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PubMed2000

Assessment of the ion-trap mass spectrometer for routine qualitative and quantitative analysis of drugs of abuse extracted from urine.

The ion-trap mass spectrometer (MS) has been available as a detector for gas chromatography (GC) for nearly two decades. However, it still occupies a minor role in forensic toxicology drug-testing laboratories. Quadrupole MS instruments make up the majority of GC detectors used in drug confirmation. This work addresses the use of these two MS detectors, comparing the ion ratio precision and quantitative accuracy for the analysis of different classes of abused drugs extracted from urine. Urine specimens were prepared at five concentrations each for amphetamine (AMP), methamphetamine (METH), benzoylecgonine (BZE), delta9-carboxy-tetrahydrocannabinol (delta9-THCCOOH), phencyclidine (PCP), morphine (MOR), codeine (COD), and 6-acetylmorphine (6-AM). Concentration ranges for AMP, METH, BZE, delta9-THCCOOH, PCP, MOR, COD, and 6-AM were 50-2500, 50-5000, 15-800, 1.5-65, 1-250, 500-32000, 250-21000, and 1.5-118 ng/mL, respectively. Sample extracts were injected into a GC-quadrupole MS operating in selected ion monitoring (SIM) mode and a GC-ion-trap MS operating in either selected ion storage (SIS) or full scan (FS) mode. Precision was assessed by the evaluation of five ion ratios for n = 15 injections at each concentration using a single-point calibration. Precision measurements for SIM ion ratios provided coefficients of variation (CV) between 2.6 and 9.8% for all drugs. By comparison, the SIS and FS data yielded CV ranges of 4.0-12.8% and 4.0-11.2%, respectively. The total ion ratio failure rates were 0.2% (SIM), 0.7% (SIS), and 1.2% (FS) for the eight drugs analyzed. Overall, the SIS mode produced stable, comparable mean ratios over the concentration ranges examined, but had greater variance within batch runs. Examination of postmortem and quality-control samples produced forensically accurate quantitation by SIS when compared to SIM. Furthermore, sensitivity of FS was equivalent to SIM for all compounds examined except for 6-AM.

Gas Chromatography-Mass Spectrometry↗
PubMed1991

Validation of quantitative analysis of intravascular ultrasound images.

This study investigated the accuracy and reproducibility of a computer-aided method for quantification of intravascular ultrasound. The computer analysis system was developed on an IBM compatible PC/AT equipped with a framegrabber. The quantitative assessment of lumen area, lesion area and percent area obstruction was performed by tracing the boundaries of the free lumen and original lumen. Accuracy of the analysis system was tested in a phantom study. Echographic measurements of lumen and lesion area derived from 16 arterial specimens were compared with data obtained by histology. The differences in lesion area measurements between histology and ultrasound were minimal (mean +/- SD: -0.27 +/- 1.79 mm2, p greater than 0.05). Lumen area measurements from histology were significantly smaller than those with ultrasound due to mechanical deformation of histologic specimens (-5.38 +/- 5.09 mm2, p less than 0.05). For comparison with angiography, 18 ultrasound cross-sections were obtained in vivo from 8 healthy peripheral arteries. Luminal areas obtained by angiography were similar to those by ultrasound (-0.52 +/- 5.15 mm2, p greater than 0.05). Finally, intra- and interobserver variability of our quantitative method was evaluated in measurements of 100 in vivo ultrasound images. The results showed that variations in lumen area measurements were low (5%) whereas variations in lesion area and percent area obstruction were relatively high (13%, 10%, respectively). Results of this study indicate that our quantitative method provides accurate and reproducible measurements of lumen and lesion area. Thus, intravascular ultrasound can be used for clinical investigation, including assessment of vascular stenosis and evaluation of therapeutic intervention.

Angiography↗
PubMed2006

Quantitative analysis of residual protein contamination on reprocessed surgical instruments.

'Ready-for-use' instruments from surgical instrument trays were examined after routine cleaning and sterilization in a blinded study. These reprocessed instruments originated from five National Health Service hospital trust sterile service departments in England and Wales. Determination of residual protein and peptide contamination was carried out by acid stripping of the instrument surfaces, hydrolysis of the constituent amino acids and quantitative total amino acid analysis. One hundred and twenty instruments were analysed, and the median levels of residual protein contamination per instrument for the individual trays were 267, 260, 163, 456 and 756 microg. Scanning electron microscopy and energy dispersive X-ray spectroscopic analyses of the instruments showed that tissue deposits were localized on surfaces, but there was no significant correlation between overall protein soiling and instrument complexity. The highest levels of residual contamination were found on instruments used for tonsillectomy and adenoid surgery.

Amino Acids↗
PubMedDate not supplied

Quantitative analysis of fentanyl in pharmaceutical preparations by gas chromatography-mass spectrometry.

Fentanyl (1-[2-phenethyl]-4-N-[N-propionylanilino]piperidine) is a potent synthetic opiate commonly used for surgical analgesia and sedation. Reports of abuse of this highly addictive drug among health care personnel have prompted the need to verify the concentration in the unused portion of single-dose ampules returned to the pharmacy. We describe a simple quantitative method for the analysis of fentanyl citrate (Sublimaze) in syringes returned to the pharmacy following surgery. Fentanyl citrate (0.1 mL) and 2H5-fentanyl (internal standard, 0.05 mL, 100 mg/L) were extracted with Toxi-A tubes (Toxi-Lab, Irvine, CA) and analyzed by gas chromatography-mass spectrometry. Calibration was linear from 1 to 60 mg/L (correlation coefficient of 0.997, n = 13) and had a limit of detection of 0.4 mg/L. Mean recovery at concentrations from 5 to 50 mg/L was 89% (range, 69-104%). No interferences were found with morphine, ketamine, midazolam, sufentanil, or alfentanil. These drugs were not selected for their potential chromatographic interference but for their availability in surgical syringes. This assay is useful in verifying that any unused fentanyl is discarded according to narcotic regulations, thereby avoiding the possibility of diversion for illicit consumption.

Alfentanil↗
PubMed2004

Simultaneous quantitative analysis of isobars by tandem mass spectrometry from unresolved chromatographic peaks.

A method was developed for the simultaneous quantitation of isobars from unresolved chromatographic peaks. The method is based on differences in branching ratios of ion abundances in their tandem mass spectra and an assumption that the product ion mass spectra of a mixture can be considered as a linear combination of the spectra of individual constituents. We present analytical equations and a matrix-based approach for deconvoluting the concentration of individual components from the total peak intensity for two and three isobars and also a matrix-based generalization to any number of compounds. The feasibility of the simultaneous analysis of mixtures containing two compounds was assessed. The approach was evaluated for the analysis of structural isomers of methylmalonic and succinic acids in human plasma and urine samples for a group of 270 samples. The linear regression equation, standard error and correlation coefficient for the agreement with a traditional method utilizing chromatographic separation of the isomers were y = 0.999x - 0.005, 0.024 micro mol l(-1), and 0.985, respectively. The utility of a spectral contrast angle as a predictor of analysis feasibility was evaluated.

Algorithms↗
PubMed1997

Rapid quantitative analysis of oleandrin in human blood by high-performance liquid chromatography.

A simple and rapid method for quantitation of oleandrin in human blood has been developed using an Extrelut column and high-performance liquid chromatography (HPLC). Blood samples spiked with oleandrin were mixed with distilled water and applied to an Extrelut column for elution with ethyl acetate before HPLC. The HPLC separation of the compound from endogeneous impurities was generally satisfactory with the use of a reversed-phase column. Oleandrin showed excellent linearity in the range of 0.05-10 micrograms/g and the limit of detection was 0.02 microgram/g for human blood. The recovery of the compound, which had been spiked to human blood, was more than 90%. The present method is simple and more rapid than those so far reported, and seems useful for analysis of oleandrin in the cases of oleander poisoning.

Cardenolides↗
PubMed1991

Age-related decline in prostacyclin synthesis by human aortic endothelial cells. Qualitative and quantitative analysis.

To investigate the functional alteration of human aortic endothelial cells with aging, prostacyclin synthesis was qualitatively and quantitatively examined. The endothelial cells of human aortas and umbilical veins or inferior vena cavae were immunohistochemically examined and found positive for prostacyclin, but the intensity of aortic endothelial cells from older subjects was low. In addition to the endothelial cells, smooth muscle cells in the thickened intima, not the media, of the aorta were also immunoreactive. Endothelial cells were successfully cultured from human aortas obtained from infants through aged subjects and were subdivided into three groups: young, middle, and old. Prostacyclin synthesis by endothelial cells from all types of blood vessels was extremely great at the primary culture, but decreased abruptly in the following subcultures. Among the aortic endothelial cells, the young group synthesized the largest amount of prostacyclin in a conventional culture condition, with synthesis progressively decreasing in the older groups. The in vitro prostacyclin biosynthesis was supported by the qualitative analysis on the tissue sections. These results indicate that prostacyclin synthesis of the aortic endothelial cells decreases with age, but intimal smooth muscle cells potentially have a back-up mechanism and substitute this synthesis to some extent. The decreased synthesis of prostacyclin with age may play an important role in the development and advancement of thrombosis and atherosclerosis.

6-Ketoprostaglandin F1 alpha↗
PubMed1998

Quantitative analysis of cerebral vasculopathy in patients with Fabry disease.

OBJECTIVE: This study's purpose was to obtain a quantitative natural history of the cerebrovascular involvement in Fabry disease. BACKGROUND: Fabry disease is an X-linked recessive disorder due to alpha-galactosidase A deficiency. Progressive accumulation of ceramidetrihexoside within the intima and media of cerebral blood vessels causes ischemic lesions in the majority of affected patients. Determination of the natural history of the cerebral vasculopathy in Fabry disease is important to assess the effects of therapeutic intervention in this disorder. METHODS: A longitudinal MRI study of 50 patients who had a total of 129 MRI scans was performed. The burden of cerebrovascular disease was determined using direct linear measurement. RESULTS: On T2-weighted MRI scans, 32% of the patients had no lesions (mean age, 33 years), 16% had gray matter lesions only (mean age, 36 years), 26% had lesions in white matter only (mean age, 43 years), and 26% had lesions in white and gray matter (mean age, 47 years). Disease burden increased with age, but no patient younger than 26 had lesions on MRI. All patients older than 54 had cerebrovascular involvement. The distribution of MRI-detectable lesions was typical of a small-vessel disease. Only 37.5% of patients with cerebral lesions had neurologic symptoms. CONCLUSION: These findings provide a predictable outcome measure to assess the effect of molecular interventions on the cerebrovascular circulation in Fabry disease.

Adolescent↗
PubMed2002

Quantitative analysis of tropane alkaloids in biological materials by gas chromatography-mass spectrometry.

A simple and rapid method for quantitation of tropane alkaloids in biological materials has been developed using an Extrelut column with gas chromatography-mass spectrometry (GC-MS). Biological materials (serum and urine) were mixed with a borate buffer and then applied to an Extrelut column. The adsorbed tropane alkaloids were eluted with dichloromethane before a GC-MS analysis. Atropine-d(3) was used as an internal standard. The extracted tropane alkaloids were converted to trimethylsilyl derivatives prior to GC analysis, to improve the instability of tropane alkaloids from heating and the property of them for a GC column. The recoveries of the compounds, which had been spiked to biological materials, were more than 80%. The GC separation of the derivatives from endogenous impurities was generally satisfactory with the use of a semi-polar capillary column. Tropane alkaloids showed excellent linearity in the range of 10-5000 ng/ml and the limit of detection was 5.0 ng/ml for biological materials. The present method is simple and more rapid than those previously reported, and was applied to a poisoning case. It is useful for the routine analysis of tropane alkaloids in cases of suspected tropane alkaloids poisoning.

Aged↗
PubMed1999

Quantitative analysis of xanthohumol and related prenylflavonoids in hops and beer by liquid chromatography-tandem mass spectrometry.

A method for quantitation of six prenylflavonoids (xanthohumol, isoxanthohumol, desmethylxanthohumol, 6- and 8-prenylnaringenins and 6-geranylnaringenin) in hops and beer by HPLC-tandem mass spectrometry has been developed. The method allows direct analysis of beer and crude methanolic extracts of hops. After HPLC separation, prenylflavonoids were detected by positive ion multiple-reaction monitoring using a triple-quadrupole mass spectrometer equipped with a heated nebulizer--atmospheric pressure chemical ionization interface. The accuracy and precision were evaluated by replicate analyses of (spiked) samples. Thirteen commercial beers were analysed with the method. Isoxanthohumol, formed by isomerization of xanthohumol during the brewing process, was the most abundant flavonoid in hopped beers, ranging from 0.04 to 3.44 mg/l.

Beer↗
PubMed1995

Quantitative analysis of synaptogenesis in the inner plexiform layer of macaque monkey fovea.

Synaptogenesis has been tracked by using quantitative electron microscopic methods in the inner plexiform layer (IPL) of the developing Macaca monkey fovea from fetal day (Fd) 55 to Fd132. Vesicle-containing profiles were classified according to whether (1) they contained a ribbon indicating that they originated from a bipolar cell, or (2) the profile formed a junction. Group 2 was further subdivided by morphological characteristics into (2a) amacrine, (2b) bipolar, or (2c) unknown profiles. Ribbon-containing bipolar profiles are clearly identifiable at Fd55 when they occur at a density of 0.9/100 microns2. Bipolar synapses increase rapidly to 4.7/100 microns2 by Fd88, similar to their density at Fd132. Identifiable amacrine profiles forming a junction are rare at Fd55-68. By Fd88, amacrine synaptic density has jumped to 6.7/100 microns2 and continues to increase to 9.5/100 microns2 at Fd132. These quantitative data strongly suggest that, at the Macaca fovea, bipolar synaptogenesis both begins and ends before amacrine synaptogenesis. The large number of immature amacrine synaptic profiles and densities at Fd132 suggests that amacrine synapses continue to form after Fd132. This study confirms that cone-dominated monkey fovea has a different sequence of synaptogenesis than the rod-dominated peripheral retina (Nishimura and Rakic, [1985] J. Comp. Neurol 241:420-434). The data support the concept that synaptic developmental sequence is determined by the type of photoreceptor which dominates a particular retinal region or species. Bipolar ribbon synapses are observed in the outer half of the IPL at Fd55, are present in the inner IPL at Fd60, and then, with increasing age, are found throughout the IPL. This pattern strongly suggests that vertical OFF bipolar pathways form earlier than ON pathways in the IPL. In contrast, amacrine profiles are found throughout the IPL at the youngest ages, with an adult-like banding pattern present by Fd132.

Age Distribution↗
PubMed1989

Quantitative analysis of trazodone hydrochloride in tablets by an ion-selective electrode.

A simple assay procedure for the quantitation of trazodone hydrochloride in tablets, without prior separation, has been developed using a trazodone-selective electrode. The electrode was based on a trazodone:tetrakis(p-chlorophenyl)borate ion-pair complex, dioctyl phthalate, and polyvinyl chloride matrix that were mounted on a PTFE membrane. The electrode showed a near-Nernstian response in the range of 10(-2) to 5 x 10(-6) M trazodone over the pH range of 2.5 to 5.0, with a cationic slope of 58 mV/concentration decade. The durability of the electrode and the reproducibility of the performance among the electrodes were sufficient. The electrode was used for the determination of the pKa value of trazodone. The selectivity of the electrode to a number of interferences was investigated. Many inorganic cations (alkali and alkaline earth metals) and pharmaceutical excipients did not interfere, but some organic ammonium compounds interfered according to their extractability. Determination of 10 to 3000 micrograms/mL of trazodone hydrochloride in aqueous solution showed an average recovery of 100.6% (mean standard deviation 0.4%) by direct potentiometry. This assay was applied to determine trazodone hydrochloride in tablets and the results compared favorably with those obtained by high-performance liquid chromatography.

Chromatography, High Pressure Liquid↗
PubMed1991

Quantitative analysis of the Hopf bifurcation in the Goodwin n-dimensional metabolic control system.

We study, from a quantitative point of view, the Hopf bifurcation in an ODE model of feedback control type introduced by Goodwin (1963) to describe the dynamics of end-product inhibition of gene activity. We formally prove that the exchange of linear stability of the positive equilibrium in the n-dimensional Goodwin system with equal reaction constants coexists with a Hopf bifurcation of nontrivial periodic solutions emanating from this equilibrium, without any further restriction on the dimension n greater than or equal to 3 or on the Hill coefficient. The direction of the bifurcation and the stability and the period of the bifurcating orbits are estimated by means of the algorithm proposed by Hassard et al. (1981).

Enzymes↗
PubMed2003

A solid-phase assay for the quantitative analysis of hyaluronic acid at the nanogram level.

A sensitive and accurate solid-phase assay for the quantitative determination of hyaluronic acid (HA) is described. The wells of the polystyrene microplates used were coated with glutaraldehyde followed, via a Schiff's base bond, with spermine to introduce amino groups. HA was added to the activated microwells in the presence of carbodiimide and left to bind via a peptide bond to the amino groups. Then aggrecan solution was added to the wells of the microtiter plates to interact with its G1 domain with hyaluronic acid, and the amounts of aggrecan bound were measured immunochemically. The inhibition of the binding between aggrecan and immobilized HA due to soluble HA present in reference solutions showed linearity in the range of concentrations 0.1 to 0.7 microg/ml. The reaction is specific and rapid and can be widely used for the calculation of HA in body fluids directly and in tissue samples after a brief digestion with a proteolytic enzyme.

Biotin↗
PubMed1997

Quantitative analysis of ligand-macromolecule interactions using differential dynamic quenching of the ligand fluorescence to monitor the binding.

Quantitative analyses of the thermodynamics and kinetics of ligand-macromolecule interactions in biological systems rely predominately on monitoring changes in the spectroscopic properties of the ligand or macromolecule, particularly fluorescence changes, which accompany the formation of the studied complexes. However, in many instances the interactions do not affect the fluorescence properties of interacting species and do not provide a resolution high enough to perform quantitative and rigorous measurements of the thermodynamic and/or kinetic parameters. In this communication, we describe the theoretical and experimental aspects of a method of studying complex, multiple ligand-macromolecule interactions by the fluorescence titration technique, when the intrinsic fluorescence changes accompanying binding do not provide a resolution necessary to perform quantitative analyses. The method is based on the fact that a fluorescent ligand, or binding sites of the macromolecule, can have different accessibility to the collisional (dynamic) quencher, when involved in the complex, rather than in the free, unbound state. The presence of an external dynamic quencher in solution, i.e., the presence of an extra collisional quenching process, transforms the fluorescence of the ligand or macromolecule, intrinsically independent of the complex formation, into a property which is dramatically different in the free state than in the bound state of the fluorophore. The approach is applicable to any model of noncooperative or cooperative ligand binding to a macromolecule and allows for the optimization of the resolution of the binding or kinetic studies for a given ligand-macromolecule system. The application of the method is illustrated by applying it to the study of the binding of the fluorescent derivative of a nucleotide cofactor, epsilon ADP, to the six interacting sites of the E. coli primary replicative helicase DnaB protein hexamer.

Adenosine Diphosphate↗
PubMed2006

Quantitative analysis of microstructures by secondary ion mass spectrometry.

The focus of this review is on trace-element quantitation of microstructures in solids. This review is aimed at the nonspecialist who wants to know how secondary ion mass spectrometry (SIMS) quantitation is achieved. Despite 35 years of SIMS research and applications, SIMS quantitation remains a fundamentally empirical enterprise and is based on standards. The most used standards are "bulk standards"-solids with a homogeneous distribution of a trace element-and ion-implanted solids. The SIMS systematics of bulk standards and ion-implanted solids are reviewed.

Journal Article↗
PubMed1978

Quantitative analysis of rat liver nucleolar and nucleoplasmic ribosomal ribonucleic acids.

rRNA from detergent-purified nuclei was fractionated quantitatively, by two independent methods, into nucleolar and nucleoplasmic RNA fractions. The two RNA fractions were analysed by urea/agar-gel electrophoresis and the amount of pre-rRNA (precursor of rRNA) and rRNA components was determined. The rRNA constitutes 35% of total nuclear RNA, of which two-thirds are in nucleolar RNA and one-third in nucleoplasmic RNA. The identified pre-rRNA components (45 S, 41 S, 39 S, 36 S, 32 S and 21 S) are confined to the nucleolus and constitute about 70% of its rRNA. The remaining 30% are represented by 28 S and 18 S rRNA, in a molar ratio of 1.4. The bulk of rRNA in nucleoplasmic RNA is represented by 28 S and 18 S rRNA in a molar ratio close to 1.0. Part of the mature rRNA species in nucleoplasmic RNA originate from ribosomes attached to the outer nuclear membrane, which resist detergent treatment. The absolute amount of nuclear pre-rRNA and rRNA components was evaluated. The amount of 32 S and 21 S pre-rRNA (2.9 x 10(4) and 2.5 x 10(4) molecules per nucleus respectively) is 2-3-fold higher than that of 45 S, 41 S and 36 S pre-rRNA.

Animals↗
PubMed1988

Quantitative analysis of the thickness of human skin and subcutaneous tissue following controlled expansion with a silicone implant.

Histologic quantitation of the thickness of human tissues that were expanded using silicone expanders showed that the epidermis underwent significant thickening after 5 weeks to 5 months of expansion. The dermis and subcutaneous tissue, on the other hand, were significantly thinner after expansion. Capsules were formed in all 19 patients. The capsule was significantly thickest after 2 to 2.5 months of expansion. Expanded tissues 2 years after cessation of expansion had the same thickness as control tissues and had no remnant fibrous capsule.

Adolescent↗