AlcoDrinks

AlcoDrinks is online calculator on correct determination of volatile compounds in alcohol products

Using this calculator, you can perform a quantitative determination of the content of volatile compounds, using ethanol as internal standard.

You should only specify the value of the area under the peaks of the analyzed compound and ethanol. As a result, you will immediately receive the concentration of analyzed compound in mg per liter of absolute alcohol (AA). Given values RRF are approximate. For more accurate results, you should enter the improved values for the calculation of RRF, corresponding to your gas chromatography.


1	STANDARD SOLUTION:		"C" (according EC 2870/2000)			Ethanol IS			Traditional IS		ANALYZED SAMPLE:			Whiskey sample #4
2	№	Compound	Concentration, mg/kg	Concentration, mg/L AA	Response	RF	RF	RRF exp.	RRF exp.	RRF tab.	RF	RRF exp.	Response (pure sample)	Response (sample + IS)	Concentration, mg/L AA	Concentration, mg/L AA	Concentration, mg/L AA	Concentration, mg/kg	Concentration, mg/L AA
3	№	Compound			Response	RF	RF				RF	RRF exp.	Response (pure sample)	Response (sample + IS)	Concentration, mg/L AA	Concentration, mg/L AA	Concentration, mg/L AA	Concentration, mg/kg	Concentration, mg/L AA
4	1	acetaldehyde	140.898	345.870	1241.600	0.269	0.279	1.921	1.993	1.290	0.113	3.645	121.688	112.806	17.667	26.309	27.254	11.301	26.786
5	2	isobutyraldehyde	0	0	0					1.410			0	0
6	3	ethyl formate	0	0	0					1.030			0	0
7	4	aceton	0	0	0					1.300			0	0
8	5	diethylformal	0	0	0					1.166			0	0
9	6	methyl acetate	207.021	512.330	2603.537	0.188	0.197	1.343	1.407	1.410	0.080	2.581	170.247	154.770	27.017	25.733	10.883	10.979	26.023
10	7	ethyl acetate	200.334	429.600	3424.161	0.139	0.125	0.993	0.893	1.030	0.059	1.903	102.241	92.946	11.852	11.426	8.619	4.861	11.522
11	8	2-butanone	0	0	0					0.900			0	0
12	9	methanol	226.220	244.810	3078.696	0.174	0.080	1.243	0.571	1.280	0.073	2.355	350.080	336.436	50.433	48.975	25.413	21.777	51.614
13	10	2-propanol	220.823	497.320	4741.121	0.110	0.105	0.786	0.750	0.810	0.047	1.516	443.135	402.850	40.398	39.201	30.223	16.786	39.785
14	11	ethanol (advanced IS)		789300	5637986.688	0.140	0.140	1.000	1.000	1.000			7013036.800	7014568	789300	789300	789300
15	12	diacetyl	0	0	0					2.019			0	0
16	13	2-butanol	0	0	0					0.853			0	0
17	14	1-propanol	229.855	522.180	5780.953	0.094	0.090	0.671	0.643	0.690	0.040	1.290	3549.605	3226.914	275.655	268.064	257.677	114.413	271.177
18	15	isobutyl alc.	229.973	592.240	6983.557	0.078	0.085	0.557	0.607	0.570	0.033	1.065	18013.562	16421.420	1155.608	1129.252	1228.593	480.684	1139.293
19	16	isoamyl acetate	0	0	0					0.707			0	0
20	17	1-butanol	223.727	520.410	6211.560	0.085	0.084	0.607	0.600	0.620	0.036	1.161	113.754	106.140	7.938	7.771	7.656	3.387	8.028
21	18	isoamyl alc.	228.957	563.930	6901.088	0.079	0.082	0.564	0.586	0.570	0.033	1.065	59923.273	54475.703	3844.203	3803.738	3938.623	1594.600	3779.440
22	19	ethylcaproate	0	0	0					0.890			0	0
23	20	hexanol	0	0	0					0.600			0	0
24	21	ethyllactate	0	0	0					1.908			0	0
25	22	ethylcaprylate	0	0	0					0.700			0	0
26	23	2-phenylethanol	0	0	0					0.850			0	0
27	24	ethyl hexanoate	0	0	0					0.679			0	0
28	25	ethyl octanoate	0	0	0					0.627			0	0
29	26	ethyl decanoate	0	0	0					0.618			0	0
30	27	benzyl alcohol	0	0	0					0.715			0	0
31	28	phenylethanol	0	0	0					0.559			0	0
32	29	Internal Standard (IS)	26.860	0	853.615	0.075			0.536		0.031	1.000		1852.000
33													M (sample), g	8.755
34													M (IS), g	0.896
35													IS conc., mg/kg	497.380
36													Density, mg/L	948060
37													ABV, (%)	40

Theoretical background and calculation

Concentration of the volatile compounds in alcohol products should be presented in mg per 1 liter of anhydrous alcohol (Absolute Alcohol - AA) in strict accordance with the regulations documents of OIV, Commission Regulation (EC) and AOAC Official Methods /1-4/. The mass concentration of ethanol in anhydrous alcohol (AA) is well known and its density is 789300 mg/L (AA). Since ethanol is present in the sample and its concentration in the anhydrous alcohol is well known, for quantitative calculation of the volatiles should use the method of internal standard (IS).
The value of the concentration of the i-th volatile compound of the test sample may be written by the following formula:

(1)

(2)

whereC_IS is the concentration of IS in the test sample; A_i and A_IS are peak areas of the i-th component and IS in the test sample; respectively, RF_i and RF_IS are coefficients of the detector response of i-th component and of IS in the standard working solution, respectively; C^st_i and C^st_IS are the concentrations of the i-th component and IS, respectively, expressed in mg per 1 liter of AA; A^st_i and C^st_IS the peak area of the i-th component and IS, respectively, in the standard working solution; RRF_i is relative response factor for the i-th component relative to IS.
Since in this case ethanol is the IS then C^st_ethanol = ρ_ethanol = 789300 mg/L is the value of the density of ethanol and the expressions (1) and (2) may be represented as follows /5/

(3)

(4)

where A^st_ethanol and A_ethanol are the peak areas of ethanol in the standard solution and in the test sample, respectively.

It should be noted that in the expression (3) there are not parameters such as:

name (kind/type) of sample

injection value

split ratio

values of air and hydrogen flows for flame-ionization detector (FID)

model, technical characteristics and methodic parameters of used gas chromatograph (GC)

volume concentration (v/v) of ethanol (strength) in sample

name of IS

quantity of injected IS

Determination of coefficients RRF

Values of coefficients RRF are calculated on experimental data of standard solutions with known values of concentration of volatile compounds by formula (4).

Table 1. Results of determination of coefficients RRF on experimental data presented in Figure 1

Determination of concentrations of volatile compounds in the sample

Determination of concentrations of volatile compounds in test sample is performed in accordance with equation (3).

Table 2. Experimental data and data from certificate CRM LGC5100 Whisky - Congeners

Peak area of analyzing volatile compounds are recorded in Table 2 in arbitrary units, for example, in "mV min"* or in "pA s"*.

The bias between the values of the concentrations from the certificate and the experimentally measured are not more than 12.0% relative.

References

International Organization of Vine and Wine (OIV). Compendium of international methods of wine and must analysis, 2009; Vols. 1 and 2.

Commission Regulation (EC) No 2870/2000 of 19 December 2000 laying down Community reference methods for the analysis of spirits drinks, 2000.

AOAC (Association of Official Analytical Chemists) Official Methods 972.10. Alcohol (higher) and ethyl acetate in distilled liquors. Alternative gas chromatographic method, 1975.

AOAC Official Methods 972.11. Methanol in distilled liquors. Gas chromatographic method, 1973.

Charapitsa S.V. et al. Direct Determination of Volatile Compounds in Spirit Drinks by Gas Chromatography. J. Agricultural and Food Chemistry, 2013, 61 (12), 2950–2956 DOI:10.1021/jf3044956.