Structure-retention relationships for basic drugs ... · and deconvolution power of mass...
1
Introduction The analysis of semi-volatile drug residues in toxicology often uses gas chromatography with a variety of detectors. The added data dimension and deconvolution power of mass spectrometry has lessened the need for the column to provide complete separation of analytes or orthogonality of methods for dual column identification. However, trends towards fast and multi-dimensional techniques have rekindled interest in alternatives to GC using PDMS and 5 % phenyl-PDMS phases. We describe here the influence of phase aromaticity on the relative separation of a range of analytes and the way in which phase selection can influence drug analysis. Results and Discussion Probes were analysed under identical conditions on a series of columns selected for their aromaticity (Figure 1). Alkane retention on all phases was similar suggesting that increasing aromatic content does not reduce non-polar retention (See Table) but other analytes show a marked deviation from a simple van der Waals – molecular weight relationship (Figure 2). The aromatic character of many drugs resulted in greater retention with increasing phase polarity. The trend is associated with the extent of steric hindrance around the aromatic centre and forced coplanarity (e.g. lignocaine) versus stable planarity (e.g. sulindac) . The perfluoroacylated steroids are clustered and less well retained on the basis of molecular weight than other analytes and show that reagents larger than methyl and acetoxy affect molecular weight, steric surface and volume and may also mask phase selective mechanisms. For PFPA derivatives, both π- and van der Waals type interactions are reduced by a perfluoro ‘barrier-layer’. A GCxGC space shows that increasing phase aromaticity is associated with deviation from equivalent retention (Figure 3). Orthogonality to BP1 was approached with BPX50 as elution orders were changed for several analyte pairs (Figure 4). HT8 was complimentary to BPX5 with enhanced selectivity observed for some hindered and planar analytes (e.g. diphenoxylate, sulindac and lignocaine). Retention of the aliphatic heptaminol is largely unaffected by polarity. Mechanistically, HT8 can interact with aromatics in the presence of ring substituents (e.g. halogens and sulphur substituents) that might hinder their approach to phenyl or silphenylene phases. Purely phenyl phases are restricted and are selective towards terminal phenyl groups (e.g. fenspiride). Like the carboranes, silphenylene based phases are capable of interacting with planar and mid-mounted aromatics (e.g. promazines, benzodiazepines) but are hindered by steric and free rotational barriers generated by terminal aliphatic groups (c.f. benzocaine and lignocaine). Similarly, the aromaticity of buprenorphine is masked but exposed for diphenoxylate and so the retention of the two compounds on different phases changes with the balance of non- polar, sterically hindered aromatic and planar aromatic moieties. The reversal of retention order for this pair on BPX50 is more correctly observed as greater affinity for diphenoxylate and decreased capacity for non-polar shape adaption in the rigid BPX50 ‘baskets’. Conclusion Increasing the aromatic content of the GC phase alters selectivity and may offer increased separation without increasing run time by spreading peaks across the chromatographic space. Unclustering of analytes on BPX35 and 50 is based on steric assessibility to pendant aromatic rings over core unsaturation. Both BPX35 and HT8 offer selectivity towards many drug classes without significant changes in elution order. Highly aromatic phases such as BPX50 offer a degree of orthogonality to 5 % phenyl equivalent phases and may be useful in multi-dimensional or confirmatory strategies. TP-0202-M © SGE Analytical Science Pty Ltd 02/2010 Structure-retention relationships for basic drugs separated on different GC phases Linda Glowacki 1 , John Vine 1 and Paul Wynne 2 1 Racing Analytical Services Limited, Flemington, Victoria, Australia 2 SGE Analytical Science, Ringwood, Victoria, Australia Experimental A collection of 75 drugs and steroids and 15 n-alkanes were derivatised (pentafluoropropanoylation of anabolic steroids, acetylation of bases and methylation of acids) and dissolved in ethyl acetate at concentrations of 1 µg/mL. EI-GCMS was performed on a Hewlett Packard 6890 GC - 5975 MSD equipped with a 7683B Autoinjector (Palo Alto, USA). The GC was equipped with either a BP1, BPX5, BPX35, BPX50 or HT8 column (30 m x 0.25 mm x 0.25 µm, SGE, Melbourne, Australia) and used helium as the carrier gas with a constant flow of 1.2 mL/min. The oven temperature was held at 40 °C for 2 minutes then heated at 10 °C/min to 300 °C with a final holding time of 20 minutes. Injections of 2 µL were splitless at 250 °C with a nominal head pressure of 66 kPa. A scan range of 50-550 Da at 2.48 scan/sec was used. Compound MWt BP1 BPX5 BPX35 BPX50 HT8 Nicotine 162 14.97 15.38 17.12 16.54 17.16 Ibuprofen 220 17.60 17.69 18.60 18.36 18.33 Amphetamine 177 18.09 17.46 19.67 19.76 18.94 Methamphetamine 191 18.14 18.49 20.71 20.09 20.07 Heptaminol 229 18.26 17.04 19.10 18.68 18.66 Metronidazole 213 18.49 19.43 21.66 21.83 21.08 Prolintane 217 18.65 17.46 20.03 19.09 19.64 Amylobarbitone 226 19.69 20.27 21.87 21.11 20.45 Pentobarbitone 226 19.95 20.56 21.49 21.55 20.88 Pseudoephedrine 249 20.30 20.89 23.22 22.71 22.36 Caffeine 195 20.60 21.61 23.89 24.04 23.02 Difluisal 264 21.20 21.54 22.92 22.68 22.76 Benzocaine 207 21.26 22.10 24.85 24.32 23.83 Lignocaine 234 21.30 21.68 23.72 22.92 18.66 Prilocaine 262 21.30 23.72 19.09 25.52 25.42 Diphenhydramine 255 21.45 21.77 22.92 22.94 22.55 Flufenamic Acid 295 21.52 21.70 22.79 22.49 22.85 Fenoprofen 256 21.55 21.94 23.55 23.63 22.74 Flurbiprofen 258 21.74 22.10 23.62 23.57 23.13 Niflumic Acid 296 22.24 22.43 23.65 23.41 23.87 Naproxen 244 22.62 23.06 24.81 24.86 24.30 Nefopam 253 22.80 23.43 25.77 25.30 24.58 Flunixin 310 22.90 23.09 24.37 24.17 24.42 Xylazine 220 22.90 23.45 26.12 25.58 24.85 Mepivicaine 246 23.02 23.75 26.07 25.35 25.66 Methylphenidate 275 23.13 23.81 26.44 25.96 25.38 Mefenamic Acid 255 23.47 23.81 25.46 25.49 25.00 Ketoprofen 268 23.65 24.15 26.11 26.18 25.47 Probenecid 299 24.13 24.51 26.09 25.87 26.37 Tolfenamic Acid 275 24.16 24.54 26.22 26.21 25.81 Diclofenac 310 24.44 24.83 26.78 26.93 26.12 Tiaprofenic Acid 274 24.48 25.13 27.18 27.25 26.67 Methandrostenolone 590 24.57 24.21 24.44 23.68 25.51 Eltenac 315 24.67 25.15 27.15 27.31 26.51 Imipramine 280 24.67 25.17 27.33 26.83 26.50 Methandriol 594 24.67 24.33 24.28 23.24 25.60 5(10),3β,17β-estrenediol 566 24.70 24.25 24.01 22.96 25.54 Trimipramine 294 24.86 25.21 26.36 26.37 26.36 Etodolac 301 24.86 25.10 26.68 26.72 26.47 Tolmetin 271 25.05 25.66 27.74 27.85 27.10 5β,3β,17β estranediol 568 25.05 25.07 24.64 23.25 26.71 Tetracaine 306 25.10 29.32 27.81 28.68 29.25 Meclofenamic Acid 310 25.24 25.63 27.48 27.63 27.06 Ketorolac 269 25.39 26.12 28.39 28.61 27.60 Norethandrolone 592 25.42 25.10 25.17 25.83 26.44 Ethacrynic Acid 317 25.45 25.92 27.81 27.81 27.65 Promazine 284 25.51 26.23 28.67 28.09 27.76 Phenytoin 252 25.52 26.64 29.14 29.42 27.64 Mestanolone 594 25.55 25.96 27.31 26.82 27.87 Zomepirac 305 25.74 26.32 28.37 28.48 27.76 Phenylbutazone 308 25.99 26.55 28.56 28.67 27.84 Benzydamine 309 26.05 26.78 29.24 28.68 27.85 Vedoprofen 296 26.17 26.62 28.40 28.45 27.91 1,4-androstadiene-3,17-dione 562 26.19 26.29 27.34 26.81 28.30 Methenolone 592 26.23 25.66 25.27 23.94 27.17 5β,3β,17β androstanediol 582 26.26 25.76 25.40 24.07 27.41 Diazepam 284 26.30 27.23 30.20 29.74 29.20 Methyltestosterone 592 26.34 24.35 24.35 23.41 25.49 Diazepam 284 26.53 27.38 29.52 29.74 29.20 Fenspiride 260 26.68 27.90 31.33 30.79 30.08 Chloropromazine 318 26.92 27.64 30.10 29.41 29.25 Codeine 341 26.93 27.70 30.51 29.96 29.22 Nordiazepam 270 26.97 28.06 30.48 30.78 29.74 Mesterolone 304 27.35 27.41 28.20 27.35 29.62 Procaine 278 27.70 26.43 31.21 28.31 28.18 Morphine 369 27.85 28.64 30.88 31.22 30.29 Carprofen 287 28.07 28.93 31.46 31.69 30.82 Clanobutin 361 28.26 28.89 31.16 31.31 30.48 Acepromazine 326 28.49 29.32 32.60 31.65 31.31 Indoprofen 295 28.60 32.32 29.39 32.58 31.72 Butorphanol 411 29.24 29.89 32.97 32.35 32.02 Frusemide 344 29.74 30.74 35.84 36.89 33.82 Indomethacin 371 29.75 30.42 33.83 34.20 32.61 Sulindac 370 32.16 33.61 41.78 43.16 40.07 Diphenoxylate 452 35.50 37.63 47.60 48.76 44.77 Buprenorphine 551 35.60 44.61 49.07 44.61 45.20 nonane 128 7.90 7.92 7.72 8.02 decane 142 10.00 9.81 9.45 9.79 undecane 156 11.68 11.53 11.14 11.47 dodecane 170 13.23 13.12 12.74 13.05 tridecane 184 14.66 14.58 14.25 14.56 tetradecane 198 16.00 15.94 15.66 15.96 hexadecane 226 18.45 18.44 18.24 18.84 18.50 octadecane 252 20.65 20.68 20.54 19.89 20.77 nonadecane 268 21.67 21.72 21.61 20.89 21.83 eicosane 282 22.64 22.71 22.63 22.77 22.83 docosane 310 24.46 24.56 24.55 24.50 24.72 tetracosane 338 26.12 26.25 26.29 27.58 26.45 octacosane 394 29.10 29.26 29.42 30.27 29.55 dotriacontane (C32) 450 32.07 32.38 32.81 33.85 33.05 tetracontane (C40) 560 37.35 38.31 39.47 39.07 40.13 Figure 4. Extracted ion chromatograms showing changes in retention for selected drugs on columns with different polarity. Analytes: Diacetyl heptaminol (1), lignocaine (2), benzocaine (3), fenspiride (4), sulindac (5), diphenoxylate (6) and buprenorphine (7). Figure 3. Reconstructed relative retention space for all analytes separated on BP1 and different aromatic phases. Alkane retention shown by red markers and trend line. Figure 5. Structures of selected analytes referred to in text. Figure 1. The key retentive chemistries of aromatic phases. POLYDIMETHYLSILOXANE (PDMS) PHASE (BP1) Van der Waals retention, low steric hindrance Si Si O Si O CH 3 CH 3 CH 3 CH 3 CH 3 CH 3 B B Si CH 3 CH 3 Si CH 3 CH 3 5% m-CARBORANE MODIFIED PDMS PHASE (HT8) carborane-π* retention, low steric hindrance and wide angle of approach O Si O Si CH 3 CH 3 Si O CH 3 CH 3 O Si O Si CH 3 CH 3 Si O CH 3 CH 3 CH 3 50% SILPHENYLENE AND DIPHENYL MODIFIED PDMS PHASE (BPX50) π-π* retention, moderate steric hindrance, moderate angle of approach SILPHENYLENE AND SiILPHENYLENE-PHENYL MODIFIED PDMS PHASES (BPX5 AND BPX35) π-π* retention, moderate steric hindrance, moderate - low angle of approach N H 2 C H 3 CH 3 C H 3 OH HEPTAMINOL NH 2 O CH3 O BENZOCAINE LIGNOCAINE CH3 CH 3 NH N CH 3 O CH 3 FENSPIRIDE N H O N O SULINDAC F COOH CH 3 S O CH 3 DIPHENOXYLATE CN N O O CH3 BUPRENORPHINE O N O OH OH C H 3 C H 3 C H 3 CH 3 C H 3 Figure 2. Retention relative to eicosane for all analytes on different columns. Alkane retention is shown as a van der Waals reference. Alkane retention shown by red markers and trend line, PFP-steroid retention circled with dotted line. 0.00 0.50 1.00 1.50 2.00 2.50 0 100 200 300 400 500 600 700 BP1 Relave retenon me 0 100 200 300 400 500 600 700 BPX5 indoprofen buprenorphine diphenoxylate 0.00 0.50 1.00 1.50 2.00 2.50 0 100 200 300 400 500 600 700 BPX35 Molecular weight Relave retenon me sulindac buprenorphine diphenoxylate nicone 0 100 200 300 400 500 600 700 BPX50 Molecular weight furosemide buprenorphine diphenoxylate sulindac nicone 0 100 200 300 400 500 600 700 HT8 nicone buprenorphine diphenoxylate sulindac Molecular weight 0.00 0.50 1.00 1.50 2.00 2.50 0 0.50 1.00 1.50 2.00 BPX5 steroids Relave retenon me BPX5 BPX5 drugs 0 0.50 1.00 1.50 2.00 BPX35 steroids BPX35 drugs 0.00 0.50 1.00 1.50 2.00 2.50 0 0.50 1.00 1.50 2.00 BPX50 steroids Relave retenon me BPX50 BPX50 drugs 0 0.50 1.00 1.50 2.00 HT8 steroids HT8 drugs lignocaine heptaminol Relave retenon me BP1 Relave retenon me BP1 BPX35 1 2 3 4 5 6 7 BPX50 1 2 3 4 5 6 7 HT8 1 2, 3 4 5 6 7 BPX5 1 2 3 4 5 6, 7 BP1 1 4 5 6, 7 2, 3
Transcript of Structure-retention relationships for basic drugs ... · and deconvolution power of mass...
Introduction
The analysis of semi-volatile drug residues in toxicology often uses gas chromatography with a variety of detectors. The added data dimension and deconvolution power of mass spectrometry has lessened the need for the column to provide complete separation of analytes or orthogonality of methods for dual column identification. However, trends towards fast and multi-dimensional techniques have rekindled interest in alternatives to GC using PDMS and 5 % phenyl-PDMS phases. We describe here the influence of phase aromaticity on the relative separation of a range of analytes and the way in which phase selection can influence drug analysis.
Results and Discussion
Probes were analysed under identical conditions on a series of columns selected for their aromaticity (Figure 1). Alkane retention on all phases was similar suggesting that increasing aromatic content does not reduce non-polar retention (See Table) but other analytes show a marked deviation from a simple van der Waals – molecular weight relationship (Figure 2). The aromatic character of many drugs resulted in greater retention with increasing phase polarity. The trend is associated with the extent of steric hindrance around the aromatic centre and forced coplanarity (e.g. lignocaine) versus stable planarity (e.g. sulindac) .
The perfluoroacylated steroids are clustered and less well retained on the basis of molecular weight than other analytes and show that reagents larger than methyl and acetoxy affect molecular weight, steric surface and volume and may also mask phase selective mechanisms. For PFPA derivatives, both π- and van der Waals type interactions are reduced by a perfluoro ‘barrier-layer’.
A GCxGC space shows that increasing phase aromaticity is associated with deviation from equivalent retention (Figure 3). Orthogonality to BP1 was approached with BPX50 as elution orders were changed for several analyte pairs (Figure 4). HT8 was complimentary to BPX5 with enhanced selectivity observed for some hindered and planar analytes (e.g. diphenoxylate, sulindac and lignocaine). Retention of the aliphatic heptaminol is largely unaffected by polarity.
Mechanistically, HT8 can interact with aromatics in the presence of ring substituents (e.g. halogens and sulphur substituents) that might hinder their approach to phenyl or silphenylene phases. Purely phenyl phases are restricted and are selective towards terminal phenyl groups (e.g. fenspiride).
Like the carboranes, silphenylene based phases are capable of interacting with planar and mid-mounted aromatics (e.g. promazines, benzodiazepines) but are hindered by steric and free rotational barriers generated by terminal aliphatic groups (c.f. benzocaine and lignocaine). Similarly, the aromaticity of buprenorphine is masked but exposed for diphenoxylate and so the retention of the two compounds on different phases changes with the balance of non-polar, sterically hindered aromatic and planar aromatic moieties. The reversal of retention order for this pair on BPX50 is more correctly observed as greater affinity for diphenoxylate and decreased capacity for non-polar shape adaption in the rigid BPX50 ‘baskets’.
Conclusion
Increasing the aromatic content of the GC phase alters selectivity and may offer increased separation without increasing run time by spreading peaks across the chromatographic space. Unclustering of analytes on BPX35 and 50 is based on steric assessibility to pendant aromatic rings over core unsaturation. Both BPX35 and HT8 offer selectivity towards many drug classes without significant changes in elution order. Highly aromatic phases such as BPX50 offer a degree of orthogonality to 5 % phenyl equivalent phases and may be useful in multi-dimensional or confirmatory strategies.
TP-0
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M ©
SG
E A
naly
tica
l Sci
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Pty
Ltd
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/201
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Structure-retention relationships for basic drugs separated on different GC phases
Linda Glowacki1, John Vine1 and Paul Wynne2
1Racing Analytical Services Limited, Flemington, Victoria, Australia2SGE Analytical Science, Ringwood, Victoria, Australia
ExperimentalA collection of 75 drugs and steroids and 15 n-alkanes were derivatised (pentafluoropropanoylation of anabolic steroids, acetylation of bases and methylation of acids) and dissolved in ethyl acetate at concentrations of 1 µg/mL. EI-GCMS was performed on a Hewlett Packard 6890 GC - 5975 MSD equipped with a 7683B Autoinjector (Palo Alto, USA). The GC was equipped with either a BP1, BPX5, BPX35, BPX50 or HT8 column (30 m x 0.25 mm x 0.25 µm, SGE, Melbourne, Australia) and used helium as the carrier gas with a constant flow of 1.2 mL/min. The oven temperature was held at 40 °C for 2 minutes then heated at 10 °C/min to 300 °C with a final holding time of 20 minutes. Injections of 2 µL were splitless at 250 °C with a nominal head pressure of 66 kPa. A scan range of 50-550 Da at 2.48 scan/sec was used.
Compound MWt BP1 BPX5 BPX35 BPX50 HT8 Nicotine 162 14.97 15.38 17.12 16.54 17.16Ibuprofen 220 17.60 17.69 18.60 18.36 18.33Amphetamine 177 18.09 17.46 19.67 19.76 18.94Methamphetamine 191 18.14 18.49 20.71 20.09 20.07Heptaminol 229 18.26 17.04 19.10 18.68 18.66Metronidazole 213 18.49 19.43 21.66 21.83 21.08Prolintane 217 18.65 17.46 20.03 19.09 19.64Amylobarbitone 226 19.69 20.27 21.87 21.11 20.45Pentobarbitone 226 19.95 20.56 21.49 21.55 20.88Pseudoephedrine 249 20.30 20.89 23.22 22.71 22.36Caffeine 195 20.60 21.61 23.89 24.04 23.02Difluisal 264 21.20 21.54 22.92 22.68 22.76Benzocaine 207 21.26 22.10 24.85 24.32 23.83Lignocaine 234 21.30 21.68 23.72 22.92 18.66Prilocaine 262 21.30 23.72 19.09 25.52 25.42Diphenhydramine 255 21.45 21.77 22.92 22.94 22.55Flufenamic Acid 295 21.52 21.70 22.79 22.49 22.85Fenoprofen 256 21.55 21.94 23.55 23.63 22.74Flurbiprofen 258 21.74 22.10 23.62 23.57 23.13Niflumic Acid 296 22.24 22.43 23.65 23.41 23.87Naproxen 244 22.62 23.06 24.81 24.86 24.30Nefopam 253 22.80 23.43 25.77 25.30 24.58Flunixin 310 22.90 23.09 24.37 24.17 24.42Xylazine 220 22.90 23.45 26.12 25.58 24.85Mepivicaine 246 23.02 23.75 26.07 25.35 25.66Methylphenidate 275 23.13 23.81 26.44 25.96 25.38Mefenamic Acid 255 23.47 23.81 25.46 25.49 25.00Ketoprofen 268 23.65 24.15 26.11 26.18 25.47Probenecid 299 24.13 24.51 26.09 25.87 26.37Tolfenamic Acid 275 24.16 24.54 26.22 26.21 25.81Diclofenac 310 24.44 24.83 26.78 26.93 26.12Tiaprofenic Acid 274 24.48 25.13 27.18 27.25 26.67Methandrostenolone 590 24.57 24.21 24.44 23.68 25.51Eltenac 315 24.67 25.15 27.15 27.31 26.51Imipramine 280 24.67 25.17 27.33 26.83 26.50Methandriol 594 24.67 24.33 24.28 23.24 25.605(10),3β,17β-estrenediol 566 24.70 24.25 24.01 22.96 25.54Trimipramine 294 24.86 25.21 26.36 26.37 26.36Etodolac 301 24.86 25.10 26.68 26.72 26.47Tolmetin 271 25.05 25.66 27.74 27.85 27.105β,3β,17β estranediol 568 25.05 25.07 24.64 23.25 26.71Tetracaine 306 25.10 29.32 27.81 28.68 29.25Meclofenamic Acid 310 25.24 25.63 27.48 27.63 27.06Ketorolac 269 25.39 26.12 28.39 28.61 27.60Norethandrolone 592 25.42 25.10 25.17 25.83 26.44Ethacrynic Acid 317 25.45 25.92 27.81 27.81 27.65Promazine 284 25.51 26.23 28.67 28.09 27.76Phenytoin 252 25.52 26.64 29.14 29.42 27.64Mestanolone 594 25.55 25.96 27.31 26.82 27.87Zomepirac 305 25.74 26.32 28.37 28.48 27.76Phenylbutazone 308 25.99 26.55 28.56 28.67 27.84Benzydamine 309 26.05 26.78 29.24 28.68 27.85Vedoprofen 296 26.17 26.62 28.40 28.45 27.911,4-androstadiene-3,17-dione 562 26.19 26.29 27.34 26.81 28.30Methenolone 592 26.23 25.66 25.27 23.94 27.175β,3β,17β androstanediol 582 26.26 25.76 25.40 24.07 27.41Diazepam 284 26.30 27.23 30.20 29.74 29.20Methyltestosterone 592 26.34 24.35 24.35 23.41 25.49Diazepam 284 26.53 27.38 29.52 29.74 29.20Fenspiride 260 26.68 27.90 31.33 30.79 30.08Chloropromazine 318 26.92 27.64 30.10 29.41 29.25Codeine 341 26.93 27.70 30.51 29.96 29.22Nordiazepam 270 26.97 28.06 30.48 30.78 29.74Mesterolone 304 27.35 27.41 28.20 27.35 29.62Procaine 278 27.70 26.43 31.21 28.31 28.18Morphine 369 27.85 28.64 30.88 31.22 30.29Carprofen 287 28.07 28.93 31.46 31.69 30.82Clanobutin 361 28.26 28.89 31.16 31.31 30.48Acepromazine 326 28.49 29.32 32.60 31.65 31.31Indoprofen 295 28.60 32.32 29.39 32.58 31.72Butorphanol 411 29.24 29.89 32.97 32.35 32.02Frusemide 344 29.74 30.74 35.84 36.89 33.82Indomethacin 371 29.75 30.42 33.83 34.20 32.61Sulindac 370 32.16 33.61 41.78 43.16 40.07Diphenoxylate 452 35.50 37.63 47.60 48.76 44.77Buprenorphine 551 35.60 44.61 49.07 44.61 45.20 nonane 128 7.90 7.92 7.72 8.02decane 142 10.00 9.81 9.45 9.79undecane 156 11.68 11.53 11.14 11.47dodecane 170 13.23 13.12 12.74 13.05tridecane 184 14.66 14.58 14.25 14.56tetradecane 198 16.00 15.94 15.66 15.96hexadecane 226 18.45 18.44 18.24 18.84 18.50octadecane 252 20.65 20.68 20.54 19.89 20.77nonadecane 268 21.67 21.72 21.61 20.89 21.83eicosane 282 22.64 22.71 22.63 22.77 22.83docosane 310 24.46 24.56 24.55 24.50 24.72tetracosane 338 26.12 26.25 26.29 27.58 26.45octacosane 394 29.10 29.26 29.42 30.27 29.55dotriacontane (C32) 450 32.07 32.38 32.81 33.85 33.05tetracontane (C40) 560 37.35 38.31 39.47 39.07 40.13
Figure 4. Extracted ion chromatograms showing changes in retention for selected drugs on columns with different polarity. Analytes: Diacetyl heptaminol (1), lignocaine (2), benzocaine (3), fenspiride (4), sulindac (5), diphenoxylate (6) and buprenorphine (7).
Figure 3. Reconstructed relative retention space for all analytes separated on BP1 and different aromatic phases. Alkane retention shown by red markers and trend line.
Figure 5. Structures of selected analytes referred to in text.
Figure 1. The key retentive chemistries of aromatic phases.
POLYDIMETHYLSILOXANE (PDMS) PHASE (BP1)
Van der Waals retention, low steric hindrance
SiSiO
SiO
CH3CH3
CH3
CH3
CH3CH3
B BSi
CH3
CH3
Si
CH3
CH3
5% m-CARBORANE MODIFIED PDMS PHASE (HT8)
carborane-π* retention, low steric hindrance and wide angle of approach
OSi
OSi
CH3
CH3
Si O
CH3
CH3
OSi
OSi
CH3
CH3
Si OCH3
CH3
CH3
50% SILPHENYLENE AND DIPHENYL MODIFIED PDMS PHASE (BPX50)
π-π* retention, moderate steric hindrance,moderate angle of approach
SILPHENYLENE AND SiILPHENYLENE-PHENYL MODIFIED PDMS PHASES (BPX5 AND BPX35)
π-π* retention, moderate steric hindrance,moderate - low angle of approach
N H 2
C H 3 C H 3 C H 3
O H
HEPTAMINOL
N H 2
O C H 3
O
BENZOCAINE
LIGNOCAINE
C H 3
C H 3
N H N C H 3
O C H 3
FENSPIRIDE
N H O
N
O
SULINDAC
F C O O H
C H 3
S
O
C H 3
DIPHENOXYLATE
C N
N
O
O
C H 3
BUPRENORPHINE
O
N
O
O H
O H C H 3
C H 3
C H 3
C H 3
C H 3
Figure 2. Retention relative to eicosane for all analytes on different columns. Alkane retention is shown as a van der Waals reference. Alkane retention shown by red markers and trend line, PFP-steroid retention circled with dotted line.
0.00
0.50
1.00
1.50
2.00
2.50
0 100 200 300 400 500 600 700
BP1
Molecular weight
Relative retention time
0.00
0.50
1.00
1.50
2.00
2.50
0 100 200 300 400 500 600 700
BPX5
Molecular weight
Relative retention time
indoprofen
buprenorphinediphenoxylate
0.00
0.50
1.00
1.50
2.00
2.50
0 100 200 300 400 500 600 700
BPX35
Molecular weight
Relative retention time
sulindac
buprenorphine
diphenoxylate
nicotine
0.00
0.50
1.00
1.50
2.00
2.50
0 100 200 300 400 500 600 700
BPX50
Molecular weight
Relative retention time
furosemide
buprenorphine
diphenoxylate
sulindac
nicotine
0.00
0.50
1.00
1.50
2.00
2.50
0 100 200 300 400 500 600 700
HT8
Molecular weight
Relative retention time
nicotine
buprenorphine
diphenoxylate
sulindac
0.00
0.50
1.00
1.50
2.00
2.50
0 100 200 300 400 500 600 700
BPX50
Molecular weight
Relative retention time
furosemide
buprenorphine
diphenoxylate
sulindac
nicotine
0.00
0.50
1.00
1.50
2.00
2.50
0 0.50 1.00 1.50 2.00
BPX5 steroids
Relative retention time BP1
Relative retention time BPX5
BPX5 drugs
0.00
0.50
1.00
1.50
2.00
2.50
0 0.50 1.00 1.50 2.00
BPX35 steroids
Relative retention time BP1
Relative retention time BPX35
BPX35 drugs
0.00
0.50
1.00
1.50
2.00
2.50
0 0.50 1.00 1.50 2.00
BPX50 steroids
Relative retention time BP1
Relative retention time BPX50
BPX50 drugs
0.00
0.50
1.00
1.50
2.00
2.50
0 0.50 1.00 1.50 2.00
HT8 steroids
Relative retention time BP1
Relative retention time HT8
HT8 drugs
lignocaine
heptaminol
0.00
0.50
1.00
1.50
2.00
2.50
0 0.50 1.00 1.50 2.00
HT8 steroids
Relative retention time BP1
Relative retention time HT8
HT8 drugs
lignocaine
heptaminol
0.00
0.50
1.00
1.50
2.00
2.50
0 0.50 1.00 1.50 2.00
HT8 steroids
Relative retention time BP1
Relative retention time HT8
HT8 drugs
lignocaine
heptaminol
BPX35
1
2 3 45
6 7
BPX50
1
2 3 4
5
67
HT8
1
2, 3 4 5 6 7
BPX5
1
2 3 4 5 6, 7
BP1
1
4 5 6, 72, 3
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