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 1

Conceptual schematic of experimental (Exp) approaches to estimate response factor (RF) values of compounds lacking authentic standards/surrogates (CLASS).

Order	Type^a	This study	Previous study (reference)
		Exp-TD	Exp-DI	Exp-SPME
1	Reference	This study	Ahn et al. (2011) [4]	Ahn et al. (2011) [4]
2	Standard	Lab-made mix	The 502/524 volatile organics calibration mix	The 502/524 volatile organics calibration mix
		(Primary grade chemical: Sigma-Aldrich, USA)	(Supelco, St. Louis, MO)	(Supelco, St. Louis, MO)
3	Compounds	18 compounds are used among 19 compounds (a list of offensive odorants plus a few reference compound)	49 compounds are analyzed among 54 compounds (haloalkane, chloropropene, chloroethene, aromatic, and diene)	49 compounds are analyzed among 54 compounds (haloalkane, chloropropene, chloroethene, aromatic, and diene)
4	Method of calibration	Injection of liquid standard on sorbent tube and thermal desorption analysis (ST analysis)	Direct injection of liquid standard (DILS)	Vapor phase injection via SPME (SPME)
5	Calibration results^b	𝑅^2 = 0.9954 ± 0.0075 (n = 19)	𝑅^2 = 0.9963 ± 0.0278 (n = 51)	𝑅^2 = 0.9854 ± 0.0414 (n = 50)
		RSE = 1.39 ± 0.82 (n = 19)	RSE = 2.85 ± 2.26% (n = 51)	RSE = 1.59 ± 1.17% (n = 49)
6	Percent difference (PD) between actual versus best projected RF	5.60 ± 5.63% (n = 18)	27.5 ± 34.2% (n = 49)	30.3 ± 45.3% (n = 49)

aPretreatment approaches: (1) Exp-TD: thermal desorption, (2) Exp-DI: direct injection, and (3) Exp-SPME: solid-phase microextraction (SPME).
^bComparison of mean values of correlation coefficients and relative standard error (RSE) derived for each individual compound using each calibration method.
*Same experimental conditions between this and a previous study.
(1) Raw standard phase: liquid phase.
(2) Method of detection: GC (Shimadzu GC-2010, Japan) and MS (Shimadzu GCMS-QP2010, Japan).