Rxi-624Sil MS Columns

• Optimized selectivity for volatiles and polar compounds ensures good separations.
• Highly inert columns improve accuracy and allow lower detection limits, even for active compounds.
• Most thermally stable 624 column available up to 320 °C; low bleed, fully MS compatible.

Increase Confidence in Data Accuracy

While midpolarity 624 columns are widely used for analyzing polar analytes and volatile organic compounds (VOCs), not all columns combine the selectivity needed for critical separations with the high inertness and low bleed that can further improve data quality. Whether you are developing methods for residual solvents, analyzing environmental VOCs, or running other applications for volatile organics, you can improve data quality with Rxi-624Sil MS columns. These columns incorporate an optimized stationary phase chemistry, unique column deactivation, and tightly controlled manufacturing process that is specifically designed to provide the high inertness and thermal stability needed for greater accuracy and lower detection limits. The unique selectivity, inertness, and thermal stability of the Rxi-624Sil MS column make it ideal for numerous applications, from detecting impurities in pharmaceuticals to monitoring environmental VOCs.

Exceptional Inertness Provides Better Peak Shape, Higher Sensitivity, and More Accurate Data

Column inertness is difficult to achieve but critical to improving data quality. The deactivation process used for Rxi-624Sil MS columns yields a fully passivated surface that is demonstrably more inert than other 624-type columns. Comprehensive deactivation results in higher responses, more symmetrical peaks, and easy, accurate integration, even for active compounds at low levels (Figures 1 and 2). Rxi-624Sil MS columns, with their superior deactivation, provide the inertness needed for improved linearity, greater accuracy, and lower detection limits.

	Peaks	Conc. (µg/mL)
1.	Isopropylamine	100
2.	Diethylamine	100
3.	Triethylamine	100

Column	Rxi-624Sil MS, 30 m, 0.32 mm ID, 1.8 µm (cat.# 13870)
Standard/Sample
Diluent:	DMSO
Conc.:	100 µg/mL
Injection
Inj. Vol.:	1 µL split (split ratio 20:1)
Liner:	5 mm Single taper with wool (cat.# 22974-207)
Inj. Temp.:	250 °C
Oven
Oven Temp.:	50 °C (hold 1 min) to 200 °C at 20 °C/min (hold 5 min)
Carrier Gas	He, constant flow
Linear Velocity:	37 cm/sec

Detector	FID @ 250 °C
Instrument	Agilent/HP6890 GC

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Figure 2: Active compounds like isopropylamine can be more accurately integrated on an Rxi-624Sil MS column, lowering limits of quantification (LOQs) and increasing data accuracy.

Same conditions as Figure 1.

Rxi-624Sil MS

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Lowest Bleed 624 Available—Assured GC-MS Compatibility

In addition to providing greater inertness and more accurate results for active compounds, the Rxi-624Sil MS column offers higher temperature stability than any other column in its class (Table I, Figure 3). Even though most 624 columns provide adequate selectivity for polar compounds, poor thermal stability results in stationary phase bleed that can reduce column lifetime, decrease detector sensitivity, and interfere with the quantification of later eluting compounds. The highly effective stationary phase bonding chemistry of the Rxi-624Sil MS column ensures extremely low bleed up to 320 °C. While other 624 columns generate too much bleed to be useful for continuous mass spectrometry work, the Rxi-624Sil MS column is fully compatible with both quadrupole and ion trap mass spectrometers. In addition to MS compatibility, higher thermal stability results in more stable baselines, longer column lifetimes, and improved method reproducibility.

Table I: The Rxi-624Sil MS column has the highest thermal stability of any 624 column.

Data obtained from company website or literature for a 30 m x 0.25 mm x 1.4 μm df column.

	Peaks
1.	Fluorobenzene

Column	Rxi-624Sil MS (see notes), 30 m, 0.25 mm ID, 1.4 µm (cat.# 13868)
Standard/Sample	Fluorobenzene (cat.# 30030)
Diluent:	Methanol
Conc.:	200 µg/mL
Injection
Inj. Vol.:	1 µL split (split ratio 20:1)
Liner:	4 mm Split liner with wool
Inj. Temp.:	220 °C
Oven
Oven Temp.:	40 °C (hold 5 min) to 60 °C at 20 °C/min (hold 5 min) to 120 °C at 20 °C/min (hold 5 min) to 200 °C at 20 °C/min (hold 10 min) to 260 °C at 20 °C/min (hold 10 min) to 300 °C at 20 °C/min (hold 20 min)
Carrier Gas	He, constant flow
Linear Velocity:	40 cm/sec

Detector	FID @ 250 °C
Instrument	Agilent/HP6890 GC
Notes	Liner cat.# 20781 was used to produce this chromatogram, but it has since been discontinued. We recommend cat.# 20782 [or cat.# 23300] as an alternative. For assistance choosing a replacement for this application, contact Restek Technical Service or your local Restek representative. - - - - - - Columns are of equivalent dimensions and were tested after equivalent conditioning.

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Assure Reliable Separation of Volatile Impurities in Pharmaceuticals

In the pharmaceutical industry, timing and certainty are everything. Time-to-market is a key driver for new drugs, and efficient batch testing is critical for releasing approved products. Whether developing new methods or conducting routine analysis, increasing productivity depends on choosing the right column for the application. Rxi-624Sil MS columns provide enhanced retention of polar compounds and volatile analytes, as well as full MS compatibility, making them the best choice for many drug analyses.

Fast, Effective Method Development

Often, 1- and 5-type columns are used initially for GC-MS method development because of their thermal stability; however, their nonpolar character results in poor retention for polar compounds, which increases method development time. In contrast, effective methods can be developed quickly on midpolarity Rxi-624Sil MS columns because they provide greater retention and selectivity for polar compounds as well as good thermal stability. For example, highly volatile, polar alkyl halide genotoxic impurities are difficult to retain on 1s and 5s, but Rxi-624Sil MS columns provide the retention needed to ensure adequate separation (Figure 4). Increased retention makes GC-MS analysis easier to control and ultimately allows faster method development.

Improving Results for Routine Analysis

Once a drug is approved, fast, reliable methods are needed for routine batch analysis. Establishing system suitability is an important part of these procedures and a major factor in overall lab productivity. Rxi-624Sil MS columns provide the optimized selectivity and guaranteed reproducibility needed to increase pass rates. For example, batch throughput can be improved for residual solvent testing under USP <467> by using a column that provides increased resolution for system suitability components (Figure 5). Greater resolution of critical pairs means higher system suitability pass rates, which allows more batches to be analyzed per shift.

Optimized phase chemistry, complete column deactivation, and tightly-controlled manufacturing make Rxi-624Sil MS columns the best choice for many pharmaceutical applications. With better retention of polar volatiles, lower bleed, and higher inertness, Rxi-624Sil MS columns can improve lab productivity by allowing new methods to be developed quickly and routine applications to be run more reliably.

TECH TIP!   Tim Herring, Technical Service Specialist   When running USP <467> by headspace, using a smaller bore liner (1 mm) can improve system suitability pass rates. Larger bore liners (4 mm) are used with direct liquid injection because the sample is vaporized in the injection port, and the liner must be able to accommodate the solvent expansion volume. In contrast, in headspace analysis, the sample is vaporized in a vial instead of the injection port, so a large volume liner is not needed, and, in fact, it can be deleterious. In headspace methods, using a smaller bore liner reduces band broadening by increasing linear velocity, allowing faster sample transfer and improving resolution.

Resolution passes USP <467> criteria when using a 1 mm liner (red line) but fails if a 4 mm liner is used (black line).

	Peaks	tR (min)
1.	2-Chloropropane	2.10
2.	Bromoethane	2.36
3.	1-Chloropropane	2.72
4.	2-Bromopropane	3.393
5.	Butyl chloride	4.627
6.	1-Bromobutane	5.973

Column	Rxi-624Sil MS, 20 m, 0.18 mm ID, 1.00 µm (cat.# 13865)
Standard/Sample
Diluent:	DMSO
Conc.:	1 µg/mL
Injection
Inj. Vol.:	1 µL splitless (hold 0.5 min)
Liner:	3.5 mm Single Gooseneck Liner with wool placed 3 cm from top (middle)
Inj. Temp.:	220 °C
Purge Flow:	3 mL/min
Oven
Oven Temp.:	40 °C (hold 3 min) to 200 °C at 20 °C/min
Carrier Gas	He, constant flow
Linear Velocity:	40 cm/sec

Detector	MS
Mode:	Scan
Transfer Line Temp.:	280 °C
Analyzer Type:	Quadrupole
Source Temp.:	280 °C
Solvent Delay Time:	0.5 min
Ionization Mode:	EI
Scan Range:	30-300 amu
Scan Rate:	5 scans/sec
Instrument	Shimadzu 2010 GC & QP2010+ MS
Notes	Liner cat.# 22286 was used to produce this chromatogram, but it has since been discontinued. We recommend cat.# 22287 [or cat.# 23321] as an alternative. For assistance choosing a replacement for this application, contact Restek Technical Service or your local Restek representative. - - - - - - Ions displayed: 42, 43, 57, 108 m/z

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	Peaks	tR (min)	Conc. (µg/mL)
1.	1,1-Dichloroethene	3.586	0.07
2.	1,1,1-Trichloroethane	8.536	0.08
3.	Carbon tetrachloride	9.042	0.03
4.	Benzene	9.787	0.02
5.	1,2-Dichloroethane	10.112	0.04

* DMSO interference

Column	Rxi-624Sil MS, 30 m, 0.32 mm ID, 1.80 µm (cat.# 13870)
Standard/Sample	Residual Solvents - Class 1 (cat.# 36279)
Diluent:	water
Injection	headspace-loop split (split ratio 5:1)
Liner:	1mm Split
Inj. Port Temp.:	140 °C
Headspace-Loop
Instrument:	Tekmar HT3
Inj. Time:	1 min
Transfer Line Temp.:	110 °C
Valve Oven Temp.:	110 °C
Sample Temp.:	80 °C
Sample Equil. Time:	60 min
Vial Pressure:	10 psi
Pressurize Time:	0.5 min
Pressure Equilibration Time:	0.05 min
Loop Pressure:	5 psi
Loop Fill Time:	0.1 min
Oven
Oven Temp.:	40 °C (hold 20 min) to 240 °C at 10 °C/min (hold 20 min)
Carrier Gas	He, constant flow
Linear Velocity:	35 cm/sec
Dead Time:	1.45 min @ 40 °C

Detector	FID @ 250 °C
Data Rate:	5 Hz
Instrument	Agilent/HP6890 GC
Notes	Liner cat.# 20972 was used to produce this chromatogram, but it has since been discontinued. We recommend cat.# 20973 [or cat.# 23333] as an alternative. For assistance choosing a replacement for this application, contact Restek Technical Service or your local Restek representative. - - - - - - Columns were run under identical conditions.
Acknowledgement	Teledyne Tekmar

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Improve Productivity and Resolve Critical Pairs in Environmental Samples

Fast sample throughput is a primary concern for environmental labs interested in improving productivity. Volatiles methods typically are time-consuming, but developing optimized procedures can be challenging because compound lists are extensive, and analytes vary significantly in chemical characteristics. The selectivity and inertness of Rxi-624Sil MS columns make them ideal for optimizing environmental volatiles methods for better resolution and faster analysis time.

Establishing conditions that maximize sample throughput can be difficult because conditions optimized for speed can result in problematic coelutions while conditions optimized for resolution can result in long analysis times. The exceptional inertness of Rxi-624Sil MS columns produces highly symmetrical peaks for active compounds, which improves resolution and allows separations to be maintained even under faster conditions. As shown in Figure 6, an optimized method was developed using an Rxi-624Sil MS column to maintain adequate resolution while throughput was maximized by synchronizing purge-and-trap cycles with instrument cycles.

Initially, several critical pairs were chosen for computational modeling using Pro EZGC software. The temperature program first determined by the software provided the best resolution but also resulted in an analysis time of 19 minutes. Since the purge-and-trap cycle time was 16.5 minutes, other conditions were evaluated to see if adequate resolution could be maintained using a faster instrument cycle. The final program reduced instrument downtime by better synchronizing purge-and-trap cycles with instrument cycles, and also provided excellent resolution. Using these conditions, up to 36 samples can be analyzed following EPA Method 8260 in a 12-hour shift.

Labs interested in optimizing both sample throughput and resolution of VOCs can adopt the synchronized conditions established here on Rxi-624Sil MS columns to maximize productivity and assure accurate, reliable results.

	Peaks	tR (min)
1.	Dichlorodifluoromethane (CFC-12)	2.198
2.	Chloromethane	2.459
3.	Vinyl chloride	2.659
4.	Bromomethane	3.226
5.	Chloroethane	3.434
6.	Trichlorofluoromethane (CFC-11)	3.876
7.	Diethyl ether (ethyl ether)	4.44
8.	1,1-Dichloroethene	4.909
9.	1,1,2-Trichlorotrifluoroethane (CFC-113)	4.998
10.	Acetone	5.029
11.	Iodomethane	5.195
12.	Carbon disulfide	5.323
13.	Acetonitrile	5.637
14.	Allyl chloride	5.715
15.	Methyl acetate	5.723
16.	Methylene chloride	5.981
17.	tert-Butyl alcohol	6.234
18.	Acrylonitrile	6.451
19.	Methyl tert-butyl ether (MTBE)	6.509
20.	trans-1,2-Dichloroethene	6.512
21.	1,1-Dichloroethane	7.315
22.	Vinyl acetate	7.359
23.	Diisopropyl ether (DIPE)	7.407
24.	Chloroprene	7.429
25.	Ethyl tert-butyl ether (ETBE)	7.97
26.	2-Butanone (MEK)	8.193
27.	cis-1,2-Dichloroethene	8.193
28.	2,2-Dichloropropane	8.193
29.	Ethyl acetate	8.265
30.	Propionitrile	8.276
31.	Methyl acrylate	8.318
32.	Methacrylonitrile	8.476
33.	Bromochloromethane	8.507
34.	Tetrahydrofuran	8.521
35.	Chloroform	8.651

	Peaks	tR (min)
36.	1,1,1-Trichloroethane	8.843
37.	Dibromofluoromethane	8.848
38.	Carbon tetrachloride	9.026
39.	1,1-Dichloropropene	9.037
40.	1,2-Dichloroethane-d4	9.246
41.	Benzene	9.262
42.	1,2-Dichloroethane	9.334
43.	Isopropyl acetate	9.34
44.	Isobutyl alcohol	9.421
45.	tert-Amyl methyl ether (TAME)	9.421
46.	Fluorobenzene	9.598
47.	Trichloroethene	9.976
48.	1,2-Dichloropropane	10.243
49.	Methyl methacrylate	10.29
50.	1,4-Dioxane (ND)	10.299*
51.	Dibromomethane	10.326
52.	Propyl acetate	10.346
53.	2-Chloroethanol (ND)	10.368*
54.	Bromodichloromethane	10.496
55.	2-Nitropropane	10.698
56.	cis-1,3-Dichloropropene	10.904
57.	4-Methyl-2-pentanone (MIBK)	11.026
58.	Toluene-D8	11.148
59.	Toluene	11.21
60.	trans-1,3-Dichloropropene	11.407
61.	Ethyl methacrylate	11.435
62.	1,1,2-Trichloroethane	11.585
63.	Tetrachloroethene	11.662
64.	1,3-Dichloropropane	11.729
65.	2-Hexanone	11.749
66.	Butyl acetate	11.837
67.	Dibromochloromethane	11.921
68.	1,2-Dibromoethane (EDB)	12.035
69.	Chlorobenzene-d5	12.412
70.	Chlorobenzene	12.44

	Peaks	tR (min)
71.	Ethylbenzene	12.507
72.	1,1,1,2-Tetrachloroethane	12.507
73.	m-Xylene	12.612
74.	p-Xylene	12.612
75.	o-Xylene	12.935
76.	Styrene	12.949
77.	n-Amyl acetate	13.018
78.	Bromoform	13.118
79.	Isopropylbenzene (cumene)	13.226
80.	cis-1,4-Dichloro-2-butene	13.268
81.	4-Bromofluorobenzene	13.385
82.	1,1,2,2-Tetrachloroethane	13.456
83.	trans-1,4-Dichloro-2-butene	13.496
84.	Bromobenzene	13.515
85.	1,2,3-Trichloropropane	13.526
86.	n-Propylbenzene	13.565
87.	2-Chlorotoluene	13.657
88.	1,3,5-Trimethylbenzene	13.699
89.	4-Chlorotoluene	13.751
90.	tert-Butylbenzene	13.965
91.	Pentachloroethane	14.007
92.	1,2,4-Trimethylbenzene	14.01
93.	sec-Butylbenzene	14.14
94.	4-Isopropyltoluene (p-cymene)	14.254
95.	1,3-Dichlorobenzene	14.263
96.	1,4-Dichlorobenzene-D4	14.321
97.	1,4-Dichlorobenzene	14.34
98.	n-Butylbenzene	14.579
99.	1,2-Dichlorobenzene	14.635
100.	1,2-Dibromo-3-chloropropane (DBCP)	15.252
101.	Nitrobenzene	15.407
102.	1,2,4-Trichlorobenzene	15.935
103.	Hexachloro-1,3-butadiene	16.04
104.	Naphthalene	16.196
105.	1,2,3-Trichlorobenzene	16.396

* ND = not detected; retention time determined by wet needle injection

Column	Rxi-624Sil MS, 30 m, 0.25 mm ID, 1.40 µm (cat.# 13868)
Standard/Sample
	8260A surrogate mix (cat.# 30240)
	8260A internal standard mix (cat.# 30241)
	8260B MegaMix calibration mix (cat.# 30633)
	VOA calibration mix #1 (ketones) (cat.# 30006)
	8260B acetate mix (revised) (cat.# 30489)
	California oxygenates mix (cat.# 30465)
	502.2 calibration mix #1 (gases) (cat.# 30042)
Conc.:	25 ppb in RO water
Injection	purge and trap split (split ratio 30:1)
Inj. Temp.:	225 °C
Purge and Trap
Instrument:	OI Analytical 4660
Trap Type:	10 Trap
Purge:	11 min @ 20 °C
Desorb Preheat Temp.:	180 °C
Desorb:	0.5 min @ 190 °C
Bake:	5 min @ 210 °C
Interface Connection:	injection port
Oven
Oven Temp.:	35 °C (hold 5 min) to 60 °C at 11 °C/min to 220 °C at 20 °C/min (hold 2 min)
Carrier Gas	He, constant flow
Flow Rate:	1.0 mL/min

Detector	MS
Mode:	Scan
Transfer Line Temp.:	230 °C
Analyzer Type:	Quadrupole
Source Temp.:	230 °C
Quad Temp.:	150 °C
Electron Energy:	70 eV
Solvent Delay Time:	1.5 min
Tune Type:	BFB
Ionization Mode:	EI
Scan Range:	36-260 amu
Instrument	Agilent 7890A GC & 5975C MSD
Notes	Other Purge-and-Trap Conditions: Sample Inlet: 40°C Sample: 40°C Water Management: Purge 110°C, Desorb 0°C, Bake, 240°C
Acknowledgement	Eclipse 4660 purge-and-trap courtesy of O.I. Analytical, College Station, TX.

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