A Statistical Estimation Approach for Quantitative Concentrations of Compounds Lacking Authentic Standards/Surrogates Based on Linear Correlations between Directly Measured Detector Responses and Carbon Number of Different Functional Groups

Table 7

Results of the best projected RF for individual compound when matching the best fit equation with each of the six original VOC functional groups representing all 18 reference compounds.

Order	Grouping code^a	Compound	Carbon number	Actual RF	Projected RF^b	PD^c
1	Aldehyde (I)^d	PA	3	11,984	14,217	18.6
2		BA	4	43,520	39,053	10.3
3		IA	5	65,981	63,888	3.17
4		VA	5	59,563	63,888	7.26
5	Aromatic (II)	B	6	131,520	133,598	1.58
6		T	7	167,211	163,054	2.49
7		S	8	189,954	192,510	1.35
8		p-X	8	186,274	192,510	3.35
9		m-X	8	195,478	192,510	1.52
10		o-X	8	196,258	192,510	1.91
11	Carboxylic; (II + III + VI)	PPA	3	26,269	27,588	5.02
12		BTA	4	69,546	60,582	12.9
13		IVA	5	97,015	93,576	3.54
14		VLA	5	79,282	93,576	18.0
15	Ketone (I + II + III + IV)	MEK	4	48,773	49,955	2.42
16		MIBK	6	117,515	120,904	2.88
17	Alcohol (II + V)	i-BuAl	4	93,223	89,250	4.26
18	Ester (III + VI)	BuAc	6	119,453	119,773	0.27
	Mean					5.60
	SD					5.63

aPredictive equations ((1) slopes and (2) intercepts) developed for 29 arbitrary groups (codes) in Table 6 are used.
(1) Slope: Eqn (I) = 24,836, Eqn (II) = 29,456, Eqn (II + III + VI) = 32,994, Eqn (I + II + III + IV) = 35,474, Eqn (II + V) = 25,484, and Eqn (III +VI) = 29,615.
(2) Intercept: Eqn (I) = −60,290, Eqn (II) = −43,139, Eqn (II + III + VI) = −71,393, Eqn (I + II + III + IV)) = −91,942, Eqn (II + V) = −12,686, and Eqn (III + VI) = −57,914.
^bThe best projected RFs are derived by taking the minimum PD value for each compound (out of 18) after testing against 29 linear regression equations (between the number of carbon (x-axis) and actual RF values (y-axis)).
^cPercent difference (PD) = |(RF(Projected)−RF(Actual))| × 100/RF (Actual): here, the AA data are excluded due to the eccentricity.
^dBest fit equation (Roman letter) for a given chemical group is shown in the parenthesis.