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Analytical and Bioanalytical Chemistry

, Volume 410, Issue 22, pp 5617–5628 | Cite as

Determination of phthalic acid esters in different baby food samples by gas chromatography tandem mass spectrometry

  • Bárbara Socas-Rodríguez
  • Javier González-Sálamo
  • Antonio V. Herrera-Herrera
  • Álvaro Santana-Mayor
  • Javier Hernández-BorgesEmail author
Research Paper
Part of the following topical collections:
  1. Food Safety Analysis

Abstract

In this work, a new method has been developed for the determination of 14 phthalic acid esters (i.e., benzylbutyl phthalate (BBP), bis-2-n-butoxyethyl phthalate (DBEP), dibutyl phthalate (DBP), dicyclohexyl phthalate (DCHP), bis-2-ethoxyethyl phthalate (DEEP), diethyl phthalate (DEP), diisodecyl phthalate (DIDP), diisononyl phthalate (DINP), bis-isopentyl phthalate (DIPP), bis (2-methoxyethyl) phthalate (DMEP), dimethyl phthalate (DMP), di-n-octyl phthalate (DNOP), bis-n-pentyl phthalate (DNPP), dipropyl phthalate (DPP)) and one adipate (bis (2-ethylhexyl) adipate (DEHA)) in different baby foods. Separation was carried out by gas chromatography triple quadrupole tandem mass spectrometry while the previous extraction of the samples was carried out using the QuEChERS method. The methodology was validated for four baby food samples (two fruit compotes of different compositions and two meat and fish purees with vegetables) using dibutyl phthalate-3,4,5,6-d4 (DBP-d4) as internal standard. Determination coefficients (R2) of matrix-matched calibration curves were above 0.9922 in all cases while relative recovery values ranged between 70 and 120%, with relative standard deviation values below 19%. The limits of quantification of the method ranged between 0.03 and 1.11 μg/kg. Finally, the analysis of commercially available samples was carried out finding the presence of BBP, DEHA, DEP, DIDP, and DPP in some of the studied samples.

Keywords

Phthalic acid esters Baby foods QuEChERS Gas chromatography Tandem mass spectrometry 

Introduction

Phthalic acid esters (PAEs), especially those of the family of o-phthalic acid, are widely used nowadays as plasticizers in the manufacture of an extensive variety of plastics, in order to facilitate their transformation [1, 2]. In particular, certain PAEs are also used for the fabrication of food contact materials (FCMs) but since they are additives of low molecular weight which are not chemically linked to the polymeric matrix, they have a certain migration capacity which finally constitutes a source of food contamination as it has already been demonstrated in the literature [3, 4]. Such migration has attracted much attention nowadays since many PAEs have a significant endocrine-disrupting activity, even at extremely low concentrations [5, 6, 7, 8].

Depending on the country, PAEs to be used in FCMs are authorized or not and their migration into food or relevant food simulants should also be below certain migration limits that are evaluated by tests in which the rate of transference from the plastic is studied under certain established conditions. In the European Union, the composition of plastic materials and articles intended to come into contact with food is regulated by Commission Regulation (EU) No. 10/2011 [9] in which PAEs like dibutyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP), benzylbutyl phthalate (BBP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP) shall not be used above certain concentrations. In the USA, the Environmental Protection Agency (EPA) [10] has also initiated actions to address the manufacturing, processing, distribution in commerce, and/or use of PAEs like DBP, diisobutyl phthalate (DIBP), BBP, bis-n-pentyl phthalate (DNPP), DEHP, di-n-octyl phthalate (DNOP), DINP, and DIDP.

Nowadays, among the different types of foods that are currently consumed, baby foods, which are specifically intended for infants (children under the age of 12 months) and young children (between 1 and 3 years) as they progress onto a mixed family diet, are of special concern, because they constitute one of the most vulnerable groups of the population. In fact, children’s food intake related to their weight is higher than that of adult. Concerning the analysis of PAEs, it should be remarked that a relatively low number of works (compared to other types of samples) have been published in the literature in which baby foods have been analyzed. This is the case of the analysis of breast milk [11, 12, 13, 14, 15] and infant formulae [15, 16, 17, 18, 19, 20, 21], which are the most common. But, others such as food packed in recycled paperboard [22], baby snacks and retort-pouched baby food [21], freeze-dried baby foods [23], fruit jellies [24], school meals [25, 26], or fruit compotes [26] have been also evaluated. In many of these works, a relatively low number of PAEs have been analyzed.

Nowadays, it is widely known that the QuEChERS method [27, 28, 29, 30, 31] has demonstrated to be efficient for the extraction of hundreds of analytes in a wide variety of commodities, being very rugged particularly for pesticides in food matrices. Even though, the frontiers of its application fields are not completely established yet and there are many areas in which the procedure could be applied in the future, taking into account the versatility shown until now. In this sense, and concerning the application of the QuEChERS method for the extraction of PAEs from food samples, some works have also been published [24, 32, 33, 34, 35, 36, 37]. This is the case of the analysis of fruit jellies [24], packed foods and heated microwave foods (grated cheese, meat, fish, vegetables broths, white and red wine) [32], milk and milk products [33, 37], wheat [34], tea [35, 36], and grain, meat, biscuit, and canned food [37]. However, only one of these attempts has specifically analyzed baby food samples [33], in particular infant formulae.

The analysis of PAEs is not an easy task due to the fact that they are present at relatively high concentration in the environment. Plastic tubes, caps, filters, septa, pipette tips, etc., can be sources of contamination in the laboratory as well as sources of high background [2, 3, 38]. High-purity solvents [38] and even Milli-Q water may also contain certain PAEs [3, 39]. Even though, several strategies can be developed to try to correct or to minimize such contamination [38]. Among them, the most important is probably the daily analysis of procedural blanks that allow to know the levels of contamination and, consequently, its influence on the sensitivity of the methodology, but it is also relevant to minimize the use of plastics by using glassware, Teflon, aluminum, or stainless steel materials. The cleaning of glassware should also be carefully considered, and it is recommend to calcine it or to clean it with strong oxidizing agents, which is compulsory for volumetric glassware. Besides, the use of phthalate-free gloves and pipette tips is also compulsory as well as high-purity solvents which may contain a lower amount of PAEs.

Taking into account the above, the aim of this work was to apply and validate the QuEChERS method for the analysis of a group of 14 PAEs and one adipate, in different fruit compotes and meat and fish purees (baby foods). To the best of our knowledge, this is the first time that the QuEChERS method is applied to the analysis of PAEs in this type of samples. Furthermore, this work constitutes one of the few articles in the literature dealing with the determination of PAEs in baby foods and also one of the few articles in which the content of PAEs in these samples is reported.

Experimental

Chemicals and materials

Analytical standards of dimethyl phthalate (DMP, CAS 131-11-3), diethyl phthalate (DEP, CAS 84-66-2), bis-isopentyl phthalate (DIPP, CAS 605-50-5), bis-2-ethoxyethyl phthalate (DEEP, CAS 605-54-9), DNPP (CAS 131-18-0), BBP (CAS 85-68-7), bis (2-ethylhexyl) adipate (DEHA, CAS 103-23-1), and bis-2-n-butoxyethyl phthalate (DBEP, CAS 117-83-9) from Dr. Ehrenstorfer (Augsburg, Germany) and of dipropyl phthalate (DPP, CAS 131-16-8), DBP (CAS 84-74-2), dibutyl phthalate-3,4,5,6-d4 (DBP-d4, CAS 93952-11-5) as internal standard (IS), bis (2-methoxyethyl) phthalate (DMEP, CAS 117-82-8), dicyclohexyl phthalate (DCHP, CAS 84-61-7), DNOP (CAS 117-84-0), DINP (CAS 20548-62-3), and DIDP (CAS 89-16-7) from Sigma-Aldrich Chemie (Madrid, Spain) were used without further purification (purity ≥ 96%).

Individual stock solutions of each analyte were prepared in cyclohexane at 150 mg/L (for DBP-d4), 500 mg/L (for DIPP, DEEP, DNPP, BBP, DEHA, DBEP, DPP, DBP, DMEP, DCHP, DNOP, DINP, and DIDP), and 1000 mg/L (for DMP and DEP) and stored in the darkness at − 18 °C. Working standard solution mixtures of all PAEs were prepared daily at different concentrations by combination and dilution with cyclohexane. Different volumes of these solutions were used to spike the samples with the target analytes.

All chemicals were of analytical reagent grade and were used as received (unless otherwise indicated). Acetonitrile (ACN) of high performance liquid chromatography (HPLC)-mass spectrometry (MS) grade and cyclohexane of gas chromatography (GC)-MS grade were from Merck (Darmstadt, Germany). Magnesium sulfate anhydrous (98%) was from Scharlau Chemie S.A. (Barcelona, Spain), sodium chloride was from Sigma-Aldrich Chemie (Madrid, Spain), primary secondary amine (PSA) was from Supelco (Pennsylvania, USA), and octadecylsilane (C18) sorbent was from Macherey-Nagel (Dürem, Germany).

Volumetric glassware was cleaned using Nochromix® (prepared as indicated by the manufacturer) from Godax Laboratories (Maryland, USA), while non-volumetric glassware was calcined at 550 °C during 4 h. Phthalate-free gloves and pipette tips were used.

Apparatus and software

For PAEs determination, an Agilent 7890B GC system coupled to a 7000C triple quadrupole (QqQ) mass spectrometer with an electron impact interface (Agilent 7000C Triple Quadrupole GC/MS System; Agilent Technologies, Waldbronn, Germany) was used, equipped with a CombiPAL autosampler (Minnesota, USA). GCQQQ/Enhanced MassHunter software (Agilent Technologies) was used to control the GC-MS system. Two identical (5% phenyl)-methylpolysiloxane-bonded fused silica capillary columns (HP-5ms; 15 m × 0.25 mm, 0.25 μm film thickness; Agilent Technologies) were connected by means of a backflush valve that allows a negative He flow that favors the cleaning of the first column between injections. Helium flows in the first and second columns were set at 1.5 and 1.7 mL/min, respectively. The column temperature was initially set at 70 °C and held for 2 min, then increased to 200 °C at a rate of 25 °C/min, increased to 260 °C/min at a rate of 3 °C/min, and finally increased to 300 °C at a rate of 30 °C/min and held for 4 min. Total run time was 32.53 min. Two microliters of a standard or sample solution was injected in the splitless mode at 280 °C (after 1.5 min, the split was opened at a ratio of 1:50). The QqQ MS was operated in the multiple reaction monitoring (MRM) mode, taking two different transitions for each analyte with quantification and confirmation purposes as listed in Table S1 of the Electronic Supplementary Material (ESM). Mass spectrometer was used under the following conditions: transfer line and ion source were set at 280 °C with an electron ionization energy level of − 70 eV, the temperature of the first and second quadrupoles was 180 °C, and the collision cell gases were nitrogen (1.5 mL/min) and helium (2.25 mL/min, quenching gas).

Sample selection

Four different baby food samples, including apple jar (apple 99.9%, lemon juice, l-ascorbic acid), fruits jar (100% of apple, banana, pear, apricot, orange, pineapple, grape, lemon, l-ascorbic acid), vegetables with chicken and beef jar (56% of potato, green beans, carrot, tomato, peas and onion, cooking water, 6.5% of chicken meat, 2.5% of beef meat, cornflour, extra virgin olive oil), and vegetables with fish jar (49% of potato, carrot, green beans, peas, tomato, onion and celery, unskimmed milk, 9% of hake, cooking water, cornflour, virgin olive oil) were selected with the aim of validating the methodology.

Additionally, four more samples were analyzed in order to evaluate the applicability of the methodology for the analysis of real baby food samples, including an apple compote packed in a doypack recipient (99.9% of apple, ascorbic acid), a three-fruit jar (30% of banana, 15.6% of apple and mandarin orange juice, 15% of pear, carrot, orange juice, cornflour, rice starch, lemon juice, l-ascorbic acid), a four-fruit jar (42% of banana, 39.7% of pear, 15.4% of apple, 2.5% of orange, lemon juice, l-ascorbic acid), and a fruit compote packed in a plastic recipient (apple, peach, banana, maize starch, grape and orange juice, and l-ascorbic acid). All baby food samples were purchased in local supermarkets of Tenerife (Canary Islands, Spain). Nutritional information of all matrices is included in Table S2 of the ESM.

QuEChERS extraction procedure

The QuEChERS method was applied for the extraction of the target analytes from the selected baby food samples. Briefly, 10 g of each sample was weighted into a 50-mL glass centrifuge tube, 10 mL of ACN was added, and the mixture was manually shaken for 1 min, followed by the addition of 4 g of MgSO4 and 1 g of NaCl, and it was shaken again during 2 min. Then, the mixture was centrifuged at 3000 rpm for 15 min in a 5702 centrifuge from Eppendorf (Hamburg, Germany). The supernatant was transferred to a 15-mL glass centrifuge tube containing 1.2 g of MgSO4 and 200 mg of PSA (cleanup step), shaken for 1 min, and centrifuged at 4000 rpm for 8 min. Afterwards, the supernatant was collected and evaporated at 40 °C and 175 mbar in a rotary evaporator R-200 equipped with a V-800 vacuum controller and a V-500 vacuum pump from Büchi Labortechnik (Flawil, Switzerland). Finally, the residue was reconstituted in 500 μL of cyclohexane and filtered through a 0.22-μm Corning® Costar® Spin-X® cellulose acetate membrane PP centrifuge tube filter. In the case of fish and meat jars, 200 mg of C18 was also added to remove fats from the matrix during the cleanup step.

Results and discussion

GC-QqQ-MS/MS method

As target analytes for this study, a group of 14 PAEs of interest and one adipate (which is currently being used as a substitute of DEHP) were selected. The deuterated dibutyl phthalate (DBP-3,4,5,6-d4) was chosen as IS. Among the selected compounds, we have included four PAEs for which the EU has set down specific migration limits (SMLs) from plastic material destined to be in contact with food (DBP, BBP, DINP, and DIDP). Furthermore, six of them (DBP, BBP, DNPP, DNOP, DINP, and DIDP) are also included in the group of plastic migrants under study by the US EPA.

PAEs have enough volatility to be determined by GC without derivatization [40], though other methodologies based on liquid chromatography (LC) [2] or even capillary electrophoresis (CE) have been proposed [41, 42, 43, 44]. In this case, the selected group of PAEs was separated by GC-MS/MS by applying the conditions previously optimized by our group [39], using two apolar columns of 15 m (HP-5ms). The first of them was operated in the backflush mode once the analytes were eluted. The MS system was operated in MRM mode using one or two precursors and two product ions as well as the retention time as identification points and establishing a maximum tolerance of ± 20% for the relative ion intensities of the product and precursor ions [45]. The separation and detection conditions (MS/MS transitions and collision energies) selected were those indicated in the “Experimental” Section. Figure 1 shows the chromatogram obtained under MRM mode of the selected compounds. As can be seen, all PAEs were completely separated due to the fact that, as it has already been described in the literature [46, 47], most of them share the same parent/precursor ion for the quantification transition (the most intense) and which corresponds to fragment 149 m/z [48] (that is not the case of DMP, the IS (DBP-3,4,5,6-d4), and the adipate (DEHA)).
Fig. 1

GC chromatogram of a standard mixture of the target analytes obtained under MRM mode. Concentration = 200 μg/L (cyclohexane). 1, DMP; 2, DEP; 3, DPP; 4, DBP; IS: DBP-d4; 5, DMEP; 6, DIPP; 7, DEEP; 8, DNPP; 9, BBP; 10, DEHA; 11, DBEP; 12, DCHP; 13, DNOP; 14, DINP; 15, DIDP

With the aim of demonstrating the linearity of the developed GC-MS/MS method, solvent calibration curves based on analyte peak area-to-IS peak area ratios were obtained by injecting seven increasing concentration levels (n = 7) in triplicate for each analyte. As it is shown in Table 1, in which the studied linear ranges were also included, determination coefficients (R2) higher than 0.9944 were obtained for all target analytes. Taking into account the good instrumental sensitivity, the lowest calibration levels (LCLs) were established in the range 0.5–10 μg/L.
Table 1

Solvent calibration data (range of concentration studied and R2) of the selected compounds

Analyte

Retention time (min)

Calibration data (n = 7)

Range of concentration studied (μg/L)

R 2a

DMP

6.91

0.5–250

0.9993

DEP

7.63

0.5–250

0.9992

DPP

8.76

0.5–250

0.9986

DBP

10.39

1–250

0.9994

DMEP

10.82

10–250

0.9965

DIPP

11.64

0.5–250

0.9990

DEEP

12.24

10–250

0.9959

DNPP

12.75

0.5–250

0.9976

BBP

15.96

1–250

0.9998

DEHA

16.79

10–250

0.9995

DBEP

18.29

5–250

0.9968

DCHP

19.08

0.5–250

0.9996

DNOP

23.58

5–250

0.9990

DINP

26.09

5–250

0.9982

DIDP

28.81

10–250

0.9944

DBP-d4 was used as IS in all cases

aDetermination coefficient

QuEChERS-GC-QqQ-MS/MS method validation

In this work, the QuEChERS method based on the original procedure proposed by Anastassiades et al. [27] followed by the determination by GC-MS/MS was applied for determination of a group of 14 PAEs and one adipate in different types of baby foods. Taking into account that such methodology has not been applied for the analysis of this kind of samples so far, an exhaustive validation of the procedure was carried out. For this purpose, and since PAEs may also appear in the studied matrices, blank samples were analyzed finding the presence of some of the selected analytes. For this reason, and in order to carry out an appropriate validation of the procedure for all the target compounds, their peak areas were subtracted when necessary. Figure S1 (see the ESM) shows the chromatograms of the analytes found in the different matrices validated.

In addition to that, and taking into account the ubiquitous presence of PAEs in the environment, laboratory blanks submitted to the whole method (no sample was added) were also analyzed each day in order to evaluate the influence of the background contamination in the results obtained. DNOP, DINP, BBP, DEHA, and DEP were detected at levels lower than the LCL of the solvent calibration shown in Table 1.

As it is widely known, the injection of the matrix extract could bring about the obtaining of biased results due to the effect of suppression or enhancement of the detector signal of the analytes [49]. In order to evaluate this possible effect, the comparison between the slope of the solvent calibration and the slope of the matrix-matched calibration of each matrix, following the equation: percent matrix effect (ME%) = [1 − (slope solvent calibration / slope matrix-matched calibration)] × 100, previously applied [50]. As can be seen in Table S3 of the ESM, in which ME% values of all analytes and matrices are shown, most of analyte signals show a clear enhancement effect in the presence of all matrices with values of ME% in the range 50–90%. On the contrary, DBP, DPP, DEP, and DMP present signal suppression with ME% below 0. Especially remarkable is the case of DMP for which the signal decreases to less than half with ME% higher than − 100%.

Taking into account these results, the strategies most used to compensate matrix effects (that is to say, the development of a matrix-matched calibration which equalizes the response for calibration standards and sample extracts as well as the use of ISs, which, in addition, allows the correction of the possible errors produced during sample preparation and the improvement of the reproducibility of the methodology [51, 52]) were applied in this work.

Matrix-matched calibration curves were obtained by injecting seven different levels of concentrations (n = 7) in triplicate. Seven samples were treated as blanks and spiked with the target analytes and the IS (150 μg/L) after evaporation to dryness in the rotary evaporator and reconstituted with cyclohexane for their injection in the GC-MS system. Table 2 shows the studied linear range and the determination coefficients (R2) which were higher than 0.9922 in all cases. For all compounds and matrices, the LCLs were in the range 0.5–15 μg/L.
Table 2

Matrix-matched calibration data (range of concentration studied and R2) of the selected compounds in the different matrices

Analyte

Type of baby food

Calibration data (n = 7)

Range of concentration studied (μg/L)

R 2a

DMP

Fruit

10–250

0.9999

Apple

0.5–250

0.9977

Vegetables with chicken and beef

0.5–250

0.9999

Vegetables with fish

0.5–250

0.9979

DEP

Fruit

1–250

0.9976

Apple

0.5–250

0.9998

Vegetables with chicken and beef

0.5–250

0.9964

Vegetables with fish

15–250

0.9996

DPP

Fruit

10–250

0.9999

Apple

1–250

0.9989

Vegetables with chicken and beef

1–250

0.9999

Vegetables with fish

0.5–250

0.9975

DBP

Fruit

1–250

0.9989

Apple

1–250

0.9996

Vegetables with chicken and beef

1–250

0.9977

Vegetables with fish

0.5–250

0.9995

DMEP

Fruit

15–250

0.9923

Apple

0.5–250

0.9969

Vegetables with chicken and beef

5–250

0.9994

Vegetables with fish

10–250

0.9922

DIPP

Fruit

0.5–250

0.9999

Apple

0.5–250

0.9992

Vegetables with chicken and beef

0.5–250

0.9998

Vegetables with fish

0.5–250

0.9961

DEEP

Fruit

5–250

0.9994

Apple

5–250

0.9986

Vegetables with chicken and beef

5–250

0.9999

Vegetables with fish

5–250

0.9937

DNPP

Fruit

10–250

0.9943

Apple

15–250

0.9968

Vegetables with chicken and beef

5–250

0.9972

Vegetables with fish

5–250

0.9971

BBP

Fruit

1–250

0.9997

Apple

0.5–250

0.9990

Vegetables with chicken and beef

0.5–250

0.9999

Vegetables with fish

1–250

0.9954

DEHA

Fruit

1–250

0.9971

Apple

0.5–250

0.9992

Vegetables with chicken and beef

0.5–250

0.9990

Vegetables with fish

0.5–250

0.9994

DBEP

Fruit

5–250

0.9999

Apple

5–250

0.9994

Vegetables with chicken and beef

5–250

0.9998

Vegetables with fish

5–250

0.9962

DCHP

Fruit

5–250

0.9996

Apple

5–250

0.9990

Vegetables with chicken and beef

0.5–250

0.9998

Vegetables with fish

10–250

0.9955

DNOP

Fruit

5–250

0.9999

Apple

5–250

0.9991

Vegetables with chicken and beef

5–750

0.9997

Vegetables with fish

5–250

0.9961

DINP

Fruit

10–250

0.9993

Apple

15–250

0.9981

Vegetables with chicken and beef

10–250

0.9963

Vegetables with fish

10–250

0.9972

DIDP

Fruit

5–250

0.9997

Apple

0.5–250

0.9993

Vegetables with chicken and beef

0.5–250

0.9999

Vegetables with fish

5–250

0.9994

DBP-d4 was used as IS in each case

aDetermination coefficient

With the aim of studying the trueness and the extraction efficiency of the procedure, recovery studies were developed for all samples at two levels of concentration (17.5 and 100 μg/kg) carrying out five extractions at each level. The IS was added before the extraction step at a concentration of 75 μg/kg in both cases. A blank matrix of each type was also extracted and spiked at the same concentration level at the end of the extraction procedure. Relative recovery values were calculated, taking into account the matrix effect, that is to say, comparing samples spiked at the beginning and at the end of the methodology. The obtained results, which are shown in Table 3, demonstrated the excellent trueness as well as the good efficiency of the extraction procedure applied in this case, since relative recovery values were in the range 77–117% for the fruit jar, 72–119% for the apple jar, 78–120% for the jar of vegetables with chicken and beef, and 70–120% for the jar of vegetables with fish, with RSD values lower than 19% for all samples and analytes, which is in accordance with the SANTE guidelines [53]. LOQs of the method were also obtained as the lowest matrix-matched calibration concentration which provided a signal-to-noise ratio higher than 10 for the quantification transition and at least 3 for the confirmation transition (if it was available), taking the recovery of the method into account. LOQ values of the method, which are shown in Table 3, were in the ranges 0.07–1.11 μg/kg for the fruit jar, 0.03–1.08 μg/kg for the apple jar, 0.03–0.98 μg/kg for the jar of vegetables with chicken and beef, and 0.03–0.95 μg/kg for the jar of vegetables with fish, which demonstrates the good detection power achieved with the developed QuEChERS-GC-MS/MS method.
Table 3

Results of the recovery study (n = 5) of the QuEChERS-GC-MS/MS method for the selected compounds in the different baby food matrices at two levels of concentration

Analyte

Type of baby food

Level 1a (n = 5)

Level 2b (n = 5)

LOQmethodc (μg/kg)

Recovery % (RSD, %)

Recovery % (RSD, %)

DMP

Fruit

80 (12)

77 (7)

0.97

Apple

90 (18)

72 (6)

0.05

Vegetables with chicken and beef

101 (4)

94 (6)

0.04

Vegetables with fish

96 (6)

103 (15)

0.04

DEP

Fruit

103 (13)

97 (6)

0.08

Apple

107 (8)

84 (9)

0.04

Vegetables with chicken and beef

116 (11)

104 (10)

0.03

Vegetables with fish

112 (15)

109 (5)

0.95

DPP

Fruit

93 (4)

94 (2)

0.84

Apple

97 (6)

90 (4)

0.08

Vegetables with chicken and beef

101 (2)

102 (1)

0.07

Vegetables with fish

100 (3)

118 (1)

0.03

DBP

Fruit

115 (8)

106 (8)

0.07

Apple

98 (4)

96 (2)

0.08

Vegetables with chicken and beef

120 (5)

106 (3)

0.07

Vegetables with fish

112 (6)

120 (3)

0.03

DMEP

Fruit

110 (13)

87 (3)

1.11

Apple

95 (14)

78 (6)

0.05

Vegetables with chicken and beef

101 (4)

96 (6)

0.38

Vegetables with fish

103 (11)

120 (3)

0.62

DIPP

Fruit

98 (3)

99 (3)

0.04

Apple

101 (4)

95 (5)

0.04

Vegetables with chicken and beef

99 (3)

78 (2)

0.04

Vegetables with fish

95 (3)

120 (1)

0.03

DEEP

Fruit

80 (8)

82 (6)

0.47

Apple

90 (12)

86 (9)

0.43

Vegetables with chicken and beef

97 (5)

101 (5)

0.38

Vegetables with fish

97 (4)

119 (2)

0.31

DNPP

Fruit

113 (11)

101 (7)

0.73

Apple

116 (19)

101 (5)

1.00

Vegetables with chicken and beef

92 (2)

102 (1)

0.39

Vegetables with fish

95 (4)

119 (1)

0.33

BBP

Fruit

107 (4)

98 (4)

0.08

Apple

108 (4)

99 (5)

0.04

Vegetables with chicken and beef

116 (3)

107 (2)

0.03

Vegetables with fish

111 (2)

119 (2)

0.06

DEHA

Fruit

117 (1)

111 (8)

0.07

Apple

119 (3)

113 (6)

0.03

Vegetables with chicken and beef

89 (5)

99 (4)

0.04

Vegetables with fish

112 (15)

111 (1)

0.03

DBEP

Fruit

94 (6)

95 (3)

0.42

Apple

98 (5)

93 (6)

0.38

Vegetables with chicken and beef

106 (5)

102 (1)

0.36

Vegetables with fish

97 (3)

117 (1)

0.32

DCHP

Fruit

101 (5)

99 (3)

0.39

Apple

101 (5)

97 (5)

0.37

Vegetables with chicken and beef

95 (3)

98 (1)

0.04

Vegetables with fish

93 (3)

116 (1)

0.67

DNOP

Fruit

102 (5)

101 (3)

0.40

Apple

103 (5)

98 (4)

0.37

Vegetables with chicken and beef

78 (1)

87 (2)

0.46

Vegetables with fish

78 (5)

95 (1)

0.40

DINP

Fruit

101 (6)

104 (7)

0.78

Apple

107 (6)

98 (4)

1.08

Vegetables with chicken and beef

71 (8)

85 (3)

0.98

Vegetables with fish

77 (2)

90 (7)

0.84

DIDP

Fruit

94 (4)

97 (5)

0.42

Apple

101 (4)

95 (5)

0.04

Vegetables with chicken and beef

78 (3)

78 (2)

0.05

Vegetables with fish

70 (3)

78 (1)

0.48

aConcentrations of the analytes in the samples = 17.5 μg/kg

bConcentrations of the analytes in the samples = 100 μg/kg

cDefined as the lowest matrix-matched calibration concentration which provided a signal-to-noise ratio higher than 10 for the quantification transition and at least 3 for the confirmation transition (if it was available), taking the recovery of the method into account

Real sample analysis

Once the validation of the methodology was completed, and taking into account the good results obtained, a group of eight different samples from diverse brands acquired in several supermarkets of Tenerife was analyzed using the QuEChERS-GC-QqQ-MS/MS method. The group includes three samples of mixed fruits commercialized in glass containers and another in plastic, two apple compotes (one of them in a glass jar and another in a doypack recipient), one jar of vegetable with chicken and beef, and one jar of vegetable with fish. The content of fats, carbohydrates, fibers, proteins, and salt is indicated in Table S2 of the ESM. As can be seen in Table 4, which includes the concentration found and the confidence interval, results showed the presence of BBP (ranged between 0.64 and 2.92 μg/kg) and DIDP (0.28–0.66 μg/kg) that have been included both by the EU [9] and the US EPA [10] in the group of substances with a restricted use in the preparation and production of plastic material susceptible to be in contact with food. In addition, also BBP, DEHA, DEP, and DPP have been found in the majority of the analyzed commercial samples. The rest of the studied PAEs were not detected. The highest concentrations, in the range 2.70–8.71 μg/kg, were for DEHA in most of the samples, except in the case of the sample commercialized in the doypack container for which the concentration was 0.50 μg/kg. DPP was the less common phthalate found. In fact, it was only determined for the fruit compote commercialized in a plastic recipient at a concentration of 1.65 μg/kg (see Fig. 2). The presence of these phthalates is especially remarkable in the products packed in glass containers. Such aspect could be associated with the use of tap plastic coatings as well as the possible contamination during the production and manufacturing processes [54].
Table 4

Results of the analysis of different baby food samples using the developed QuEChERS-GC-MS/MS method

Analytes

Analyte concentration ± confidence interval (μg/kg)a

M1

M2

M3

M4

M5

M6

M7

M8

BBP

1.20 ± 0.14

1.28 ± 0.14

0.64 ± 0.14

1.13 ± 0.14

1.78 ± 0.23

n.d.

2.69 ± 0.05

2.92 ± 0.45

DEHA

4.93 ± 0.40

3.79 ± 0.41

8.71 ± 0.41

2.70 ± 0.42

5.80 ± 0.20

0.50 ± 0.21

5.38 ± 0.19

3.18 ± 1.18

DEP

1.41 ± 0.40

1.68 ± 0.40

1.88 ± 0.40

3.53 ± 0.39

2.72 ± 0.09

2.36 ± 0.08

3.08 ± 0.39

2.84 ± 0.15

DIDP

0.66 ± 0.13

n.d.

n.d.

n.d.

0.28 ± 0.20

n.d.

n.d.

n.d.

DPP

n.d.

n.d.

n.d.

1.65 ± 0.09

n.d.

n.d.

n.d.

n.d.

M1, a jar of eight fruits; M2, a jar of three fruits; M3, a jar of four fruits; M4, fruit compote with a plastic container; M5, apple jar; M6, apple compote with a doypack container; M7, a jar of vegetables with chicken and beef; M8, a jar of vegetables with fish

n.d. not detected

aResults obtained as an average of two analyses for each product

Fig. 2

Extracted ion chromatograms of the analytes found in the fruit-based baby food commercialized in a plastic container (BBP, DEHA, DEP, and DPP)

As it has been commented above, the evaluation of PAEs in baby food has been fundamentally based on the study of other matrices that are different from those analyzed here. That is why a comparison between the results obtained in this work and the other few occasions, in which similar products were analyzed, is of great relevance to know the suitability of the developed methodology. In this sense, Cariou et al. [26] found the presence of BBP in the range 0.5–10.9 μg/kg in macaroni chicken and rice-fish mixes as well as apple-banana compote; Tsumura et al. [21] determined BBP and DEHA in baby food of varied nature at levels around 3 and 10–44 μg/kg, respectively; Ma et al. [24] found DEP and BBP in the ranges 0.49–1.2 and 2.8–14.7 mg/kg in fruit jellies, and Russo et al. [23] detected DEP at 14 μg/kg in chicken- and turkey-based baby foods. These results show a clear concordance with the ones obtained in the present work, except in the case of Ma et al. [24] whose results involve concentrations considerably higher than the rest of the studies. Such aspect could be related to the fact that in such case, the analyzed baby foods were commercialized in plastic packaging.

Comparison of the QuEChERS-GC-MS/MS method with other methodologies

Among the different methodologies applied until now for the extraction of PAEs in baby food with similar nature to the matrices selected in this work, liquid-liquid extraction (LLE) [22, 25, 26] and solid-phase extraction (SPE) [21, 25] have been the most commonly applied. In this sense, Cirillo et al. [25] applied a LLE with acetonitrile and n-hexane followed by a cleanup step in a SPE column with Florisil, PSA, and Na2SO4 before the analysis by GC-flame ionization detection (FID) for the determination of DBP, among other compounds, in several school meals obtaining a LOQ of 22.5 μg/kg. Tsumura et al. [21] carried out the determination of ten plasticizers (DBP, BBP, DEHP, DINP, DEHA, diisononyl adipate, dialkyl adipate, dibutyl sebacate, O-acetyl tributyl citrate, and diacetyllauroyl glycerol) in retort-pouched and snack baby food using a Florisil, PSA, and Na2SO4 SPE column prior to GC-MS analysis, obtaining LOQs in the range 3–67 μg/kg. Cariou et al. [26] developed an ultrasound-assisted LLE-GC-MS/MS method for the determination of four PAEs (DIBP, DBP, BBP, and DEHP) in pasta-, meat-, fish-, and fruit-based baby foods, but no LOQs were determined. In this case, the reported limits were calculated as three times the standard deviation of the procedural contamination due to the remarked presence of the target analytes in blank samples. In addition, Gärtner et al. [22] applied an accelerated solvent extraction followed by GC-MS determination for the analysis of five PAEs (DIBP, DBP, BBP, DEHP, and DNOP) in cereal baby food, and Russo et al. [23] developed an ultrasound-vortex-liquid-liquid microextraction-GC-MS method for determining six PAEs (DMP, DEP, DBP, butyl cyclohexyl phthalate (BCHP), BBP, and DEHP) in freeze-dried baby foods obtaining LOQs in the ranges 21–48 and 11–20 μg/kg, respectively. As can be seen, in all cases, LOQ values were higher than the ones obtained in this work (0.03–1.11 μg/kg), though similar detection systems were used. This fact shows the great efficiency of the applied QuEChERS method for the extraction of PAEs from baby food of different nature as well as the wide field of application of such technique since it allows the extraction of a larger number of compounds than the rest of applied procedures.

Conclusions

In this work, a QuEChERS-GC-MS/MS method has been successfully validated and applied for the determination of a group of fourteen PAEs (DMP, DEP, DPP, DBP, DMEP, DIPP, DEEP, DNPP, BBP, DBEP, DCHP, DNOP, DINP, DIDP) and one adipate (DEHA) of interest from baby foods of different nature, including fruit and vegetables and meat purees as well as vegetables and fish-based food products. Good recovery values (70–120%) and RSDs lower than 19% were obtained for all analytes and matrices. Low LOQs of the method, ranging between 0.03 and 1.11 μg/kg, were achieved. In order to demonstrate the applicability of the methodology, several samples of each type were analyzed. BBP, DBEP, DEHA, DEP, and DIDP were detected in most of the samples, especially DEHA with concentrations in the range 0.50–8.71 μg/kg, while DPP was only detected in a plastic-packed product (see Fig. 2) but not in the rest of the evaluated products. The proposed method fulfills the main principles of QuEChERS procedures since it is quick, easy, cheap, effective, rugged, and safe and, in addition, it provides an excellent extraction of the analytes as it is probed by the low LOQs obtained. Taking into account the good results provided by the method, it could be proposed as an interesting alternative for the determination of PAEs in such complex matrices in which the determination of these compounds present a remarkable interest due to the vulnerability of the group of consumers to which they are aimed at.

Notes

Acknowledgements

J.G.S. would like to thank the Canary Agency of Economy, Industry, Trade and Knowledge of the Government of the Canary Islands for the FPI fellowship (co-financed with an 85% from European Social Funds). The authors would like to acknowledge the use of the Research Support General Service (SEGAI) of the University of La Laguna.

Funding information

This work was supported by the Spanish Ministry of Economy and Competitiveness (project CTQ2014-57195-P).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.

Supplementary material

216_2018_977_MOESM1_ESM.pdf (431 kb)
ESM 1 (PDF 430 kb)

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Bárbara Socas-Rodríguez
    • 1
  • Javier González-Sálamo
    • 2
  • Antonio V. Herrera-Herrera
    • 3
  • Álvaro Santana-Mayor
    • 2
  • Javier Hernández-Borges
    • 2
    Email author
  1. 1.Servicio General de Apoyo a la Investigación (SEGAI)Universidad de La Laguna (ULL)San Cristóbal de La LagunaSpain
  2. 2.Departamento de Química, Unidad Departamental de Química Analítica, Facultad de CienciasUniversidad de La Laguna (ULL)San Cristóbal de La LagunaSpain
  3. 3.Instituto Universitario de Bio-Orgánica Antonio GonzálezUniversidad de La Laguna (ULL)San Cristóbal de La LagunaSpain

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