A Sensitive Gas Chromatographic Method for the Determination of Metoprolol in Human Plasma

Abstract

A sensitive method for the determination of metoprolol in plasma has been developed. The procedure is based on gas chromatographic measurements of derivatized metoprolol, using 9-bromophenanthrene as internal standard. Metoprolol is derivatized with pentafluoropropionic anhydride. The resulting derivative gives a four-fold increase in sensitivity compared to the published methods where trifluoroacetic anhydride was used for derivatization.     

Stability-Indicating High-Pressure Liquid Chromatographic Assay for L-Lysine

Abstract

A high-pressure liquid chromatographic method for the assay of L-Lysine is described. L-lysine was derivatized by reacting with 2,4-dinitrofluorobenzene. A fixed wavelength detector (254 nm) and a LiChrosorb RP-18, 10 μm, Hibar-II column from MCB Manufacturing Chemists, Inc., was employed. The method is simple, precise, accurate and stability-indicating.     

High Performance Liquid Chromatographic Determination of Neomycin in Milk Using a Hisep Column

Abstract

A high performance liquid chromatographic (HPLC) method for the determination of neomycin in milk is described. Milk is passed directly through an amberlite CG-50 ion exchange resin column, and the neomycin which is retained on the column is derivatized with ortho-phthalaldehyde (OPA) reagent. The derivatized neomycin is eluted from the column with potassium borate buffer/methanol and analyzed by HPLC. A HISEP HPLC column with fluororoetric detection was used. Recoveries ranged from 94 to 102% in samples fortified between 0.1 to 5ppra levels. The detection limit is 50ppb.     

Detection of Anabolic Steroids By Gc/Sim/Ms With Trifluoroacetylation in Equine Plasma and Urine

ABSTRACT

A method to detect three anabolic steroids (boldenone, nandrolone and mesterolone) is presented. The anabolic steroids are isolated from equine plasma and urine by extraction with diethyl ether and C₁₈ Sep-Pak cartridge adsorption, respectively. The extracts obtained were derivatized with trifluoroacetyl anhydride and analyzed by GC/SIM/MS. The selected ion monitoring (SIM) mode was applied to increase the sensitivity and, when possible, the higher m/z ions were selected to improve identification. Stability of derivatives was good and compounds having hydroxy and conjugated ketone groups produced trifluoroacetyl ester derivatives that were also stable. Repeatability of the chromatographic analysis was evaluated on the basis of area repeatability, and the coefficient of variation obtained was lower than 4.4. The detection limit was 1 and 5 ng/ml for all the anabolic steroids studied in equine plasma and urine, respectively.     

Quantitative Analysis of Terbutaline (Bricanyl®) in Human Plasma with Liquid Chromatography and Electrochemical Detection Using On-Line Enrichment

Abstract

A liquid chromatographic method with electrochemical detection (LC-EC) has been developed for the quantitative analysis of terbuta-line in the range 5–50 pmole ml^?1 of human plasma. Terbutaline is isolated from 2 ml of plasma on an ion-exchange column and the eluate is concentrated on a hydrophobic precolumn on-line in the chromatographic system. The precolumn is then back-flushed for further separation onto a hydrophobic analytical column. The mobile phase is a methanol-aqueous buffer to which sodium perchlorate is added to achieve resolution from interfering peaks. A glassy carbon electrode is used for detection. Comparison has been made with gas chromatography-mass spectrometry (GC-MS) to examine the accuracy of the method.     

Determination of Amikacin Isomers by High Pressure Liquid Chromatography

Abstract

A high-pressure liquid chromatographic (HPLC) method for quantitative monitoring of amikacin isomers is described. Four isomers, BB-K8, BB-K29, BB-K6 and BB-K11 were applied to a silica gel column. While adsorbed, the isomers were derivatized with o-phthalaldehyde and the derivatized products eluted with ethanol. A decrease in the fluorescence of the derivatized products with time was observed. Heating at 50°C for 5 min produced products with stable fluorescence for at least three hours. Using the fluorescent properties of the amikacin derivative for detection, the four isomers of amikacin were separated by reverse phase (HPLC). A linear relationship from 1 to 10 μg/mL was obtained for all four isomers.     

Structure-retention index relationships for derivatized monosaccharides on non-polar gas chromatography columns.

A gas chromatographic method for predicting the retention index of a derivatized monosaccharide is presented. The procedures are especially useful to detect and predict minute quantities of sugars in biological or chemical samples. Monosaccharides are first converted to the alditols and then derivatized by acetylation, permethylation or silylation. The derivatized monosaccharide structure-retention index relationship that has been developed is useful in the identification of unknown monosaccharides that can be readily confirmed by gas chromatography-mass spectrometry.     

Determination of Cyanide Ion by Derivatization-Gas Chromatography

Abstract

A new gas chromatographic method is described for the determination of cyanide ion in water. Cyanide is converted to benzonitrile by reaction with aniline, sodium nitrite, and copper(II) sulfate. The resulting benzonitrile is extracted into chloroform and determined by gas chromatography with a flame ionization detector. The influences of several ions which may coexist with cyanide on this gas chromatographic method were investigated briefly.     

Determination of (E)-2,3-dichloro-4-methoxyphenyl)-2-furanylmethanone-O-[2-(diethylamino) ethyl]oxime methanesulphonate (ANP-4364) in plasma using gas chromatography with electron-capture detection

A gas chromatographic method has been developed that permits the accurate and specific determination of the antianginal agent ANP-4364 in plasma. ANP-4364 is extracted with n-hexane containing ethyl chloroformate and, after a clean-up procedure, derivatized to the trichloroethyl carbamate, which is assayed on a gas chromatograph equipped with an electron-capture detector. Accurate determinations are possible over a concentration range from 1 to 50 ng/ml of ANP-4364 in plasma with a relative standard deviation of 7.5%. The minimum detectable concentration is 0.5 ng/ml. Plasma levels of ANP-4364 in dogs receiving oral (10 mg/kg) or intravenous (0.1 mg/kg) dosing have been determined.     

A new approach to determining derivatization degree and its use for the investigation of silylation of methyltestosterone in nano-/microgram amounts

A new approach to establishing the yield of derivatization reactions of difficult-to-derivatize steroids is proposed on the basis of the comparison of the areas of chromatographic peaks between the native form of the analyte and its derivative. The influence of material to be derivatized, i.e., methyltestosterone, in an amount of 5 and 500 ng, and the time of reaction, 5–120 min, on the degree of conversion is studied. Methyltestosterone is derivatized at 80°C in a mixture of pyridine and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane. Prior to the injection of samples into the gas chromatograph, pyridine and BSTFA are replaced with an inert organic solvent, methyl tert-butyl ether. The degree of methyltestosterone derivatization is shown statistically independent of the amount of the steroid processed. The performance of the reaction for 1 h at 80°C ensures reaction yield of around 90%.     

An HPLC Assay for a Prostacyclin Analogue,Ciprostene Calcium,in Human Plasma

Abstract

A sensitive assay has been developed for the quantification of the prostacyclin analogue, ciprostene calcium, in human plasma. The method involves solid phase extraction of ciprostene calcium and internal standard, carbacyclin, from a small volume of human plasma. The extract is derivatized with 4-bramamethyl-7-acetoxycoumarin, and the derivatized product extracted with a polar solid phase cartridge and concentrated by evaporation. The final extract is separated by reversed phase HPIC and measured by a fluorimetric detector following post-column alkaline hydrolysis. The overall extraction efficiency is better than 75%, and the assay is linear over the concentration range studied (5–20 ng/ml). The limit of quantification was approximately 5 ng/ml. Ultimate sensitivity was limited by interfering peaks endogenous to the biological matrix. Coefficients of variation at mid-range concentrations are less than 10%.     

Square wave anodic stripping voltammetric determination of Pb2+ using acetylene black paste electrode based on the inducing adsorption ability of I-

In the study, we developed a simple, rapid and sensitive method for the determination of tiopronin (TP) in human plasma, which was based on derivatization with p-bromophenacyl bromide (p-BPB) followed by liquid-liquid extraction and reverse-phase HPLC-UV detection. For the first time, the p-BPB was introduced into the derivatization of TP. The thiol group of TP was trapped with p-BPB to form a TP-p-BPB adduct, which can be very suitable for UV detection. From acidified plasma samples, the derivatized TP was extracted with 5 mL dichloromethane. Effective chromatographic separation was achieved using a C18 column (DIAMONSIL 150 mm × 4 mm i.d., 5 μm) based on an acetonitrile-water-trifluoroacetic acid (40:59.88:0.12, v/v/v) elution at a flow-rate of 1 mL/min. The IS and the derivatized TP were detected at 263 nm. No endogenous substances were found to interfere. The limit of quantification for derivatized TP (TP-p-BPB) in plasma was 40 ng/mL. The calibration curve for the derivatized TP showed linearity in the range 0.04-4 μg/mL with a regression coefficient corresponding to 0.9991 and the coefficient of the variation of the points of the calibration curve being lower than 10%. Extraction recoveries of the derivatized TP in plasma were greater than 72%. The method was suitably validated and successfully applied to determination of TP in human plasma samples.     

Simultaneous Determination of Methadone,Heroin, Cocaine and their Metabolites in Urine by GC‐MS

Abstract

A gas chromatographic‐mass spectrometric (GC‐MS) method for the determination of methadone, heroin, cocaine, and their metabolites in urine using Selected Ion Monitoring (SIM) was developed. Following a liquid‐liquid extraction with Toxitubes A^® and using their deuterated analogs as internal standards, the analytes were derivatized with 99:1 (v/v) N,O‐bis‐trimethylsilyl‐trifluoroacetamide/trimethylchlorosilane and injected by hand, in the splitless mode, at 240°C and a purging time of 0.75 min. The mass selective detector was kept at 300°C and molecules were ionized in the electron impact mode, using an energy of 70 eV. The detector response was linear for all drugs studied over the range 50–1000 ng/mL.     

Gas chromatographic analysis of ketamine and norketamine in plasma and urine: nitrogen-sensitive detection

A sensitive gas chromatographic method for quantitative analysis of ketamine and norketamine in human and animal biological fluids is described. The nitrogen-sensitive detection procedure used is more stable than electron-capture detection and reduced analysis time. The method used bromo-ketamine as an internal standard for quantitation and is linear from 10-25,000 ng/ml. No interferences were shown with drugs commonly associated with cardiac surgery with cardiopulmonary by-pass. This assay is sensitive, specific, using either native or derivatized drugs and can be used for routine analysis of ketamine and norketamine in plasma or urine.     

Determination of 1,2-benzisoxazole-3-acetamidoxime hydrochloride (PE-257) in plasma using electron-capture gas chromatography

A gas chromatographic method has been developed that permits the accurate and specific determination of a new psychotropic agent, PF-257, in plasma. PF-257 is extracted with ethyl acetate from alkaline plasma and, after a clean-up procedure, derivatized with heptafluorobutyric anhydride to form 3-[(5-n-heptafluoropropyl-1,2, 4-oxadiazol-3-yl)methyl]-1,2-benzisoxazole (HOMB). The HOMB is assayed on a gas chromatograph equipped with an electron-capture detector. Accurate determinations of PF-257 are possible in the concentration range from 1-40 ng/ml with a relative standard deviation of 6.8%. The minimum detectable concentration in plasma is 0.1 ng/ml. Plasma levels of PF-257 in rats receiving intravenous or oral dosing (10 mg/kg) were determined.     

A fully validated method for the determination of lacosamide in human plasma using gas chromatography with mass spectrometry: Application for therapeutic drug monitoring

A simple gas chromatographic method with mass spectrometry detection was developed and validated for the determination of lacosamide in human plasma. Lacosamide and the internal standard, levetiracetam‐d₆, were extracted from 200 μL plasma, by a solid‐phase extraction through HF Bond Elut C₁₈ columns, and derivatized using N‐methyl‐N‐tert‐butyldimethylsilyltrifluoroacetamide with 1% tert‐butyldimethylsilylchloride in acetonitrile. The limit of quantification was found to be 0.20 μg/mL and the assay was linear up to 20.0 μg/mL with correlation coefficient ≥0.994. The intra‐ and interday precision values were <4.1% in terms of relative standard deviation (%) and the values of intra‐ and interday accuracy were found to be within –7.2 and 5.3% in terms of relative error (%). Absolute recovery of the method for lacosamide was determined at three concentration levels and ranged from 92.5 to 97.6%. The developed method uses small volumes of plasma and proved to be simple, rapid, and sensitive for the determination of lacosamide in plasma. This method can be used in routine every day analysis of plasma samples obtained from patients who follow respective antiepileptic treatment and for the investigation of clinical and forensic cases where lacosamide is involved.     

Rapid and Sensitive Analysis of Diclofenac in Human Plasma by GC/SIM/MS

ABSTRACT

An analytical method for the determination of diclofenac with tolfenamic acid as the internal standard was developed and validated in human plasma by capillary gas chromatography-mass spectrometry (GC/MS). After the addition of the internal standard, the compounds were extracted from plasma at acidic pH into diethylether, which was then evaporated to dryness. The compounds were derivatized with pentafluoropropionic anhydride (PFPA) and a mixture (1000:2:3, v/w/w) of N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), ammonium iodide (NH₄I), and dithioerythritol (DTE). They were determined by GC/MS at m/z 349 (a molecular ion) for diclofenac and m/z 270 (a base ion) for tolfenamic acid. The recovery of this procedure was 97.8%, and the linearity for calibration was 0.9907 as the coefficient factor. The detection and quantitation limits were 0.1 and 0.5 ng/mL, respectively.     

A Rapid and Quantitative Gas Chromatographic Determination of Glutamine in the Presence of Glutamic Acid

Abstract

Glutamine can be converted to a stable volatile derivative by treatment with methanol and acetic anhydride. The method is suitable for the quantitative gas chromatographic determination of glutamine in the presence of glutamic acid.     

Permethylated cyclodextrins in the GC separation of racemic mixtures of volatiles: Part 1

The chromatographic separation of racemic mixtures of volatile compounds by 2,3,6-trimethyl-α-, β- and γ-cyclodextrins is discussed. Columns were prepared by mixing the derivatized cyclodextrin with OV-1701 or hydroxy-terminated OV-1701 (OV-1701-OH) following Schurig's method [1]. About 130 racemates with widely differing structures were used to test the performances of 2,3,6-permethylated-α, β- and, γ-cyclodextrins mixed with the polysiloxane polymers in different ratios. The influence of the different types of cyclodextrin on racemate separation is shown, and some phenomena which might be helpful in the elucidation of the chromatographic behavior involved are also described. The influence both of the percentage of cyclodextrin in the polysiloxane, and of the operating conditions (carrier gas, flow rate, and temperature) in the separation of flavor and fragrance racemates is also evaluated.     

Gas Chromatographic Determination of Hexamethylene Bisacetamide in Plasma and Urine

Abstract

A rapid, simple and specific gas chromatographic method has been developed to measure the differentiating agent hexamethylene bisacetamide (HMBA) in biological samples. Addition of a homolog as an internal standard, ultrafiltration and then direct packed column GC-FID analysis of the ultrafiltrate gives a detection limit of less than 50 μg/ml (0.25 mM) for HMBA in plasma or urine. Ultrafiltration is quantitative and assay precision is better than 4.3% for the 1–5 mM range. This method has been applied to determine the bolus dose pharmacokinetics and disposition of HMBA in a single small animal such as a rat. The developed assay should be suitable for therapeutic monitoring of human patients undergoing HMBA treatment.