Rapid LPGC-MS Analysis of Arylamines Increases Throughput and Reduces Helium Use

• Analyze arylamines 3.3x faster than conventional GC-MS.
• Cut costs by reducing helium consumption 81%.
• Pre-connected LPGC column kit prevents leaks, simplifies installation, and allows large-volume injection.

Azo dyes are synthetically produced colorants that are commonly used in the food, cosmetic, pharmaceutical, and textile industries. They are present in a wide variety of consumer products, and some can produce carcinogenic or mutagenic arylamines as breakdown products. Due to concerns about human health and exposure, effective methods are needed for the analysis of arylamines. Testing is usually performed by conventional GC-MS or LC-MS, but long analysis times limit sample throughput. 

A much faster alternative, low-pressure GC-MS (LPGC-MS) is a paired-column technique that can bring significant speed gains to labs analyzing arylamines. This approach uses the MS vacuum to lower pressure within the analytical column, thus increasing speed. For example, in the analysis of arylamines (22 of which are regulated by EU REACH legislation [1]) shown in Figure 1, the run time was 3.3x faster than the conventional method, and it also used 81% less helium, which provides a substantial cost savings. 

LPGC-MS only works because the inlet pressure is maintained by pairing the analytical column to a narrow restrictor column. However, due to the difference in tubing diameters, it can be difficult to make a robust connection manually, which has limited adoption of the technique. LPGC column kits from Restek solve this problem because they are factory connected and individually leak checked, which ensures a leak-free connection and simplifies setup. Visit www.restek.com/lpgc to learn more about this powerful technique.

References

1. Regulation (EC) No. 1907/2006 of the European Parliament and of the Council of 18 December 2006 Concerning the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH). https://osha.europa.eu/en/legislation/directives/regulation-ec-no-1907-2006-of-the-european-parliament-and-of-the-council.

	Peaks	tR (30 m)	tR (LPGC)	Conc. (ppm)	Quant Ion
1.	o-Toluidine	3.217	1.207	2	107
2.	o-Anisidine	4.42	1.589	2	123
3.	4-Chloroaniline	4.832	1.71	2	127
4.	p-Cresidine	5.519	1.92	2	137
5.	2,4,5-Trimethylaniline	5.582	1.935	2	135
6.	3-Chloro-o-toluidine	5.902	2.026	2	141
7.	4-Chloro-o-toluidine	6.025	2.061	2	141
8.	2,4-Diaminotoluene	7.637	2.523	2	122
9.	2,4-Diaminoanisole	8.89	2.872	2	138
10.	2-Naphthylamine	9.773	3.112	2	143
11.	2-Aminobiphenyl	9.892	3.148	2	169
12.	2-Amino-4-nitrotoluene	10.537	3.325	2	152

	Peaks	tR (30 m)	tR (LPGC)	Conc. (ppm)	Quant Ion
13.	4-Aminobiphenyl	12.154	3.767	2	169
14.	p-Aminoazobenzene	15.95	4.805	2	197
15.	4,4'-Oxydianiline	16.613	4.99	2	200
16.	4,4'-Diaminodiphenylmethane	16.714	5.016	2	198
17.	Benzidine	16.787	5.034	2	184
18.	o-Aminoazotoluene	17.53	5.24	2	225
19.	3,3'-Dimethyl-4,4'-diaminodiphenylmethane	18.23	5.436	2	226
20.	3,3'-Dimethylbenzidine	18.483	5.504	2	212
21.	4,4’-Thiodianiline	19.439	5.765	2	216
22.	3,3'-Dichlorobenzidine	19.795	5.864	2	252
23.	4,4'-Methylenebis(2-chloroaniline)	19.795	5.864	2	266
24.	3,3'-Dimethoxybenzidine	19.905	5.898	2	244

Column	See notes
Standard/Sample	AccuStandard carcinogenic aryl amine mix (AE-00049-R1-10X)
	AccuStandard 2,4-diaminoanisole (ALR-070S-R2)
Diluent:	Ethyl acetate
Conc.:	20 µg/mL
Injection
Inj. Vol.:	1 µL split (split ratio 10:1)
Liner:	Topaz, splitless, single taper inlet liner, 4.0 mm x 6.5 x 78.5 (cat.# 23303)
Inj. Temp.:	280 °C
Carrier Gas	He

Detector	MS
Mode:	Scan
Transfer Line Temp.:	300 °C
Analyzer Type:	Quadrupole
Source Temp.:	230 °C
Quad Temp.:	150 °C
Electron Energy:	70 eV
Tune Type:	PFTBA
Ionization Mode:	EI
Instrument	Agilent 7890B GC & 5977A MSD
Sample Preparation	The standards were diluted with ethyl acetate to 20 ppm; analyzed in a 2 mL, short-cap, screw-thread vial (cat.# 21143); and capped with a short-cap, screw-vial closure (cat.# 24495).
Notes	Conventional (30 m) Analysis: Column: Rxi-35Sil MS, 30 m, 0.25 mm ID, 0.25 µm (cat.# 13823) Temp. program: 200 °C (hold 0.5 min) to 320 °C at 9.5 °C/min (hold 5 min) Flow: 2.0 mL/min Scan start time: 2 min Scan range: 30-300 amu Scan rate: 10 scans/sec LPGC-MS Analysis: Column: LPGC Rxi-35Sil MS column kit, includes 10 m x 0.32 mm ID x 0.25 μm Rxi-35Sil MS analytical column and 5 m x 0.15 mm ID Rxi restrictor factory connected via SilTite connector (cat.# 11806) Temp. program: 100 °C (hold 0.5 min) to 300 °C at 35 °C/min (hold 5 min) Flow: 0.9 mL/min Scan start time: 1 min Scan range: 35-300 amu Scan rate: 9.7 scans/sec Compound list based on EU legislation of Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Appendix 8 (https://reachonline.eu/reach/en/appendix-8.html). The 3-chloro-o-toluidine and 2-aminibiphenyl compounds are not part of the list.

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