Finn Tønnesen

Solid-phase microextraction for the determination of the free concentration of valproic acid in human plasma by capillary gas chromatography

The potential of solid-phase microextraction in the bioanalysis of drugs is demonstrated. The free concentration of valproic acid in human plasma was determined by equilibrium dialysis at room temperature. To the dialysate was added an internal standard and the pH was adjusted to 2.5. The polymethylsiloxane-coated fused-silica fibre of the solid-phase microextraction device was inserted into the dialysate for 3 min. The sorbed analytes were then thermally desorbed at 210 degrees C in the split-splitless injection port of the gas chromatograph, separated on a Nukol capillary column and detected with a flame ionization detector. The method was shown to be highly reproducible with a detection limit of 1 microgram/ml of free valproic acid in human plasma.

Analysis of drug seizures of heroin and amphetamine by capillary electrophoresis

Abstract Capillary electrophoresis has been used to separate heroin and amphetamine from structurally related compounds and commonly occurring adulterants in drug seizures. The method was based on micellar electrokinetic chromatography with a running buffer of pH 9.0 containing sodium dodecyl sulphate as surfactant and acetonitrile as organic modifier. The drugs were dissolved in running buffer containing crystal violet. Crystal violet was used to calculate relative migration times for drug identification and as internal standard for quantitative analysis. Both qualitative and quantitative analysis was shown to be reproducible. Because of the speed and resolving power of the method it is a powerful alternative to the high-performance liquid chromatographic and gas chromatographic methods in current use for the analysis of illicit drugs.

Determination of psilocybin in Psilocybe semilanceata using high-performance liquid chromatography on a silica column

During the last few years an increasing number of young Norwegians have used Psilocybe semilanceczta (Fr. e-r Seer.) Kummer as a narcotic. The first report on misuse of this mushroom was made in autumn 1977, and knowledge of its hallucinogenic properties has gradually become public through reports in the popular media. The ingestion of P. semilanceata has in some cases resulted in the need for treatment in hospita11,2. Many species of the genus Psilocybe are found in Norway3, but only P. semiIanceata is regarded as hallucinogenic. It occurs on grassy sites in most parts of the country from the middle of August to the middle of October. P. semilanceata is known to contain indole alkaloids, of which psilocybin is considered to be the main constituent. In order to carry out detailed studies of the potency of Norwegian P. semilanceata a quantitative method was required for the assay of psilocybin. Several methods have previously been used for analysis of the hallucinogenic components of Psiiocybe mushrooms. Both paper chromatography4vs and thin-layer chromatography 6*7 have been employed in conjunction with calorimetric reagents as well as with UV spectroscopy. Gas chromatography and gas chromatography-r&&s spcctrometry* have been applied for the analysis of psilocin and psilocybin. Recently two high-performance liquid chromatographic (HPLC) methods have been published ‘*lo White9 separated the three compounds psilocin, psilocybin . and baeocystin on a silica column, and Perkal et al. lo described the quantitation of psilocin and psilocybin by ion-exchange chromatography. We have developed a KPLC method based on a silica column which provides a simple, rapid and accurate quantitation of the psilocybin content of Norwegian P. semilanceata.

Solid-phase extraction and high-performance liquid chromatographic determination of flumequine and oxolinic acid in salmon plasma.

Two methods for determination of oxolinic acid and flumequine in salmon plasma are described. The first method applies sample pretreatment on C2 disposable solid-phase extraction columns. The second method is based on direct plasma injection and on-line sample clean-up on a polystyrene-divinylbenzene precolumn. After column-switching, the analytes are separated on a polystyrene-divinylbenzene analytical column and detected with a fluorescence detector. Validation of the methods showed good sensitivity, precision and reproducibility. Both methods are well suited for determination of plasma levels of the drugs in pharmacokinetic studies in Atlantic salmon.

Volatile oil constituents of two Thymus species from Ethiopia.

The volatile oils from Thymus schimperi Ronninger and T. serrulatus Hochst. ex Benth. (Lamiaceae) grown in Ethiopia, have been examined by means of GC and GC–MS. The main constituents of the essential oils of T. schimperi from four regions — Bale, Gonder, Shewa, and Wello — were identified as p-cymene (9–23%), γ-terpinene (8–17%), thymol (6–38%) and carvacrol (5–63%). The oil from T. serrulatus was found to contain p-cymene (13%), γ-terpinene (13%) and thymol (49%) as major components. Both species belong to the thymol–carvacrol chemotypes. Copyright

Determination of psilocybin in Psilocybe semilanceata by capillary zone electrophoresis

A capillary zone electrophoretic (CZE) method was developed for the rapid determination of psilocybin in Psilocybe semilanceata. Following a simple two step extraction with 3.0+2.0 ml methanol, the hallucinogenic compound was effectively separated from matrix components by CZE utilizing a 10 mM borate-phosphate running buffer adjusted to pH 11.5. The identity of psilocybin was confirmed by migration time information and by UV spectra, while quantitation was accomplished utilizing barbital as internal standard. The calibration curve for psilocybin was linear within 0.01-1 mg/ml, while intra-day and inter-day variations of quantitative data were 0.5 and 2.5% R.S.D., respectively. In addition to psilocybin, the method was also suitable for the determination of the structurally related compound baeocystin.

Peptide imprinted receptors for the determination of the small cell lung cancer associated biomarker progastrin releasing peptide.

Peptide imprinted polymers were developed for detection of progastrin releasing peptide (ProGRP); a low abundant blood based biomarker for small cell lung cancer. The polymers targeted the proteotypic nona-peptide sequence NLLGLIEAK and were used for selective enrichment of the proteotypic peptide prior to LCMS based quantification. Peptide imprinted polymers with the best affinity characteristics were first identified from a 96-polymer combinatorial library. The effects of functional monomers, crosslinker, porogen, and template on adsorption capacity and selectivity for NLLGLIEAK were investigated and optimized. Ultimately, a solid phase extraction method was developed for highly selective enrichment of the target peptide from tryptic digests.

Glass capillary column gas chromatography of carboxylic acids after flash-heater trimethylsilylation

Abstract Glass capillary column gas chromatography has been used for quantitative and qualitative analyses of carboxylic acids. The acids are first converted into non-polar derivatives by flash-heater derivatization, to make them more suitable for gas chromatography. Benzoic, nicotinic, salicylic, acetylsalicylic and p-aminobenzoic acids were used as model substances, and reagents suitable for forming trimethylsilyl derivatives were studied. The method was successful for benzoic, nicotinic and salicylic acid with N,O-bis(trimethylsilyl)trifluoroacetamide as derivatization reagent. With acetylsalicylic acid some decomposition to salicylic acid was observed and with p-aminobenzoic acid two derivatives were occasionally formed. Calibration graphs in the concentration range 5–50 μg/ml and the linearity up to 300 μg/ml were evaluated. The relative standard deviation for the quantitative analyses was calculated for the different acids.

Profiling of impurities in illicit amphetamine samples by high-performance liquid chromatography using column switching.

A simple high-performance liquid chromatographic method, suitable for routine profiling of impurities in illegally produced amphetamine, has been developed. Amphetamine is dissolved in acetonitrile-citrate buffer (pH 3) (2:8) and injected directly without further sample pre-treatment. The impurities are enriched on-line on a C8 extraction column, while amphetamine and polar diluents are washed out with water. After washing for 1.5 min, a six-port valve is switched and an acetonitrile-0.2 M butylamine in water (pH 8) gradient elutes the impurities from the extraction column on to a C18 analytical column where they are separated. The compounds are monitored by UV detection at 220 and 254 nm. The total extraction and analysis time is 30 min. The method allows automated extraction and analysis to be performed.

Column-switching high-performance liquid chromatographic detection of pholcodine and its metabolites in urine with fluorescence and electrochemical detection

A sensitive and selective method for the detection of pholcodine and its metabolite morphine in urine using high-performance liquid chromatography is described. It involves on-line clean-up of urine on a trace enrichment column packed with a polymeric strong cation-exchange material. Pholcodine and its metabolites were separated on two analytical columns with different selectivities. Pholcodine was detected by a fluorescence detector and morphine was detected electrochemically. One system, based on reversed-phase chromatography, applied a polystyrene-divinylbenzene column and gradient elution. The other system was based on normal-phase chromatography with a silica column and isocratic elution. Morphine was confirmed to be a metabolite of pholcodine by reversed-phase chromatography and electrochemical detection. Two unidentified metabolites of pholcodine were separated from pholcodine by normal-phase chromatography and detected by fluorescence detection.