LC Enantioseparation of 30-Component Diastereomeric Mixture of Amino Acids and Detection of d-Isomers Using New Reagents with Amines as Chiral Auxiliaries in Cyanuric Chloride

Two enantiomerically pure amines, viz., (R)-(+)-naphthylethyl amine and (S)-(+)-1-benzyl-3-aminopyrrolidine, were used as chiral auxiliaries for nucleophilic substitution of chlorine atoms in cyanuric chloride or its 6-butoxy derivative. The chiral derivatizing reagents so obtained were characterized and their chiral purity was ascertained. Diastereomers of 15 dl-proteinogenic amino acids were synthesized under microwave irradiation using these reagents. Separation of diastereomeric pairs along with separation of a mixture of 30 diastereomers in a single chromatographic run was carried out on a reversed-phase C₁₈ column. Mixtures of acetonitrile with aqueous trifluoroacetic acid were used as mobile phase. The detection was made at 230 nm using photo diode array detector. The separation behavior in terms of retention times and resolutions was compared on the basis of effect of chiral auxiliaries (i.e. amines) and achiral substituents (i.e. chlorine or butoxy group) in the chiral derivatizing reagents and the hydrophobic side chains of amino acids. The separation method was validated in terms of accuracy, precision, linearity, recovery, limit of detection and limit of quantitation. The method was successful for determination of d-amino acids in the absence of pure d-enantiomers and for separation of 19 diastereomers from a mixture of 30.     

Evaluation of applied biosystems MicroSEQ real-time PCR system for detection of Salmonella spp. in food

Real-time PCR methods for detecting foodborne pathogens offer the advantages of simplicity and quick time-to-results compared to traditional culture methods. In this study, the MicroSEQ real-time PCR system was evaluated for detection of Salmonella spp. in 10 different food matrixes following the AOAC Research Institute's Performance Tested Method validation program. In addition, the performance of the MicroSEQ system was evaluated for the detection of Salmonella in peanut butter as a part of the Emergency Response Validation Program sponsored by the AOAC Research Institute. The system was compared to the ISO 6579 reference method using a paired-study design for detecting Salmonella spp. in raw ground beef, raw chicken, raw shrimp, Brie cheese, shell eggs, cantaloupe, chocolate, black pepper, dry infant formula, and dry pet food. For the peanut butter study, the system was compared to the U.S. Food and Drug Administration's Bacteriological Analytical Manual procedures using an unpaired-study design. No significant difference in performance was observed between the MicroSEQ Salmonella spp. detection system and the corresponding reference methods for all 11 food matrixes. The MicroSEQ system detected all Salmonella strains tested, while showing good discrimination against detection of an exclusivity panel of 30 strains, with high accuracy.     

Evaluation of applied biosystems MicroSeq real-time PCR system for detection of Listeria monocytogenes in food. Performance Tested Method 011002

Increasingly, more food companies are relying on molecular methods, such as PCR, for pathogen detection due to their improved simplicity, sensitivity, and rapid time to results. This report describes the validation of a new Real-Time PCR method to detect Listeria monocytogenes in nine different food matrixes. The complete system consists of the MicroSEQ L. monocytogenes Detection Kit, sample preparation, the Applied Biosystems 7500 Fast Real-Time PCR instrument, and RapidFinder Express software. Two sample preparation methods were validated: the PrepSEQ Nucleic Acid extraction kit and the PrepSEQ Rapid Spin sample preparation kit. The test method was compared to the ISO 11290-1 reference method using an unpaired-study design to detect L. monocytogenes in roast beef, cured bacon, lox (smoked salmon), lettuce, whole cow's milk, dry infant formula, ice cream, salad dressing, and mayonnaise. The MicroSEQ L. monocytogenes Detection Kit and the ISO 11290-1 reference method showed equivalent detection based on Chi-square analysis for all food matrixes when the samples were prepared using either of the two sample preparation methods. An independent validation confirmed these findings on smoked salmon and whole cow's milk. The MicroSEQ kit detected all 50 L. monocytogenes strains tested, and none of the 30 nontargeted bacteria strains.     

General Synthesis of Two‐Dimensional Patterned Conducting Polymer‐Nanobowl Sheet via Chemical Polymerization

Summary: A general method for the generation of two‐dimensional (2D) ordered, large‐area, and liftable conducting polymer‐nanobowl sheet has been demonstrated via chemical polymerization for the first time. The sheet is made using the monolayer self‐assembled from polystyrene (PS) spheres at the aqueous/air interface as template, followed by depositing conducting polymer on the part of PS monolayer submerging in the aqueous phase via chemical polymerization, and core extraction. During the process of polymerization, no substrate is required, which caused the as‐prepared patterned conducting polymer sheet can be easily lifted‐off and deposited, in full size, on any flat substrate. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectrum were used to characterize the products.

Morphology of the polyaniline‐CSA nanobowl sheet.