Between-day Relative Standard Deviations Research Articles

Expedient measurement of total protein in human serum and plasma via the biuret method using fiber optic probe for patient samples and certified reference materials.

The biuret method is currently recognized as a reference measurement procedure for serum/plasma total protein by the Joint Committee for Traceability in Laboratory Medicine (JCTLM). However, as the reaction involved in this method is highly time-dependent, to ensure identical measurement conditions for calibrator and samples for high accuracy, a fast and simple measurement procedure is critical to ensure the precision and trueness of this method. We measured serum/plasma total protein using a Cary 60 spectrophotometer coupled with a fiber optic probe, which was faster and simpler than the conventional cuvette method. The biuret method utilizing alkaline solutions of copper sulfate and potassium sodium tartrate was added to the sample and calibrator (NIST SRM 927e) incubated for 1h before measurement. A panel of samples consisting of pooled human serum, single donor serum, and certified reference materials (CRMs) from three sources were measured for method validation. Sixteen native patient samples were measured using the newly developed biuret method and compared against clinical analyzers. Additionally, the results of three cycles of a local External Quality Assessment (EQA) Programme submitted by participating clinical laboratories were compared against the biuret method. Our biuret method using fiber optic probe demonstrated good precision with within-day relative standard deviation (RSD) of 0.04 to 0.23% and between-day RSD of 0.58%. The deviations between the obtained values and the certified values for all three CRMs ranged from -0.38 to 1.60%, indicating good method trueness. The routine methods using clinical analyzers were also found to agree well with the developed biuret method using fiber optic probe for EQA samples and native patient samples. The biuret method using a fiber optic probe represented a convenient and reliable way of measuring serum total protein. It also demonstrated excellent precision and trueness using CRMs and patient samples, which made the method a simpler candidate reference method for serum protein measurement.

Calcium/Copper Alginate Framework Doped with CuO Nanoparticles as a Novel Adsorbent for Micro-extraction of Benzodiazepines from Human Serum

Background:Sample preparation is one of the most challenging phases in pharmaceutical analysis, especially in biological matrices, affecting the whole analytical methodology.Objective:In this study, a new Ca(II)/Cu(II)/alginate/CuO Nanoparticles Hydrogel Fiber (CCACHF) was synthesized through a simple, green procedure and applied for fiber micro solid-phase extraction (FMSPE) of diazepam (DIZ) and oxazepam (OXZ) as model drugs prior to high-performance liquid chromatography-UV detection (HPLC-UV).Methods:Composition and morphology of the prepared fiber were characterized and the effect of main parameters on the fiber fabrication and extraction efficiency have been studied and optimized.Results:In optimal conditions, calibration curves were linear, ranging between 0.1–500 μg L−1with regression coefficients of 0.9938 and 0.9968. Limit of Detection (LOD) (S/N=3) and Limit of Quantification (LOQ) (S/N=10) of the technique for DIZ and OXZ were 0.03 to 0.1 μg L−1. Within-day and between-day Relative Standard Deviations (RSDs) for DIZ and OXZ were 6.0–12.5% and 3.3–9.4%, respectively.Conclusion:The fabricated adsorbent has been substantially employed to the extraction of selected benzo-diazepines (BZDs) from human serum real specimens and the obtained recoveries were also satisfactory (82.1-109.7%).

Application of redox reactions for the determination of valganciclovir hydrochloride in pharmaceuticals

Two simple, selective and sensitive spectrophotometric methods were developed and validated for the determination of valganciclovir hydrochloride (VLGH) in pure drug and tablets. The first method was based on the reduction of iron(III) to iron(II) by VLGH and subsequent formation of iron(III)-ferricyanide complex (Prussian blue) in acid medium which was measured at 730 nm (method A). In the second method (method B), permanganate was reduced by VLGH to bluish green manganate in alkaline medium and the absorbance was measured at 610 nm. The absorbance measured in each case was related to VLGH concentration. The experimental conditions were carefully studied and optimized. Beer’s law was obeyed over the concentration ranges of 2.5-20.0 and 2.0-40.0 µg mL-1 for method A and method B, respectively, with corresponding molar absorptivity values of 1.28×104 and 6.88×103 L mol-1 cm-1. The limits of detection (LOD) and quantification (LOQ) were 0.11 and 0.33 µg mL-1 (method A) and 0.21 and 0.64 µg mL-1 (method B). Within-day and between-day relative standard deviations (%RSD) at three different concentrations levels were < 2.4%, and the respective relative errors (%RE) were ≤ 3%. The proposed methods were successfully applied to the determination of VLGH in tablets, and the results confirmed that the proposed methods were equally precise and accurate as the official method.

Sensitive and Selective Extractive Spectrophotometric Method for the Determination of Hydroxyzine Dihydrochloride in Pharmaceuticals

Hydroxyzine dihydrochloride (HDH), a piperazine H1-receptor antagonist and antihistamine, is a rapid acting anxiolytic used principally as an anti-emetic. A sensitive, selective, and precise and accurate spectrophotometric method based on the formation of an ion-pair with orange II (ORG II) as ion-pair complexing agent was developed and validated for the determination of HDH in pharmaceuticals. The chloroform-extractable ion-pair complex exhibited an absorption maximum at 480 nm. Optimization of different experimental conditions is described. Beer’s law is obeyed in the range of 1.5-15 μg mL-1 with an apparent molar absorptivity value of 2.07 x 104 L mol-1 cm-1 and Sandell’s sensitivity value of 0.0216 μg cm-2. The limit of detection (LOD) and limit of quantification (LOQ) are 0.14 and 0.41 μg mL-1, respectively. A Job’s plot of absorbance versus molar ratio of HDH to ORG II indicated (1:2) stoichiometric ratio. Within- and between-day relative standard deviations at three different concentration levels were &lt; 3%. The developed method was successfully applied to commercial tablets. The results obtained were in good agreement with those obtained using the official method.&#x0D; No interference was encountered from co-formulated substances.&#x0D; Recoveries were 96-109 %.

Analysis of 7 volatile N-nitrosamines in Chinese Sichuan salted vegetables by gas chromatography-tandem mass spectrometry coupled to modified QuEchERS extraction

A gas chromatography-tandem mass spectrometry coupled to QuEchERS extraction method was developed for the determination of 7 volatile N-nitrosamines (VNAs) in Chinese Sichuan salted vegetables, and the method detection limit (MDL), method quantification limit (MQL), recovery and relative standard deviation (RSD) were determined. Furthermore, the VNA contents of 406 Sichuan salted vegetables were measured and discussed. The MDL of the 7 VNAs ranged from 0.02 to 0.15 ng/g, and their recoveies when spiked with 10 ng/g standards ranged from 91.5 to 106.1%. The within-day RSD and between-day RSD were 2.1–4.6% and 2.4–7.2%, respectively. These results indicate that the method developed was of good accuracy, repeatability and reproducibility. The mean content of total VNAs in the 406 Sichuan salted vegetables was 0.56 ng/g, and more than 95% of them (n = 386) were at low VNA content (<3 ng/g), which suggests good control of VNAs in Sichuan salted vegetables. Preparation method and packaging mode significantly affected the VNA content of Sichuan salted vegetables (P < 0.05), while vegetable type and production region did not (P > 0.05). The VNA with both the highest concentration and the highest occurrence frequency of ≥3 ng/g was N-nitrosopyrrolidine.

Determination of Ciprofloxacin, Enrofloxacin, and Marbofloxacin in Bovine Urine, Serum, and Milk by Microextraction by a Packed Sorbent Coupled to Ultra-High Performance Liquid Chromatography

This article reports new, easy, and rapid microextraction by packed sorbent (MEPS)–ultra high performance liquid chromatography with photodiode array detection for the simultaneous determination in bovine urine, serum, and milk of three antibiotics belonging to the class of the fluoroquinolones, namely ciprofloxacin, enrofloxacin, and marbofloxacin, approved for veterinary and human use (ciprofloxacin). The chromatographic separation of the analytes and all aspects influencing the MEPS performance were optimized for the extraction from the considered biological samples. The optimized procedure required simple sample pretreatment, a short (<8 min) isocratic elution, and provided sufficient sensitivity for the determination of the analytes at trace levels in compliance with current legislation. Limits of quantitation were in the range from 0.002 (ciprofloxacin, urine) to 0.048 μg/mL (enrofloxacin, milk). Recoveries from 79% (enrofloxacin, milk) to 88% (ciprofloxacin, urine/serum) were obtained on spiked samples. The within-day (n = 6) and between-day (n = 6 over 3 days) relative standard deviation percentages in bovine urine, serum, and milk samples ranged from 2.2 (ciprofloxacin, urine) to 2.5 (enrofloxacin, serum) and from 3.1 (ciprofloxacin, urine) to 3.7 (enrofloxacin, milk), respectively, and were not concentration dependent. To the best of our knowledge, this is the first study describing a fast and simple method for the determination of fluoroquinolones in bovine biological samples.

Utilidad de un método que determina simultáneamente retinol y α-tocoferol en leche materna por cromatografía líquida de alta resolución

ObjectiveTo present the results obtained in the development of a simplified method, with a direct extraction of breast milk and detection by reverse phase high-performance liquid chromatography of retinol and α-tocopherol. Materials and methodsAn experimental 2x3 factorial design was used, with temperature variables, type of solvent and antioxidant effect, at 2 levels. Subsequent to the extraction, the samples were saponified with potassium hydroxide in methanol, then extracted with petroleum ether, and dried and reconstituted with ethanol. The chromatography conditions were established using microbondapak columns with UV/visible detector: methanol/water (96:4) mobile phase, wavelength for retinol 325, and 290nm for α-tocopherol. ResultsThe analytics parameters were: linearity; r2=0.9955 (retinol), r2=0.9808 (α-tocopherol); detection and quantification limits: 1.1μg/dL and 2.7μg/dL (retinol), 0.9μg/dL and 2.3μg/dL (α-tocopherol). Method accuracy: the within-day relative standard deviation was 4.5%, and a between-day relative standard deviation of 4.8% for retinol, and 4.9% within-day and 4.1% between-day forα-tocopherol. For accuracy, recovery=85.8±7.8% for retinol and 98±1.9% for α-tocopherol. Once validated, the method was applied to the quantification of retinol and α-tocopherol in 100 samples of breast milk. The values obtained were 63.9±5.2μg/dL for retinol and 359.0±115.0μg/dL for α-tocopherol. ConclusionThe method is selective, linear, precise, sensitive and accurate. These characteristics together with their simplicity make the validated method convenient for the determination of retinol and α-tocopherol in breast milk.

A scattering methodology for droplet sizing of e-cigarette aerosols

Context: Knowledge of the droplet size distribution of inhalable aerosols is important to predict aerosol deposition yield at various respiratory tract locations in human. Optical methodologies are usually preferred over the multi-stage cascade impactor for high-throughput measurements of aerosol particle/droplet size distributions.Objective: Evaluate the Laser Aerosol Spectrometer technology based on Polystyrene Sphere Latex (PSL) calibration curve applied for the experimental determination of droplet size distributions in the diameter range typical of commercial e-cigarette aerosols (147–1361 nm).Materials and methods: This calibration procedure was tested for a TSI Laser Aerosol Spectrometer (LAS) operating at a wavelength of 633 nm and assessed against model di-ethyl-hexyl-sebacat (DEHS) droplets and e-cigarette aerosols. The PSL size response was measured, and intra- and between-day standard deviations calculated.Results: DEHS droplet sizes were underestimated by 15–20% by the LAS when the PSL calibration curve was used; however, the intra- and between-day relative standard deviations were < 3%. This bias is attributed to the fact that the index of refraction of PSL calibrated particles is different in comparison to test aerosols. This 15–20% does not include the droplet evaporation component, which may reduce droplet size prior a measurement is performed. Aerosol concentration was measured accurately with a maximum uncertainty of 20%. Count median diameters and mass median aerodynamic diameters of selected e-cigarette aerosols ranged from 130–191 nm to 225–293 nm, respectively, similar to published values.Discussion and conclusion: The LAS instrument can be used to measure e-cigarette aerosol droplet size distributions with a bias underestimating the expected value by 15–20% when using a precise PSL calibration curve. Controlled variability of DEHS size measurements can be achieved with the LAS system; however, this method can only be applied to test aerosols having a refractive index close to that of PSL particles used for calibration.

Spectrophotometric determination of ethionamide in pharmaceuticals using Folin–Ciocalteu reagent and iron(III)-ferricyanide as chromogenic agents

Two simple and sensitive spectrophotometric methods are described for the determination of ethionamide (ETM) in pure drug and tablets. The first method is based on the reduction of Folin–Ciocalteu (F–C) reagent by ETM in sodium carbonate medium to form a blue coloured complex, which was measured at 760nm (Molybdenum–tungsten blue method). In the second method (Prussian blue method), iron(III) was reduced to iron(II) by ETM in HCl medium, in which iron(II) was complexed with ferricyanide, and the resulting Prussian blue was also measured at 760nm. The absorbance measured in each case was related to the ETM concentration. The experimental conditions were carefully studied and optimised. Beer's law was obeyed in concentration ranges of 1–40μg/ml and 0.2–4.0μg/ml with the Molybdenum-tungsten blue method and the Prussian blue method, respectively, with corresponding molar absorptivity values of 5.72×103 and 3.18×104l/(mol·cm). The limits of detection (LOD) and quantification (LOQ) were 0.09 and 0.27μg/ml for the Molybdenum-tungsten blue method and 0.01 and 0.04μg/ml for the Prussian blue method. Within-day and between-day relative standard deviations (%RSD) at three different concentration levels were <3%, and the respective relative errors (%RE) were ≤2%, implying good accuracy and precision of the methods. The proposed methods were successfully applied to the determination of ETM in bulk powder and tablets, and the results demonstrated that the methods were as accurate and precise as the official method.

Molecularly imprinted polymer on a SiO2 -coated graphene oxide surface for the fast and selective dispersive solid-phase extraction of Carbamazepine from biological samples.

A surface carbamazepine-imprinted polymer was grafted and synthesized on the SiO2 /graphene oxide surface. Firstly SiO2 was coated on synthesized graphene oxide sheet using the sol-gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO2 /graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross-linker and porogen, respectively. Nonimprinted polymer was also prepared for comparison. The properties of the molecularly imprinted polymer were characterized using field-emission scanning electron microscopy and Fourier-transform infrared spectroscopy. The surface molecularly imprinted polymer was utilized as an adsorbent of dispersive solid-phase extraction for separation and preconcentration of carbamazepine. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the nonimprinted polymer was examined in absence and presence of competitive drugs. The carbamazepine calibration curve showed linearity in the ranges 0.5-500 μg/L. The limits of detection and quantification under the optimized conditions were 0.1 and 0.3 μg/L, respectively. The within-day and between-day relative standard deviations (n = 3) were 3.6 and 4.3%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 85%.

1-Butyl-3-aminopropyl imidazolium—functionalized graphene oxide as a nanoadsorbent for the simultaneous extraction of steroids and β-blockers via dispersive solid–phase microextraction

In this study, we describe the synthesis of graphene oxide functionalized with the ionic liquid 1-butyl-3-aminopropyl imidazolium chloride and its use as an adsorbent for the dispersive solid–phase microextraction (micro SPE) of four anabolic steroids and six β-blockers from aqueous samples of environmental importance, prior to their HPLC-diode array detector analysis. As the ionic liquid is covalently attached to graphene oxide sheets, it is made possible for it to participate in the dispersive micro SPE procedure. The limits of detection and limits of quantification of the proposed method were found to be in the range of 7–23ng/L and between 20 and 70ng/L, respectively. The linearity was satisfactory, with the determination coefficients to range from 0.9940 to 0.9998 while the within- and between-day relative standard deviation of the method ranged between 3.1 and 7.6% and from 4.0 to 8.5%, respectively. In order to test the applicability of the proposed method in real-life samples, the effluent from a municipal wastewater treatment plant as well as natural water samples from two rivers and a lake were collected and analyzed. After the analysis of samples, the effluent from municipal wastewater treatment plant was fortified with the analytes, at concentrations equal to 2 and 10 times the LOQs. Recoveries were calculated after subtracting the native (no-spike) concentrations of analytes, when needed. All the recoveries were in the range of 87–98%. A comparison study attests to the superiority of the developed nanomaterial over graphene oxide and graphene for the dispersive micro SPE of steroids and β-blockers.

Determination of a selection of synthetic cannabinoids and metabolites in urine by UHPSFC-MS/MS and by UHPLC-MS/MS.

Two different analytical techniques, ultra-high performance supercritical fluid chromatography-tandem mass spectrometry (UHPSFC-MS/MS) and reversed phase ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), were used for the determination of two synthetic cannabinoids and eleven metabolites in urine; AM-2201 N-4-OH-pentyl, AM-2233, JWH-018 N-5-OH-pentyl, JWH-018 N-pentanoic acid, JWH-073 N-4-OH-butyl, JWH-073 N-butanoic acid, JWH-122 N-5-OH-pentyl, MAM-2201, MAM-2201 N-4-OH-pentyl, RCS-4 N-5-OH-pentyl, UR-144 degradant N-pentanoic acid, UR-144 N-4-OH-pentyl, and UR-144 N-pentanoic acid. Sample preparation included a liquid-liquid extraction after deconjugation with ß-glucuronidase. The UHPSFC-MS/MS method used an Acquity UPC(2 TM) BEH column with a mobile phase consisting of CO2 and 0.3% ammonia in methanol, while the UHPLC-MS/MS method used an Acquity UPLC® BEH C18 column with a mobile phase consisting of 5 mM ammonium formate (pH 10.2) and methanol. MS/MS detection was performed with positive electrospray ionization and two multiple reaction monitoring transitions. Deuterated internal standards were used for six of the compounds. Limits of quantification (LOQs) were between 0.04 and 0.4 µg/L. Between-day relative standard deviations at concentrations ≥ LOQ were ≤20%, with biases within ±19%. Recoveries ranged from 40 to 90%. Corrected matrix effects were within 100 ± 10%, except for MAM-2201 with UHPSFC-MS/MS, and for UR-144 N-pentanoic acid and MAM-2201 N-4-OH-pentyl with UHPLC-MS/MS. Elution order obtained by UHPSFC-MS/MS was almost opposite to that obtained by UHPLC-MS/MS, making this instrument setup an interesting combination for screening and confirmation analyses in forensic cases. The UHPLC-MS/MS method has, since August 2014, been successfully used for confirmation of synthetic cannabinoids in urine samples revealing a positive immunoassay screening result. Copyright © 2015 John Wiley & Sons, Ltd.

Development and application of FD-LC-MS/MS proteomics analysis revealing protein expression and biochemical events in tissues and cells

It is routine to search for and recognized genetic defects in human disorders to provide knowledge for diagnosis, treatment, and protection against diseases. It is also important to investigate and demonstrate the cause of a disease from the proteomic perspective, because intracellular signaling systems depend on protein dynamics. Demonstrating changes in protein levels enables us to understand biochemical events during the initiation and progression of a disease. To understand changes in protein levels in tissues and cells, we have developed a novel proteomics approach, FD-LC-MS/ MS. This consists of fluorogenic derivatization (FD), HPLC separation and detection/quantification of proteins in a biological sample, followed by the isolation and tryptic digestion of target proteins, and then their identification using HPLC and tandem mass spectrometry (MS/MS) with a database-searching algorithm. The method is highly sensitive (femtomole-level detection) through the use of less noisy fluorogenic rather than fluorescence derivatization, and enables precise and comprehensive relative quantitation of protein levels (between-day relative standard deviation of peak heights of ca. 20%) by combining FD with HPLC separation. In this paper, after a simple review of differential profiling using FD-LC-MS/MS, for example the analysis of stimulated vs. unstimulated samples, we introduce the development and application of the FD-LC-MS/MS method for comprehensive differential proteomics of several tissues, including mouse liver, mouse brain, and breast cancer cell lines, to reveal protein levels and biochemical events in tissues and cells.

Determination of myo-inositol in infant formulae and milk powders using capillary gas chromatography with flame ionisation detection

A gas chromatography–flame ionisation detection method was developed to establish the content of myo-inositol in milk powders and infant formulations subsequent to formation of the volatile trialkylsilyl derivative. Samples were prepared by acid digestion, thereby releasing inositol from its multiple bound forms. A digestion time of 4 h at 114 °C was sufficient to hydrolyse potentially interfering carbohydrates and quantitatively recover bound inositol from milk-based products. Single laboratory method validation showed a within-day relative standard deviation (RSDr) of 5.9% and between-day relative standard deviation (RSDiR) of 9.6%. A between-laboratory (n = 7) collaborative study yielded an average reproducibility (RSDR) of 12.8%, considered fit-for-purpose as a quality control method for milk-based infant formulations. Soy-based products, containing significant inositol hexaphosphate (IP6, phytic acid), required 32 h for release of all inositol. Although current regulations do not specify the inclusion of IP6 in an inositol measurement, the current method allows for its discrimination if present.

A fully validated microbiological assay to evaluate the potency of ceftriaxone sodium

Ceftriaxone (CFTX) sodium is a third-generation, broad-spectrum cephalosporin that is resistant to beta-lactamases. An alternative bioassay for the assessment of the potency of this drug in pharmaceutical formulations has not been previously reported. Thus, this paper reports the development and full validation of a 3 x 3 agar diffusion bioassay using a cylinder-plate method to quantify CFTX sodium in pharmaceutical samples. The strain Staphylococcus aureus ATCC 6538P was used as the test microorganism, and the results of the proposed bioassay displayed high linearity, precision, accuracy, specificity and robustness. All potency results were statistically analyzed using an analysis of variance (ANOVA) and were found to be linear (r=0.99999) in the range of 16-64 µg/mL, accurate (100.5%), and precise [repeatability: relative standard deviation (RSD)=1.4%; intermediate precision: between-day RSD=2.1% and between-analyst RSD=2.5%]. The specificity of the bioassay was determined by evaluating a degraded sample (50 ºC) at 0, 24 and 48 hours as compared against the results from the pharmacopeial liquid chromatography method for CFTX. The results validated the proposed microbiological assay, which allows reliable quantitation of CFTX in pharmaceutical samples. Moreover, it is a useful, simple and low-cost alternative method for monitoring the quality of this medicine.

Simultaneous determination of EDTA, sorbic acid, and diclofenac sodium in pharmaceutical preparations using high-performance liquid chromatography.

A simple high-performance liquid chromatographic method for simultaneous determination of ethylenediaminetetraacetic acid (EDTA), sorbic acid, and diclofenac sodium was developed and validated. Separation was achieved on a C(18) column (10 cm×4.6 mm) using gradient elution. The mobile phase consisted of acetonitrile-ammonium dihydrogen phosphate buffer solution (0.01 M, pH=2.5, containing 0.8% tetra-n-butyl ammonium hydroxide). The detector wavelength was set at 254 nm. Under these conditions, separation of three compounds was achieved in less than 10 min. The effect of two metal salts and metal concentration on peak area of EDTA was investigated. The pH effect on retention of EDTA and sorbic acid was studied. The method showed linearity for EDTA, sorbic acid, and diclofenac in the ranges of 2.5-100.0, 5.0-200.0, and 20.0-120.0 μg/mL, respectively. The within- and between-day relative standard deviations ranged from 0.52 to 1.94%, 0.50 to 1.34%, and 0.78 to 1.67% for EDTA, sorbic acid, and diclofenac, respectively. The recovery of EDTA, sorbic acid, and diclofenac from pharmaceutical preparation ranged from 96.0-102.0%, 99.7-101.5%, to 97.0-102.5%, respectively. To the best of our knowledge, this is the first report about simultaneous determination of EDTA, sorbic acid, and diclofenac.

Simple and rapid liquid chromatography method for simultaneous determination of isoniazid and pyrazinamide in plasma

Introduction: Treatment of tuberculosis (TB) requires a combination of drugs. Isoniazid (INH) and pyrazinamide (PZA) are key components of the fi rst-line regimen used in the treatment of TB and monitoring these drug levels in plasma would help in better patient care. The objective of the study is to develop and validate a simple and rapid high performance liquid chromatographic method for simultaneous determination of INH and PZA in human plasma. Methodology: The method involved deproteinisation of plasma with para hydroxy benzaldehyde and trifl uoroacetic acid and analysis using a reversed-phase C8 column and UV detection at 267nm. The fl ow rate was set at 1.5 ml/min at ambient temperature. The accuracy, linearity, precision, specifi city, stability and recovery of the method were evaluated. The method was applied to estimate plasma INH and PZA collected from six children with TB. Results: Well resolved peaks of PZA and INH at retention times of 3.2 and 6.1 minutes respectively were obtained. The assay was linear from 0.25 - 10.0 ìg/ml for INH and 1.25 – 50.0 ìg/ml for PZA. The within-day and between-day relative standard deviation for standards were below 10%. The average recoveries of INH and PZA from plasma were 104 and 102% respectively. Conclusions: A rapid and accurate method for simultaneous determination of INH and PZA in plasma was validated. The assay spans the concentration range of clinical interest. The easy sample preparation and small sample size makes this assay highly suitable for pharmacokinetic studies of INH and PZA in TB patients. SAARC Journal of Tuberculosis, Lung Diseases &amp; HIV/AIDS 2012; IX (1) 13-18 DOI: http://dx.doi.org/10.3126/saarctb.v9i1.6960

Gas chromatography–mass spectrometry determination of pharmacologically active substances in urine and blood samples by use of a continuous solid-phase extraction system and microwave-assisted derivatization

A sensitive method based on gas chromatography–mass spectrometry was used to determine 22 pharmacologically active substances (frequently used in the treatment of human and animal's diseases) including analgesics, antibacterials, anti-epileptics, antiseptics, β-blockers, hormones, lipid regulators and non-steroidal anti-inflammatories in blood and urine samples. Samples were subjected to continuous solid-phase extraction in a sorbent column (Oasis HLB), and then the target analytes were eluted with ethyl acetate and derivatized in a household microwave oven at 350W for 3min. Finally, these products were determined in a gas chromatograph–mass spectrometer equipped with a DB-5 fused silica capillary column. The analyte detection limits thus obtained ranged from 0.2 to 1.3ngL−1 for urine samples and 0.8–5.6ngL−1 for blood samples. Recoveries from both blood and urine ranged from 85 to 102%, and within-day and between-day relative standard deviations were all less than 7.5%. The proposed method offers advantages in reduction of the exposure danger to toxic solvents used in conventional sample pretreatment, simplicity of the extraction processes, rapidity, and sensitivity enhancement. The method was successfully used to quantify pharmacologically active substances in human and animal (lamb, veal and pig) blood and urine. The hormones estrone and 17β-estradiol were detected in virtually all samples, and so were other analytes such as acetylsalicylic acid, ibuprofen, ketoprofen and triclosan in human samples, and florfenicol, pyrimethamine and phenylbutazone in animal samples.

Combined microwave-assisted extraction and continuous solid-phase extraction prior to gas chromatography–mass spectrometry determination of pharmaceuticals, personal care products and hormones in soils, sediments and sludge

This paper reports a sensitive analytical method based on microwave-assisted extraction and continuous solid-phase extraction (SPE), followed by gas chromatography–mass spectrometry (GC−MS), for the simultaneous determination of residues of 18 pharmaceuticals (analgesics, antibacterials, anti-epileptics, β-blockers, lipid regulators and non-steroidal anti-inflammatories), one personal care product and 3 hormones in soils, sediments and sludge. The analytes are extracted with 3:2 methanol/water under the action of microwave energy and the resulting extract is passed through a SPE column to clean up the sample matrix and preconcentrate the analytes. Then, the analytes, trapped on Oasis-HLB sorbent, are eluted with ethyl acetate, silylated and determined by GC–MS. The proposed method provides a linear response over the concentration range 2.5–20000ng/kg with correlation coefficients higher than 0.994 in all cases. Also, it features low limits of detection (0.8–5.1ng/kg), good precision (within- and between-day relative standard deviation less than 7%) and recoveries ranging from 91 to 101%. The method was successfully applied to agricultural soils, river and pond sediments, and sewage sludge. All samples contained some target analyte and sludge contained most —some at considerably high concentrations.

A simple and sensitive gas chromatographic-tandem mass spectrometric method for the determination of cantharidin in cosmetic products

Summary The analysis of cantharidin, a potent antitumor yet highly toxic chemical, is reported in this article. In regions including the United States, Europe, and China, cantharidin is either a banned ingredient or being highly regulated in cosmetic products. In this article, a gas chromatographic-tandem mass spectrometric (GC-MS/MS) method has been established for the determination of cantharidin in cosmetic products. Cosmetic samples were divided into two groups according to whether they contained aqueous ethanol or not. Samples containing aqueous ethanol in the formulation were dried under an air flow prior to extraction by methanol. The multiple reaction monitoring (MRM) mode with the parent ion at m/z 128 and the product ions at m/z 55 and 85 was employed. The linear range covered from 0.1 to 30.00 μg mL−1 (R = 0.9996) for cantharidin. The detection limit (LOD) was 0.3 μg kg−1. The intraday and between-day relative standard deviations (RSDs) were <8.7%. The mean recoveries were within the range 101....