Polymeric C18 Research Articles

Whiter and Greener RP-HPLC Method for Simultaneous Determination of Dorzolamide, Brinzolamide, and Timolol Using Isopropanol as a Sustainable Organic Solvent in the Mobile Phase

A sustainable reversed-phase chromatographic method has been developed and validated for the simultaneous determination of three active pharmaceutical ingredients, dorzolamide, brinzolamide, and timolol, used to treat glaucoma. The eco-friendly solvent isopropanol has been used as an organic mobile phase constituent. According to the Hansen space green solvent selection tool, isopropanol has a G score of 6.5, comparable to ethanol, which has a G score of 6.6. The mobile phase consists of isopropanol: aqueous sodium acetate buffer (0.1 M, pH 4.25) in the ratio of 10:90 (v/v). The flow rate was maintained at 1 mL/min. Dorzolamide and brinzolamide were detected at 254 nm, and timolol was detected at 295 nm. A high-purity silica with a polymeric C18 modification column (150 × 4.6 mm, 5 µm particle size) was used for this separation. The three compounds were eluted within 8 min. The method was validated according to ICH guidelines. The calibration curves were linear in the range of 20–70 µg/mL, 40–140 µg/mL, and 20–70 µg/mL for dorzolamide, brinzolamide, and timolol, respectively. The LODs were found to be 1.61 µg/mL, 1.60 µg/mL, and 3.16 µg/mL for dorzolamide, brinzolamide, and timolol, respectively. Good accuracy and precision were obtained for the three compounds. The greenness and whiteness of the method were indicated using the AGREE, ChlorTox, and RGB12 tools.

Maximizing two-dimensional liquid chromatography peak capacity for the separation of complex industrial samples

We report on a study on the use of 2D-LC in industry wherein we maximized the peak capacity by serially coupling up to six 15 cm long columns in the 1st dimension. For the considered aromatic amine oligomer sample, the combination of reverse phase pentafluorophenyl column providing selectivity based on π–π interaction in the 1st and a more retaining reverse phase polymeric C18 column in the 2nd dimension proved to give the highest orthogonality, calculated to be 0.82. Whereas a 1D run on a single column revealed around 120 compounds, the optimized 2D-LC system revealed around 940 compounds. To achieve this, flow splitting to improve the peak capacity in the 1st dimension and shifting gradients in the 2nd dimension were used. The overall peak capacity of the system was calculated to be 11,000 with correction for orthogonality and undersampling. The total analysis time with the 6-column system was around 20 h.

Simultaneous Capillary Liquid Chromatography Determination of Drugs in Pharmaceutical Preparations Using Tunable Platforms of Polymethacrylate Monolithic Columns Modified with Octadecylamine

Nowadays, analytical techniques tend to develop cheap and green approaches to reduce the costs and minimize environmental impacts. In this study, poly(glycidyl methacrylate-co-ethylene dimethacrylate) monoliths were prepared in capillary columns (0.25 mm i.d. × 20 cm length) as reactive and tunable platforms, and then simply functionalized based on a ring-opening reaction of epoxide with octadecylamine. The columns were successfully used as reversed-phase stationary phases for determination of ascorbic acid, paracetamol, caffeine, aspirin, and ibuprofen in pharmaceutical combinations. The synthesized monoliths have been estimated by FT-IR spectroscopy, SEM and specific surface area; also, the porous and hydrodynamic properties have verified the differences before and after modification. While the columns before modification were unable to separate the drugs, the columns after amination allowed for the complete separation of the five drugs in about 10 min at 23 µL min−1 flow rate with chromatographic resolution more than 2.12. The developed assay showed excellent suitability (RSDs < 2.6%), wide linear ranges (0.07–300 µg mL−1), sensitive detection limits (0.022–0.060 µg mL−1), good repeatability (RSDs < 4.76%) and acceptable columns reproducibility (RSDs < 18.58%). The method was successfully applied for commercial pharmaceutical preparations; the average recovery values were found to be in the range of 98.03–104.54% (RSDs < 5.51%). The satisfactory recovery percentages along with the perfect correlation between the retentions of standard compounds and the active ingredients extracted from the commercial tablets indicate the accuracy and selectivity of the developed method. The prepared columns and validated method were finally compared with previous reports, particularly commercial C18 stationary phases. This is a very useful comparison due to the structural similarity between the prepared polymeric materials and C18 particulate stationary phases. The prepared capillary columns exhibited various advantages such as the fast separation time, wide linear ranges, low analysis costs, and trivial environmental wastes.

Development of a Reversed-Phase Liquid Chromatography and Fluorescence Method with Multichannel Selective Wavelength Detection for the Determination of Benzo[a]pyrene and Six of Its Isomers

The baseline separation of benzo[a]pyrene in complex samples via reversed-phase liquid chromatography (RPLC) is particularly challenging due to the potential for interferences from other molecular mass (MM) 252 (g mol− 1) polycyclic aromatic hydrocarbons (PAHs). The work presented here explores the use of different types of RPLC stationary phases and different fluorescence (FL) detection conditions for application to method development. Six different stationary phases were investigated with SRM 869b and SRM 1647f for potential use in the development of PAH methods: polymeric C18, monomeric C18, narrow pore C30, wide pore C30, phenylhexyl, and pentafluorophenyl phases. Although the best chromatographic separation was obtained with the polymeric C18 stationary phase, seven MM 252 PAH isomers were not fully resolved and selective detection was utilized to eliminate interferences. Stop-flow fluorescence (excitation and emission) spectra were recorded for the seven PAHs; these spectra differed significantly among the isomers. Based on these spectra, the appropriate excitation/emission wavelengths were determined to be 406/440 nm, 243/509 nm, and 290/411 nm. These conditions were used in the new RPLC/FL method and the seven MM 252 PAH isomers were baseline resolved in their respective chromatograms. The new RPLC/FL method was used to identify the MM 252 PAHs in a diesel particulate extract (SRM 1975).

Risk assessment of pharmaceutically active compounds (PhACs) in the Klang River estuary, Malaysia.

The concentration profile, distribution and risk assessment of pharmaceutically active compounds (PhACs) in the coastal surface water from the Klang River estuary were measured. Surface coastal water samples were extracted using offline solid phase, applying polymeric C18 cartridges as extraction sorbent and measuring with liquid chromatography mass spectrometry-mass spectrometry (LC MS-MS) technique. Extraction method was optimized for its recovery, sensitivity and linearity. Excellent recoveries were obtained from the optimized method with percentage of recoveries ranging from 73 to 126%. The optimized analytical method achieved good sensitivity with limit of detection ranging from 0.05 to 0.15ngL-1, while linearity of targeted compounds in the LC MS-MS system was more than 0.990. The results showed that amoxicillin has the highest concentration (102.31ngL-1) followed by diclofenac (10.80ngL-1) and primidone (7.74ngL-1). The percentage of contribution (% of total concentration) for the targeted PhACs is in the following order; amoxicillin (92.90%) > diclofenac (3.95%) > primidone (1.23%) > dexamethasone (0.75%) > testosterone (0.70%) > sulfamethoxazole (0.33%) > progesterone (0.14%). Environmental risk assessment calculated based on deterministic approach (the RQ method), showed no present risk from the presence of PhACs in the coastal water of Klang River estuary. Nonetheless, this baseline assessment can be used for better understanding on PhACs pollution profile and distribution in the tropical coastal and estuarine ecosystem as well as for future comparative studies.

Revisiting shape selectivity in liquid chromatography for polycyclic aromatic hydrocarbons (PAHs) – six-ring and seven-ring Cata-condensed PAH isomers of molecular mass 328 Da and 378 Da

The relationship of reversed-phase liquid chromatography (RPLC) retention on a polymeric C18 stationary phase and the shape of polycyclic aromatic hydrocarbons (PAHs) was investigated for three-ring to seven-ring cata-condensed isomers. We report the first RPLC separation for six-ring and seven-ring cata-condensed PAH isomers. Correlations of LC retention and shape parameters (length-to-breath ratio, L/B and thickness, T) were investigated for 2 three-ring isomers (molecular mass 178Da), 5 four-ring isomers (molecular mass 228Da), 11 five-ring isomers (molecular mass 278Da), 17 six-ring isomers (molecular mass 328Da), and 20 seven-ring isomers (molecular mass 378Da). Significant linear correlations were found for all isomer groups (r=0.71 to 0.94). Nonplanarity of the PAH isomers was found to influence retention (i.e., nonplanar isomers eluting earlier than expected based on L/B) and linear correlations of retention vs. T for isomer groups containing nonplanar isomers were significant (r=0.71 to 0.86). Graphical abstract.

Retention behavior of isomeric polycyclic aromatic sulfur heterocycles in reversed-phase liquid chromatography

Retention indices for 70 polycyclic aromatic sulfur heterocycles (PASHs) were determined using reversed-phase liquid chromatography (LC) on a monomeric and a polymeric C18 stationary phase. Molecular shape parameters [length, breadth, thickness (T), and length-to-breadth ratio (L/B)] were calculated for all the compounds studied. Correlations between the retention on the polymeric C18 phase and PASH geometry (L/B and T) were investigated for six specific PASH isomer groups with molecular mass (MM) 184Da, 234Da, 258Da, 284Da, 334Da, and 384Da. Similar to previous studies for polycyclic aromatic hydrocarbons (PAHs), PASH elution order on the polymeric C18 phase was generally found to follow increasing L/B values. Correlation coefficients for retention vs L/B ranged from r=0.45 (MM 184Da) to r=0.89 (MM 284Da). In the case of smaller PASHs (MM≤258Da), the location of the sulfur atom in the bay-region of the structure resulted in later than expected elution of these isomers based on L/B. In the case of the larger PASHs (MM≥284Da), nonplanarity had a significant influence on earlier than predicted elution based on L/B values.

Retention behavior of alkyl-substituted polycyclic aromatic sulfur heterocycles in reversed-phase liquid chromatography

Retention indices for 79 alkyl-substituted polycyclic aromatic sulfur heterocycles (PASHs) were determined by using reversed-phase liquid chromatography (LC) on a monomeric and polymeric octadecylsilane (C18) stationary phase. Molecular shape parameters [length, breadth, thickness (T), and length-to-breadth ratio (L/B)] were calculated for all the compounds studied. Based on separations of isomeric methylated polycyclic aromatic hydrocarbons on polymeric C18 phases, alkyl-substituted PASHs are expected to elute based on increasing L/B ratios. However, the correlation coefficients had a wide range of values from r=0.43 to r=0.93. Several structural features besides L/B ratios were identified to play an important role in the separation mechanism of PASHs on polymeric C18 phases. First, the location of the sulfur atom in a bay-like-region results in alkylated-PASHs being more retentive than non-bay-like-region alkylated-PASHs, and they elute later than expected based on L/B value. Second, the placement of the alkyl group in the k region of the structure resulted in a later elution than predicted by L/B. Third, highly nonplanar methyl-PASHs (i.e., 1-Me and 11-MeBbN12T) elute prior to the parent PASH (BbN12T).

Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure

Separation of diastereomers of dl-α-tocopherol was studied by reversed-phase liquid chromatography using three types of stationary phases, polymeric ODS, polymeric C30, and monomeric ODS. Polymeric ODS stationary phase (Inertsil ODS-P, 3mmID, 20cm) was effective for the separation of the isomers created by the presence of three chiral centers on the alkyl chain of synthetic dl-α-tocopherol. Considerable improvement of the separation of isomers was observed on ODS-P phase at high pressure and at low temperature. Complete separation of four pairs of diastereomers was achieved at 12.0°C, 536bar, while three peaks were observed when the separation was carried out either at 12.0°C at low pressure or at 20°C at 488bar. Higher temperature (30.0°C) with the ODS-P phase resulted in only partial separation of the diastereomers even at high pressure. Only slight resolution was observed for the mixture of diastereomers with the C30 stationary phase (Inertsil C30) at 12.0°C and 441bar, although the stationary phase afforded greater resolution for β- and γ-tocopherol than ODS-P. A monomeric C18 stationary phase did not show any separation at 12.0°C and 463bar. The results suggest that the binding site of the polymeric ODS-P phase is selective for flexible alkyl chains that provided the longest retention for the natural form, (R,R,R) form, and the enantiomer, (S,S,S) form, of dl-α-tocopherol.

Preparation and chromatographic evaluation of new branch-type diamide-embedded octadecyl stationary phase with enhanced shape selectivity

A novel branch-type diamide-embedded octadecyl stationary phase was prepared by facile amidation. The preparation of this new phase involves the synthesis of new bifunctional silane ligand and surface modification of spherical silica via anchoring of silane coupling agent. The obtained diamide-embedded octadecyl stationary phase demonstrated excellent hydrophobic selectivity, as well as enhanced shape and planarity selectivity in comparison to commercial polymeric and monomeric C18 phases, respectively, as revealed by the systematic investigation into its liquid chromatographic retention of isomeric polycyclic aromatic hydrocarbons. The applicability of this new stationary phase was further testified by the effective separation of isomeric compounds belong to different chemical classes, including chain isomers of alkylbenzenes, and positional isomers of substituted aromatics. An in-depth analysis of the separation mechanisms other than molecular shape recognition involved in the new stationary phase was performed using a linear solvation energy relationships model and compared with its monoamide and pure C18 counterparts correspondingly. The performance of the new stationary phase in quantitative analysis of phenols from real-world samples was also evaluated.

Chlorophylls Contents in &lt;i&gt;Echinocactus grusonii&lt;/i&gt; Extract

Currently, Golden Barrel cactus extract is formulated in dietary supplements, on account of its powerful weight loss profit and antioxidant activity. Golden Barrel cactus grusonii (Echinocactus grusonii), a Thai cultivar Golden Barrel cactus which is known as the golden barrel Golden Barrel cactus was therefore investigated for total chlorophylls with the aim of developing as a dietary supplement in future. The chlorophyll contents of 3 and 6 years Echinocactus grusonii extracts were evaluated by High Performance Liquid Chromatography with a Grace-Vydac 201TP54 reversed-phase polymeric C18 column. The results showed that chlorophyll a and chlorophyll b are the main components of Echinocactus grusonii crude extracts also at higher level at age 3 years. It was found that the main chlorophylls contents are chlorophyll a and chlorophyll b at 2.94±0.55μg/ml and 1.63±0.14 μg/ml for 3 years Echinocactus grusonii. In addition, the amount of chlorophyll a and chlorophyll b show lower content at 1.11±0.25μg/ml and 0.67±0.01μg/ml for 6 years Echinocactus grusonii. In conclusion, Echinocactus grusonii age 3 years crude extracts showed total chlorophylls contents higher than at age 6 years. The phytochemical profile study of Echinocactus grusonii age 3 years and 6 years crude extracts are planned in the near future.

Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure

A high-density, polymeric C18 stationary phase (Inertsil ODS-P) or a polymeric C30 phase (Inertsil C30) provided improved resolution of the isomeric fatty acids (FAs), FA methyl esters (FAMEs), triacylglycerols (TAGs), and tocopherols with an increase in pressure of 20–70MPa in reversed-phase HPLC. With respect to isomeric C18 FAMEs with one cis-double bond, ODS-P phase was effective for recognizing the position of a double bond among petroselinic (methyl 6Z-octadecenoate), oleic (methyl 9Z-octadecenoate), and cis-vaccenic (methyl 11Z-octadecenoate), especially at high pressure, but the differentiation between oleic and cis-vaccenic was not achieved by C30 phase regardless of the pressure. A monomeric C18 phase (InertSustain C18) was not effective for recognizing the position of the double bond in monounsaturated FAME, while the separation of cis- and trans-isomers was achieved by any of the stationary phases. The ODS-P and C30 phases provided increased separation for TAGs and β- and γ-tocopherols at high pressure. The transfer of FA, FAME, or TAG molecules from the mobile phase to the ODS-P stationary phase was accompanied by large volume reduction (−30∼−90mL/mol) resulting in a large increase in retention (up to 100% for an increase of 50MPa) and improved isomer separation at high pressure. For some isomer pairs, the ODS-P and C30 provided the opposite elution order, and in each case higher pressure improved the separation. The two stationary phases showed selectivity for the isomers having rigid structures, but only the ODS-P was effective for differentiating the position of a double bond in monounsaturated FAMEs. The results indicate that the improved isomer separation was provided by the increased dispersion interactions between the solute and the binding site of the stationary phase at high pressure.

Determination of triterpenoic acids in fruits of Ziziphus jujuba using HPLC-MS with polymeric ODS column

A simple and sensitive method has been developed to simultaneously determine betunilic acid, oleanolic acid and ursolic acid in the fruits of Ziziphus jujuba from different regions by HPLC-MS. This HPLC assay was performed on PAH polymeric C18 bonded stationary phase column with mobile phase contained acetonitrile-water (90: 10) and with negative ESI detection mode. The developed approach was characterized by short time consumption for chromatographic separation, high sensitivity and good reliability so as to meet the requirements for rapid analysis of large-batch fruits of Z. jujuba from different habitats.

Determination of oleanolic acid and ursolic acid in Chinese medicinal plants using HPLC with PAH polymeric C18

Background:The RP-HPLC resolution of two triterpenic acid isomers was unstable. Objective: To separate the oleanolic acid (OA) and ursolic acid (UA) simply within RP-HPLC.Materials and Methods:The separation ability of five stationary phases was studied with the retention effect of their carbon loads. Also the resolution effects of mobile phase composition and different column temperatures were systematically investigated by using Drylab® (Rheodyne LLC.) after evaluating chromatograms automatically.Results:The best available resolution of two bioactive isomers was achieved (r = 3.4) via using PAH (polycyclic aromatic hydrocarbons) polymeric C18 bonded phase column. The chromatographic system was applied to the quantification in ten Chinese medicinal plants and the validation was carried out and the precision (RSD ≤1.34%), the linearity (r ≥ 0.9998) and the recovery (range from 92.1% to 102.6%) were acceptable.Conclusion:It is clear that the method was simple, rapid and reliable for the quantification of two compounds in new HPLC method within PAH polymeric C18.

Molecular Shape Recognition through Self-Assembled Molecular Ordering: Evaluation with Determining Architecture and Dynamics

The relationship between molecular gel-forming compound-based double-alkylated L-glutamide-derived functional group-integrated organic phase (Sil-FIP) structure and chromatographic performance is investigated and compared with widely used alkyl phases (C(30), polymeric and monomeric C(18)) as references. The functional group-integrated molecular gel on silica is chemically designed newly in a way that the weak interaction sites are integrated with high orientation and high selectivity can be realized by multiple interactions with the solutes. Its functions can be emphasized by being immobilizable with a terminal carboxyl group and the fact that five amide bonds including β-alanine subunit are integrated per molecule. Furthermore, its self-assembling function can be detected by monitoring of the chiroptical property. Temperature-dependent circular dichroism (CD) intensity was determined as an indicator of chirality for the gel forming compounds. (13)C cross-polarization magic angle spinning (CP/MAS) NMR spectra of the Sil-FIP phase indicate that predominance of gauche conformations exists at higher temperature (above 30 °C). (29)Si CP/MAS NMR were carried out to investigate the degree of cross-linking of the silane and silane functionality of the modified silica. Temperature-dependent (13)C CP/MAS NMR and suspended-state (1)H NMR measurements of the Sil-FIP phase exhibit the dynamic behavior of the alkyl chains. To correlate the NMR and CD results with temperature-dependent chromatographic studies, standard reference materials (SRM 869b and SRM 1647e), column selectivity test mixture for liquid chromatography was employed. Additional shape selectivity text mixtures were also used to clarify the mechanism of shape selectivity performance of Sil-FIP compared with commercially available columns. The evaluation with the spectroscopic and chromatographic analyses presents very important information on the surface morphology of the new organic phase and the molecular recognition process. Integrated and ordered functional groups were investigated to be the main driving force for very high molecular shape selectivity of the Sil-FIP phase.

An improved high performance liquid chromatography–diode array detection–mass spectrometry method for determination of carotenoids and their precursors phytoene and phytofluene in human serum

An improved high performance liquid chromatography–diode array detection–mass spectrometry method was developed for determination of various carotenoids and their precursors phytoene and phytofluene in human serum. A polymeric C30 column and mobile phase of (A) methanol/acetonitrile/water (84:14:4, v/v/v) and (B) dichloromethane (100%) were employed with the gradient condition of 100% A and 0% B initially, raised to 10% B at 4min, 18% B at 12min, 21% B at 17min, 30% B at 20min and maintained until 25min and increased further to 39% B at 28min, 60% B at 40min and returned to 100% A and 0% B at 45min. A total of 30 carotenoids, including 6 all-trans forms, 20 cis-isomers, 2 β-carotene epoxides, phytoene and phytofluene, were resolved within 45min at a flow-rate of 1mL/min, column temperature 25°C and detection wavelengths 450, 348 and 286nm. Identification of carotenoids was carried out by comparing retention behavior, absorption and mass spectral data with those of reference standards, isomerized standards and reported values. An internal standard parared was found appropriate for quantitation of all the carotenoids. The developed method provided high sensitivity with low detection and quantitation limits (2–14 and 6–43ng/mL), high recovery (91–99%), and small intra-day and inter-day variations (0.14–6.01% and 0.31–7.28%). Application of the developed method to Taiwan subjects supplemented with carotenoid-rich capsules revealed β-carotene plus its cis isomers as well as epoxide derivatives to be present in largest amount (1069.8–2783.1ng/mL) in serum, followed by lutein plus its cis isomers (511.6–2009.5ng/mL), phytofluene plus its cis isomer (515.0–1765.0ng/mL), lycopene plus its cis isomers (551.1–1455.1ng/mL), β-cryptoxanthin plus its cis isomers (458.0–965.0ng/mL), all-trans-zeaxanthin (110.0–177.0ng/mL), phytoene (41.8–165.0ng/mL) and all-trans-α-carotene (37.5–95.9ng/mL).

Screening and Determination of Polycyclic Aromatic Hydrocarbons in Seafoods Using QuEChERS-Based Extraction and High-Performance Liquid Chromatography with Fluorescence Detection

A rapid, sensitive, and accurate method for the screening and determination of polycyclic aromatic hydrocarbons (PAHs) in edible seafood is described. The method uses quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction and HPLC with fluorescence detection (FLD). The method was developed and validated in response to the massive Deepwater Horizon oil spill in the Gulf of Mexico. Rapid and highly sensitive PAH screening methods are critical tools needed for oil spill response; they help to assess when seafood is safe for harvesting and consumption. Sample preparation involves SPE of edible seafood portions with acetonitrile, followed by the addition of salts to induce water partitioning. After centrifugation, a portion of the acetonitrile layer is filtered prior to analysis via HPLC-FLD. The chromatographic method uses a polymeric C18 stationary phase designed for PAH analysis with gradient elution, and it resolves 15 U.S. Environmental Protection Agency priority parent PAHs in fewer than 20 min. The procedure was validated in three laboratories for the parent PAHs using spike recovery experiments at PAH fortification levels ranging from 25 to 10 000 microg/kg in oysters, shrimp, crab, and finfish, with recoveries ranging from 78 to 99%. Additional validation was conducted for a series of alkylated homologs of naphthalene, dibenzothiophene, and phenanthrene, with recoveries ranging from 87 to 128%. Method accuracy was further assessed based on analysis of National Institute of Standards and Technology Standard Reference Material 1974b. The method provides method detection limits in the sub to low ppb (microg/kg) range, and practical LOQs in the low ppb (microg/kg) range for most of the PAH compounds studied.

Novel Approach for the Separation of Shape-Constrained Isomers with Alternating Copolymer-Grafted Silica in Reversed-Phase Liquid Chromatography

This paper describes a novel packing material for high selective reversed-phase high-performance liquid chromatography (RP-HPLC). The organic phase on silica is chemically designed in a way that the weak interaction sites are integrated with high orientation along the polymer main chain and high selectivity can be realized by multiple interactions with solutes. For the above purpose, we synthesized poly(octadecyl acrylate-alt-N-octadecylmaleimide)-grafted silica (Sil-poly(ODA-alt-OMI)) stationary phase. The alternating copolymerization was carried out from 3-marcaptopropyltrimethoxysilane (MPS)-modified silica via surface-initiated radical-chain transfer reaction. Elemental analysis, diffuse reflectance infrared Fourier transform (DRIFT),(1)H NMR, solid-state (13)C cross polarization magic angle spinning (CP/MAS) NMR, and suspended-state (1)H NMR were used to characterize the new organic phase. Aspects of shape selectivity was evaluated with Standard Reference Material (SRM 869b), Column Selectivity Test Mixture for Liquid Chromatography. Enhanced molecular shape selectivity was observed, that lead to the separation of SRM 1647e (16 polycyclic aromatic hydrocarbons, PAHs) in an isocratic elution. The effectiveness of this phase was also demonstrated by the separation of several beta-carotene and tocopherol isomers. The complete baseline separation of the tocopherol isomers was achieved using the Sil-poly(ODA-alt-OMI) phase. Chromatographic study revealed that Sil-poly(ODA-alt-OMI) has extremely high separation ability compared to monomeric and polymeric C(18) columns. Higher shape selectivity of the new RP material can be explained by a pi-pi and dipole-dipole interaction mechanism.

Determination of the class III antiarrhythmic drugs dronedarone and amiodarone, and their principal metabolites in plasma and myocardium by high-performance liquid chromatography and UV-detection

Dronedarone, a noniodinated benzofuran derivative of amiodarone, is believed to have a better side effect profile, and is currently undergoing phase III clinical trials. A novel method was developed for the determination of dronedarone and its principal metabolite debutyldronedarone in both plasma and myocardial tissue by high-performance liquid chromatography (HPLC) coupled with UV-detection. The assay was also validated for determination of amiodarone and desethylamiodarone. Samples were obtained from healthy humans (plasma) and goats (plasma and myocardium). Sample preparation included deproteinization with acetonitrile and extraction with a mixture of heptane and dichloromethane (50/50, v/v). Chromatographic separation was performed on a Pathfinder PS polymeric C18 column (50 mm × 4.6 mm, 2.5 μm) with a mobile phase of acetonitrile, isopropanol, water and ammonia (80/10/10/0.025, v/v/v/v) at a flow-rate of 1 ml/min. Calibration curves of all analytes were linear in the range of 0.01–5 μg/ml for plasma samples, with a lower limit of quantification (LLOQ) of 0.04 μg/ml. For myocardial tissue samples, linear curves of all analytes were observed in the range of 0.02–500 μg/g, with a LLOQ of 0.08 μg/g. Within- and between-day precision was <18%, and within- and between-day accuracy ranged from 97.5 to 109.7%, with a recovery of 67.6–79.9%. The present method enables sensitive and specific detection of dronedarone, amiodarone and principal metabolites in plasma as well as myocardial tissue.

Separation of free sterols by high temperature liquid chromatography

Increasing the column temperature accelerates markedly elution in HPLC. The separation of five free sterols was studied on three packing materials that can withstand high temperatures. These stationary phases included graphitic carbon, a polymeric C18 silica, and a zirconia-based adsorbent. Measurements of retention data were made at up to 150 °C with mobile phases of different compositions. Since the columns tested afford different retention mechanisms, a variety of elution patterns were observed, with some being more advantageous than others for certain sterol separations. Effects observed include some selectivity improvements and some elution order reversals. The separation of free sterols in selected fruit juices is also presented. Albeit at the expense of a longer analysis time, the graphitic carbon column produced the best separation of the sterols in this study.