-volume sample stacking (LVSS) technique was optimized and used to preconcentrate non-detectable polyphenols of white polished rice. Rice extracts were concentrated on-line by LVSS prior to separation by non-aqueous capillary electrophoresis. An improvement of 10–55 times in detectability was achieved with injection at 50 mbar for 30 s followed by voltage inversion (?20 kV) for 5 s. Linear calibration range of 1–300 μg L^?1 and 0.01–60 μg L^?1 was observed for NACE and NACE-LVSS method respectively, with the detection limit of 0.33–2.0 and 0.006–0.19 μg L^?1. Good reproducibility with standard deviations of less than 5 % was achieved. Polyphenol contents of different rice varieties were determined using developed method.     

Development of an ELISA and Immunochromatographic Assay for Tetracycline,Oxytetracycline, and Chlortetracycline Residues in Milk and Honey Based on the Class-Specific Monoclonal Antibody

A sensitive class-specific monoclonal antibody against tetracyclines (TCs) was generated and used to develop an enzyme-linked immunosorbent assay (ELISA) and an immunochromatographic assay for TC, oxytetracycline (OTC), and chlortetracycline (CTC) detection in milk and honey samples. The dynamic range of detection for TC in ELISA was 0.26–2.00 μg L^?1 with an IC₅₀ of 0.72 μg L^?1. The IC₅₀ value of OTC and CTC was 3.2 and 6.4 μg L^?1, respectively. The recovery of TC, OTC, and CTC in milk samples was 82–102, 91–105, and 90–101 %, respectively, and 88–101, 89–101, and 89–95 % in honey samples, respectively. In the immunochromatographic assay, the cutoff values for TC, OTC, and CTC were 15, 15, and 50 μg L^?1 in milk, respectively, and 40, 40, and 40 μg L^?1 in honey, respectively. The results revealed that ELISA and the immunochromatographic assay can be applied for the rapid and sensitive detection of TC, OTC, and CTC in milk and honey samples.     

Determination of patulin in apple juice using magnetic solid-phase extraction coupled with high-performance liquid chromatography

ABSTRACT

An efficient magnetic sorbent consisting of benzofuran-2-carboxylic acid-loaded magnetic nanocomposite was successfully synthesised for pre-concentration of patulin from apple juice. The prepared magnetic nanocomposite was characterised by scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectroscopy. Determination of enriched patulin was performed by high-performance liquid chromatography. The best adsorption conditions were 40 mg of sorbent, 50 ml of apple juice sample, pH 5, ambient temperature and 25 min; the elution conditions were 500 μl methanol, pH 5, ambient temperature, and 4 min. Under optimised conditions, pre-concentration factor was 100, linearity range was 1–400 μg l^–1 of patulin, limit of detection was 0.15 μg l^–1 and limit of quantification was 0.5 μg l^–1. When samples were determined 20 times, the recovery was 93.9–102.6% and the relative standard deviation was below 5.3%. In terms of proposed procedure, the developed method was successfully applied for patulin detection in apple juice samples.     

Effects of post-harvest stigmasterol treatment on quality-related parameters and antioxidant enzymes of green asparagus (Asparagus officinalis L.)

The effects of immersion of green asparagus spears in stigmasterol solution (0, 0.5 and 1.0 g l^?1, 15 min, 25°C) on weight loss, surface colour, enzyme activities and content of malondialdehyde, total phenol, lignin and chlorophyll were investigated during 40 days of storage at 4 ± 0.5°C. Of the concentrations tested, 0.5 g l^?1 treatment was most effective. Stigmasterol (0.5 g l^?1) treatment significantly reduced colour changes and losses of fresh weight and chlorophyll content. Superoxide dismutase (SOD) and catalase (CAT) activities were maintained higher in stigmasterol-treated (0.5 g l^?1) asparagus, whereas the activity of peroxidase (POD) was significantly reduced. Stigmasterol treatment (0.5 g l^?1) also significantly decreased the content of malondialdehyde (MDA) and increased total phenol content. Accumulation of lignin was positively correlated to activity of guaiacol-POD (r = 0.960, p < 0.01) in stigmasterol-treated (0.5 g l^?1) asparagus. The polyphenol oxidase (PPO) activity decreased and showed a significant negative correlation with the chroma L* value (r = –0.899, p < 0.01) in stigmasterol-treated (0.5 g l^?1) asparagus. It was concluded that stigmasterol treatment (0.5 g l^?1) could inhibit the senescence of green asparagus, and therefore prolong its shelf-life, maintaining the quality of post-harvest green asparagus.     

Simultaneous Determination of Cyclamate,Acesulfame, and Aspartame in Beverages by Titania-Based RP-HPLC

This paper aims at establishing a rapid method for simultaneous separation and determination of the sweeteners including cyclamate, acesulfame, and aspartame in beverages by titania-based reversed-phase high-performance liquid chromatography. The chromatographic conditions were as follows: a titania Sachtopore-RP C18 column (250?×?4.6 mm; 5 μm) as a separation column, a mixture of water and methanol at a volume ratio of 95:5 containing 1.0 % phosphate acid used as mobile phase, flow rate of 1.0 mL min^?1, and the detection wavelength was 205 nm. The linear ranges of cyclamate and aspartame were 0.02–8.0 mg mL^?1 with limits of detection (LODs) of 16.35 and 19.56 μg mL^?1, respectively, and their limits of quantitation (LOQs) were 55.50 and 68.50 μg mL^?1, respectively. The recoveries of cyclamate were between 93.52 and 103.54 %. The recoveries of aspartame were between 93.31 and 102.63 %. The linear range of acesulfame was 0.125–50 μg mL^?1 with LOD of 0.08 μg mL^?1 and LOQ of 0.25 μg mL^?1. The recoveries of acesulfame were between 94.34 and 103.21 %. Relative standard deviation (n?=?8) for all determinations was less than 0.72 %.     

Co-occurrence of aflatoxins,ochratoxin A and citrinin in “egusi” melon (Colocynthis citrullus L.) seeds consumed in Ireland and the United Kingdom

The natural co-occurrence of aflatoxins (AFs), ochratoxin A (OTA) and citrinin (CIT) in melon seed samples obtained from retailers and households in Ireland and the United Kingdom (UK) was evaluated. AFs and OTA were determined by HPLC with fluorescence detection while CIT was analysed by HPLC-MS/MS. AFB₁ was detected in all (100%) samples (mean = 9.7 μg kg^?1; range = 0.2–66.5 μg kg^?1). Mean total AFs was 12.0 μg kg^?1 (range = 0.3–82 μg kg^?1). Commercially retailed samples showed a significantly higher AFB₁ contamination (p < 0.05) than the household samples. OTA occurred in 3 (13.6%) samples, while 4 (18.2%) were contaminated with CIT at very low levels. In this study, 68% of the melon seed samples were contaminated above the 2 μg kg^?1 EU limit for AFB₁ in oilseeds. These results highlight the need for the development of strategies to reduce AF contamination in “egusi” for human consumption.     

Bisphenol A contamination in soft drinks as a risk for children’s health in Italy

Bisphenol A (BPA) was determined in sugary carbonated, non-carbonated and milk-based beverages, through HLPC-fluorescence detection and confirmed by LC-MS/MS, in a selection of brands that are mostly consumed by Italian children. The daily intake was determined through the WHO budget method (BM). BPA was found at detectable levels in 57% of carbonated beverages, in 50% of non-carbonated and in 100% of milk-based beverages. The median concentrations were 1.24 µg l^–1 (range = < LOD–4.98 µg l^–1) in canned carbonated beverages and 0.18 µg l^–1 (< LOD–1.78 µg l^–1) in non-canned carbonated beverages. In non-carbonated beverages, median concentrations were 0.80 µg l^–1 (< LOD–2.79 µg l^–1) and 0.18 µg l^–1 (< LOD–3.58 µg l^–1), respectively, for canned and non-canned beverages; in milk-based products the BPA median concentration was 3.60 µg l^–1 (1.00–17.65 µg l^–1). BPA daily intake from sugary drink consumption in children ranged from 0.008 to 1.765 µg kg^–1 bw day^–1. The median exposure values for the ‘best’ and ‘worst’ cases were 0.16% and 0.47% respectively of the EFSA t-TDI for BPA (4 µg kg^–1 bw day^–1), and 10.59% and 35.30% of the t-TDI when the maximum levels were considered.     

Dual-Label Chemiluminescence Strategy for Multiplexed Immunoassay of 20 Fluoroquinolones, 15 β-Lactams, 15 Sulfonamides,and CAP in Milk

In this paper, a novel dual-label time-resolved chemiluminescent multiplexed immunoassay (DLTRC-MIA) based on the distinction of the kinetic characteristics of horseradish peroxidase (HRP) and alkaline phosphatase (ALP) with approximate estimation approach for simultaneous determination of 20 fluoroquinolones (FQs), 15 β-lactams, 15 sulfonamides (SAs), and chloramphenicol (CAP) in milk was developed. The strategy integrated a single-chain variable fragment–alkaline phosphatase fusion protein (scFv-ALP), a recombinant penicillin-binding protein (PBP) 2×*, a monoclonal antibody (MAb), and a polyclonal antibody (PAb) in one immunoassay and in a single well together to fulfill the simultaneous detection of 51 low-molecular weight contaminants (20 FQs, 15 β-lactams, 15 SAs, and CAP). The limits of detection for FQs, β-lactams, SAs, and CAP range from 0.29 μg L^?1 for ciprofloxacin (CIP) to 81.6 μg L^?1 for trovafloxacin (TRO), 0.27 μg L^?1 for ceftiofur (CEF) to 44.1 μg L^?1 for cephalexin (CEL), 0.089 μg L^?1 for sulfadimethoxine (SDM) to 2.7 μg L^?1 for sulfadiazine (SDZ), and 0.028 μg L^?1 for CAP, respectively. The results demonstrated that the detection limits of DLTRC-MIA meet the requirement of detection levels for 51 drug residues in milk, suitable for high-throughput screening of low-molecular weight contaminants.     

Gas Purge Microsyringe Extraction Coupled with Dispersive Liquid-Liquid Microextraction for the Determination of Acidic Compounds in Food Packaging Materials

A green, simple and sensitive method was developed for the analysis of volatile carboxylic acids (VFAs) and perfluorocarboxylic acids (PFCAs) in food packaging materials. The acidic compounds in food packaging materials were first extracted by gas purge microsyringe extraction (GP–MSE) with 1.0 mL 0.1 mol·L^?1 NaOH solution, then the analytes were dispersive liquid-liquid microextracted (DLLME) by 50 μL chloroform as extraction solvent and 200 μL acetonitrile as dispersive solvent. The 2-(5-Benzoacridine) ethyl-p-toluenesulfonate (BAETS) with excellent fluorescence property was applied to enhance the high performance liquid chromatography (HPLC) sensitivity. The obtained recoveries for the VFAs ranged from 92.0 to 101 %. The method LODs calculated at a signal-to-noise ratio (S/N) of 3 were in the range of 0.80–3.40 μg·kg^?1, while the LOQs calculated at S/N of 10 were in the range of 2.5–10.2 μg·kg^?1. All compounds were in good linearity with concentration coefficients of higher than 0.997. Perfluorooctanoic acid (PFOA) was found in all of the 15 kinds of samples analyzed with concentrations ranging from 4.86–7.56 μg·kg^?1. Acetic acid, butyric acid, and caprylic acid were found in half of the samples analyzed. The other analytes were also found in more than 30 % samples with concentrations varied between 3.96 and 293 μg·kg^?1.