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Article • J. Braz. Chem. Soc. 29 (11) • Nov 2018 • https://doi.org/10.21577/0103-5053.20180102 copy

Development, Optimization and Validation of a GC Method by Polarity Phase Constants and Statistical Design of Experiments for the Determination of Monoterpenes in Alpinia zerumbet Essential Oil

Authorship SCIMAGO INSTITUTIONS RANKINGS

In this report, a rapid and selective analytical method for the determination of monoterpenes in Alpinia zerumbet essential oil (AZEO) by gas chromatography (GC) flame ionization detection (FID) was developed, optimized and validated. The suitability of six different capillary columns was investigated by polarity phase constants calculated based on the methodology proposed by Rohrschneider and McReynolds. The most suitable column was then used in a central composite design applying the following GC factors to investigate responses based on peak resolutions and analysis time: initial oven temperature, heating rate and carrier gas flow rate. The optimized method has initial oven temperature of 60 ºC, heating rate of 5.1 ºC min^-1 and flow rate of 1.0 mL min^-1 using the DB-35 capillary column. The validation acceptance criteria were met in all cases. The method was successfully applied for the quantification of major monoterpenes found in AZEO in different samples of Alpinia zerumbet.

Keywords:
Alpinia zerumbet; essential oils; gas chromatography; polarity phase constants; central composite design

Experiment^a a Experiments 15 and 16 are center point replicates;	IOT^b b codified and original values (the latter between parentheses): A = +1.682; a = -1.682. IOT: initial oven temperature; HR: heating rate; CGFR: carrier gas flow rate. / ºC	HR^b b codified and original values (the latter between parentheses): A = +1.682; a = -1.682. IOT: initial oven temperature; HR: heating rate; CGFR: carrier gas flow rate. / (ºC min^-1)	CGFR^b b codified and original values (the latter between parentheses): A = +1.682; a = -1.682. IOT: initial oven temperature; HR: heating rate; CGFR: carrier gas flow rate. / (mL min^-1)
1	-1 (60.0)	-1 (2.5)	-1 (1.4)
2	-1 (60.0)	-1 (2.5)	+1 (2.6)
3	-1 (60.0)	+1 (5.5)	-1 (1.4)
4	-1 (60.0)	+1 (5.5)	+1 (2.6)
5	+1 (80.0)	-1 (2.5)	-1 (1.4)
6	+1 (80.0)	-1 (2.5)	+1 (2.6)
7	+1 (80.0)	+1 (5.5)	-1 (1.4)
8	+1 (80.0)	+1 (5.5)	+1 (2.6)
9	a (53.2)	0 (4.0)	0 (2.0)
10	A (86.8)	0 (4.0)	0 (2.0)
11	0 (70.0)	a (1.5)	0 (2.0)
12	0 (70.0)	A (6.5)	0 (2.0)
13	0 (70.0)	0 (4.0)	a (1.0)
14	0 (70.0)	0 (4.0)	A (3.0)
15	0 (70.0)	0 (4.0)	0 (2.0)
16	0 (70.0)	0 (4.0)	0 (2.0)

Experiment^a a Experiments 15 and 16 are center point replicates;	IOT^b b codified and original values (the latter between parentheses): A = +1.682; a = -1.682. IOT: initial oven temperature; HR: heating rate; CGFR: carrier gas flow rate. / ºC	HR^b b codified and original values (the latter between parentheses): A = +1.682; a = -1.682. IOT: initial oven temperature; HR: heating rate; CGFR: carrier gas flow rate. / (ºC min^-1)	CGFR^b b codified and original values (the latter between parentheses): A = +1.682; a = -1.682. IOT: initial oven temperature; HR: heating rate; CGFR: carrier gas flow rate. / (mL min^-1)
1	-1 (60.0)	-1 (2.5)	-1 (1.0)
2	-1 (60.0)	-1 (2.5)	+1 (2.2)
3	-1 (60.0)	+1 (5.5)	-1 (1.0)
4	-1 (60.0)	+1 (5.5)	+1 (2.2)
5	+1 (80.0)	-1 (2.5)	-1 (1.0)
6	+1 (80.0)	-1 (2.5)	+1 (2.2)
7	+1 (80.0)	+1 (5.5)	-1 (1.0)
8	+1 (80.0)	+1 (5.5)	+1 (2.2)
9	a (53.2)	0 (4.0)	0 (1.6)
10	A (86.8)	0 (4.0)	0 (1.6)
11	0 (70.0)	a (1.5)	0 (1.6)
12	0 (70.0)	A (6.5)	0 (1.6)
13	0 (70.0)	0 (4.0)	a (0.6)
14	0 (70.0)	0 (4.0)	A (2.6)
15	0 (70.0)	0 (4.0)	0 (1.6)
16	0 (70.0)	0 (4.0)	0 (1.6)

t_R / min	Constituent	Classification^a a MH: monoterpenes hydrocarbon, OM: oxygenated monoterpenes, and SE: sesquiterpenes;	LRI^b b the linear retention indices (LRI) were calculated from DB-5MS column, employing the preliminary method;	Identification^c c method of identification: LRI, by comparison of LRI with those from the literature;15,17,19 MS, by comparison of the mass spectra with those from Wiley's MS library; Std, by injection of an authentic standard for each constituent. tR: retention time.
3.298	α-thujene	MH	925	LRI, MS
3.427	α-pinene	MH	934	LRI, MS, Std
4.027	sabinene	MH	974	LRI, MS
4.135	β-pinene	MH	981	LRI, MS, Std
4.240	myrcene	MH	988	LRI, MS
4.533	α-phellandrene	MH	1005	LRI, MS
4.816	α-terpinene	MH	1018	LRI, MS
4.974	p-cymene	MH	1025	LRI, MS
5.067	limonene	MH	1029	LRI, MS, Std
5.157	1,8-cineole	OM	1033	LRI, MS, Std
5.682	γ-terpinene	MH	1057	LRI, MS, Std
5.965	cis-sabinene hydrate	OM	1070	LRI, MS
6.307	terpinolene	MH	1086	LRI, MS
6.626	linalool	OM	1100	LRI, MS, Std
6.708	trans-sabinene hydrate	OM	1103	LRI, MS
8.863	cis-p-menth-2-en-1-ol	OM	1125	LRI, MS
7.304	trans-p-menth-2-en-1-ol	OM	1142	LRI, MS
7.772	terpinen-4-ol	OM	1182	LRI, MS, Std
9.239	α-terpineol	OM	1196	LRI, MS
15.849	β-caryophyllene	SE	1416	LRI, MS, Std
20.566	caryophyllene oxide	SE	1578	LRI, MS, Std

	Response
	R_s(my-pi)	R_s(cin-cy)	t / min
Predicted value	1.44	1.42	22.1
Upper confidence limit	1.73	1.45	24.3
Lower confidence limit	1.16	1.40	19.9
Experimental result	1.52	1.44	21.7

Validation parameter	1,8-Cineole	γ-Terpinene	Terpinen-4-ol
Linear fit	y = 0.0032x - 0.0012	y = 0.0039x - 0.0023	y = 0.0031x - 0.0100
R²	0.99986	0.99995	0.99993
Linear range / (µg mL^-1)	63.9-639.0	31.7-317.0	79.9-799.0
Limit of detection / (µg mL^-1)	3.2	1.0	2.9
Limit of quantitation / (µg mL^-1)	9.8	3.1	8.8
Mean recovery (n = 9) ± RSD / %	95.7 ± 1.12	94.7 ± 0.91	100.2 ± 1.76
Analyst 1 repeatability (mean content ± RSD) / %	19.5 ± 0.99	8.6 ± 0.80	21.7 ± 0.97
Analyst 2 repeatability (mean content ± RSD) / %	19.6 ± 1.07	8.6 ± 1.46	21.5 ± 1.83
Intermediate precision (mean content ± RSD) / %	19.6 ± 1.02	8.6 ± 1.15	21.6 ± 2.01

Sample	Constituent content / % (m/m)				Total / %
Sample	Sabinene	1,8-Cineole	γ-Terpinene	Terpinen-4-ol	Total / %
AZ1	20.0	19.5	8.6	21.7	69.8
AZ2	12.7	15.7	11.5	18.7	58.6
AZ3	6.7	15.1	13.7	21.9	57.4
AZ4	14.1	16.6	12.6	16.9	60.2
AZ5	6.7	16.5	12.8	25.4	61.4

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