FeS2 nanosheets-luminol-O2 chemiluminescence method for determination of venlafaxine hydrochloride, imipramine hydrochloride, and cefazolin sodium.

This study introduces a novel chemiluminescence (CL) approach utilizing FeS2 nanosheets (NSs) catalyzed luminol-O2 CL reaction for the measurement of three pharmaceuticals, namely venlafaxine hydrochloride (VFX), imipramine hydrochloride (IPM), and cefazolin sodium (CEF). The CL method involved the phenomenon of quenching induced by the pharmaceuticals in the CL reaction. To achieve the most quenching efficacy of the pharmaceuticals in the CL reaction, the concentrations of reactants comprising luminol, NaOH, and FeS2 NSs were optimized accordingly. The calibration curves demonstrated exceptional linearity within the concentration range spanning from 4.00 × 10-7 to 1.00 × 10-3 mol L-1, 1.00 × 10-7 to 1.00 × 10-4 mol L-1, and 4.00 × 10-6 to 2.00 × 10-4 mol L-1 with detection limits (3σ) of 3.54 × 10-7, 1.08 × 10-8, and 2.63 × 10-6 mol L-1 for VFX, IPM, and CEF, respectively. This study synthesized FeS2 NSs using a facile hydrothermal approach, and then the synthesized FeS2 NSs were subjected to a comprehensive characterization using a range of spectroscopic methods. The proposed CL method was effective in measuring the aforementioned pharmaceuticals in pharmaceutical formulations as well as different water samples. The mechanism of the CL system has been elucidated.

Stability and Sterility of Extemporaneously Prepared Nonpreserved Cefazolin, Ceftazidime, Vancomycin, Amphotericin B, and Methylprednisolone Eye Drops.

PURPOSE: To determine in-use stability and sterility of fortified cefazolin, ceftazidime, vancomycin, amphotericin B, and methylprednisolone eye drops in a simulated inpatient setting with and without a mobile refrigerated container (MR). METHODS: Each drug was prepared and divided into 4 groups: 1) simulated patient use with the MR group: stored at 4°C and kept in the MR during drug administration, 2) simulated patient use without the MR (NoMR) group: stored at 4°C and no MR, 3) refrigerated control group: stored at 4°C, and 4) room temperature control group: stored at room temperature. Stability and sterility data were evaluated at days 0, 4, 7, 14, 21, and 28. Linear mixed-effects model and survival analysis were performed. RESULTS: Median time to 10% loss of concentration for in-use medications (MR/NoMR groups) was >28/27.9, 22.2/22.2, 19.4/19.4, 10.18/<4, and >28/>28 days for cefazolin, ceftazidime, vancomycin, amphotericin B, and methylprednisolone, respectively. There was no significant difference in the predicted concentration loss per day among all groups for vancomycin and methylprednisolone (all P > 0.05). For the other study medications, all room temperature control groups, the cefazolin NoMR group, and the ceftazidime NoMR group had significantly greater predicted concentration loss per day compared with the refrigerated control groups (all P ≤ 0.02). Culture results were negative for all drugs throughout the study. CONCLUSIONS: The NoMR group showed that the drug significantly degraded rapidly for cefazolin, ceftazidime, and amphotericin B. Implementation of MR could decrease the predicted loss of concentration per day for cefazolin and ceftazidime. In vitro antimicrobial activity and sterility were retained for 28 days.

Quantitative analysis of cefazolin sodium in lyophilized powder by infrared spectrophotometry: Green, low cost, fast and effective.

Cefazolin sodium is a broad-spectrum antibiotic used in the treatment of infectious diseases in humans and in the surgical prophylaxis. Thus, since a considerable number of people have access to this drug, it is of great interest of quality control. The aim of this study was development and validation of a green method by Fourier-Transform Infrared (FT-IR) transmission spectrophotometry for the quantification of cefazolin sodium in lyophilized powder. This technique is widely used in the pharmaceutical industry due to its ease of execution, low cost, safety and high precision and accuracy. It has been employed in the quality control routine of numerous pharmaceuticals in order to identify them and quantify their active principles. The proposed method was completely validated according ICH guidelines, showing selectivity, accuracy, precision, robustness and linearity. It was linear over the concentration range of 0.4-1.7 mg with correlation coefficient 0.999, limits of detection and quantification of 0.017 mg and 0.052 mg, respectively, precise, accurate and robust when changes in the time, pressure and mark of potassium bromide were carried out during the preparation of the pellets. The proposed method was successfully applied to the qualitative and quantitative quality control of cefazolin sodium in lyophilized powder. In addition, the method is considered green, clean and sustainable since it uses only a single reagent; it is a fast, low-cost and environmentally friendly method.

The Effect of Blood Loss on Cefazolin Levels in Women Undergoing Cesarean Delivery.

OBJECTIVE: To quantify the effects of operative blood loss during cesarean on tissue and plasma cefazolin concentrations. STUDY DESIGN: This was a prospective observational study of singleton pregnancies undergoing scheduled cesarean between 34 and 40 weeks. Cefazolin administered prior to skin incision. Maternal plasma samples were obtained (Time 1[T1]: immediately, T2: 20 minutes, T3: 40 minutes, and T4: 60 minutes after cefazolin infusion). Subcutaneous adipose tissue sampled before and after fascia. Primary outcome was subcutaneous adipose cefazolin level after fascial closure. Formal quantitative blood loss (QBL) performed. Women with higher QBL, those at/above 75% of QBL in this population, were compared with those with lower QBL (QBL below 75%). Data analyzed using bivariable statistics. RESULTS: Ninety-two women were screened, 32 were eligible, and 20 enrolled. Median QBL was 630 mL (interquartile range [IQR]: 473-818) and 1,160 mL (IQR: 1,000-1,560) in the low and high QBL groups, respectively. Demographics and operative characteristics were similar. Median adipose cefazolin level after fascial closure did not differ between the groups (3.5 vs. 3.9 µg/g, p = 0.75). No differences in maternal plasma cefazolin concentrations between the groups at any time point or in pharmacokinetic parameters were seen. CONCLUSION: Intraoperative maternal plasma concentrations and adipose levels of cefazolin are similar between women with high and low blood loss at the time of cesarean delivery.

Simultaneous Determination of Cefalexin, Cefazolin, Flucloxacillin, and Probenecid by Liquid Chromatography-Tandem Mass Spectrometry for Total and Unbound Concentrations in Human Plasma.

BACKGROUND: Pharmacokinetic studies and therapeutic drug monitoring of antibiotics require a simple, rapid, and reliable analytical method for monitoring the concentrations in plasma, including unbound concentrations for highly protein-bound drugs. The aim of the current work was to develop and validate a liquid chromatography-tandem mass spectrometry method for the simultaneous determination of total and unbound concentrations of 3 widely used ß-lactam antibiotics (cefalexin, cefazolin, and flucloxacillin) and the often coadministered drug probenecid in human plasma, suitable for pharmacokinetic studies and for routine use in ordinary, busy hospital laboratories. METHODS: Unbound drug was separated from bound drug by ultrafiltration. A simple 1-step protein precipitation was used for sample preparation. Cefalexin, cefazolin, flucloxacillin, probenecid, and their corresponding isotopically labeled internal standards were then resolved on a C18 (2) column. All the compounds were detected using electrospray ionization in the positive mode. RESULTS: Standard curves were linear for all compounds over the concentration range of 0.2-100 mg/L (r > 0.99) for total drug in plasma and 0.01-10 mg/L (r > 0.99) for unbound drug in plasma ultrafiltrate. For both total and unbound drugs, bias was <±10%, and intra- and interday coefficients of variation (imprecision) were <10%. The limit of quantification was 0.2 mg/L for total plasma concentrations and 0.01 mg/L for plasma ultrafiltrate concentrations of all drugs. CONCLUSIONS: The method has proven to be simple, rapid, robust, and reliable and is currently being used in clinical pharmacokinetic studies and in the routine clinical service to enhance the effective use of the ß-lactam antibiotics.

Simultaneous Retrodialysis by Calibrator for Rapid In Vivo Recovery Determination in Target Site Microdialysis.

Concentrations in the interstitial tissue space are of clinical interest for many antibiotics and can be directly measured by microdialysis. Quantitative microdialysis strongly depends on reliable recovery estimates obtained from a suitable calibrator. Cefazolin (CFZ) is frequently used as a prophylactic antibiotic to prevent surgical site infections. This study aimed to develop a reliable and rapid calibration technique for CFZ microdialysis using cefuroxime (CFR) as a calibrator, which is applied simultaneously in the opposite direction via retrodialysis. Liquid chromatography-tandem mass spectrometry method was used for the measurement of both CFZ and CFR in microdialysate. Results from in vitro microdialysis experiments confirmed that CFR does not interfere with physicochemical properties of CFZ, and the loss of CFR is proportional to the gain of CFZ in microdialysis studies. Therefore, the validated bioanalytical assay is suitable to be applied in clinical microdialysis study of CFZ where microdialysis probes are simultaneously calibrated by retrodialysis of CFR. This approach shortens the overall sampling time of in vivo microdialysis studies significantly since calibration and sampling can be performed simultaneously and not in sequence as usually done. It also eliminates the necessary washout period if probe calibration is carried out before the actual sampling time.

Cefazolin Concentration in the Mediastinal Adipose Tissue of Patients Undergoing Cardiac Surgery.

OBJECTIVE: To measure the concentration of cefazolin in the anterior mediastinal adipose tissue of patients undergoing cardiac surgery, determining the variation of cefazolin concentration. METHODS: Two samples of approximately 1g of subcutaneous tissue were collected from 19 patients who underwent surgery in December 2015: the first sample was collected right after sternotomy and the second one, before sternal synthesis with steel wires. Antibiotic dosage was administered through high performance liquid chromatography. RESULTS: We observed a positive and statistically significant correlation between time 1 and cefazolin concentration (r=0.489 and P=0.039). For time 2 and cefazolin concentration, there was a negative and statistically significant correlation between both variables (r=-0.793 and P<0.001). A negative correlation was also observed between body mass index and cefazolin concentration at time 2 (r=-0.510 and P=0.031). The regression model showed that every 1-minute increase in time 1 corresponded to an increase of 0.240 µg/dL in cefazolin concentration, whereas every 1-minute increase in time 2 corresponded to a reduction of 0.046 µg/dL in cefazolin concentration. As for body mass index, every 1 kg/m2 increase corresponded to a reduction of about 0.510 µg/dL in cefazolin concentration. CONCLUSION: There was a positive and significant correlation between the initial time of surgery and cefazolin level in the first dosage. The evaluation of the second dosage showed a negative and significant correlation between cefazolin level and the second time of dosage. The concentration of cefazolin is under the influence of body mass index.

Cefazolin concentration in the mediastinal adipose tissue of patients undergoing cardiac surgery

Abstract Objective: To measure the concentration of cefazolin in the anterior mediastinal adipose tissue of patients undergoing cardiac surgery, determining the variation of cefazolin concentration. Methods: Two samples of approximately 1g of subcutaneous tissue were collected from 19 patients who underwent surgery in December 2015: the first sample was collected right after sternotomy and the second one, before sternal synthesis with steel wires. Antibiotic dosage was administered through high performance liquid chromatography. Results: We observed a positive and statistically significant correlation between time 1 and cefazolin concentration (r=0.489 and P=0.039). For time 2 and cefazolin concentration, there was a negative and statistically significant correlation between both variables (r=-0.793 and P<0.001). A negative correlation was also observed between body mass index and cefazolin concentration at time 2 (r=-0.510 and P=0.031). The regression model showed that every 1-minute increase in time 1 corresponded to an increase of 0.240 µg/dL in cefazolin concentration, whereas every 1-minute increase in time 2 corresponded to a reduction of 0.046 µg/dL in cefazolin concentration. As for body mass index, every 1 kg/m2 increase corresponded to a reduction of about 0.510 µg/dL in cefazolin concentration. Conclusion: There was a positive and significant correlation between the initial time of surgery and cefazolin level in the first dosage. The evaluation of the second dosage showed a negative and significant correlation between cefazolin level and the second time of dosage. The concentration of cefazolin is under the influence of body mass index.

Quantification of three beta-lactam antibiotics in breast milk and human plasma by hydrophilic interaction liquid chromatography/positive-ion electrospray ionization mass spectrometry.

The use of cephalosporins during breast feeding raises several issues, including the risk of drug exposure through breast milk for the infant. In this paper, a hydrophilic interaction liquid chromatography/positive ion electrospray mass spectrometric assay (HILIC/ESI-MS) was developed for the quantitation of cefuroxime, cefoxitin, and cefazolin in breast milk and human plasma. The assay was based on the use of small sample size, 25 µL of biological samples, following acetonitrile precipitation of proteins and filtration that enabled injection into the HILIC/ESI-MS system. All analytes and the internal standard, alfuzosin, were separated by using a ZIC®-HILIC analytical column (150.0 × 2.1 mm i.d., particle size 3.5 µm, 200 Å) with isocratic elution. The mobile phase was composed of a 6% 12.5 mM ammonium acetate water solution in acetonitrile and pumped at a flow rate of 0.25 mL min-1 . The assay was linear over a concentration range of 0.2 to 5 µg mL-1 and 0.4 to 20 µg mL-1 for all the analytes in breast milk and in human plasma, respectively. Intermediate precision was found to be less than 4.2% over the tested concentration ranges. A run time of less than 12 min for each sample made it possible to analyze a large number of biological samples per day. The method is the first reported application of HILIC in the analysis of antibiotics in breast milk and human plasma and it can be used to support a wide range of clinical studies. Copyright © 2016 John Wiley & Sons, Ltd.

Determination of Relative Response Factors of Cefazolin Impurities by Quantitative NMR.

The relative response factors (RRFs) of ten cefazolin impurities were determined by quantitative nuclear magnetic resonance (qNMR) and high-performance liquid chromatography (HPLC) equipped with an ultraviolet (UV) detector. The purities of these ten cefazolin impurities were successfully measured by qNMR for the purpose of RRFs determination by HPLC. The RRF values and their uncertainties determined by the two approaches are comparable. While the qNMR approach is effective and makes it easier to determine the RRFs for impurities, it also has the advantage of allowing the universal detection of protons without the limitations of common mass detectors. The use of qNMR provides a reliable and universal method for the RRF determination of impurities.

Oxidation of cefazolin by potassium permanganate: Transformation products and plausible pathways.

Cefazolin was demonstrated to exert high reactivity toward permanganate (Mn(VII)), a common oxidant in water pre-oxidation treatment. In this study, five transformation products were found to be classified into three categories according to the contained characteristic functional groups: three (di-)sulfoxide products, one sulfone product and one di-ketone product. Products analyses showed that two kinds of reactions including oxidation of thioether and the cleavage of unsaturated CC double bond occurred during transformation of cefazolin by Mn(VII). Subsequently, the plausible transformation pathways under different pH conditions were proposed based on the identified products and chemical reaction principles. More importantly, the simulation with real surface water matrix indicated that the proposed transformation pathways of cefazolin could be replayed in real water treatment practices.

Cupric oxide nanoparticles-enhanced chemiluminescence method for measurement of ß-lactam antibiotics.

A simple, sensitive cupric oxide nanoparticles (CuO NPs) enhanced chemiluminescence (CL) method was developed for the measurement of ß-lactam antibiotics, including amoxicillin and cefazolin sodium. The method was based on suppression of the CuO NPs-luminol-H2O2 CL reaction by ß-lactam antibiotics. Experimental parameters that influenced the inhibitory effect of the antibiotic drugs on the CL system, such as NaOH (mol/L), luminol (µmol/L), H2O2 (mol/L) and CuO NPs (mg/L) concentrations, were optimized. Calibration graphs were linear and had dynamic ranges of 1.0 × 10(-6) to 8.0 × 10(-6) mol/L and 3.0 × 10(-5) to 5.0 × 10(-3) mol/L for amoxicillin and cefazolin sodium, respectively, with corresponding detection limits of 7.9 × 10(-7) mol/L and 1.8 × 10(-5) mol/L. The relative standard deviations of five replicate measurements of 5.0 × 10(-6) amoxicillin and 5 × 10(-4) cefazolin sodium were 5.43 and 5.01%, respectively. The synthesized CuO NPs were characterized by X-ray diffraction (XRD) and transmission electronmicroscopy (TEM). The developed approach was exploited successfully to measure antibiotics in pharmaceutical preparations.

Tantalum electrodes modified with well-aligned carbon nanotube-Au nanoparticles: application to the highly sensitive electrochemical determination of cefazolin.

Carbon nanotube/nanoparticle hybrid materials have been proven to exhibit high electrocatalytic activity suggesting broad potential applications in the field of electroanalysis. For the first time, modification of Ta electrode with aligned multi-walled carbon nanotubes/Au nanoparticles introduced for the sensitive determination of the antibiotic drug, cefazolin (CFZ). The electrochemical response characteristics of the modified electrode toward CFZ were investigated by means of cyclic and linear sweep voltammetry. The modified electrode showed an efficient catalytic activity for the reduction of CFZ, leading to a remarkable decrease in reduction overpotential and a significant increase of peak current. Under optimum conditions, the highly sensitive modified electrode showed a wide linear range from 50 pM to 50 µM with a sufficiently low detection limit of 1 ± 0.01 pM (S/N = 3). The results indicated that the prepared electrode presents suitable characteristics in terms of sensitivity (458.2 ± 2.6 µAcm(-2)/µM), accuracy, repeatability (RSD of 1.8 %), reproducibility (RSD of 2.9 %), stability (14 days), and good catalytic activity in physiological conditions. The method was successfully applied for accurate determination of trace amounts of CFZ in pharmaceutical and clinical preparations without the necessity for samples pretreatment or any time-consuming extraction or evaporation steps prior to the analysis.

Antibiotic prophylaxis in bariatric surgery with continuous infusion of cefazolin: determination of concentration in adipose tissue.

BACKGROUND: The aim of this study was to evaluate the concentration of cefazolin in adipose tissue of patients undergoing bariatric surgery. METHODS: Eighteen patients undergoing bariatric surgery were evaluated during the period from October 2011 to May 2012. All patients had a dosage schedule of antibiotic prophylaxis with cefazolin administered as follows: first, 2 g in anesthetic induction, followed by continuous infusion of 1 g diluted in 250 ml of saline solution. Adipose samples, collected soon after the incision (initial) and before the skin synthesis (final), were analyzed using reverse phase high-pressure liquid chromatography. The level of significance adopted was 5 %. RESULTS: The cefazolin concentration in the adipose tissue samples at the beginning of surgery was an average of 6.66 ± 2.56 ug/ml. The mean concentration before the skin synthesis was 7.93 ± 2.54 ug/ml. Patients with BMI < 40 kg/m(2) had higher initial and final sample concentrations of cefazolin than patients with BMI ≥ 40 kg/m(2). There was no surgical site infection (SSI) in any of the patients. CONCLUSIONS: In bariatric surgeries, addition of a 1 g increase of cefazolin, administered through continuous intravenous infusion, to the currently recommended dose of 2 g administered in anesthetic induction provided a concentration in the adipose tissue above the minimum inhibitory concentration (MIC) of the main causal agents of SSI. An inverse correlation between BMI and concentration of cefazolin in adipose tissue was observed.

Validation of analytical methodology for quantification of cefazolin sodium pharmaceutical dosage form by high performance liquid chromatography to be applied for quality control in pharmaceutical industry

A reversed-phase high performance liquid chromatography method was validated for the determination of cefazolin sodium in lyophilized powder for solution for injection to be applied for quality control in pharmaceutical industry. The liquid chromatography method was conducted on a Zorbax Eclipse Plus C18 column (250 x 4.6 mm, 5 μm), maintained at room temperature. The mobile phase consisted of purified water: acetonitrile (60: 40 v/v), adjusted to pH 8 with triethylamine. The flow rate was of 0.5 mL min-1 and effluents were monitored at 270 nm. The retention time for cefazolin sodium was 3.6 min. The method proved to be linear (r2=0.9999) over the concentration range of 30-80 µg mL-1. The selectivity of the method was proven through degradation studies. The method demonstrated satisfactory results for precision, accuracy, limits of detection and quantitation. The robustness of this method was evaluated using the Plackett–Burman fractional factorial experimental design with a matrix of 15 experiments and the statistical treatment proposed by Youden and Steiner. Finally, the proposed method could be also an advantageous option for the analysis of cefazolin sodium, contributing to improve the quality control and to assure the therapeutic efficacy.

Um método cromatográfico em fase reversa foi validado para a determinação de cefazolina sódica em pó liofilizado, a ser aplicado no controle de qualidade em indústrias farmacêuticas. O método por cromatografia líquida foi conduzido em coluna Zorbax Eclipse Plus C18 (250 × 4,6 mm, 5 µm) mantida à temperatura ambiente. A fase móvel consistiu de água purificada: acetonitrila (60 : 40 v/v), com o pH ajustado para 8 com trietilamina. A vazão usada foi de 0,5 mL min-1 e os analitos de interesse foram monitorizados a 270 nm. O tempo de retenção da cefazolina sódica foi de 3,6 min. As áreas dos picos de cefazolina sódica foram lineares na faixa de concentração de 30-80 µg mL-1 (r2 = 0,9999). A seletividade do método foi demonstrada através de estudos de degradação. O método demonstrou resultados satisfatórios para precisão, exatidão, limites de detecção e de quantificação. A robustez do método foi avaliada utilizando o esquema fatorial de Plackett-Burman com uma matriz de 15 experimentos simultâneos, e analisados por tratamento estatístico proposto por Youden e Steiner. Finalmente, o método proposto pode ser também uma opção de êxito para a análise de cefazolina sódica, contribuindo para o controle de qualidade e para garantir a eficácia terapêutica.

Development of a novel chemiluminescence method for the determination of cefazolin sodium in injectable powder and human urine based on a luminol-Cu(III) complex reaction in alkaline medium.

A novel chemiluminescence (CL) method was developed for the determination of cefazolin sodium based on the CL reaction between the [Cu(HIO6)2](5-) Cu(III) complex and luminol in alkaline solution. Results showed that CL emission of Cu(III) complex-luminol in alkaline medium was significantly different from that in acidic medium. A possible mechanism of the enhanced effect of cefazolin on CL emission of the [Cu(HIO6)2](5-)-luminol system was proposed. The effect of the reaction conditions on CL emissions was examined. Under optimized conditions, a good linear relationship was obtained between CL intensity and concentrations of cefazolin sodium in the range of 2.0 x 10(-8) to 2.0 x 10(-6) g/mL with a correlation coefficient of R(2) = 0.9978. The limit of detection was 4.58 x 10(-9) g/mL. The proposed method was applied for the determination of cefazolin sodium in real samples with recoveries of 82.0-109% with an RSD of 0.7-2.1%. The proposed method was successfully used for the determination of cefazolin sodium in injectable powder preparations and human urine with satisfactory results.

Spectrophotometric complexation of cephalosporins with palladium (II) chloride in aqueous and non-aqueous solvents.

The complexation reaction of cephalosporins namely cefotaxime (CTX), cefuroxime (CRX), and cefazolin (CEFAZ) with palladium (II) ions have been studied in water and DMF in 25 °C by the spectrophotometric methods. The method is based on the formation of yellow to yellowish brown complex between palladium (II) chloride and the investigated cephalosporins in the presence of sodium lauryl sulfate (SLS) as surfactant. The complexation process was optimized in terms of pH, temperature and contact time. The stoichiometry of all the complexes was found to be 2:1 (metal ion/ligand) for CTX, CRX, and 1:2 for CEFAZ. The stoichiometry of palladium (II)-cephalosporins was estimated by mole ratio and continuous variation methods and emphasized by the KINFIT program. These drugs could be determined by measuring the absorbance of each complex at its specific λmax. The results obtained are in good agreement with those obtained using the official methods. The proposed method was successfully applied for the determination of these compounds in their dosage forms.

[Spectrophotometric determination of cefazolin in mixed saliva of practically healthy subjects and patients with infective somatic pathology].

The behaviour of cefazolin in aqueous and biological media with varying the antibiotic concentration was studied by UV-spectroscopy. Range of the contents and the detection limits of cefazolin were determined. The procedure of UV-spectroscopy of cefazolin in mixed saliva of patients with urinary tract infection was developed.

Kinetic spectrophotometric determination of certain cephalosporins using oxidized quercetin reagent.

A simple, precise and accurate kinetic spectrophotometric method for determination of cefoperazone sodium, cefazolin sodium and ceftriaxone sodium in bulk and in pharmaceutical formulations has been developed. The method is based upon a kinetic investigation of the reaction of the drug with oxidized quercetin reagent at room temperature for a fixed time of 30 min. The decrease in absorbance after the addition of the drug was measured at 510 nm. The absorbance concentration plot was rectilinear over the range 80-400 microg mL(-1) for all studied drugs. The concentration of the studied drugs was calculated using the corresponding calibration equation for the fixed time method. The determination of the studied drugs by initial rate, variable time and rate-constant methods was feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The analytical performance of the method, in terms of accuracy and precision, was statistically validated; the results were satisfactory. The method has been successfully applied to the determination of the studied drugs in commercial pharmaceutical formulations. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision.

Fast screening procedure for antibiotics in wastewaters by direct HPLC-DAD analysis.

Growing concern about the contamination of wastewaters by antibiotics demands fast but sensitive analytical methodologies, for the screening of a large number of samples. The purpose of this work was to develop a simple methodology, using direct injection of the samples, by HPLC with diode array detection (DAD), for a multiresidue analysis of five antibiotics of different classes. Wastewater from an urban water treatment plant was selected as a model to study possible coelution of interfering compounds. The linearity interval ranged from 40 to 400 microg/L for amoxicillin (Amox), metronidazole (Metro), cefazolin (Cefa), and chloramphenicol (Chloram) and from 20 to 200 microg/L for sulfamethoxazole (Sulfa), with LODs lower than 14 microg/L. Repeatability, expressed by the CV of six repeated injections, ranged from 1 to 8%, while the intermediate precision varied between 2 and 11%. The recovery ranged from 90 to 109%. This method enables the fast screening of a large number of samples, with an expanded uncertainty in the 1-22% range. The advantage of the proposed method is to significantly reduce the number of samples to be analyzed by more complex methods.