Determining Volatile Organic Compounds in Energy Drinks with Purge and Trap Sample Concentration

The energy drinks and shots industry, is worth approximately $30 billion dollars, with major beverage companies such a PepsiCo, and focused energy drinks supplier such as Red Bull GmbH participating1.

According to a 2014 World Health Organization report, it is estimated that 30% of adults, 68% of adolescents and 18% of children below the age of 10 consume energy drinks2.

Before public outcry due to the discovery of benzene in soft drinks in the earl 1990s, prepared beverages were not regulated. They are still not widely held to the National Primary Drinking Water Regulations, although benzene content is now regulated to 5 ppb.

As beverages can be foamy when analyzed by purge and trap method, conventionally they have been analyzed by headspace coupled to a GC-MS. A set of these challenging samples have been analyzed using GC-MS with a new purge and trap sample concentrator.

Some qualitative and quantitative data on identified VOCs that are both on and off the list of National Primary Drinking Water Regulations (NPDWRs) are presented with good outcomes.

Experiment

An OI Analytical 4760 Purge and Trap and a 4100 Sample Processor were used to perform sample concentration and introduction, and sample separation and detection were performed using an Agilent 5975C Mass Spectrometer and 7890A Gas Chromatograph.

A photograph of the equipment used can be seen in Figure 1, and the method parameters can be seen in Table 1.

20 samples from top U.S. brands (Figure 2) were analyzed. Due to the possibility of extreme foaming, samples were run in the “soil mode” of the 4100, where they are purged in a 40 ml vial instead of in a frit sparger.

OI Analytical 4760 Purge and Trap and a 4100 Sample Processor

Figure 1. The equipment used for the study

Table 1. Method Parameters

Purge-and-Trap Eclipse 4760
P&T Sample Concentrator
rap #10 trap; Tenax® / Silica gel / CMS
Purge Gas Zero grade Helium at 40 mL/min
Purge Time 11 min
Sparge Mount Temperature 45°C soil
Sample Temperature 45°C soil
Desorb Time 0.5 min
Bake Time 5 min
OI #10 Trap Temperature Ambient during purge
180°C during desorb pre-heat
190°C during desorb
210°C during bake
Water Management 120°C during purge
Ambient during desorb
240°C during bake
ransfer Line Temperature 140°C
Six-port Valve Temperature 140°C

Gas Chromatograph Agilent 7890A
Column Restek Rxi-624 Sil
MS 30 meter,
0.25 mm, 1.4 µm film
Carrier Gas Zero grade helium
Inlet Temperature 250 °C
Inlet Liner Agilent Ultra Inert 1 mm straight, taper
Column Flow Rate 0.8 mL/min
Split Ratio 150:1
Oven Program Hold at 40°C for 1.5 min
16°C/minute to 180°C
40°C/minute to 220°C
Hold at 220°C for 2.0 min
Total GC Run is 13.25 min

Mass Spectrometer Agilent 5975C
Mode Scan 35 - 300 amu
Scans/Second 5.19
Solvent Delay 1.40 min
ransfer Line Temperature 250°C
Source Temperature 300°C
Quadrupole Temperature 200°C
Draw-out Plate 6 mm

Energy drinks evaluated

Figure 2. Energy drinks evaluated in the study.

A multi-point calibration was run, with regulated compounds mentioned in the NPDWRs list, and the concentration of which ranged between 20 and 200 ppb. USEPA Method 82603 was used to generate calibrations (Table 2).

All method criteria were met. This calibration was used to quantitate the samples, and for tentatively identified compounds (TICs) or peaks that were not identified by the calibration technique, a library search was conducted.

Table 2. Calibration Data

Analyte Compound AVG % RSD
1 pentafluorobenzene (IS)
2 dichlorodifluoromethane 0.154 7.19
3 chloromethane 0.197 6.43
4 vinyl chloride* 0.251 5.40
5 bromomethane 0.248 9.68
6 chloroethane 0.145 8.16
7 trichlorofluoromethane 0.515 5.21
8 ethyl ether 0.158 4.22
9 1,1-dichloroethene* 0.398 6.06
10 carbon disulfide 1.121 5.24
11 1,1,2-trichloro-1,2,2-trifluoroethane 0.409 5.61
12 methyl iodide 0.826 5.22
13 allyl chloride 0.187 2.10
14 methylene chloride* 0.420 7.19
15 acetone 0.026 9.93
16 trans-1,2-dichloroethene* 0.460 9.31
17 methyl tert-butyl ether 0.784 3.34
18 chloroprene 0.666 1.93
19 1,1-dichloroethane 0.743 3.41
20 acrylonitrile 0.115 7.14
21 cis-1,2-dichloroethene* 0.510 3.00
22 2,2-dichloropropane 0.329 6.24
23 bromochloromethane 0.250 2.78
24 chloroform* 0.847 2.78
25 methyl acrylate 0.300 4.67
26 carbon tetrachloride* 0.576 2.38
27 dibromofluoromethane (SS) 0.528 1.82
28 1,1,1-trichloroethane* 0.623 3.13
29 2-butanone 0.029 5.01
30 1,1-dichloropropene 0.570 3.99
31 1,4-difluorobenzene (IS)
32 benzene* 1.045 8.69
33 methacrylonitrile 0.113 4.17
34 1,2-dichloroethane-d4 (SS) 0.043 1.57
35 1,2-dichloroethane* 0.374 6.83
36 trichloroethene* 0.310 3.74
37 dibromomethane 0.195 2.68
38 bromodichloromethane* 0.358 3.82
39 1,2-dichloropropane* 0.263 2.33
40 methyl methacrylate 0.118 6.88
41 2-chloroethyl vinyl ether 0.073 13.29
42 cis-1,3-dichloropropene 0.350 8.09
43 chlorobenzene-d5 (IS)
44 toluene-d8(ss) 1.301 1.72
45 toluene* 0.790 3.81
46 4-methyl-2-pentanone 0.021 4.12
47 tetrachloroethene* 0.329 5.37
48 trans-1,3-dichloropropene 0.346 9.58
49 ethyl methacrylate 0.262 6.78
50 1,1,2-trichloroethane* 0.237 3.12
51 chlorodibromomethane* 0.313 9.24
52 1,3-dichloropropane 0.335 2.28
53 1,2-dibromoethane* 0.305 3.12
54 2-hexanone 0.154 5.73
55 chlorobenzene* 0.945 3.95
56 ethylbenzene* 1.496 4.11
57 1,1,1,2-tetrachloroethane 0.276 1.99
58 m,p-xylenes* 0.588 4.86
59 o-xylene* 0.575 4.39
60 styrene* 0.956 3.97
61 bromoform* 0.181 9.29
62 isopropylbenzene 1.446 4.59
63 1,4-dichlorobenzene-d4 (IS)
64 4-bromofluorobenzene (SS) 1.088 1.90
65 bromobenzene 0.880 4.57
66 n-propylbenzene 3.822 2.51
67 1,1,2,2-tertrachloroethane 0.687 4.20
68 2-chlorotoluene 2.173 3.12
69 1,3,5-trimethylbenzene 2.669 1.84
70 1,2,3-trichloropropane 0.656 6.60
71 4-chlorotoluene 2.545 3.50
72 tert-butylbenzene 2.520 1.84
73 pentachloroethane 0.382 6.77
74 1,2,4-trimethylbenzene 2.682 2.11
75 sec-butylbenzene 3.346 1.81
76 p-isopropytoluene 2.635 2.95
77 1,3-dichlorobenzene 1.478 4.77
78 1,4-dichlorobenzene* 1.449 4.65
79 n-butylbenzene 2.536 2.84
80 1,2-dichlorobenzene* 1.339 4.00
81 1,2-dibromo-3-chloropropane* 0.090 12.86
82 hexachlorobutadiene 0.574 2.68
83 1,2,4-trichlorobenzene* 0.943 4.35
84 naphthalene 1.868 9.34
85 1,2,3-trichlorobenzene 0.858 5.72

* National Primary Drinking Water Regulated Compounds (NPDWR)

Results and Discussion

The NPDWRs List includes the compounds benzene and chloroform. Although chloroform was detected in many samples at reportable levels (>2 ppb), this is still well below the maximum contaminant level (MCL) set by the United States Environmental Protection Agency (USEPA).

It is known that chloroform develops as a disinfectant byproduct in drinking water. Flavoring agent p-cymene, which is not listed but used as part of the calibration, was also found above the reporting limit.

Benzene, a carcinogenic at high concentrations, is monitored in the analysis of drinking water. It may form in the presence of ascorbic acid and benzoate salts. While factors such as exposure to heat and light, among others, foster the formation, sugar and EDTA can inhibit it4.

In 2005, the United States Food and Drug Administration (FDA) recieved private laboratory results showing low levels of benzene in soft drinks containing ascorbic acid and benzoate salts. As the FDA has no standard for benzene in beverages other than bottled water, the NPDWR limit of 5 ppb was set as a standard5.

Two of the evaluated drinks contained benzene at trace levels of 2.17 and 1.85ppb. These drinks did not contain ascorbic acid, but contained benzoate salts.

Varying amounts of other compounds (TICs) identified as artificial or natural flavorings often found in fruit-flavored beverages were also found in the samples. Appreciable ethanol (>200 ppb), possibly left over from decomposition of ethyl esters or as an aid to dissolve necessary oils, was found in most drinks.

50 ppb calibration standard

Figure 3. 50 ppb calibration standard

Energy drink 1 analysis

Figure 4. Energy drink 1

Energy drink 2 analysis

Figure 5. Energy drink 2

Energy drink 3 analysis

Figure 6. Energy drink 3

Conclusion

This article demonstrates the use of purge and trap for foaming liquid samples for a range of somewhat difficult matrices. Instead of fritted sparge vessel, vials were used for purging the samples, and usable results for samples generally analyzed by headspace were acquired.

Several samples contained trace levels of chloroform, which is attributed to disinfectant byproducts in drinking water. A few drinks containing benzoate preservatives were found to contain benzene.

Depending upon the use of flavorings, the presence of compounds such as limonene, p-cymene, and butanoate esters is also to be expected. Almost all energy drinks contain an appreciable level of ethanol, although the source could not be determined from the data.

References

1. “The American Energy Drink Craze in Two Caffeinated Charts”, Roberto A. Ferdman, Quartz, March 26, 2014.

2. “Energy Drinks: Busting Your Health for the Buzz”, Pennsylvania Medical Society, September 19, 2008.

3. USEPA Method 8260B Volatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS) Revision 2 December 1996.

4. ICBA Guidance Document to Mitigate the Potential for Benzene Formation in Beverages, International Council of Beverages Associations, 2006.

5. Data on Benzene in Soft Drinks and Other Beverages, U.S. FDA, 2007.

This information has been sourced, reviewed and adapted from materials provided by OI Analytical.

For more information on this source, please visit OI Analytical.

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