Planar chromatography - Current practice and future prospects

Planar chromatography, in the form of thin-layer or high-performance thin-layer chromatography (TLC, HPTLC), continues to provide a robust and widely used separation technique. It is unrivaled as a simple and rapid qualitative method for mixture analysis, or for finding bioactive components in mixtures. The format of TLC/HPTLC also provides a unique method for preserving the separation, enabling further investigation of components of interest (including quantification/structure determination) separated in both time and space from the original analysis. The current practice of planar chromatography and areas of development of the technology are reviewed and promising future directions in the use of TLC/HPTLC are outlined.

Determination of triclosan, triclocarban and methyl-triclosan in aqueous samples by dispersive liquid-liquid microextraction combined with rapid liquid chromatography

In this study, dispersive liquid-liquid microextraction (DLLME) combined with ultra-high-pressure liquid chromatography (UHPLC)-tunable ultraviolet detection (TUV), has been developed for pre-concentration and determination of triclosan (TCS), triclocarban (TCC) and methyl-triclosan (M-TCS) in aqueous samples. The key factors, including the kind and volume of extraction solvent and dispersive solvent, extraction time, salt effect and pH, which probably affect the extraction efficiencies were examined and optimized. Under the optimum conditions, linearity of the method was observed in the range of 0.0500-100 microg L(-1) for TCS, 0.0250-50.0 microg L(-1) for TCC, and 0.500-100 microgL(-1) for M-TCS, respectively, with correlation coefficients (r(2))>0.9945. The limits of detection (LODs) ranged from 45.1 to 236 ng L(-1). TCS in domestic waters was detected with the concentration of 2.08 microg L(-1). The spiked recoveries of three target compounds in river water, irrigating water, reclaimed water and domestic water samples were achieved in the range of 96.4-121%, 64.3-84.9%, 77.2-115% and 75.5-106%, respectively. As a result, this method can be successfully applied for the rapid and convenient determination of TCS, TCC and M-TCS in real water samples.

Simultaneous determination of benzo[a]pyrene and eight of its metabolites in Fundulus heteroclitus bile using ultra-performance liquid chromatography with mass spectrometry

A sensitive and fast method was developed to quantitate the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) and eight of its oxidized metabolites by ultra-performance liquid chromatography (UPLC) coupling with mass spectrometry (MS). The UPLC method, using an acetonitrile:water gradient as a mobile phase, provided baseline separation of the BaP metabolites including three BaP diones. Linearity of detection was in the range of 0.2-5.0ng/microL, and limits of detection (LOD) were lower than 0.01ng/microL for BaP and all of the metabolites except BaP tetrol. In order to test this method in environmentally relevant samples, we exposed the small fish Fundulus heteroclitus to BaP and quantitated biliary BaP metabolites. Extraction recovery of all compounds varied from 65.4+/-21.3% to 92.4+/-3.0%. In exposed fish bile, the BaP diones, BaP-7,8-dihydrodiol, and 3-hydroxy BaP metabolites predominated, existing mainly as glucuronic acid conjugates. This UPLC-MS method will be useful for further defining the roles of cytochrome P450s with both in vivo and in vitro models in the understanding of the mechanisms of metabolic activation and detoxification of BaP.

Ultra-performance liquid chromatography/tandem mass spectrometric determination of diastereomers of SCH 503034 in monkey plasma

This paper describes the development and qualification of a fast, sensitive and specific ultra-performance liquid chromatography/tandem mass spectrometric (UPLC/MS/MS) method for the determination of diastereomers of SCH 503034 in monkey plasma. The analytical method involves direct protein precipitation with a mixture of methanol/acetonitrile (10/90) containing an internal standard, followed by separation of the stereoisomers on an Acquity UPLC C(18) column and detected by selected reaction monitoring (SRM) in positive ionization mode using atmospheric pressure chemical ionization (APCI). The effects of ion-pairing agents on separation and ionization efficiency were investigated. The two diastereomers were well separated (R=1.3) with a runtime of 5 min under an isocratic condition. The method was qualified. The linear concentration range was 1-2500 ng/ml for the both stereoisomers. Inter-assay mean bias and relative standard deviation (R.S.D.) were in the range of -1.2% to 3.6% and 2.8-10%, respectively. Intra-assay mean bias and R.S.D. were in the range of -1.3% to 5.5% and 2.3-7.8%, respectively. Recoveries of the stereoisomers at concentration levels of 2.5, 50 and 1000 ng/ml were 87.2-90.0%, 89.1-90.4% and 92.3-94.3%, respectively. The LLOQ for this assay was 1 ng/ml. No matrix interferences were observed in six different sources of blank monkey plasma.

Ultra-performance liquid chromatography coupled to linear ion trap mass spectrometry for the identification of drug metabolites in biological samples

The coupling of ultra-performance liquid chromatography, operating at elevated pressures, to a linear ion trap mass spectrometer provides a high-performance system suitable for drug metabolite characterisation. This system demonstrates improved chromatographic efficiency and sensitivity and at the same time provides diagnostic MSn data often critical for metabolite structural assignment. The linear ion trap was capable of dealing with the high chromatographic efficiencies and hence narrow peak widths associated with 1.7 microm particle-packed column separations. Polarity switching and data-dependent MSn data were generated with ease, and applied to the identification of metabolites found in human plasma.

Ultra-performance liquid chromatography/tandem mass spectrometric determination of testosterone and its metabolites in in vitro samples

This paper describes the development and partial validation of a fast, sensitive and specific ultra-performance liquid chromatography/tandem mass spectrometric (UPLC/MS/MS) method for the determination of testosterone (T) and its four metabolites, 6beta-OH-T, 16alpha-OH-T, 16beta-OH-T and 2alpha-OH-T, in in vitro samples. The analytical method involves direct dilution of samples with acetonitrile containing an internal standard, followed by separation of testosterone and the four metabolites on an Acquity UPLCtrade mark C(18) column and detected by selected reaction monitoring (SRM) in positive ionization mode using turbo ionspray ionization. The parent compound and its metabolites investigated were well separated (Rs >1.5) with a run time of 4 min under a gradient condition. The method was partially validated. The linear concentration range was 0.01 to 5 microM for all the compounds of interest. Inter-assay mean bias and relative standard deviation (RSD) were in the range of -12% to 8% and 4.1% to 8.5%, respectively. Intra-assay mean bias and RSD were in the range of -8.0% to 5.2% and 3.4% to 9.6%, respectively. The lower limit of quantitation for this assay was 0.01 microM. The differences in LC/MS performance were investigated by conducting a comparison of UPLC with another method previously optimized for HPLC-based separation and quantification of testosterone and its metabolites.