Attila Gáspár

Thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) — a simple method for trace element determination with microsamples in the μg/l concentration range

Abstract A new flame method of atomic absorption spectrometry has been developed. The liquid sample to be analyzed is transported through a very hot, simple metal capillary tip acting as a flame-heated thermospray into a glowing atomization tube (flame furnace) which is positioned into the air/acetylene flame of a standard flame-AAS burner head. Both the complete introduction of the whole sample and the extended residence time inside the absorption volume result in an improvement of detection limits from 14 to 67 for five investigated elements. The detection limits determined using 10-μl samples amount to 0.19 ng/ml (Cd), 1.3 ng/ml (Cu), 5.2 ng/ml (Tl), 13 ng/ml (Pb) and 21 ng/ml (Hg). A relative standard deviation of 1.4–3.4% ( N =12, 10 μl) was achieved. Sample volumes between 2.5 μl and 200 μl have been investigated. In the case of 10 μl the sampling frequency was three per minute. The method can also be considered as a simple, effective interface between HPLC or FIA techniques and flame AAS. The determinations can be easily automated.

Application of capillary zone electrophoresis to the analysis and to a stability study of cephalosporins

The applicability of capillary zone electrophoresis (CZE) for the determination of cephalosporin antibiotics has been studied. In the case of the separation conditions optimised for fourteen cephalosporins, the precision of migration times was smaller than 1.3% RSD, and the values of the limit of detection ranged between 0.42 and 1.62 microg/ml. The proposed CZE method was applied to study the stability of cephalosporins in water at different temperatures (+25, +4 and -18 degrees C). It was established that the degradation of most cephalosporins was not higher than 20% at room temperature within 4 h of dissolution of these antibiotics.

Analysis and stability study of temozolomide using capillary electrophoresis

The applicability of micellar electrokinetic capillary chromatography (MEKC) for the analysis of temozolomide (TMZ) and its degradants, 3-methyl-(triazen-1-yl)imidazole-4-carboxamide (MTIC) and 5-amino-imidazole-4-carboxamide (AIC) has been studied. Using short-end injection, the analysis of TMZ and its degradants could be performed within 1.2 min. The obtained precision of migration times was better than 1.6 RSD%, and the limit of quantitation (LOQ) was 0.31-0.93 microg/mL. The therapeutic concentration of TMZ in blood samples can be determined after direct sample injection and conventional on-capillary UV detection. The proposed MEKC method was applied to study the stability of TMZ in water and serum at different pH values. It was established that the half-life of the TMZ in vitro serum at room temperature was 33 min, close to the half-life (28 min) obtained in water at pH 7.9.

Electrochromatography in microchips packed with conventional reversed-phase silica particles

This paper shows the applicability of a disposable and inexpensive microfluidic chip for electrochromatographic separations. The chip, recently developed by us for chip‐based LC, was fabricated from PDMS incorporating conventional chromatographic RP silica particles (C18) without the use of frits. Three cephalosporin antibiotics were used to demonstrate the applicability of the chip‐based chromatographic packing for electrochromatographic determinations. The used sample injection method utilizes hydrodynamic pressure, thereby, reducing the propensity for sample bias during the injection.

Role of pathogenic oral flora in postoperative pneumonia following brain surgery

BackgroundPost-operative pulmonary infection often appears to result from aspiration of pathogens colonizing the oral cavity. It was hypothesized that impaired periodontal status and pathogenic oral bacteria significantly contribute to development of aspiration pneumonia following neurosurgical operations. Further, the prophylactic effects of a single dose preoperative cefazolin on the oral bacteria were investigated.MethodsA matched cohort of 18 patients without postoperative lung complications was compared to 5 patients who developed pneumonia within 48 hours after brain surgery. Patients waiting for elective operation of a single brain tumor underwent dental examination and saliva collection before surgery. Bacteria from saliva cultures were isolated and periodontal disease was scored according to type and severity. Patients received 15 mg/kg cefazolin intravenously at the beginning of surgery. Serum, saliva and bronchial secretion were collected promptly after the operation. The minimal inhibitory concentrations of cefazolin regarding the isolated bacteria were determined. The actual antibiotic concentrations in serum, saliva and bronchial secretion were measured by capillary electrophoresis upon completion of surgery. Bacteria were isolated again from the sputum of postoperative pneumonia patients.ResultsThe number and severity of coexisting periodontal diseases were significantly greater in patients with postoperative pneumonia in comparison to the control group (p = 0.031 and p = 0.002, respectively). The relative risk of developing postoperative pneumonia in high periodontal score patients was 3.5 greater than in patients who had low periodontal score (p < 0.0001). Cefazolin concentration in saliva and bronchial secretion remained below detectable levels in every patient.ConclusionPresence of multiple periodontal diseases and pathogenic bacteria in the saliva are important predisposing factors of postoperative aspiration pneumonia in patients after brain surgery. The low penetration rate of cefazolin into the saliva indicates that its prophylactic administration may not be sufficient to prevent postoperative aspiration pneumonia. Our study suggests that dental examination may be warranted in order to identify patients at high risk of developing postoperative respiratory infections.

Cefazolin prophylaxis in neurosurgery monitored by capillary electrophoresis

&NA; Prophylactic use of antibiotics to prevent postoperative infections is a routine method in neurosurgery. Little is known about the period of effectiveness of antibiotics applied only for the purposes of operation. The actual concentration of cefazolin was determined in the serum, in the contents of wound drains, and in the cerebrospinal fluid in a 24‐hour postoperative period after the administration of 1 g of cefazolin just prior to skin incision in 8 patients undergoing lumbar discectomy and 11 patients undergoing craniectomy. The concentration of the antibiotic was then compared with the minimal inhibitory concentration values of cefazolin for 10 different bacterial species. For evaluating the concentration of cefazolin, capillary electrophoresis was used, which is a new clinical application of this separation technique. Results showed that the antibiotic was effective against bacterial breeding in the serum and in the drainage up to 12 hours. The drug concentration in the cerebrospinal fluid remained less than the value of the serum, and it exceeded the minimal inhibitory concentration values only for approximately 5 hours.

Possibilities of determination of mercury compounds using capillary zone electrophoresis

Abstract Capillary zone electrophoresis (CZE) has been used to separate inorganic (Hg 2+ ) and organic mercury (methyl-, ethyl- and phenylmercury) compounds. In order to achieve the proper CZE separation and UV detection of mercury compounds, their different complexes had to be formed. The advantages of four different complexing agents having thiol group (cysteine, glutathione, 2-mercaptonicotinic acid and mercaptoacetic acid) were studied. In the case of all four agents the optimized electrophoretic separation was achieved in fused silica capillary at 25 kV using 25 mM sodium borate buffer (pH 9.3). Identification and quantification of the mercury species at mg/l levels was carried out by the use of UV spectrophotometric detection at 200, 260 and 300 nm depending on the used complexing agent.

On-line chromatographic separation and determination of chromium(III) and chromium(VI) with preconcentration of the chromium(III) using potassium hydrogen phthalate, in various samples by flame atomic absorption spectrometry

A method has been developed for the on-line LC separation of CrIII on a reversed-phase C18 column in the presence of potassium hydrogen phthalate, which is a recently introduced reagent for chromatography. It is much more selective for CrIII in contrast to many other complex-forming agents discussed in the literature, so that in its presence virtually no ions are sorbed onto the C18 column except for CrIII. Hence almost no interferences due to the matrix are found during the detection of CrIII. The CrIII sorbed onto the column was eluted into the flame of an atomic absorption spectrometer using a mixture of methanol and water [80–20(%(v/v))]. With 100 µl of sample solution the detection limits (3σ) were found to be 0.024 and 0.075 mg l–1 for the separation of CrIII and CrVI with FAAS detection and the period needed for separation was under 60 s. For the preconcentration of the CrIII content of a 5 ml sample solution, the detection limit (3σ) was 0.73 ng ml–1, the accuracy of the measurement was 3.8% RSD for the preconcentration of 20 ng ml–1 of CrIII. The sensitivity of the method enabled the determination of the CrIII and CrVI content of surface waters and various samples of natural origin at concentrations below ng ml–1 to be made. After reduction of CrVI to CrIII with ascorbic acid and its preconcentration, the total Cr content of various samples could be determined.

Integration of ground aerogel particles as chromatographic stationary phase into microchip

C16 modified and ground monolithic silica aerogel particles in submicrometer size, as a new type of stationary phase was prepared and integrated in polydimethylsiloxane (PDMS) microchip. The aerogel particles were packed into the microfluidic channel using a simple procedure, which does not require any special frit or fabrication step to retain the particles. The subnanoliter volume of samples can be transported through the porous, short length of packing with low pressure (< 3 bar). Food dyes as test components could be separated using low pressure within 6s. A 50-fold preconcentration could be achieved by retaining 100 nL volume of sample on the packing and elution with methanol.

Capillary electrophoretic determination of mercury compounds in different matrixes

SummaryCapillary electrophoresis has been used to separate inorganic (Hg2+) and organic (methyl-, ethyl-, and phenylmercury) mercury compounds as their cysteine complexes. The optimized electrophoretic separation was performed in fused-silica capillary tubing at 25 kV with 25mm sodium borate buffer (pH 9.3). Identification and quantification of the mercury species at mg L−1 levels was achieved by use of UV detection at 200 nm. The relative standard deviation (n=10) ranged from 0.38 to 0.51% for migration times and from 0.43 to 2.94% for corrected peak areas. Good recovery (>90%) was obtained for all four mercury species in surface waters, and for inorganic mercury and methylmercury in five- to tenfold diluted biofluids (urine, saliva, and cerebrospinal fluid). TheLOQ values obtained were too high to be useful for determination of mercury species in real samples.