Quantitative analysis of morphine in dried blood spots by using morphine-d3 pre-impregnated dried blood spot cards

Two different internal standard dried blood spot (DBS) pre-impregnation procedures (prior to blood spotting) were investigated. In the first procedure DBS pre-impregnation is performed by immersing the DBS card fully into an internal standard solution. In the second procedure pre-impregnation is performed by pipetting a certain volume of an internal standard solution onto the DBS card. Morphine-d3 was used as the model compound for all experiments. The pre-impregnation procedure by immersing was further investigated with respect to homogeneity of impregnation, influence of different blood spotting techniques and the influence of spotting different blood volumes on the internal standard distribution, calibration and stability of pre-impregnated cards. Finally, the immersing procedure was used for the analysis of morphine in dried blood spots and the results were compared to the conventional procedure in which the internal standard morphine-d3 was added to the extraction solvent. The new pre-impregnated cards couple simplicity of operation and convenient use in the field to results equivalent to the conventional procedure.     

Determination of a platelet activating factor antagonist (CV-3988): methodology and clinical application

A high-performance liquid chromatographic method was developed for determination of the platelet activating factor antagonist CV-3988 in human plasma and urine. After development of a column extraction procedure without an internal standard, a more satisfactory organic extraction procedure was set up with amiodarone as internal standard. Linearity of the calibration curves was found in the range 0.0625-10 micrograms/ml CV-3988. Reproducibility was higher than 10% for the column extraction and lower than 10% for the organic extraction procedure. Recovery of CV-3988 from plasma averaged 81.7% for the column procedure and 40% for the organic extraction. Urine samples could be extracted only by the organic extraction procedure. The organic extraction procedure was applied to the determination of CV-3988 in plasma and urine samples after intravenous administration to normal volunteers.     

Starting SCF calculations by superposition of atomic densities

We describe the procedure to start an SCF calculation of the general type from a sum of atomic electron densities, as implemented in GAMESS-UK. Although the procedure is well known for closed-shell calculations and was already suggested when the Direct SCF procedure was proposed, the general procedure is less obvious. For instance, there is no need to converge the corresponding closed-shell Hartree-Fock calculation when dealing with an open-shell species. We describe the various choices and illustrate them with test calculations, showing that the procedure is easier, and on average better, than starting from a converged minimal basis calculation and much better than using a bare nucleus Hamiltonian.     

Comparison study of RNAA and ICP-MS for the determination of ultra-traces of Th and U in geological and cosmochemical samples

In order to determine thorium and uranium traces in geochemical and cosmochemical samples, we developed an ICP-MS procedure, in which an anion-exchange step was introduced after sample digestion to separate major matrix elements, leading to decrease the dilution factor and increase the sensitivity for Th and U. The ICP-MS procedure was compared to the RNAA procedure which we recently developed for the same purpose. Both ICP-MS and RNAA procedures developed were found to yield similar detection limits (sub ppb) for Th and U.     

Enzymic analysis of organophosphate insecticides using an enzyme thermistor

Quantitative analysis of water soluble insecticides using an enzyme thermistor was examined for organophosphates. A procedure based on an insecticide hydrolyzing enzyme was found suitable for continuous determination of insecticides at concentrations down to 30 µM. A more sensitive procedure, < 3.4µM, suitable for discontinuous monitoring was developed using reversible immobilization of acetylcholine esterase.     

An Improved Method for the Determination of Molybdenum in Plants,Soils, and Rocks

Abstract

Improvements to the thiocyanate colorimetric procedure for analysis of ppm levels of molybdenum have been made. The complete procedure was studied and revisions made to the solvent extraction system to increase sensitivity. The solvent itself was stabilized by elution through an adsorption column. Revisions to the fusion procedure were made to eliminate hand fusion of samples. The use of desiceants for solvent drying was replaced by filtration before absorbance readings to eliminate turbidity. Total solution of rock samples requires a special digestion procedure with atomic absorption finish.     

Determination of Chloroacetic Acids in Drinking Water by Reaction Gas Chromatography

A procedure was developed for determining chloroacetic acids in drinking water. The procedure is based on solid-phase extraction followed by the conversion of chloroacetic acids to trifluoroacetic esters and their separation and determination by gas–liquid chromatography with an electron capture detector. Esterification conditions were optimized. The procedure was used for analyzing samples of drinking water.     

Comparison of the ammonium oxalate extraction of fertilizer for K2O, method 983.02, with the ammonium citrate/EDTA extraction, method 993.31

The direct available method for phosphorus in fertilizers, Method 960.03, is an Official Method for extraction of both P2O5 and K2O. Because K2O is much more soluble and easier to extract than P2O5, the conditions of the extraction procedure are set for efficient extraction of P2O5, and the extraction of K2O is, in effect, a bonus. In 1993, a modified extraction procedure, using an extractant of ammonium citrate/ethylenediaminetetraacetic acid (EDTA) solution, was evaluated for P2O5 and then collaboratively studied. This now-modified extraction procedure for phosphorus is Official Method 993.31, which is used extensively as an alternative to Method 960.03 for phosphorus because it is less labor-intensive. Method 993.31 was also evaluated in our laboratory for K2O extraction, but it was never formally collaboratively studied for K2O. To demonstrate the suitability of Method 993.31 as an extraction procedure for K2O, as well as P2O5 in fertilizers, Method 993.31 extraction for K2O was compared with Method 983.02, the traditional ammonium oxalate extraction procedure for K2O. A wide range of fertilizer samples was extracted by using both procedures. The t-test for samples containing < 30% K2O had a t-value of 1.23 and a probability of 0.22, which indicates there was no significant difference in the results obtained by the 2 extraction methods. The t-test for samples containing > 30% K2O had a t-value of 0.30 and a probability of 0.77, also indicating no significant difference. It is recommended that Method 983.02 be modified to include the ammonium citrate/EDTA extraction procedure as an additional option for extraction of K2O from commercial fertilizers.     

Supramolecular microextraction of cobalt from water samples before its microsampling flame atomic absorption spectrometric detection

The supramolecular solvent system consists of tetrahydrofuran (THF) and 1-decanol, that was used as an extraction solvent for a microextraction procedure for the preconcentration and separation of Co(II). The proposed supramolecular-based procedure was combined with microsampling flame atomic absorption spectrometry for the determination of cobalt at trace levels in water samples. N-Benzoyl-N,N-diisobutylthiourea was used to chelate Co(II) in an aqueous solution. Quantitative extraction efficiency was obtained at pH 6.5. The effects of analytical parameters including pH, amount of ligand, type, ratio and volume of supramolecular solvent, sample volume and interfering ions were investigated for optimisation of the procedure. The proposed supramolecular solvent-based microextraction procedure (Ss-ME) exhibits a limit of detection (LOD) of 1.29 µg L^?1 and a limit of quantification (LOQ) of 3.88 µg L^?1. The procedure was validated by addition/recovery tests and by applying TMDA 64.2 and TMDA 53.3 water certified reference materials. The microextraction method was successfully applied for the preconcentration and determination of cobalt in water samples.     

Photometric determination of mercaptans in light petroleum products

A procedure for the photometric determination of mercaptan sulfur in light petroleum products was developed. This procedure is based on the formation of colored analytical species in an aqueous extract to an alkaline solution of sodium nitroprusside. The determination level was 3 mg/L at a sample volume of 1 mL.     

Quantitative analysis of the Maksikold multicomponent anticatarrhal preparation by pH-gradient high-performance liquid chromatography

A procedure was developed for the rapid analysis of a new multicomponent anticatarrhal medication Maksikold by high-performance liquid chromatography (HPLC). The possibility of the simultaneous determination of all active substances in the preparation, including ascorbic acid, is an advantage of the proposed procedure. For the efficient resolution of the peaks of analytes and interfering additives, a mobile phase with the pH varied in the course of an experimental run was used. The procedure was used to analyze pilot samples of the preparation. The results obtained exhibit a high precision.     

Blister-colorimetric determination of phosphate ions in water,agricultural samples,and biological samples

A procedure was proposed for the determination of phosphate ions in a blister cell (pellet cartridge) with a dry reagent mixture. The procedure is suitable for the quantitative determination of phosphate in different samples using a dry reagent mixture in an ampule or a blister without dissolving the reagents. After an ampule or a blister cell was opened and several drops of a test liquid were added, a color developed, whose intensity was proportional to the concentration of phosphate ions in the solution. The solution was then diluted to 2 mL with water and analyzed by photometry. The composition of the mixture was determined, and the procedure for the quantitative determination of phosphate ions was proposed; the procedure involves the formation and reduction of phosphomolybdic acid and the use of auxiliary reagents. The error of the colorimetric determination of phosphate ions in aqueous solutions, soil extracts, and urine was estimated with the participation of inexperienced operators.     

A selective method for the determination of benzo[a]pyrene in soil using porous graphitic carbon liquid chromatography columns

A back-flushing procedure using porous graphitic carbon (PGC) HPLC columns has been used successfully for the cleanup of soil samples for the determination of benzo[a]pyrene in ppb levels by an ODS-fluorescence HPLC column. The procedure was tested on nine random soil samples taken from an industrial area of the Kingdom of Bahrain. The mean percent recovery from the PGC column was 96% and the average coefficient of variation for the whole method was 5.2%.     

Development and validation of a near infrared method for the analytical control of a pharmaceutical preparation in three steps of the manufacturing process

A near infrared diffuse reflectance spectroscopy (NIRS) procedure for the quantitative control analysis of the active compound (otilonium bromide) in a pharmaceutical preparation in three steps of the production process (blended product, cores and coated tablets) and a methodology for its validation are proposed. The analytical procedure is composed by two consecutive steps. First, the sample is identified by comparing its spectrum with a second derivative spectral library. If the sample is positively identified, the active compound is quantified by using a previously established partial least squares (PLS) calibration model. The procedure was validated by studying repeatability, intermediate precision, accuracy and linearity. To this end, an adaptation of ICH (International Conference on Harmonisation) validation methodology to an NIR multivariate calibration procedure is proposed. The relative standard error of prediction (RSEP) was < or = 1% and the suitability of the procedure for control analysis was confirmed by the results obtained analysing new production samples produced over a three-month period.     

Development and validation of a near infrared method for the analytical control of a pharmaceutical preparation in three steps of the manufacturing process

A near infrared diffuse reflectance spectroscopy (NIRS) procedure for the quantitative control analysis of the active compound (otilonium bromide) in a pharmaceutical preparation in three steps of the production process (blended product, cores and coated tablets) and a methodology for its validation are proposed. The analytical procedure is composed by two consecutive steps. First, the sample is identified by comparing its spectrum with a second derivative spectral library. If the sample is positively identified, the active compound is quantified by using a previously established partial least squares (PLS) calibration model. The procedure was validated by studying repeatability, intermediate precision, accuracy and linearity. To this end, an adaptation of ICH (International Conference on Harmonisation) validation methodology to an NIR multivariate calibration procedure is proposed. The relative standard error of prediction (RSEP) was ≤ 1% and the suitability of the procedure for control analysis was confirmed by the results obtained analysing new production samples produced over a three-month period.     

Arsenic Speciation in Water by High-Performance Liquid Chromatography with Electrothermal Atomic Absorption Detection

A procedure was developed for determining arsenite, arsenate, monomethylarsonate, and dimethylarsinite ions in natural waters in concentrations 0.05–0.07 mg/L. The procedure involved separation by high-performance liquid chromatography and off-line determination by electrothermal atomic absorption spectrometry. The procedure was used to study arsenic transformations in the aquatic ecosystem of a tailing pit of an ore-dressing industrial plant.     

Liquid Chromatographic Analysis of Ciprofloxacin and Ciprofloxacin Metabolites in Body Fluids

Abstract

An isocratic HPLC assay procedure for analysis of ciprofloxacin and three metabolites was developed. The procedure requires only dilution of bile, saliva, and urine samples prior to reverse-phase chromatography on a polystyrene-divinylbenzene (PSDVB) column; analysis of serum samples requires a cleanup step on a PSDVB cartridge prior to chromatography. The dependence of chromatographic efficiency on flow rate and temperature was investigated and the accuracy, precision, selectivity, and sensitivity of the procedure were evaluated. The developed procedure was also compared to a modified version of a published ciprofloxacin procedure that requires an octadecyl-silane (ODS) column for chromatographic separation. Similar efficiency, precision, and accuracy were observed with both procedures and both were used for analysis of clinical samples. However, the procedures were used for different purposes. The PSDVB procedure, because of more favorable column selectivity, was used to assay ciprofloxacin and its metabolites in bile, urine and saliva samples. The ODS procedure, because of a simpler serum preparation step, was used t o assay ciprofloxacin in serum samples.     

Synthesis and application of a new thiazolylazo reagent for cloud point extraction and determination of cobalt in pharmaceutical preparations

The synthesis and characterization of the reagent 2-(5-bromothiazolylazo)-4-chlorophenol and its application in the development of a preconcentration procedure for cobalt determination using flame atomic absorption spectrometry after cloud point extraction is presented. This procedure is based on cobalt complexing and entrapment of the metal chelates into micelles of a surfactant-rich phase of Triton X-114. The preconcentration procedure was optimized by using a response surface methodology through the application of the Box-Behnken matrix. Under optimum conditions, the procedure determined the presence of cobalt with an LOD of 2.8 microg/L and LOQ of 9.3 microg/L. The enrichment factor obtained was 25. The precision was evaluated as the RSD, which was 5.5% for 10 microg/L cobalt and 6.9% for 30 microg/L. The accuracy of the procedure was assessed by comparing the results with those found using inductively coupled plasma-optical emission spectrometry. After validation, the procedure was applied to the determination of cobalt in pharmaceutical preparation samples containing cobalamin (vitamin B12).     

Analysis of epinine and its metabolites in man after oral administration of its pro-drug ibopamine using high-performance liquid chromatography with electrochemical detection

Ibopamine (N-methyldopamine O,O'-diisobutyrol ester, hydrochloride) is an ester prodrug of epinine. Epinine is a cardiovascular agent used in congestive heart failure because of its dopaminergic and adrenoreceptor agonist properties. Quantitative analytical methods, using high-performance liquid chromatography coupled with electrochemical detection, were developed for the determination of epinine and its known metabolites in biological media. Epinine was extracted from human plasma and urine via an alumina adsorption procedure; this procedure was also used to estimate epinine conjugates after prior enzymatic hydrolysis. Penicillamine was added to the incubation mixture to inhibit isoquinoline production. Urinary dihydroxyphenylacetic acid levels were obtained using the same alumina adsorption procedure, while a separate analytical procedure utilizing a direct high-performance liquid chromatographic analysis of samples was developed for homovanillic acid and its conjugates. Coefficients of variation for all the assays were below 8%. These methods were used to study the pharmacokinetics and metabolic fate of epinine after oral administration of ibopamine to healthy volunteers.     

Preparation of 5-diaminomethylenebarbiturates by barbituric acid addition to carbodiimides

Through NMR spectroscopic monitoring of barbituric acid addition to carbodiimide, a general synthetic procedure for the preparation of 5-diaminomethylenebarbiturates (DABA) was developed. This procedure is very simple and applicable to the preparation of large quantities of DABA derivatives. Through an X-ray structural study of one of the DABA derivatives, it was established that these compounds have an ylide-type structure with strong charge separation within the molecule.