Semi-quantitative analysis of cefaclor in human serum by capillary high performance liquid chromatography/fast atom bombardment mass spectrometry

Insights into antibiotic cefaclor mineralization by electro-Fenton and photoelectro-Fenton processes using a Ti/Ti4O7 anode: Performance, mechanism, and toxic chlorate/perchlorate formation

A comparative degradation of antibiotic cefaclor (CEC) between Ti/Ti4O7 and Ti/RuO2 anodes, in terms of degradation kinetics, mineralization efficiency, and formation of toxic chlorate (ClO3-) and perchlorate (ClO4-), was performed with electrochemical-oxidation (EO), electro-Fenton (EF), and photoelectro-Fenton (PEF) processes. Besides, CEC degradation by EF with boron-doped diamond (BDD) anode was also tested. Results showed CEC decays always followed pseudo-first-order kinetics, with increasing apparent rate constants in the sequence of EO < EF < PEF. The mineralization efficiency of the processes with Ti/Ti4O7 anode was higher than that of Ti/RuO2 anode, but slightly lower than that of BDD anode. Under the optimal conditions, 94.8% mineralization was obtained in Ti/Ti4O7-PEF, which was much higher than 64.4% in Ti/RuO2-PEF. The use of Ti/RuO2 gave no generation of ClO3- or ClO4-, while the use of Ti/Ti4O7 yielded a small amount of ClO3- and trace amounts of ClO4-. Conversely, the use of BDD led to the highest generation of ClO3- and ClO4-. The reaction mechanism was studied systematically by detecting the generated H2O2 and •OH. The initial N of CEC was released as NH4+ and, in smaller proportion, as NO3-. Four short-chain carboxylic acids and nine aromatic intermediates were also detected, a possible reaction sequence for CEC mineralization was finally proposed.

Identification and characterization of 17 phenothiazine compounds by capillary high-performance liquid chromatography/fast atom bombardment mass spectrometry

Phenothiazines are widely prescribed as neuroleptics; some are used as antihistaminics. These compounds are important in clinical and forensic toxicology. Seventeen phenothiazine compounds with heavy side chain structures have been found to be detectable by high-performance liquid chromatography/fast atom bombardment-mass spectrometry (HPLC/FAB-MS) method. Authentic samples of the compounds were subjected to our HPLC/FAB-MS system; their mass spectra were obtained by positive and negative modes. Four typical phenothiazines, in the serum samples of two patients, were also analyzed. All 17 phenothiazines were sufficiently separated on the chromatogram. In the positive mode, all the base peaks were quasimolecular ions; their main fragment ions observed were [M-R(1)+CH(2)](+), [R(1)](+), [M-R(1)](+) and [M+H+Gly](+). In the negative mode, the base peaks were [Cl](-) for chlorpromazine, prochlorperazine and perphenazine, three compounds containing chloride. For the other compounds, they were [M-R(1)-CH(3)](-), [M-R(1)-CH(2)CH(3)](-) or [M-R(1)-(CH(3))(2)](-) ions. We observed [M+H](-) ions in all the compounds, however, the ir intensities were variable (3-74%). The spectra and mass chromatograms of four compounds and their metabolites in the extracted serum samples from two patients, were also obtained. The approximate detection limits for phenothiazines were less than 1 ng on-column in the positive mode, and about 1 microg on-column in the negative mode. We have succeeded in the identification and characterization of 17 phenothiazine compounds at therapeutic concentrations in body fluids using our HPLC/FAB-MS system. The present method would be useful in forensic toxicological practice.

Sensitive determination of midazolam and identification of its two metabolites in human body fluids by column-switching capillary high-performance liquid chromatography/fast atom bombardment-mass spectrometry

Midazolam is a benzodiazepine and is widely prescribed for preanesthesia or general anesthesia. Overdose or intoxication cases of midazolam have been reported. In Japan, smuggled midazolam tablets could be involved in some criminal cases. Midazolam and its two metabolites were extracted by the solid-phase extraction method using Bond Elut SCX cartridges. The compounds were analyzed by on-line capillary high-performance liquid chromatography/fast atom bombardment-mass spectrometry. Midazolam and its two metabolites were well separated on the chromatogram, and each mass spectra gave [M+H](+) ion as a base peak. Deuterium-labeled midazolam was synthesized as an internal standard; it has enabled precise and reproducible quantitation of midazolam in blood samples. The calibration curve showed excellent linearity in the range of 2-200 ng/ml in spiked serum. The detection limit was 300 pg/ml (signal-to-noise ratio=3). The whole blood and urine samples from the victim of a homicide case were analyzed, and the midazolam concentration in the whole blood was estimated to be 163 ng/ml. The present method should be useful in clinical and forensic toxicology, because of its high sensitivity and specificity.

Determination of cefaclor by selective sample enrichment/clean-up on silica gel bonded polyelectrolyte in ion-exchange column chromatography

A silica gel-bound cationic polyelectrolyte, poly[N-chloranil N,N,N',N'- tetramethylethylene diammonium dichloride], modified as ion-exchanger capable of molecular recognition of beta-lactam antibiotic, was used in solid phase extraction through column chromatography for a sample clean-up and enrichment of analyte from a dilute solution. The optimum and selective sorption conditions for a model antibiotic, cefaclor, were established. The high selectivity of polymer at pH 9.5 and flow rate as high as 5 ml/min were observed for the quantitative sorption of cefaclor. The desorption by 0.1 N HCl at flow rate of 0.1 ml/min and subsequent heating at 80 degrees C for 2 h allowed the antibiotic to be detected as corresponding oxazolone form in UV-spectrophotometric and differential pulse adsorptive stripping voltammetric measurements. The potential of the suggested approach was illustrated by estimating cefaclor in urine and blood plasma samples.

Capillary high-performance liquid chromatography-fast atom bombardment mass spectrometry of 24 cephem antibiotics

Using capillary high-performance liquid chromatography (HPLC)-fast atom bombardment (FAB) mass spectrometry (MS), both positive and negative FAB mass spectra of 24 cephem antibiotics with diethanolamine (DEA) and glycerol (GLY) as matrices are presented. In the positive mode, an internal quasi-molecular peak together with relatively abundant fragment peaks were obtained from all 24 drugs with both matrices, though DEA provided more information on molecular mass of a compound than did GLY for some drugs. In the negative mode, the background was generally lower than that in the positive, but neither the quasi-molecular nor molecular peak was detected in several drugs with either matrix. The drugs were isolated from serum samples using an octadecyl reversed-phase cartridge; recoveries were generally over 60%, With this isolation and the capillary HPLC-FAB-MS in the positive mode, ceftriaxone and cefazolin, two of the most popular cephem antibiotics, were successfully identified in 0.5 ml of sera obtained from a clinical or an autopsy case.