Analyzing volatiles in brown rice vinegar by headspace solid-phase microextraction (SPME)–Arrow: Optimizing the extraction conditions and comparisons with conventional SPME

Figures & data

Figure 1. Relative peak areas as functions of extraction conditions: (a) SPME–Arrow fiber, (b) extraction time, (c) extraction temperature, and (d) concentration of added NaCl

Table 1. Volatile components of brown rice vinegar identified using SPME–Arrow and conventional SPME fibers

Peak No.	R.T. (min)	R.I.	Volatiles	Relative concentration^x (mg L^−1)
				SPME-Arrow	Conventional SPME
1	6.580	890	Ethyl acetate	8.53 ± 0.25^ya	6.50 ± 0.34^b
2	7.550	934	Ethanol	2.36 ± 0.10^a	2.24 ± 0.08^a
3	11.900	1083	Hexanal	0.02 ± 0.00^a	0.02 ± 0.00^a
4	17.900	1220	2-Hexenal	0.19 ± 0.00^a	0.09 ± 0.02^b
5	20.180	1266	Hexyl acetate	0.05 ± 0.00	nd
6	24.677	1356	1-Hexanol	0.39 ± 0.01	nd
7	26.284	1388	(Z)-3-Hexen-1-ol	0.03 ± 0.00	nd
8	27.363	1409	(E)-2-Hexen-1-ol	0.05 ± 0.00	nd
9	29.590	1454	Acetic acid	0.49 ± 0.01^a	0.28 ± 0.04^b
10	30.154	1465	Furfural	0.42 ± 0.01^a	0.24 ± 0.01^b
11	32.250	1507	2-Acetylfuran	0.05 ± 0.01^a	0.03 ± 0.01^b
12	39.620	1660	2-Furanmethanol	0.03 ± 0.00	nd

^x Relative concentrations of volatile compounds are expressed as equivalents of the internal standard (2 mg/L of 4-methyl-2-pentanol) for SPME–Arrow- and SPME-GC/MS.

^y All data are presented as means ± SD (n = 3).

Different letters in the same row indicate significant differences at p < 0.05 (assessed by student’s t-test).

R.T., retention time; R.I., retention index; nd, not detected.

Figure 2. Cumulative areas as functions of the number of accumulated analytes: depicting the sensitivities of CAR/PDMS SPME-Arrow and conventional CAR/PDMS fibers to different categories of VOC

Figure 3. Reproducibilities of the CAR/PDMS SPME–Arrow and conventional CAR/PDMS SPME fibers: standard deviation of the average relative standard deviation (RSD) as a function of the average RSD for brown rice vinegar VOCs