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. 2019 Dec 19;25(1):26. doi: 10.3390/molecules25010026

Table 1.

Concentrations of the volatile compounds identified by headspace solid-phase microextraction gas-chromatography mass spectrometry (HS-SPME GC-MS) analysis of the feed samples (grass (GRS), grass/clover (CLV) and TMR); values indicate average area values of triplicate analysis for each compound. CAS no. = Chemical Abstracts Service number. One-way ANOVA statistical analysis *** p < 0.001. 1 LRI: Linear retention index. 2 Ref LRI: Linear retention index reference for compounds identified by standards and/or NIST library where available.

Compound LRI 1 Ref LRI 2 CAS No. Grass Grass/Clover TMR p-Value
Aldehyde
2-Methyl butanal 700 700 96-17-3 6.25 × 108 2.03 × 108 6.29 × 108 NS 0.067
3-Methyl butanal 690 692 590-86-3 5.69 × 108 7.97 × 108 2.28 × 109 *** <0.001
Acetaldehyde 449 452 75-07-0 1.19 × 108 2.73 × 108 4.38 × 107 *** 0.002
Butanal 627 622 123-72-8 8.78 × 107 1.81 × 108 0.00 × 00 *** <0.001
Decanal 1251 1256 112-31-2 4.39 × 109 4.90 × 109 2.08 × 109 NS 0.315
Furfural 870 899 98-01-1 1.09 × 108 4.31 × 107 2.20 × 107 *** 0.017
Heptanal 941 943 111-71-7 1.83 × 109 2.75 × 109 4.26 × 107 *** 0.004
Hexanal 837 839 66-25-1 1.69 × 1010 3.59 × 1010 1.15 × 109 *** 0.001
Nonanal 1147 1150 124-19-6 2.60 × 109 5.02 × 109 2.43 × 108 *** 0.001
Octanal 1044 1047 124-13-0 1.47 × 109 2.44 × 109 0.00 × 00 *** 0.001
Pentanal 735 733 110-62-3 1.49 × 109 2.07 × 109 0.00 × 00 *** 0.002
Propanal 526 523 123-38-6 1.83 × 108 4.92 × 108 0.00 × 00 *** <0.001
Methacrolein 570 574 78-85-3 0.00 × 00 6.23 × 106 0.00 × 00 *** 0.006
Ketone
1-Hydroxy-2-propanone 734 734 116-09-6 0.00 × 00 2.80 × 108 4.22 × 107 *** 0.001
2-Butanone 638 639 78-93-3 0.00 × 00 0.00 × 00 1.08 × 108 NS 0.080
2-Heptanone 932 936 110-43-0 6.22 × 108 1.16 × 109 2.60 × 108 *** 0.011
2-Hexanone 831 834 591-78-6 1.10 × 108 1.94 × 108 0.00 × 00 *** 0.017
2-Nonanone 1137 1140 821-55-6 1.18 × 109 1.61 × 109 0.00 × 00 *** 0.010
2-Pentanone 728 730 107-87-9 5.36 × 108 6.40 × 108 4.79 × 107 *** 0.027
4-Hydroxy-4-methyl-2-pentanone 913 913 123-42-2 4.00 × 109 3.50 × 109 1.43 × 108 *** 0.027
6-Methyl-5-hepten-2-one 1031 1034 110-93-0 7.89 × 108 2.84 × 109 1.07 × 109 *** <0.001
Acetoin 778 778 513-86-0 1.33 × 109 1.62 × 109 2.74 × 108 NS 0.053
Acetone 532 533 67-64-1 3.31 × 108 2.85 × 109 5.43 × 107 *** <0.001
Acetophenone 1141 1030 98-86-2 1.08 × 108 1.77 × 108 9.55 × 107 NS 0.188
Acetyl valeryl (2,3-heptanedione) 875 - 96-04-8 0.00 × 00 4.32 × 108 0.00 × 00 *** <0.001
Cyclohexanone 958 957 108-94-1 1.28 × 109 1.33 × 109 0.00 × 00 *** 0.017
Methyl Isobutyl Ketone 781 784 108-10-1 1.80 × 108 0.00 × 00 0.00 × 00 *** <0.001
Ester
2-Methylbutyl acetate 906 906 624-41-9 0.00 × 00 0.00 × 00 1.44 × 108 NS 0.076
2-Methylbutyl butanoate 1080 - 51115-64-1 0.00 × 00 8.43 × 106 9.70 × 108 *** 0.005
Amyl isobutyrate (or isomer) 1121 - 2445-72-9 0.00 × 00 2.73 × 109 2.60 × 1010 *** <0.001
Amyl propionate 992 - 105-68-0 2.59 × 107 3.19 × 107 6.81 × 108 *** <0.001
Butyl acetate 842 842 123-86-4 0.00 × 00 0.00 × 00 9.12 × 108 *** <0.001
B-Phenylethyl acetate 1339 - 103-45-7 0.00 × 00 3.75 × 107 2.21 × 108 *** 0.009
Dimethyl succinate 1081 1082 106-65-0 2.91 × 107 2.87 × 107 0.00 × 00 *** 0.019
Ethyl heptanoate 1121 - 106-30-9 6.69 × 107 1.13 × 109 6.42 × 109 *** <0.001
Ethyl acetate 641 642 141-78-6 4.27 × 108 1.06 × 109 1.10 × 109 *** 0.002
Ethyl benzoate 1229 - 93-89-0 7.81 × 107 7.40 × 107 1.37 × 107 NS 0.083
Ethyl butanoate 823 826 105-54-4 0.00 × 00 2.68 × 109 3.02 × 1010 *** <0.001
Ethyl decanoate 1420 1422 110-38-3 0.00 × 00 2.22 × 108 1.45 × 108 *** <0.001
Ethyl dodecanoate 1622 1621 106-33-2 0.00 × 00 1.93 × 108 3.05 × 108 *** <0.001
Ethyl hexanoate 1021 1024 123-66-0 2.33 × 109 8.03 × 109 5.44 × 1010 *** <0.001
Ethyl lactate 861 862 97-64-3 0.00 × 00 1.62 × 108 2.60 × 109 *** <0.001
Ethyl nonanoate 1319 - 123-29-5 0.00 × 00 6.26 × 108 4.45 × 108 NS 0.104
Ethyl octanoate 1220 - 106-32-1 4.51 × 108 1.80 × 109 4.76 × 109 *** <0.001
Ethyl pentanoate 923 924 539-82-2 2.25 × 108 1.22 × 109 1.34 × 1010 *** <0.001
Ethyl propanoate 735 737 105-37-3 2.65 × 108 7.16 ×108 1.26 × 109 *** <0.001
Hexyl acetate 1038 - 142-92-7 1.83 × 108 3.43 × 108 2.09 × 109 *** <0.001
Isoamyl acetate 902 902 123-92-2 2.48 × 108 3.21 × 108 5.19 × 108 *** 0.029
Isoamyl isobutanoate 1038 - 2050-01-3 3.07 × 107 8.29 × 106 2.96 × 109 *** <0.001
Isobutyl butyrate 978 - 539-90-2 0.00 × 00 0.00 × 00 7.09 × 108 *** <0.001
Isopentyl hexanoate 1276 - 2198-61-0 0.00 × 00 2.15 × 107 6.22 × 108 *** <0.001
Methyl butanoate 748 - 623-42-7 9.77 × 107 9.73 × 108 3.04 × 109 *** <0.001
Methyl decanoate 1351 - 110-42-9 0.00 × 00 2.91 × 108 0.00 × 00 *** <0.001
Methyl dodecanoate 1550 - 111-82-0 0.00 × 00 1.19 × 108 6.07 × 107 *** <0.001
Methyl hexanoate 949 - 106-70-7 5.52 × 108 7.42 × 109 1.13 × 1010 *** <0.001
Methyl propionate 657 - 554-12-1 1.95 × 107 1.63 × 108 1.08 × 108 *** <0.001
n-Propyl acetate 739 - 109-60-4 1.60 × 109 1.97 × 109 3.43 × 109 *** 0.008
Pentyl acetate 901 - 628-63-7 6.38 × 108 1.72 × 108 7.74 × 108 *** 0.012
Propyl 2-methylbutanoate 969 - 37064-20-3 3.67 × 107 5.63 × 107 0.00 × 00 NS 0.112
Propyl butyrate 921 - 644-49-5 2.57 × 109 3.56 × 109 3.28 × 1010 *** <0.001
Propyl hexanoate 1118 - 626-77-7 1.53 × 109 3.07 × 109 3.57 × 1010 *** <0.001
Alcohol *** <0.001
1-Hexanol 903 916 111-27-3 7.07 × 108 1.95 × 109 8.42 × 108 NS 0.502
1-Octanol 1112 1118 111-87-5 1.56 × 109 2.39 × 109 0.00 × 00 *** 0.008
1-Pentanol 816 815 71-41-0 1.02 × 109 1.30 × 109 0.00 × 00 *** 0.018
1-Propanol 612 612 71-23-8 2.10 × 109 3.68 × 109 1.06 × 109 *** 0.007
1-Methoxy-2-propanol 713 713 107-98-2 4.91 × 108 4.80 × 108 1.49 × 107 *** 0.043
2-Methyl-1-butanol 783 789 137-32-6 2.75 × 108 3.89 × 108 2.77 × 108 NS 0.418
2-Methyl-1-propanol 678 678 78-83-1 4.48 × 107 8.06 × 107 7.45 × 106 *** 0.005
2-Methyl propanol 609 - 78-84-2 6.69 × 107 7.84 × 107 0.00 × 00 NS 0.112
2-Butanol 648 648 78-92-2 4.15 × 108 6.63 × 108 1.28 × 108 *** 0.005
3-Methyl-1-butanol 783 784 123-51-3 2.41 × 108 1.54 × 108 2.45 × 107 *** 0.043
Ethanol 506 506 64-17-5 1.23 × 109 4.60 × 109 1.33 × 109 *** <0.001
Isopropyl Alcohol 543 - 67-63-0 6.64 × 107 1.23 × 108 1.80 × 107 *** 0.011
Phenylethyl Alcohol 1199 - 60-12-8 0.00 × 00 9.02 × 107 8.73 × 108 *** <0.001
Acid
2,2-Dimethyl-propanoic acid 837 869 75-98-9 0.00 × 00 2.13 × 108 0.00 × 00 *** 0.004
3-Methyl-butanoic acid 918 - 503-74-2 0.00 × 00 0.00 × 00 1.04 × 1010 *** <0.001
Acetic acid 690 690 64-19-7 8.94 × 109 1.02 × 1010 9.85 × 1010 *** <0.001
Butanoic acid 864 864 107-92-6 8.80 × 109 9.17 × 109 1.04 × 1011 *** <0.001
Pentanoic acid 995 - 109-52-4 0.00 × 00 0.00 × 00 2.51 × 1010 *** <0.001
Propanoic acid 778 802 79-09-4 1.51 × 109 1.09 × 109 2.02 × 1010 *** <0.001
Hexanoic acid 1052 1052 142-62-1 3.23 × 109 2.90 × 109 2.49 × 1010 *** <0.001
Fatty acid esters *** <0.001
Propanoic acid, butyl ester 931 - 590-01-2 1.79 × 108 0.00 × 00 9.44 × 108 *** <0.001
Butanoic acid, butyl ester 978 - 109-21-7 0.00 × 00 0.00 × 00 6.04 × 109 *** <0.001
Terpene
3-Carene 1035 1027 13466-78-9 5.45 × 107 2.41 × 107 0.00 × 00 NS 0.084
α-Pinene 954 951 80-56-8 1.34 × 107 0.00 × 00 8.17 × 106 NS 0.270
Cumene 991 - 98-82-8 6.13 × 107 1.11 × 108 5.04 × 107 NS 0.166
Mesitylene 1029 - 108-67-8 8.64 × 108 2.03 × 109 1.11 × 107 *** 0.044
Furan
2-Ethyl furan 717 720 3208-16-0 4.50 × 108 1.25 × 109 1.89 × 107 *** <0.001
2-Methyl furan 615 615 534-22-5 1.64 × 107 4.55 × 107 0.00 × 00 *** 0.005
2-Pentyl furan 1010 1012 3777-69-3 1.12 × 109 2.52 × 109 5.17 × 108 *** 0.004
2-n-Butyl furan 917 - 4466-24-4 0.00 × 00 6.00 × 107 0.00 × 00 NS 0.079
2,4-Dimethyl furan 733 - 3710-43-8 3.27 × 107 3.11 × 107 0.00 × 00 *** 0.019
Hydrocarbon
1,3-bis(1,1-dimethylethyl)-benzene 1284 - 1014-60-4 1.31 × 1011 1.73 × 1011 5.81 × 1010 NS 0.060
2,4-Dimethyl-benzaldehyde 1305 - 15764-16-6 7.46 × 108 9.18 × 108 2.93 × 108 *** 0.019
Benzaldehyde 1027 1032 100-52-7 3.41 × 109 3.44 × 109 2.05 × 109 NS 0.466
Benzothiazole 1320 - 95-16-9 4.06 × 108 6.04 × 108 5.28 × 108 NS 0.156
Ethylbenzene 897 890 100-41-4 0.00 × 00 0.00 × 00 6.02 × 107 *** <0.001
Mesitylene 1028 - 108-67-8 8.64 × 108 2.03 × 109 1.11 × 107 *** 0.044
o-Cymene 1056 - 527-84-4 1.72 × 107 4.73 × 106 0.00 × 00 NS 0.055
o-xylene 925 916 95-47-6 1.09 × 108 9.63 × 108 0.00 × 00 NS 0.108
p-Xylene 895 895 106-42-3 7.52 × 108 1.32 × 109 5.47 × 108 NS 0.146
p-Cresol 1193 - 106-44-5 4.52 × 108 2.89 × 108 4.40 × 108 NS 0.113
Styrene 927 929 100-42-5 1.21 × 108 2.37 × 108 1.07 × 108 NS 0.078
tert-Butylbenzene 1024 - 98-06-6 4.74 × 108 6.60 × 108 1.53 × 108 *** 0.037
Toluene 792 794 108-88-3 8.30 × 107 1.31 × 108 3.62 × 107 *** 0.040
Phenolic
Phenol 1096 1112 108-95-2 0.00 × 00 0.00 × 00 5.87 × 108 *** <0.001
2-Methoxy-4-vinylphenol 1150 - 7786-61-0 0.00 × 00 0.00 × 00 3.98 × 107 *** <0.001
Sulfur
Dimethyl sulfide 537 538 75-18-3 1.78 × 108 2.90 × 108 6.17 × 107 *** 0.004
Dimethyl sulfone 1054 1055 67-71-0 2.21 × 108 6.32 × 107 0.00 × 00 *** 0.014
Methanethiol 459 462 74-93-1 9.29 × 106 1.02 × 107 8.84 × 106 NS 0.855
Ether
Vinylisopentyl ether 765 - 39782-38-2 1.10 × 108 2.89 × 108 3.71 × 107 *** 0.033
Lactone
y-Hexalactone 1166 - 695-06-7 8.51 × 108 1.07 × 109 4.06 × 108 *** 0.040
y-Nonalactone 1489 - 104-61-0 4.69 × 108 6.44 × 108 3.75 × 108 NS 0.279
Pyrazine
2,3,5-Trimethyl-6-ethylpyrazine 1190 - 17398-16-2 0.00 × 00 0.00 × 00 1.48 × 108 *** <0.001
2,3-Dimethyl-pyrazine 961 - 5910-89-4 1.27 × 108 3.77 × 107 1.33 × 109 *** <0.001
3-Ethyl-2,5-dimethyl-pyrazine 1055 - 5910-89-4 0.00 × 00 0.00 × 00 4.71 × 107 *** <0.001
Pyrazine 771 - 290-37-9 5.46 × 107 5.55 × 107 4.79 × 107 NS 0.847
Trimethyl-pyrazine 1041 1041 14667-55-1 8.50 × 107 3.89 × 107 9.03 × 108 *** <0.001