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PubMed1993

Ion-exchange liquid chromatographic analysis of bisphosphonates in pharmaceutical preparations.

A simple, fast and uniform method has been developed for the quantitative determination of bisphosphonates in the quality control of pharmaceutical preparations. The method is based on ion-exchange liquid chromatography with conductivity detection. Separation is performed on a Waters IC-PAK Anion column using 2 mM nitric acid or 25 mM succinic acid as the mobile phase. Retention of the bisphosphonates can be influenced by pH and the anion concentration of the mobile phase. Sensitivity and selectivity are sufficient for the assay of bisphosphonates in bulk drug and pharmaceutical preparations. Sample preparation comprises dissolution or dilution of the sample in the mobile phase followed, if necessary, by filtration prior to HPLC analysis. Since the method is stability indicating, it is also well suited for shelf-life studies of bisphosphonate pharmaceutical preparations. Validation of the analytical method for the assay of pamidronate injection indicated an intra-day reproducibility of 1.7% (n = 6) and an inter-day reproducibility of 2.7% (n = 6). A linear relationship between response and concentration was found in the concentration range studied from 200 ng to 10 micrograms pamidronate per 20 microliters injected. The lower limit of detection (signal-to-noise ratio = 3) of pamidronate was about 100 ng.

Chemistry, Pharmaceutical↗
PubMed2004

Rapid gas chromatography-mass spectrometry screening method for human pharmaceuticals, hormones, antioxidants and plasticizers in water.

A rapid gas chromatography-mass spectrometry (GC-MS) method was developed and validated allowing quantification at the ng/l level of 19 analytes in water including human pharmaceuticals, hormones, antioxidants and a plasticizer. On-line continuous liquid-liquid extraction with dichloromethane of 10-401 unfiltered water samples was used to achieve a 10000-40000-fold concentration factor. No sample cleanup or derivatization was required. Recoveries ranged from 57 to 120%. Application of the method to water recycling plant effluent demonstrated the presence of nearly all targeted compounds at ng/l to microgram/l levels. Screening for nontarget compounds in the treated effluent samples indicated the method could be readily extended to include additional analytes.

Antioxidants↗
PubMed1999

On-line combination of aqueous-sample preparation and capillary gas chromatography.

An overview is presented of methods currently in use to combine the preparation of aqueous samples on-line with capillary gas chromatography. Two approaches can be distinguished: heartcut-orientated reversed-phase liquid chromatography-gas chromatography (GC) and analyte-isolation-orientated analyte extraction-GC. These approaches either use techniques in which water is directly introduced onto the GC column, or an indirect approach in which water is eliminated, i.e., by solid-phase extraction, solid-phase microextraction or liquid-liquid extraction, prior to introduction of the analytes onto the GC column. The latter type of approach is much more successful and user friendly, and many applications have been reported.

Chromatography, Gas↗
PubMed2000

Optimization of the extraction of polycyclic aromatic hydrocarbons from wood samples by the use of microwave energy.

A simple and rapid microwave-assisted extraction (MAE) procedure was developed and optimized for benzo[a]anthracene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene in wood samples. The spiked wood used was prepared 3 months before analysis to simulate weathering processes and to allow the formation of analyte-matrix interaction. The samples, immersed in acetonitrile were irradiated with microwaves in a closed-vessel system. Optimization of the method was achieved by using a factorial design approach on parameters such as extraction time, temperature and sample amount. The analysis of extracts has been carried out by reversed-phase high-performance liquid chromatography with fluorescence detection for quantification and UV-diode-array detection for confirmation. The MAE procedure yielded extracts that could be analyzed directly without any preliminary clean-up or solvent exchange steps.

Chromatography, High Pressure Liquid↗
PubMed2004

A pilot study of routine quality control of sampling by the SAD method, applied to packaged and bulk foods.

A recently proposed method of looking at sampling uncertainty has been tested by its application to the sampling and analysis of several types of food and an animal feedstuff. In this 'SAD' method, increments comprising the conventional sample (that is, collected in the fashion prescribed by the standard sampling protocol) are allocated to either of two equal sized 'splits', which are prepared and analysed separately. The absolute difference between the analytical results for the two splits (the split absolute difference, or SAD) is plotted on a one-sided control chart. A non-compliance indicates that the combined uncertainty of sampling or analysis is larger than expected and the result of the measurement (the mean of the two split results) is possibly not fit for purpose. In addition, the SAD results give rise to a rugged estimate the uncertainty associated with the sampling protocol, often a major part of the total measurement uncertainty.

Animals↗
PubMed2005

Study of acrylamide in coffee using an improved liquid chromatography mass spectrometry method: Investigation of colour changes and acrylamide formation in coffee during roasting.

An improved analytical method for the determination of acrylamide in coffee is described using liquid chromatography coupled to mass spectrometric detection (LC-MS). A variety of instant, ground and laboratory roasted coffee samples were analysed using this method. The sample preparation entails extraction of acrylamide with methanol, purification with Carrez I and II solutions, evaporation and solvent change to water, and clean-up with an Oasis HLB solid-phase extraction (SPE) cartridge. The chromatographic conditions allowed separation of acrylamide and the remaining matrix co-extractives with accurate and precise quantification of acrylamide during MS detection in SIM mode. Recoveries for the spiking levels of 50, 100, 250 and 500?microg/kg ranged between 99 and 100% with relative standard deviations of less than 2%. The effects of roasting on the formation of acrylamide and colour development were also investigated at 150, 200 and 225 degrees C. Change in the CIE (Commission Internationale de l'Eclairage) a* colour value was found to show a good correlation with the change in acrylamide. CIE a* and acrylamide data was fitted to a non-linear logarithmic function for the estimation of acrylamide level in coffee. Measured acrylamide levels in commercial roasted coffees compared well with the predicted acrylamide levels from the CIE a* values.

Acrylamide↗
PubMed1980

Use of a GC concentrator to improve analysis of low levels of airborne hydrazine and unsymmetrical dimethylhydrazine.

New findings from animal studies indicate that there is a serious cancer risk associated with exposures to hydrazines. In June, 1978, NIOSH announced more restrictive occupational exposure levels for these compounds. Adherence to these limits requires improved analytical methodology. This paper describes a modified method for monitoring hydrazine and unsymmetrical dimethylhydrazine in atmospheric samples below the ceiling concentrations recommended by NIOSH. The method utilizes a GC concentrator for which a "trap" (ventable GC precolumn) was prepared and tested. Using this trap, up to 40 microL sample injections (injections much too large for conventional GC work) are effectively chromatographed. Presented are data on the overall efficiency of the method for airborne hydrazine and unsymmetrical dimethylhydrazine in the concentration ranges of 0.02 - 0.67 mg/m3 and 0.04 - 1.04 mg/m3, respectively.

Air Pollutants↗
PubMed1983

Determination of azarole plus its reduction product by HPLC.

An analytical methodology for the assay of azarole plus its reduced product in plasma was developed. The method consists of oxidation of the sample with potassium ferrocyanide, extraction, and subsequent analysis by high performance liquid chromatography. Assays of prepared plasma samples demonstrated an overall precision of +/- 6.2%; accuracy ranged from -9.1% low to 5.1% high, based on mean values at several concentrations. Analysis of variance for the effects of concentration, time, and the interactive term concentration X time were all insignificant.

Chromatography, High Pressure Liquid↗
PubMed1995

Peroxisome proliferators differentially regulate long-chain acyl-CoA thioesterases in rat liver.

We have investigated the effects of peroxisome proliferators on rat liver long-chain acyl-CoA thioesterase activities. Subcellular fractionations of liver homogenates from control, clofibrate- and di(2-ethylhexyl)phthalate-treated rats confirmed earlier studies which demonstrated that peroxisome-proliferating drugs induce long-chain acyl-CoA thioesterase activity mainly in the mitochondrial and cytosolic fractions. The aim of the present study was to investigate whether the induced activities were due to increases in normally expressed enzymes, or due to induction of novel enzymes. To investigate whether structurally different peroxisome proliferators differentially induced thioesterase activities, we tested the effects of di(2-ethylhexyl)phthalate (a plastisizer) and the hypolipidemic drug clofibrate. For this purpose, we established an analytical size exclusion chromatography method. Chromatography of solubilised mitochondrial matrix proteins showed that the activity in control mitochondria was mainly due to enzymes with molecular masses of about 50 kDa and 35 kDa. The activity in samples prepared from clofibrate- and di(2-ethylhexyl)phthalate-treated rats eluted as proteins of about 40 kDa and 110 kDa. Highly purified peroxisomes contained two peaks of activity, which were not induced, that corresponded to molecular masses of 40 kDa and 80 kDa. The 80-kDa peak was shown to be due to dimerization by addition of glycerol. Chromatography of cytosolic fractions from control rat livers indicated the presence of long-chain acyl-CoA thioesterases with molecular masses of approximately 35 kDa and 125 kDa and a broad peak corresponding to a high-molecular-mass protein. The activity in cytosolic fractions from peroxisome-proliferator-treated rats eluted mainly as peaks corresponding to 40, 110 and 150 kDa. In addition, in the 110-kDa peak, a different degree of induction and different chain-length specificities were caused by clofibrate and di(2-ethylhexyl)phthalate, suggesting that these peroxisome proliferators differentially regulate the cytosolic acyl-CoA thioesterase activities. Western blot analysis showed that enzymes in the 40-kDa peak of the peroxisomal and cytosolic fractions were structurally related, but not identical, to a 40-kDa mitochondrial very-long-chain acyl-CoA thioesterase. Our data show that the increased acyl-CoA thioesterase activities in mitochondria and cytosol were mainly due to induction of acyl-CoA thioesterases which are not, or only weakly, expressed under normal conditions.

Animals↗
PubMed1971

A quantitative method for blood lipoproteins using cellulose acetate electrophoresis.

A rapid, inexpensive, and quantitative method is described for obtaining the levels of plasma very low, low, and high density lipoproteins using cellulose acetate electrophoresis and lipid assays without prior separation by ultracentrifuge or other techniques. It involves separation of the lipoproteins by cellulose acetate electrophoresis, followed by their identification with the ozone-Schiff reaction. The total lipoprotein concentration is estimated from the total plasma phospholipid, and the percentage of each component obtained by densitometric analysis of the stained electrophoretograms, using reflected light. For samples with a raised level of very low density lipoprotein, plasma triglyceride analysis is also required. The results obtained by the cellulose acetate electrophoresis method are in good agreement with those by the analytical ultracentrifuge and the preparative ultracentrifuge with refractometry. The theoretical assumptions on which the method is based have been shown to be valid.

Cellulose↗
PubMed2006

Application of mass spectrometry for metabolite identification.

Metabolism studies play a pivotal role in drug discovery and development. Characterization of metabolic "hot-spots" as well as reactive and pharmacologically active metabolites is critical to designing new drug candidates with improved metabolic stability, toxicological profile and efficacy. Metabolite identification in the preclinical species used for safety evaluation is required in order to determine whether human metabolites have been adequately tested during non-clinical safety assessment. From an instrumental standpoint, high performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) dominates all analytical tools used for metabolite identification. The general strategies employed for metabolite identification in both drug discovery and drug development settings together with sample preparation techniques are reviewed herein. These include a discussion of the various ionization methods, mass analyzers, and tandem mass spectrometry (MS/MS) techniques that are used for structural characterization in a modern drug metabolism laboratory. Mass spectrometry-based techniques, such as stable isotope labeling, on-line H/D exchange, accurate mass measurement to enhance metabolite identification and recent improvements in data acquisition and processing for accelerating metabolite identification are also described. Rounding out this review, we offer additional thoughts about the potential of alternative and less frequently used techniques such as LC-NMR/MS, CRIMS and ICPMS.

Animals↗
PubMed1998

Illegal use of beta-adrenergic agonists in the United States.

Clenbuterol (CBL) is a member of the class of drugs called beta-agonists, which have powerful desirable and undesirable effects. Clenbuterol has the ability to increase muscle mass and residues in tissue of treated animals but can cause symptoms of acute poisoning in people. Symptoms, but no deaths, from CBL residue-induced food poisoning have been reported from investigations of separate events in Spain and France. In 1991, FDA sent letters to all states and USDA/FSIS advising them of the possibility of illegal CBL use in domestic animals and of our concern about adverse effects on public health if residue was present in food. The FDA asked U.S. Customs to be alert to attempts at illegal importation and to advise that we were prepared to investigate distribution, sale, or use of the drug. Analytical methods are available to assay for CBL residue in edible tissues and in the retinal tissues of the eye. Methods are being developed for assay of noninvasive samples such as hair. Residues of CBL have been found in one sample of edible tissue and several samples of retinal tissues from show animals and in some classes of commercial meat-producing animals. Several individuals have been found guilty of distributing CBL, cases are pending, and investigations are continuing. It is possible that CBL will be approved for safe conditions of use. The scenario of ultimately one or more beta-agonist drugs approved for legal use in food-producing animals and the probable continued availability of several illegal analogs will be a challenging containment task for regulators and the leaders of the meat-producing livestock industries.

Adrenergic beta-Agonists↗
PubMedDate not supplied

Kuwait's total diet study: dietary intake of organochlorine, carbamate, benzimidazole and phenylurea pesticide residues.

The State of Kuwait in cooperation with the U.S. Food and Drug Administration (FDA) conducted a Total Diet Study (TDS) to estimate intakes of pesticide residues by the population. The levels of organochlorine (OC) pesticides, carbamates, benzimidazoles, and phenylureas in the TDS core list are reported here. The TDS core list was established through a national food consumption survey. All food items (140 for the Kuwaiti adult) were prepared as eaten and analyzed for the pesticides mentioned above. The FDA's multiresidue methods in Volume I of the Pesticide Analytical Manual were used in gas, liquid, and gel permeation chromatographic analyses. Only vegetable and fruit samples contained pesticide residues (mg/kg), including the carbamates 1-naphthol (1.4) and 3H-carbofuran (0.94) in carrots; the OC pesticide vinclozolin (0.47), 3H-carbofuran (0.66), and fenuron (0.6) in kiwi fruit; the OC pesticide procymidone (0.32) and carbendazim (0.5) in grapes; 3H-carbofuran (5.0) in apricots; the OC pesticides captan (0.013) and thiabendazole (0.63) in pears; captan (0.035) in plums; and carbendazim (0.4) in mandarin oranges. The levels of 3H-carbofuran found in both apricots and kiwi fruit exceeded the maximum residue limits (MRLs) of the Food and Agriculture Organization/World Health Organization (FAO/WHO) of the United Nations. The daily intakes of pesticides by the different population groups are discussed in light of the FAO/WHO acceptable daily intakes.

Benzimidazoles↗
PubMedDate not supplied

A statistical model to evaluate analyte homogeneity for a material.

An underlying assumption for collaborative studies is that the analyte variation among test samples of the material (i.e., matrix and analyte concentration combination) under study has a negligible influence on the estimates of precision for the method. This assumption is expected to be fulfilled when the material under study is prepared (i.e., thoroughly mixed) such that the analyte is distributed uniformly throughout the matrix. Statistical design and intra-class correlation analysis procedures are proposed to assess the similarity or agreement among analytical results among- and within-containers for single and multiple occasions of use (e.g., collaborative and proficiency studies).

Chemistry Techniques, Analytical↗
PubMedDate not supplied

Rapid gas chromatographic method using nitrogen-phosphorus detection for N-nitrosodimethylamine in 2,4-D and MCPA herbicide formulations.

A simple and rapid analytical method has been developed for the determination of N-nitrosodimethylamine (NDMA) in amine salts of phenoxy herbicide formulations of 2,4-D and MCPA, plus mixtures of these with mecoprop and dicamba amine salts. Sample preparation consists of direct extraction using pre-packed disposable extraction tubes eluted with dichloromethane followed by cleanup on a disposable silica gel mini-column using ethyl acetate as eluting solvent. Samples are injected on-column for gas chromatography with a Megabore fused silica column; the NDMA is measured by a thermionic specific detector (TSD) that is selective for nitrogen-phosphorus (NP). A detection limit of 0.1 microgram/mL was easily attainable without any concentration step because the solvent volume is minimal. TSD and thermal energy analyzer (TEA) results have been compared and confirmed by gas chromatography/mass spectrometry. Recovery studies were performed as well as a reproducibility study on one of the 2,4-D formulations.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1987

A commercial electrochemical method evaluated for measurement of iron status.

I evaluated a commercial electrochemical method (Environmental Science Associates), based on potentiostatic coulometry, for determining iron and total iron-binding capacity (TIBC). The method requires 25 and 100 microL of serum, respectively, for these measurements. Serum iron concentrations so determined in 99 normal volunteers satisfactorily correlated with those determined by the Iron Panel Method (Br J Haematol 1978;38:291-4), although the former required correction for lower-than-expected values. The coulometric TIBC results, on the other hand, correlated poorly with those by the Iron Panel Method. However, when the samples for TIBC were prepared according to the Iron Panel Method, by using the magnesium carbonate technique, and then read in the coulometer, there was satisfactory correlation between TIBC values as determined by the two methods. Variability and analytical recovery of the electrochemical method are satisfactory, and the method should be useful for measurement of serum iron when only relatively small volumes of blood are available.

Adolescent↗
PubMed1980

[Comparison of methods of determination of serum doxycyline assessing relative bioavailability of two commercial formulations (author's transl)].

The present study was undertaken to evaluate the accuracy of the analytical results of an investigation of relative bioavailability of two doxycycline preparations. Six methods in four laboratories were applied: one fluorimetric, three high-pressure-liquid-chromatographic and three microbiological methods. The analyses were performed after coding the samples. In all cases the two preparations were bioequivalent. When comparing the methods, it could be shown that the fluorimetric method was slightly more accurate than the others. The HPLC-methods were almost as accurate. The results of the microbiological determinations showed the lowest accuracy. Two of the results were in good agreement with the biochemical methods, whereas the third showed such a high deviation that a comparison was no longer possible. Altogether a good agreement of all compared methods (except one) could be demonstrated.

Biological Assay↗
PubMed1993

Serum concentrations of retinol, d-alpha-tocopherol and beta-carotene: effects of storage at -70 degrees C for five years.

To investigate the effects of prolonged storage of serum samples at -70 degrees C on concentrations of micronutrients, we measured concentrations of retinol, d-alpha-tocopherol, and beta-carotene in serum samples drawn in 1986. We compared values we measured in 1991 to values we obtained in 1986, using the same analytical methods. The relative concentrations obtained in 1991 (mean +/- S.D.) were: retinol 99.7 +/- 12.6% (n = 23), d-alpha-tocopherol 100.7 +/- 6.4% (n = 19), and beta-carotene 103.4 +/- 13.7% (n = 28). Using these techniques of sample preparation and high-performance liquid chromatographic analysis, we found that the effects of storage of serum at -70 degrees C for five years appear insignificant in a small population of patients. However, we did identify clinically important changes in concentration (> 20% difference) in several individual subjects.

Blood Preservation↗