NIST FOOD SAFETY WORKSHOP , October 28 - 30, 2019, Gaithersburg, MD

Screening for Ten Phthalates in Four Food Standard Reference Materials (SRMs) by 

 Gas Chromatography/Tandem Mass Spectrometry (GC/MS/MS).

Bruce A. Benner, Jr.

National Institute of Standards and Technology, Chemical Sciences Division, Gaithersburg, MD 20899

bruce.benner@nist.gov

Why are Phthalates a Concern in Food?

How are Phthalates Measured in Food?

Which Phthalates were detected?

Phthalates (diesters of 1,2-benzenedicarboxylic acid) are added to polymer formulations like polyvinyl chloride 

to increase flexibility. In such applications, phthalates are suspended in the polymer matrix and over time can 

leach from the material, possibly into food. There is concern that children’s exposure to five phthalates, including 

diisononyl phthalate (DINP), di-n-pentyl phthalate (DPENP), di-n-hexyl phthalate (DHEXP), dicyclohexyl 

phthalate (DCHP), and diisobutyl phthalate (DIBP), can cause male reproductive development issues.

O

O

O

DIBP

O

C

C

Screening for phthalates in food reference materials could estimate the levels of targeted phthalates in different 

food types. For this work, two infant/adult formula materials [SRMs 1849a (milk-based) and 1869 (milk/whey/soybased)] and two Typical Diets (SRM 1548a and candidate SRM 1548b) were screened for 10 phthalates.

Extraction: 0.5 g – 0.6 g weighed into glass centrifuge tubes, added 2 mL acetonitrile, shake for 1 min, centrifuge 

5 min at 100 % power, filtered through 0.45 μm PTFE filters into amber glass vials. Blank processed through 

procedure.

GC/MS/MS: 60 m x 0.25 mm, ZB-50, 

2 mL/min He flow, 1 μL splitless injection

at 285 °C, oven 82 °C (1 min) • 50 °C/min 

• 250 °C • 2 °C/min • 275 °C • 10 °C/min 

• 300 °C (8 min).

Target Phthalate Mass (m/z) Product Mass (m/z) Collision Energy

dimethylphthalate 194 163 10

diethylphthalate 177 149 10

diisobutyl- and di-n-butyl phthalate 223 149 10

di-n-pentyl phthalate 237 149 10

di-n-hexyl phthalate 251 149 10

bis(2-ethylhexyl) phthalate 279 149 10

benzyl butyl phthalate 206 149 10

dicyclohexyl phthalate 249 149 10

diisononyl phthalate 293 149 10

Multiple Reaction Monitoring (EI, see Ref. 1)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100 (8.88E6)

(8.88E6)

Relative Abundance

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Time (min)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Relative Abundance

Peak Identifications: 

1. dimethyl phthalate

2. diethyl phthalate

3. diisobutyl phthalate

4. di-n-butyl phthalate

5. di-n-pentyl phthalate

6. di-n-hexyl phthalate

7. bis(2-ethylhexyl) phthalate

8. benzyl butyl phthalate

9. dicyclohexyl phthalate

10. diisononyl phthalate

 

1

1

2

2

3

3

4

4

5

5

6

6

7,8

7,8

10

10

Process Blank

GC/MS/MS of Process Blank and SRM 1548a Typical Diet 

for 10 Targeted Phthalates

SRM 1548a Typical Diet

50x Process

 Blank

50x Process

 Blank

200x Process

 Blank

90x Process

 Blank

Peak Identifications: 

1. dimethyl phthalate

2. diethyl phthalate

3. diisobutyl phthalate

4. di-n-butyl phthalate

5. di-n-pentyl phthalate

6. di-n-hexyl phthalate

7. bis(2-ethylhexyl) phthalate

8. benzyl butyl phthalate

9. dicyclohexyl phthalate

10. diisononyl phthalate

 

Process Blank

GC/MS/MS of Process Blank and SRM 1548a Typical Diet 

for 10 Targeted Phthalates

10x Process

 Blank

10x Process

 Blank

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100 (1.87E6)

(1.87E6)

Relative Abundance

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Time (min)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Relative Abundance

1

1

2

2

3

3

4

4

5

5

7,8

7,8

10

10

6

6

Candidate SRM 1548b Typical Diet

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Time (min)

1

2

3

4

5 6

7, 8

Peak Identifications: 

1. dimethyl phthalate

2. diethyl phthalate

3. diisobutyl phthalate

4. di-n-butyl phthalate

5. di-n-pentyl phthalate

6. di-n-hexyl phthalate

7. bis(2-ethylhexyl) phthalate

8. benzyl butyl phthalate

9. dicyclohexyl phthalate

10. diisononyl phthalate

 

Three GC/MS/MS Runs of Process Blank 

for Ten Targeted Phthalates

 

9

10

0

10

20

30

40

50

60

Relative Abundance

70

80

90

100

Results: As indication of the ubiquity of phthalates, 

8 of the 10 targeted were detected in the process blank.

None of the targeted phthalates were observed above 

process blank levels in SRM 1849a Infant/Adult 

Formula (milk-based). SRM 1548a Typical Diet was 

the most heavily contaminated of the four materials 

screened with levels of three phthalates 50 - 200x the 

process blank. Candidate SRM 1548b Typical Diet 

was the second most contaminated material yielding 

10 - 90x the levels of the process blank for the same 

three phthalates.

Future Work: Optimize extraction method and 

quantify by GC/MS/MS using stable isotope 

labeled phthalates.

DISCLAIMER

Certain commercial equipment, instruments, software, or materials are identified in 

this presentation in order to specify the experimental procedure adequately. Such 

identification is not intended to imply recommendation or endorsement by the 

National Institute of Standards and Technology, nor is it intended to imply that the 

materials or equipment identified are necessarily the best available for the purpose.

Reference

1. Food Chemistry 196, 211-219. 2016.