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What to do when your packed/micropacked column is no longer available

23 Nov 2022

Here is a common scenario: A customer has asked you to analyze their samples using a method that uses a packed column instead of a capillary column. When you research companies that manufacture packed columns, no one offers this column because either the liquid phase/solid support or uncoated packing is no longer available.

Unfortunately, this scenario happens often. Many packed column methods were written years, if not decades, ago and in some cases the liquid phases/solid supports or uncoated packings have not been manufactured in years. Eventually, the companies that once had these materials available in their inventory have exhausted their supply. In summary, these materials no longer exist and it is highly unlikely any new supplies will be available anytime soon.

What do you do?

Before reading any further, I suggest that you review the link directly below if you are new to packed/micropacked columns, or need a very brief refresher course. I hope that it will provide you an overview of packed/micropacked columns, which should make this post easier to understand.

Packed Column information for the beginner (restek.com)

Below are my suggestions as to how you should proceed. However, this important decision should come from your customer, not me.

Look for a similar capillary column.
Look for a similar liquid phase/solid support and/or uncoated packing.
Look for a different method.

Below are topics to review to determine if similar liquid phases/solid supports and/or packings exist. I have listed them in the order I normally search for alternative packings.

USP Table
McReynolds Constants/Values Table
Application Chromatograms
Rohrschneider Polarity Scale
Kovats Retention Index

USP Table

The USP table will identify similar liquid phases/solid supports and/or packings based upon the chemical and physical properties of the materials. For example, if a packed column liquid phase is listed as OV-1 or OV-101, you should be able to substitute a Rtx-1 capillary column.

McReynolds Constants/Values Table

McReynolds Constants/Values used the probe compounds (listed directly below) to create a table (see below) which provides retention data for a large number of phases. The values in the table will provide information on a liquid phase’s polarity compared to a non-polar liquid phase (Squalene). Generally speaking, the closer two liquid phase probe values are, the more similar the liquid phases. The table below is sorted using the x’ (benzene) probe, but any of the probes, or even the name of the liquid phases, can be used to sort the list.

Probe compounds

x’ = benzene
y’ = butanol
z’ = 2-pentanone
u’ = nitropropane
s’ = pyridine

Stationary Phases and McReynolds Values

Phase [USP Code]	Solvent	Temp (°C) Min/Max	x'	y'	z'	u'	s'
SPB-Octyl		–60 to 280	3	14	11	12	11
SPB-1		–60 to 320	4	58	43	56	38
Nujol	T	0/200	9	5	2	6	11
Hexatriacontane	C	125/150	12	2	-3	1	11
SF-96	T	0/250	12	53	42	61	37
DC 330	A	0/275	13	51	42	61	36
Convoil 20	C	/200	14	14	8	17	21
M & B silicone oil	T	/300	14	57	46	67	43
E-301	C	50/300	15	56	44	66	40
SE-30 GC grade [G2]	C	50/300	15	53	44	64	41
DC-200 (500 cstks)	A	0/200	16	57	45	66	43
OV®-1 (gum) [G2]	T	100/350	16	55	44	65	42
SE-31	T	/350	16	54	45	65	43
DC-11	C	0/300	17	86	48	69	56
OV-101 (fluid) [G1]	C	0/350	17	57	45	67	43
SE-33	T	/300	17	54	45	67	42
DC 410	A	0/300	18	57	47	68	44
Montan wax	C	/175	19	58	14	21	47
SPB-5		–60 to 320	19	74	64	93	62
Polybutene 32	T	0/200	21	29	24	42	40
DC 510			25	65	60	89	57
Polybutene 128	T	0/200	25	26	25	41	42
Apiezon M	T	45/275	31	22	15	30	40
Apiezon L	C,T	50/300	32	22	15	32	42
DC 560	A	0/300	32	72	70	100	68
SE-52 [G27]	C	50/300	32	72	65	98	67
SE-54 [G36]	T	50/300	33	72	66	99	67
OV-105	A	0/275	36	108	93	139	86
DC 556			37	77	80	118	79
Apiezon J	T	50/300	38	36	27	49	57
Apiezon N	T	45/325	38	40	28	52	58
OV-73 [G27]	T	0/325	40	86	76	114	85
Apiezon T	T	45/275	41		30	55	82
Butyl stearate			41	109	65	112	71
Beeswax	C	0/200	43	110	61	88	122
OV-3	C	0/350	44	86	81	124	88
Dexsil® 300 carborane/methylsilicone	T	50/540	47	80	103	148	96
Halocarbon 10-25	C	20/100	47	70	108	133	111
Halocarbon K-352	F	0/250	47	70	73	238	146
Fluorolube HG 1200	A	/200	51	68	114	144	118
Halocarbon wax	A	50/150	55	71	116	143	123
KEL-F® wax	A	50/150	55	67	114	143	116
Butoyxethyl stearate			56	135	83	136	97
Apiezon® H	T	50/275	59	86	81	151	129
DEG stearate	A	/175	64	193	106	143	191
Dinonyl sebacate	A	0/150	66	166	107	178	118
OV-1701 (vinyl)		0/250	67	170	153	228	171
SPB-20		–25 to 300	67	116	117	174	131
SPB-1701		subambient to 280	67	170	153	228	171
OV-7 [G32]	C	0/350	69	113	111	171	128
Diisodecyl adipate	A	0/175	71	171	113	185	128
Dexsil 400 carborane/methylphenyl silicone	T	50/400	72	108	118	166	123
Dexsil 410 carborane/methylcyanoethyl	T	50/400	72	286	174	249	171
Di (2-ethylhexyl) sebacate [G11]	A	0/125	72	168	108	180	125
Dioctyl sebacate	A	0/125	72	168	108	180	123
Octoil S			72	167	107	179	123
Dina enjay			73	174	116	189	129
DC-550 [G28]	A	20/250	74	116	117	178	135
Ditridecyl phthalate			75	156	122	195	140
DC 703	C	20/250	76	123	126	189	140
Diisooctyl adipate	A	0/175	76	181	121	197	134
DC 702	A	20/250	77	124	126	189	142
Dilauryl phthalate	A	0/150	79	158	120	192	158
Hallcomid® M-18	C	40/150	79	268	130	222	146
Octyldecyl adipate	A	/125	79	179	119	193	134
Dinonyl phthalate	A	20/150	83	183	147	231	159
Diisodecyl phthalate [G24]	A	0/175	84	173	137	218	155
Hallcomid M-18-OL	C	–8/150	89	280	143	239	165
Bis (2-ethylhexyl) phthalate [G22]	M	/150	92	186	150	236	167
Dioctyl phthalate	A	0/125	92	186	150	236	167
Flexol GPE			93	210	140	224	162
Diisooctyl phthalate	A	0/175	94	193	154	243	174
Flexol 8N8	A	0/175	96	254	164	260	179
Butyloctylphthalate			97	194	157	246	174
Siponate DS-10	M	0/200	99	569	320	344	388
SPB-35		0 to 300	101	146	151	219	202
OV-11	C	0/350	102	142	145	219	178
DC-710	A	–5/250	107	149	153	228	190
Atpet 200			108	282	186	235	289
Castorwax	C	0/200	108	265	175	229	246
Diethylhexyl tetrachlorophthalate	C	0/150	109	132	113	171	168
Hercoflex 600	C	0/150	112	234	168	261	194
Amine 220	W	0/180	117	380	181	293	133
OV-17 [G3]	C	0/375	119	158	162	243	202
SP-2250		ambient to 320	119	158	162	243	202
Flexol B-400			121	284	169	259	217
Polypropyleneimine	C	0/200	122	425	168	263	224
SPB-50		30 to 310	125	175	183	268	220
Polypropylene glycol	M	0/150	128	294	173	264	226
PPG 2000	M	/150	128	294	173	264	226
Pluracol P-2010			129	295	174	266	227
Acetyltributyl citrate	A	/180	135	268	202	314	233
Diethylhexyl phthalate	A	0/125	135	254	213	320	235
Di-n-decyl phthalate	A	10/175	136	255	213	320	235
Estynox	C	0/175	136	257	182	285	227
Dibutoxyethyl adipate	C	/150	137	278	198	300	235
Elastex 50-B			140	255	209	318	239
DC QF-1 (FS 1265)	A	0/250	144	233	355	463	305
Pluronics L81			144	314	187	289	249
QF-1	A	0/250	144	233	355	463	305
Dicyclohexyl phthalate			146	257	206	316	245
OV-202 (fluid)	C	0/275	146	238	358	468	310
OV-210 (fluid) [G6]	A	0/275	146	238	358	468	310
OV-215 (gum)	E	0/275	149	240	363	478	315
Dibutoxyethyl phthalate	C	0/125	151	282	227	338	267
Diethoxyethyl sebacate			151	306	211	320	274
LSX-3-0295	A	0/250	152	241	366	479	319
OV-22	C	0/350	160	188	191	283	253
Polytergent J-300			168	366	227	350	308
Neopentyl glycol sebacate	C	50/225	172	327	225	344	326
Ethomeen 18/25	C	/75	176	382	230	353	323
OS 124	T	0/200	176	227	224	306	283
Polyphenyl ether (5 rings) OS-124	A	0/200	176	227	224	306	283
OV-25 [G17]	C	0/350	178	204	208	305	280
Polytergent J-400			180	375	234	366	317
OS 138	T	0/225	182	233	228	313	293
Polyphenyl ether (6 rings) OS-138	A	0/225	182	233	228	313	293
Oronite® NIW	A		185	370	242	370	327
Ethomeen S/25	C	0/125	186	395	242	370	339
Paraplex G-25			189	328	239	368	312
Ethofat 60/25	C	50/125	191	382	244	380	333
Igepal CO-630	M	/200	192	381	253	382	344
Polypropylene glycol sebacate	C	0/200	196	345	251	381	328
Cresyldiphenylphosphate			199	351	285	413	336
Pluronics P85			201	390	247	388	335
Emulphor® ON-870	C	0/200	202	395	251	395	344
Polytergent B-350			202	392	260	395	353
Pluronics P65			203	394	251	393	340
Polytergent G-300			203	398	267	401	360
Igepal CO-710			205	397	266	401	361
Pluronics L35			206	406	257	398	349
Polyglycol 15-200			207	410	262	401	354
Diethoxyethyl phthalate			214	375	305	446	364
Quadrol®	C	0/150	214	571	357	472	489
OV-330 silicone - Carbowax	A,T	0/250	222	391	273	417	368
Renex 678	M	0/150	223	417	278	427	381
Igepal CO-730			224	418	279	428	379
OV-225 [G19]	A	0/275	228	369	338	492	386
PPE-21	C	125/375	232	350	398	413	—
Bis(ethoxyethoxyethyl)phthalate			233	408	317	470	389
Neopentyl glycol adipate	C	50/225	234	425	312	402	438
PAG		30 to 220	252	499	310	489	416
PPE-20 (poly-M-phenoxylene)	C	125/375	257	355	348	433	—
Igepal CO-880 (Nonoxynol) [G31]	M	100/200	259	461	311	482	426
Nonoxynol (Igepal CO-880) [G31]	A	100/200	259	461	311	482	426
Pluronics F88			262	461	306	483	419
Pluronics® F68			264	465	309	488	423
Cyclohexanedimethanol succinate (CHDMS)*	C	100/250	269	446	328	493	481
Neopentyl glycol succinate [G21]	C	50/225	272	469	366	539	474
Fluorad® FC-431 (50% in solv. E)	E	40/200	281	423	297	509	360
Carbowax 4000 monostearate	C	0/200	282	496	331	517	467
Paraplex G-40			282	459	355	528	457
EPON 1001	C	50/225	284	489	406	539	601
Igepal CO-990	M	100/200	298	508	345	540	475
SUPELCOWAX 10		35 to 280	305	551	360	562	484
Ethylene glycol tetrachlophthalate	C	120/200	307	345	318	428	466
EGSP-Z	C	/210	308	474	399	548	549
Nukol		60 to 200	311	572	374	572	520
Silar 5 CP	C,A	0/250	319	495	446	637	531
Carbowax 20M-terephthalic acid [G25]	C	60/225	321	537	367	573	520
Carbowax® 20M [G16]	C	60/225	322	536	368	572	510
Carbowax 6000	C	70/200	322	540	369	577	512
Mer-21	C	70/200	322	541	370	575	512
Polyethyleneimine	A	0/175	322	800		573	524
Carbowax 600	C	30/125	323	583	382	—	—
PEG 4000	C		325	551	375	582	520
Ethylene glycol isophthalate	C	100/225	326	508	425	607	561
Carbowax 400 [G20]	C	10/100	333	653	405	—	—
OV-351	C	50/270	335	552	382	583	540
Hyprose SP-80	C	0/175	336	742	492	639	727
Free Fatty Acid Phase (FFAP) [G25]	C	50/250	340	580	397	602	627
Carbowax 1000 [G14]	A	40/125	347	607	418	626	589
PEG 600	M	30/125	350	631	428	632	605
Reoplex 400	A	0/200	364	619	449	647	671
Butanediol succinate, purified	C	50/225	370	571	448	657	611
Carbowax 1540	A	50/175	371	639	453	666	641
Carbowax 4000 [G15]	C	60/120	371	545	378	578	521
Diglycerol	M	20/100	371	826	560	676	854
Polyethylene glycol adipate (PEGA) [G23]			371	579	454	355	633
EGA	A	100/225	372	576	453	655	617
Ethylene glycol adipate	A	100/225	372	576	453	655	617
LAC IR-296	C	0/200	377	601	458	663	655
Diethylene glycol adipate (DEGA)	A	0/200	378	603	460	665	658
Mer 2	C	30/250	381	539	456	646	615
SP-2330		subambient to 250	382	610	506	710	591
Phenyldiethanolamine succinate [G12]	C	0/230	386	555	472	674	654
LAC-2-R-446	C	50/200	387	616	471	679	667
EGSS-Y	C	/205	391	597	493	693	661
SP-2380		subambient to 275	402	629	520	744	623
SP-2340		25 to 250	419	654	541	758	637
ECNSS-M	C	30/200	421	690	581	803	732
Ethylene glycol phthalate	C	100/200	453	697	602	816	872
EGSS-X	C	90/200	484	710	585	831	778
DEGS-PS	A	20/200	496	746	590	837	835
Diethylene glycol succinate (DEGS) [G4]	A	20/200	496	746	590	837	835
LAC-3-R-728	C	0/200	502	755	597	849	852
Silar 10 CP [G5]	C,A	0/250	520	757	660	942	800
EGS	C	100/200	537	787	643	903	889
Ethylene glycol succinate	C	100/200	537	787	643	903	889
Hexakis(2 cyanoethoxycyclohexane)	C,T	125/150	567	825	713	978	901
TCEP		subambient to 145	594	857	759	1031	917
Resoflex R 296		380	609	463	668	667
OV-275	A	25/250	629	872	763	1106	849
Cyanoethyl sucrose	A	0/100	647	919	797	1043	976
BCEF			690	991	853	1110	1000
n,n-Bis (2-cyanoethyl) formamide	C	0/125	690	991	583	1110	1000

Solvents
A – acetone
C – chloroform
E – ethyl acetate
F – Freon
M – methanol
P – pyridine
T – toluene
( ) – hot solvent

Application Chromatograms

Searching for application chromatograms, generated by alternative columns that are capable of performing the same, or similar separations, is often the first, and sometimes, the only resource customers use to search for a replacement of a packed column that may no longer be available. Considering both packed and capillary columns will increase your chance of finding such a column.

Chromatogram Library

Restek Pro EZGC Chromatogram Modeler

Rohrschneider Polarity Scale

This scale is similar to the information provided above for the McReynolds Constants/Values where compound probes were used to determine a liquid phase’s polarity/compound retention. See the link below for additional information.

Stationary Phase Selectivity: The Chemistry Behind the Separation (chromatographyonline.com)

A brief outline of increasing liquid phase polarity is below. The least polar column (liquid phase) is at the top; the most polar is at the bottom. I have only listed one type of Restek column, but there are often several other columns that match the same description, as shown in this poster on GC Column Selection (link directly below). In the Stationary Phase section of this poster, the least polar phases are on the left and the most polar phases are on the right.

GC Column Selection Poster (restek.com)

To view the poster, please search for: GNWC1612-UNV in the search field at the top of the page.

Rtx-1	(100% methyl polysiloxane)
Rtx-5	(5% phenyl - 95% methylpolysiloxane)
Rtx-20	(20% phenyl - 80% methylpolysiloxane)
Rtx-624	(6% cyanpropylphenyl – 94% methylpolysiloxane)
Rtx-35	(35% phenyl - 65% methylpolysiloxane)
Rtx-200	(trifluoropropyl methyl polysiloxane)
Rtx-50	(50% phenyl - 50% methylpolysiloxane)
Rtx-1701	(14% cyanopropylphenyl – 86% methylpolysiloxane)
Rtx-65	(65% phenyl - 35% methylpolysiloxane)
Rtx-225	(50% cyanopropylphenyl – 50% methylpolysiloxane)
Rtx-2330	(90% cyanopropylphenyl – 10% methylpolysiloxane)
Rtx-Wax	(polyethylene glycol)

Kovats Retention Index

Information on the Kovats Retention Index can be found in the links below. Using Kovats to assist with finding an alternative packed column is often much more involved than the other topics listed above.

I hope this post has provided you with helpful information as to how to proceed if a packed/micropacked column is no longer available. Thank you for reading.