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

23 Nov 2022
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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.

  1. Look for a similar capillary column.
  2. Look for a similar liquid phase/solid support and/or uncoated packing.
  3. 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.

  1. USP Table
  2. McReynolds Constants/Values Table
  3. Application Chromatograms
  4. Rohrschneider Polarity Scale
  5. 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.