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PubMed1989

High-performance liquid chromatographic/mass spectrometric and high-performance liquid chromatographic/tandem mass spectrometric analysis of carbamate pesticides.

The thermospray ionization mass spectra of selected carbamate pesticides were obtained using both single-stage and triple-stage quadrupole mass spectrometry in conjunction with high-performance liquid chromatography. With the use of the single-quadrupole mass spectrometer and ammonium acetate as the mobile phase, enhanced sensitivity for the analytes of interest was obtained by monitoring the relatively intact [M + 1]+ or [M + 18]+ adduct ions. Further structural characterization of the carbamates was not readily obtainable owing to the lack of diagnostic bond cleavages. The single-stage quadrupole analyses were therefore complemented by triple-stage quadrupole analyses. Here, collisionally activated daughter ion spectra exhibited structure-specific fragmentations. In addition, the enhanced selectivity and specificity provided by tandem mass spectrometry allowed use of the technique as a rapid screening tool for carbamates without the need for the chromatographic separation step.

Carbamates↗

PubMed1986

The biological performance of calcium phosphate ceramics in an infected implantation site: I. Biological performance of hydroxyapatite during Staphylococcus aureus infection.

In the present study the biological performance of macroporous and dense hydroxyapatite after implantation in the rat middle ear was evaluated during an induced Staphylococcus aureus middle ear infection. The course of the infection was similar to that in the absence of an implant. Hydroxyapatite was frequently integrated with fibrous ingrowths in the middle ear lumen, originating solely from the infection. Good epithelial covering of the implant with all types of epithelial cells of importance for middle ear defence, was found. Increase of the exudate in the pores due to the infection was relatively small, and most of the exudate was restricted to pores on the implant surface. The bony tissue in the pores was not influenced significantly by the induced infection. Degradation of hydroxyapatite was consistent with earlier results obtained in the non-infected middle ear. The results obtained so far suggest that hydroxyapatite is highly suitable for middle ear implantation.

Animals↗

PubMed1986

The biological performance of calcium phosphate ceramics in an infected implantation site. III: Biological performance of beta-whitlockite in the noninfected and infected rat middle ear.

The biological performance of macroporous beta-whitlockite implanted in the rat middle ear was evaluated. The material was studied in the non-infected middle ear and in middle ears infected by Staphylococcus aureus. beta-whitlockite was quickly covered by a normal mucosa. One week post-operatively the macropores were filled with exudate, fibrous tissue, and a small quantity of bone. Six months after the operation the greater part of the macropore area was filled with bone (74%); fibrous tissue accounted for 20%, and exudate for 5%. In histological sections, the macropore area of beta-whitlockite had increased by 68% after six months, indicating biodegradation. Macrophages and multinucleated cells were present in the vicinity of the implant and played a role in this biodegradation. Besides cytoplasmic vacuoles containing calcium phosphate, the cells showed smaller granules containing trace elements originally present in the implant material, such as silicon, titanium, aluminum, iron, and magnesium.

Animals↗

PubMed2001

Factors determining the performance of triple quadrupole, quadrupole ion trap and sector field mass spectrometers in electrospray ionization tandem mass spectrometry of oligonucleotides. 1. Comparison of performance characteristics.

The performance of triple-stage quadrupole (TSQ), quadrupole ion trap (QIT), and double focusing sector field (DFSF) mass spectrometers for the generation of fragment ions to obtain sequence information about oligonucleotides was compared. Upon electrospray ionization (ESI), the charge-state distribution of candidate precursor ions not only varied significantly with the type of mass spectrometer, but also with the size and sequence of the investigated oligonucleotides. While concentration limits of detection for an octanucleotide were in the 100 pmol/L range on the QIT and in the 5-10 nmol/L range on the TSQ and DFSF instruments, those of a 24-mer were in the 2-13 nmol/L range on all three instruments. Reproducibility of mass determination, an important prerequisite for reliable identification of fragment ions, was highest on the TSQ with 0.0037% relative standard deviation over three days. Finally, the tandem mass spectra of a dimethoxytritylated pentanucleotide recorded on the three instruments were compared. Relatively simple spectra dominated by complete series of fragment ions of the (a-B) and w type were obtained on the QIT. Complete series of (a-B) and w ions were also observed on the TSQ. However, additional fragments belonging to the b, c, d, x and z series were found in the spectrum. In the spectrum recorded after in-source fragmentation in the DFSF, only fragments corresponding to the loss of a nucleobase and a complete series of w ions were observed. All three mass spectrometers were suitable for the generation of fragment ions, from which the complete nucleotide sequence of the pentanucleotide could be deduced.

Amino Acid Sequence↗

PubMed2002

Amino acid and peptide conjugates of protoporphyrin: preparation and analysis by high-performance liquid chromatography, high-performance liquid chromatography/electrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Amino acid and peptide conjugates of protoporphyrin have been prepared by reacting protoporphyringen with cysteine, glutathione and peptides containing a free thiol group under acidic conditions. The conjugates were formed by the addition of the thioamino acids or peptides to the vinyl groups of protoporphyrin during the autoxidation of protoporphyinogen to protoporphyrin and is free-radical-mediated. The conjugates were separated by high-performance liquid chromatography (HPLC) and characterized by HPLC/electrospray ionization mass spectrometry (HPLC/ESI-MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). All the conjugates formed were diconjugates consisting of diastereoisomers.

Chromatography, High Pressure Liquid↗

PubMed1991

Prognostic significance of the Karnofsky Performance Status score in patients with acute myocardial infarction: comparison with the left ventricular ejection fraction and the exercise treadmill test performance. The MILIS Study Group.

The prognostic significance of functional status has not been previously studied in the setting of acute myocardial infarction. We assessed the Karnofsky Performance Status (KPS) score, a simple functional status scale that is commonly used to categorize physical ability, in 849 patients with acute myocardial infarction who were enrolled in the Multicenter Investigation of the Limitation of Infarct Size (MILIS) study. We then compared the KPS score with other predictors of prognosis in these patients. In patients who presented with acute myocardial infarction, a lower KPS score (less than 8 on a scale of 1 to 10) 3 weeks before the index infarction was associated with a higher incidence of congestive heart failure, in-hospital cardiac arrest, and mortality during hospitalization, as compared with patients with KPS scores greater than or equal to 8 (each p less than 0.001). Cumulative 1-year and 4-year mortality rates were significantly higher in patients with KPS scores less than 8, as compared with patients with KPS scores greater than or equal to 8 (42.5% vs. 12.6% at 1 year and 61.6% vs 25.1% at 4 years, respectively; both p less than 0.001). The left ventricular ejection fraction on admission was significantly lower in patients with KPS scores less than 8, as compared with those with KPS scores greater than or equal to 8 (p less than 0.019). The cumulative mortality rate was equally well predicted by low KPS score and by left ventricular ejection fraction (both p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Disability Evaluation↗

PubMed1991

Identification of aromatic moieties and mycosamine in antifungal heptaenes with high-performance liquid chromatography, high-performance liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry.

A high-performance liquid chromatographic (HPLC) method for the determination of the aromaticity of heptaene polyene antibiotics has been developed. The released aromatic moiety of the heptaene polyenes aureofungin, candicidin, candimycin, hamycin and trichomycin was assayed after alkaline hydrolysis. The presence of p-aminoacetophenone (PAAP) and N-methyl-p-aminoacetophenone (N-methyl-PAAP) in the hydrolysates was determined by HPLC, HPLC-mass spectrometry (HPLC-MS) and gas chromatography-MS (GC-MS). Candicidin and hamycin contained only the PAAP residue; aureofungin contained both PAAP and N-methyl-PAAP. Trichomycin contained PAAP and also some unknown component of molecular weight 179. The aromatic nature of the individual components of the heptaene complex was demonstrated using radioactivity flow detection for the determination of the incorporation of [14C]-p-aminobenzoic acid to individual candicidin components. Ammonia chemical ionization MS was successfully used for the GC-MS identification of the acetylated mycosamine moiety of heptaenes.

4-Aminobenzoic Acid↗

PubMed1996

Bonded cellulose-derived high-performance liquid chromatography chiral stationary phases. II. Influence of the porosity of the silica gel matrix on performance.

Two cellulose derivatives bearing simultaneously 10-undecenoyl and 3,5-dimethylphenylaminocarbonyl groups in different ratios were chemically bonded on allylsilica gels of different porosity. The systematic study of the effect of the silica gel pore size on the bonding of the polysaccharide derivative and on the performance of the resulting chiral supports is presented.

Cellulose↗

PubMed1987

Application of high-performance liquid chromatography and thermospray high-performance liquid chromatography-mass spectrometry to the analysis and identification of 2',3'-dideoxyadenosine and its metabolite in biological media.

Reversed-phase high-performance liquid chromatographic (HPLC) procedures are described for determining the stability of 2',3'-dideoxyadenosine (DDA) in biological fluids at therapeutic dosages. The validated methodology uses both direct injection and solid-phase extraction techniques. Deamination of DDA to 2',3'-dideoxyinosine (DDI) in plasma by adenosine deaminase was monitored by HPLC, and the identification of DDI verified by thermospray HPLC-mass spectrometry. This methodology should prove useful in future studies concerning the stability and metabolism of dideoxynucleosides.

Adenosine Deaminase↗

PubMed1996

Direct high-performance liquid chromatographic and high-performance liquid chromatographic-thermospray-mass spectrometric determination of enantiomers of methamphetamine and its main metabolites amphetamine and p-hydroxymethamphetamine in human urine.

For the identification of drug abuse, a simple and rapid method which allows us to distinguish enantiomers of methamphetamine (MA) and its metabolites amphetamine (AP) and p-hydroxymethamphetamine (p-OHMA) in human urine was explored by coupling direct HPLC and HPLC-thermospray-mass spectrometry (HPLC-TSP-MS) both of which employ a beta-cyclodextrin phenylcarbamate-bonded silica column. HPLC analysis was performed after the solid-phase extraction from the urine sample with Bond Elut SCX, and D- and L-enantiomers of MA, AP and p-OHMA could be separated well. The proposed conditions are as follows: eluent, acetonitrile-methanol-50 mM potassium phosphate buffer (pH 6.0) (10:30:60, v/v) flow-rate, 1.0 ml/min temperature, 25 degrees C. The linear calibration curves were obtained for D- and L- MA and AP in the concentration range from 0.2 to 20 micrograms/ml; the relative standard deviation for D- and L-AP and D- and, L-MA ranged from 1.67 to 2.35% at 2 micrograms/ml and the detection limits were 50 ng/ml for D- and L-AP and D-MA and 100 ng/ml for L-MA. For the verification of the direct HPLC identification, HPLC-TSP-MS was also carried out under the same conditions except that acetonitrile-methanol-100 mM ammonium acetate (pH 6.0) (10:30:60, v/v) was used as an eluent. Upon applying the scan mode, 10 ng/ml for D- and L-AP and D-MA and 20 ng/ml for L-MA were the detection limits. Using the selected ion monitoring mode, 0.5 ng/ml, 0.8 ng/ml and 1 ng/ml could be detected for D- and L-AP, D-MA and L-MA, respectively.

Amphetamine↗

PubMed2004

Direct high-performance liquid chromatographic separation of unusual secondary amino acids and a comparison of the performances of Chirobiotic T and TAG columns.

Two macrocyclic glycopeptide antibiotic-type chiral stationary phases (CSPs) based on native teicoplanin and teicoplanin aglycone, Chirobiotic T and TAG, respectively, were evaluated with regard to the high-performance liquid chromatographic separation of the enantiomers of 10 secondary alpha-amino acids (imino acids). The chromatographic results are given as the retention, separation and resolution factors, together with the enantioselective free energy difference corresponding to the separation of the enantiomers. By application of these two CSPs, excellent resolutions were achieved for the investigated compounds by using reversed-phase mobile mode systems. The separation conditions were optimized by variation of the mobile phase composition. The difference in enantioselective free energy between the aglycone CSP and the teicoplanin CSP for these particular amino acids ranged between 0.70 and -1.83 kJ mol(-1). It was established that better enantioseparations of the secondary alpha-amino acids were attained in most cases on the aglycone CSP.

Amino Acids↗

PubMed2006

Application of polymer based stationary phases in high performance liquid chromatography and capillary high performance liquid chromatography hyphenated to microcoil 1H nuclear magnetic resonance spectroscopy.

The increased demand for chromatographic materials that are able to achieve a fast separation of large quantities of structure analogues is a great challenge. It is known that polymer based chromatographic materials have a higher loadability, compared to silica based sorbents. Unfortunately these polymer materials cannot be used under high pressure which is necessary in order to obtain high flow rates, and hence long times are needed to perform a separation. However, by immobilizing a polymer on a mechanically stable porous silica core, this problem can be circumvented and higher flows become feasible on these materials. Especially for capillary liquid chromatography hyphenated with nuclear magnetic resonance a high loadability is of great importance in order to obtain sharp, resolved, and concentrated peaks thus resulting in a good signal to noise ratio in the NMR experiment. Therefore, a highly shape selective chromatographic sorbent was developed by covalently immobilizing a poly(ethylene-co-acrylic) acid copolymer (-CH(2)CH(2)-)(x)[CH(2)CH(CO(2)H)-](y) (x=119, y=2.4) with a mass fraction of acrylic acid of 5% as stationary phase on silica via a spacer molecule (3-glycidoxypropyltrimethoxysilane). First, the loadability of this sorbent compared to C(30) is demonstrated by the HPLC separation of two xanthophyll isomers. Subsequently, it has been successfully employed in the hyphenation of capillary HPLC with microcoil (1)H NMR spectroscopy by separating and identifying a highly concentrated solution of the tocopherol homologues.

Acrylic Resins↗

PubMed2003

Comparison of folate quantification in foods by high-performance liquid chromatography-fluorescence detection to that by stable isotope dilution assays using high-performance liquid chromatography-tandem mass spectrometry.

A comparison study on folate quantitation was carried out between the recently developed stable isotope dilution assay using liquid chromatography-tandem mass spectrometry (LC-MS-MS) and the frequently used HPLC with fluorimetric detection (LC-FD). By applying LC-MS-MS, spinach, wheat bread, beef, and blood plasma were found to contain 159.2, 19.8, 1.2, and 5.6 microg/100 g total folates, respectively, whereas the respective quantitative data obtained by LC-FD were 95.5, 16.2, 0.7, and 6.8 microg/100 g. In all samples, LC-MS-MS revealed superior selectivity and precision and circumvented the shortcomings of conventional LC techniques, i.e., ambiguous peak assignment as well as high detection limits for 5-formyltetrahydrofolate, 10-formylfolic acid, and folic acid. The affinity chromatography columns used in this study showed excellent cleanup performance and permitted detection limits as low as 0.1, 0.5, 0.1, 0.08, and 0.1 microg/100 g for tetrahydrofolate (H(4)folate), 5-methyl-H(4)folate, 5-formyl-H(4)folate, 10-formylfolate, and pteroylglutamic acid, respectively. Thus, a 10-fold higher sensitivity compared to solid-phase anion-exchange cartridges was achieved. However, affinity chromatography columns revealed a significantly higher affinity toward the natural vitamers than to the racemic isotopomeric standards, which has to be considered when applying the latter in stable isotope dilution assays.

Animals↗

PubMed1997

Prolonged ejection duration helps to maintain pump performance of the renal-hypertensive-diabetic rat heart: correlations between isolated papillary muscle function and ventricular performance in situ.

OBJECTIVE: The purpose of this study was to examine the degree to which mechanical alterations in left ventricular papillary muscles of renal hypertensive-diabetic rat hearts correlate with functional measurements made on the same hearts in situ. METHODS: Female Wistar rats weighing 170-200 g were made hypertensive by placing a 0.24 mm clip on the left renal artery, and made diabetic 1 week later by a single intravenous injection of streptozotocin (60 mg/kg). Approximately 3-5 months later hemodynamic measurements including left ventricular pressure and dP/dtmax, arterial pressure and aortic flow were made on control and hypertensive-diabetic hearts in situ and correlated with mechanical measurements in left ventricular papillary muscles isolated from the same hearts. Body and tissue weights and biochemical and histological measurements were made at the time of sacrifice. RESULTS: Hypertensive-diabetic rats which survived to the time of study had decreased body weights, increased left ventricular weights and increased right ventricular weight to body weight and lung weight to body weight ratios. Those rats which died before the scheduled in-situ measurements had significantly more severe hypertension, greater left ventricular hypertrophy, increased right ventricular and lung weights, and more interstitial fibrosis than either surviving hypertensive-diabetics or controls. Rates of isometric tension development (normalized) and relaxation as well as shortening and relaxation velocities were significantly depressed in papillary muscles from hypertensive-diabetic rat hearts despite unchanged developed tension and peak shortening. Time to peak tension and time to peak shortening were markedly prolonged. Mean aortic flow was maintained in the hypertensive-diabetic group despite significant depression of left ventricular dP/dtmax (normalized), peak aortic flow, peak aortic flow acceleration and heart rate. There was also significant depression of left ventricular-dP/dtmax. Ejection duration was markedly prolonged and correlated with both time to peak shortening in vitro and with stroke volume in vivo. CONCLUSIONS: Surviving hypertensive-diabetic rats were not in overt congestive heart failure; nevertheless, their hearts showed abnormal contractile performance which was qualitatively and quantitatively similar to that of left ventricular papillary muscles obtained from them. Depression of peak aortic flow, peak aortic flow acceleration and heart rate in the hypertensive-diabetic group was offset by increased ejection duration, resulting in normal mean aortic flow. The close correlation of ejection duration with time to peak shortening of the isolated papillary muscles suggests that it is a manifestation of an intrinsic change in the myocardium. To the extent that this prolongation is already maximized, further decreases in contractile speed would be expected eventually to cause depressed pump function and congestive heart failure. The possibility that this sequence of events occurred in the dying animals needs to be examined by evaluating in-vitro and in-vivo myocardial function at various stages of this disease model.

Animals↗

PubMed1997

Analytical performance and clinical usefulness of two binding assays for growth hormone binding protein (GHBP) measurement: high performance liquid chromatography (HPLC)-gel filtration and dextran-coated charcoal adsorption.

We compared two binding assays for growth hormone binding protein (GHBP) measurements, which differ in the method of bound and free GH separation: HPLC-gel filtration or dextran coated-charcoal adsorption (DCC). Two pools of sera (high and medium GHBP activity) were used for quality-control assessment. Moreover, 62 samples from 34 children and 28 adults with different nutritional status were studied. Total, between- and intra-iodination coefficients of variation (CVs) from the two methods were not different. Although percentage binding measured in the pool sera significantly differed, the concentrations assessed by Scatchard plot were comparable. Results obtained by the two methods in the 62 sera were significantly correlated (r = 0.77, P < 0.001). With both methods GHBP activity correlated with chronological age and body mass index (BMI) and differed among groups with different nutritional status. Although HPLC and DCC separation methods for GHBP measurement differ in their practicability, our study demonstrates that performance and the clinical usefulness of the two methods are comparable.

Adolescent↗

PubMed2000

Observation of exchangeable protons by high-performance liquid chromatography-nuclear magnetic resonance spectroscopy and high-performance liquid chromatography-electrospray ionization mass spectrometry: a useful tool for the hyphenated analysis of natural products.

The first high-performance liquid chromatography-nuclear magnetic resonance (HPLC-NMR) investigation of exchangeable protons of low-molecular-mass natural products is reported. Model alkaloids or crude plant extracts were dissolved in 2H2O-1H2O-MeCN (deuterium oxide-water-acetonitrile) or 2H2O-MeCN and, after direct injection or chromatographic separation, examined in a 60-microl NMR flow probe. Exchangeable amino protons initially detected by HPLC-electrospray ionization mass spectrometry were subsequently identified and investigated by stop-flow 1H-NMR, two-dimensional (2D) total correlation spectroscopy (TOCSY), and 2D nuclear Overhauser effect spectroscopy (NOESY). These experiments extend the applicability of HPLC-NMR for the investigation and structure elucidation of natural products.

Biological Products↗

PubMed2001

Monitoring of recombinant human insulin production by narrow-bore reversed-phase high-performance liquid chromatography, high-performance capillary electrophoresis and matrix-assisted laser desorption ionisation time-of-flight mass spectrometry.

An analytical scheme for monitoring recombinant human insulin (rhI) production is suggested. The scheme includes high-performance separation micro-techniques (narrow-bore RP-HPLC, HPCE) based on different separation mechanisms and matrix-assisted laser desorption ionisation time-of-flight MS, and allows one to obtain unambiguous information about purity and primary structure of all intermediates of the rhI production. The use of this scheme at all production steps provided optimisation of certain technological parameters [conditions for a fusion protein (FP) refolding, temperature and duration of the FP cleavage with trypsin, conditions for carboxypeptidase B digestion of di-ArgB31-B32-insulin] and achievement of a high purity of the end-product. The proposed scheme may be used for solving various problems in monitoring production of other recombinant proteins.

Chromatography, High Pressure Liquid↗

PubMed1991

Quantitation of insulin injection by high-performance liquid chromatography and high-performance capillary electrophoresis.

High-performance capillary electrophoresis (HPCE) was evaluated as a potential technique for the regulatory analysis of commercial dosage forms of insulin. A comparison was made to a liquid chromatographic analysis presently being proposed as an official monograph in the United States Pharmacopeia. The salient points of this comparison were accuracy, precision and ease of use. Both authentic (i.e. single blind, spiked) samples and commercial pharmaceutical formulations (injections) were examined. Chromatographic analyses of both commercial formulations and authentic samples were characterized by good precision, with accuracy being supported by results from authentic (spiked) samples. Conventional HPCE (by which is meant a non-micellar electrolyte used with an uncoated, unmodified fused-silica capillary) achieved reasonable accuracy, but less than impressive precision, when applied to authentic samples. When used for commercial formulations, this type of HPCE did not produce a level of accuracy suitable for regulatory purposes, even with the use of an internal standard.

Animals↗