Trace analysis of ethinyl estradiol in casein diet using gas chromatography with electron capture detection. (1/374)

Ethinyl estradiol (EE2) is an extremely potent synthetic estrogen and a common component in oral contraceptives. The drug has a well-characterized pharmacological profile and is used as a positive control in toxicological investigations of compounds having estrogenic activity. An analytical method developed for the determination of low microg/kg levels of EE2 in a casein-based rodent diet is presented. A methanol extract of casein diet is purified for instrumental analysis by a 3-fold solid-phase extraction process. The sample extract is derivatized with pentafluoropropionic anhydride to the pentafluoropropionyl product and analyzed by capillary gas chromatography with electron-capture detection. Recoveries of EE2 from casein diet fortified at 5, 10, and 50 microg/kg average 88.8% and have a relative standard deviation (%) of 7.2. The method limit of detection in a casein-based diet is 1 microg/kg.  (+info)

Superheated water extraction of essential oils of Origanum micranthum. (2/374)

Superheated water extraction is used to extract essential oil of leaves of Origanum micranthum. The effect of different temperatures on the essential oil profile and rate of extraction as a function of time is investigated. The components of essential oil of Origanum micranthum are removed from the aqueous extract by C18 solid-phase extraction. The identification of components is carried out using comprehensive gas chromatography-time of flight-mass spectrometry. The number of extracted components is almost the same; however, the concentrations change with changing temperature. The highest yield (0.64%) is found at a temperature of 150 degrees C, 2 mL/min and 60 bar for 30 min. The increasing temperature from 100 degrees C to 175 degrees C increased the rate of extraction of six selected components of essential oil of Origanum micranthum. cis-Sabinenehydrate exhibits the fastest rate of extraction at all temperatures studied. Some degradation products are observed at a temperature of 175 degrees C.  (+info)

Development of an impregnated reagent and automation of solid-phase analytical derivatization for carbonyls: proof of principle. (3/374)

This study undertakes reduction of scale and automation of a solid-phase analytical derivatization of carbonyls with 2,4-dinitrophenylhyrazine on a styrene-divinylbenzene resin (XAD-2). Three processes are tested. In the batch process, an aqueous phase consisting of 50 microL of sample and 150 microL of reagent solution is contacted with 6 mg XAD-2 by shaking. An impregnated reagent consisting of 2,4-dinitrophenylhydrazine hydrochloride (DNPH) deposited on XAD-2 enables two additional processes. In-vial derivatization with an impregnated reagent requires shaking 50 microL of sample with 6 mg of the impregnated reagent and reduced the reaction time from 10 to 5 min. The third process involves packing impregnated reagent a mini-column and flowing 50 microL of sample through under positive pressure supplied by a Harvard Pump. This reduces sample preparation time to 1 min. Studies are conducted with worst-case model analytes: butanone, 2-pentanone, and malonyldialdehyde. The carbonyl of the two ketones is hindered, and, thus, these two compounds react very slowly with DNPH in aqueous solution. Malonyldialdehyde is highly water soluble, and it does not react in aqueous phase but also would not sorb onto XAD-2 for reaction. Nevertheless, derivatization/extraction of all model compounds any of the three procedures result in reproducible and high yields.  (+info)

Simplified method for determining the radiochemical purity of 99mTc-MAG3. (4/374)

99mTc-Mercaptoacetyltriglycine is used for dynamic renal imaging, and the summary of product characteristics (SPC) for the European formulation specifies a shelf life of 1 or 4 h, depending on the reconstitution volume of the kit. To minimize the time required to test the radiochemical purity, a simplified quality control method was developed. METHODS: To satisfy the recommendations of the International Commission on Harmonisation, results obtained with the methods described in the European and American SPCs were compared with those obtained with the simplified method. Further validation of the new method was performed by comparison with the standard 2-strip thin-layer chromatographic method as well as tests for linearity and limits of detection and quantification. RESULTS: The simplified method provided results comparable to those provided by the registered SPC methods but was more rapid to perform and used smaller volumes of solvents. CONCLUSION: The simplified method is a reasonable alternative to the registered SPC methods.  (+info)

Improved method of plasma 8-Isoprostane measurement and association analyses with habitual drinking and smoking. (5/374)

AIM: To develop a simple and accurate method for quantifying 8-isoprostane in plasma by employing a combination of two-step solid-phase extraction of samples and a commercially available ELISA kit, and by this method to examine the effects of drinking and smoking habits against the levels of plasma 8-isoprostane in healthy Japanese volunteers. METHODS: Plasma 8-isoprostane was extracted with ODS gel suspension followed by NH(2) Sep-Pak column. The 8-isoprostane fractions were assayed using a commercially available ELISA kit. We measured plasma 8-isoprostane levels in 157 healthy Japanese volunteers divided into three groups (64 non-habitual drinkers, 56 moderate drinkers and 37 habitual drinkers) according to their alcohol consumption per week. Genotypes of aldehyde dehydrogenase 2 (ALDH2) were also determined to investigate the plasma 8-isoprostane levels with reference to drinking habits. In addition, the plasma 8-isoprostane levels of 96 non-smokers and 61 smokers from the same subjects were compared. RESULTS: Our method fulfilled all the requirements for use in routine clinical assays with respect to sensitivity, intra- and inter-assay reproducibility, accuracy and dynamic assay range. Significant increases of plasma 8-isoprostane levels were observed in female habitual drinkers when compared with those of non-habitual drinkers (t = 5.494, P<0.0001) as well as moderate drinkers (t = 3.542, P<0.005), and 8-isoprostane levels were also significantly different between ALDH2*2/1 and ALDH2*1/1 in the female habitual drinkers (t = 6.930, P<0.0001), suggesting that excessive drinking of alcohol may increase oxidization stress, especially in females. On the contrary, no significant difference of the plasma 8-isoprostane levels was observed between non-smokers and smokers. CONCLUSION: Our present method was proved to be a simple and accurate tool for measuring plasma 8-isoprostane. However, the clinical utility of plasma 8-isoprostane for drinking and smoking habits was limited since elevated 8-isoprostane levels were observed in female heavy drinkers, and no association was found between smokers and nonsmokers.  (+info)

Evidence against a direct interaction between intracellular carbonic anhydrase II and pure C-terminal domains of SLC4 bicarbonate transporters. (6/374)

Based on solid-phase binding assays with enzyme-linked immunosorbent assay detection, previous investigators suggested that intracellular carbonic anhydrase II (CA II) interacts at high affinity with the C-terminal (Ct) domains of SLC4 bicarbonate-transport proteins, expressed as glutathione S-transferase (GST) fusion proteins, to form functional HCO3- metabolons. Here we re-evaluated this protein-protein interaction using two solid-phase binding assays. We first compared the ability of the Ct domain of three SLC4 transporters, SLC4-A1 (AE1), SLC4-A4 (NBCe1), and SLC4-A8 (NDCBE), to bind immobilized CA II, using enzyme-linked immunosorbent assay detection. We found that when expressed as GST fusion proteins, all three bind to CA II (Kd 300-600 nM) better than does pure GST. However, we detected no binding of pure SLC4-Ct peptides to immobilized CA II. Second, we reversed assay orientation by immobilizing the SLC4-Ct fusion proteins or peptides. We found that more CA II binds to GST than to any of the three GST-SLC4-Ct fusion proteins. Furthermore, we detected no binding of CA II to any of the immobilized pure SLC4-Ct peptides. Finally, we used surface plasmon resonance to detect possible rapid interactions between CA II and the pure peptides. Although we detected acetazolamide binding to immobilized CA II and specific antibodies binding to immobilized SLC4-Ct peptides, we detected no binding of CA II to immobilized SLC4-Ct or vice versa. Thus, although an HCO3 metabolon may exist, CA II cannot bind directly to pure SLC4-Ct peptides and can bind to GST-SLC4-Ct fusion proteins only when the CA II is immobilized and the fusion protein is soluble, and not vice versa.  (+info)

Control of matrix effects in the analysis of urinary F2-isoprostanes using novel multidimensional solid-phase extraction and LC-MS/MS. (7/374)

F(2)-isoprostanes (F(2)-iPs), established markers of oxidative stress, exist as four sets of regioisomers. Simultaneous and specific determination of F(2)-iPs can be achieved by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We developed novel methods for urine sample preparation and HPLC to control matrix-related ion suppression effects in the LC-MS/MS analysis of F(2)-iPs. A selective solid-phase extraction (SPE) wash protocol was developed with an Oasis HLB (hydrophilic-lipophilic balance) SPE cartridge using an elution profile of [(3)H]8-iso-prostaglandin (PG)F(2alpha) (iPF(2alpha)-III) when the methanol concentration was increased under acidic, neutral, and base wash conditions. A multidimensional (MD)-SPE method that incorporated size exclusion chromatography [corrected] reverse-phase chromatography, and normal-phase chromatography was developed using an Oasis HLB SPE cartridge and an HLB microElution SPE plate. Average extraction recoveries of the deuterated internal standards of iPF(2alpha)-III and iPF(2alpha)-VI were 62 +/- 8% and 60 +/- 10%. A buffer-free HPLC method for the separation of F(2)-iP isomers was developed on base-deactivated C8 columns. Average matrix effects for iPF(2alpha)-III and iPF(2alpha)-VI were 95 +/- 6% and 103 +/- 5%. The clean extraction of urine F(2)-iPs using MD-SPE and the separation of F(2)-iP isomers using a novel HPLC method did not cause apparent ion suppression in the analysis of iPF(2alpha)-III and iPF(2alpha)-VI using LC-MS/MS. These findings should be useful for establishing a routine LC-MS/MS method for the analysis of F(2)-iPs.  (+info)

Enantioanalysis of bisoprolol in human plasma with a macrocyclic antibiotic HPLC chiral column using fluorescence detection and solid phase extraction. (8/374)

A sensitive, enantioselective, high-performance liquid chromatographic (HPLC) method was developed and validated to determine S-(-)- and R-(+)-bisoprolol in human plasma. Baseline resolution was achieved using the teicoplanin macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic T with a polar ionic mobile phase (PIM) consisting of methanol-glacial acetic acid-triethylamine (100 : 0.02 : 0.025, v/v/v) at a flow rate of 1.5 ml/min and fluorescence detection set at 275 nm for excitation and 305 nm for emission. All analyses with S-(-)-atenolol as the internal standard were conducted at ambient temperature. The assay involved the use of a solid-phase extraction procedure for human plasma samples prior to HPLC analysis. The C18 cartridge gave good recovery rates for both enantiomers without any interference. The method was validated over the range of 20-200 ng/ml for each enantiomer concentration. Recovery rates for S-(-)- and R-(+)-bisoprolol enantiomers were in the range of 95-102%. The method proved to be precise (within-run precision expressed as % RSD ranged from 1.0-6.2% and between-run precision ranged from 0.9-6.7%) and accurate (within-run accuracies expressed as percentage error ranged from 0.2-4.8% and between-run accuracies ranged from 0.3-1.7%). The limit of quantitation and limit of detection for each enantiomer in human plasma were 20 and 5 ng/ml, respectively.  (+info)