Accurate Quantitation and Analysis of Nitrofuran Metabolites, Chloramphenicol, and Florfenicol in Seafood by Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry: Method Validation and Regulatory Samples.

We developed and validated a method for the extraction, identification, and quantitation of four nitrofuran metabolites, 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), semicarbazide (SC), and 1-aminohydantoin (AHD), as well as chloramphenicol and florfenicol in a variety of seafood commodities. Samples were extracted by liquid-liquid extraction techniques, analyzed by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), and quantitated using commercially sourced, derivatized nitrofuran metabolites, with their isotopically labeled internal standards in-solvent. We obtained recoveries of 90-100% at various fortification levels.

UHPLC-MS/MS method for the quantitation of penicillin G and metabolites in citrus fruit using internal standards.

Penicillin G has been applied to citrus trees as a potential treatment in the fight against Huanglongbing (HLB). Here, we have developed and validated a method to identify and quantitate penicillin G and two of its metabolites, penillic acid and penilloic acid, in citrus fruit using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). This method improves upon a previous method by incorporating isotopically labeled internal standards, namely, penillic acid-D, and penilloic acid-D.

Identification of Penicillin G Metabolites under Various Environmental Conditions Using UHPLC-MS/MS.

In this work, we investigate the stability of penicillin G in various conditions including acidic, alkaline, natural acidic matrices and after treatment of citrus trees that are infected with citrus greening disease. The identification, confirmation, and quantitation of penicillin G and its various metabolites were evaluated using two UHPLC-MS/MS systems with variable capabilities (i.e.

LC-MS/MS Method for the Determination and Quantitation of Penicillin G and Its Metabolites in Citrus Fruits Affected by Huanglongbing.

In this study, we developed and validated a method for the extraction, identification, and quantitation of penicillin G and its metabolites (penilloic acid and penillic acid) in a variety of citrus fruits by employing sequential liquid/liquid and solid-phase extraction techniques in conjunction with UHPLC-MS/MS. Two product ion transitions per analyte were required for identification, which contributes to a high degree of selectivity. Corrected recoveries of penicillin G using an isotopically labeled internal standard were 90-100% at fortification levels of 0.

Interlaboratory comparison of a general method to screen foods for pesticides using QuEChERs extraction with high performance liquid chromatography and high resolution mass spectrometry.

An interlaboratory comparison of a multipesticide residue analytical method is reported. The goal of the comparison was to evaluate the potential for liquid chromatography/high resolution mass spectrometry along with a specific automated screening procedure to allow the determination of the presence or absence of a set of targeted compounds without additional manual review. The method utilized an off the shelf QuEChERs based extraction followed by analysis with an orbitrap mass spectrometer with the data evaluated by ToxID.

Analysis of pesticides residues in fresh produce using buffered acetonitrile extraction and aminopropyl cleanup with gas chromatography/triple quadrupole mass spectrometry, liquid chromatography/triple quadrupole mass spectrometry, gas chromatography/ion trap detector mass spectrometry, and GC with a halogen-specific detector.

A rapid and inexpensive multiresidue method for determining pesticides in fruits and vegetables is presented. Extraction of a 15 g sample with 15 mL acetonitrile was followed by buffering with magnesium sulfate, sodium chloride, sodium citrate dihydrate, and disodium citrate. Acidification with formic acid prior to dispersive cleanup with aminopropyl sorbent and magnesium sulfate was used to stabilize base-sensitive pesticides such as chlorothalonil.

Issues in mass spectrometry between bench chemists and regulatory laboratory managers: summary of the roundtable on mass spectrometry held at the 123rd AOAC International Annual Meeting.

At the 123rd AOAC International Annual Meeting in Philadelphia, PA, 45 residue chemists gathered for a roundtable discussion of mass spectrometry (MS) used for regulatory chemical residues analysis. The session was conceived to address current technical and communication issues about MS between "bench chemists and their bosses". The topics covered a range of practical, routine, and recurring issues on capabilities and limitations of MS techniques, and suggestions on how chemists may better communicate their MS results with customers.

Multilaboratory validation of a method to confirm chloramphenicol in shrimp and crabmeat by liquid chromatography-tandem mass spectrometry.

An existing method for chloramphenicol (CAP) determination in shrimp using a gas chromatograph with electron capture detector was adapted for confirmation of CAP with a liquid chromatograph interfaced to a triple quadrupole mass spectrometer. CAP residues are extracted from tissue with ethyl acetate, isolated via liquid-liquid extraction, and concentrated by evaporation. Extracts are chromatographed by using a reversed-phased column and analyzed by electrospray negative mode tandem mass spectrometry.

Pressure-induced Amorphization of R-Al5Li3Cu: A Structural Relation Among Amorphous Metals, Quasi-Crystals, and Curved Space.

A central question in the study of amorphous materials is the extent to which they are ordered. When the crystalline intermetallic R-Al(5)Li(3)Cu is compressed to 23.2 gigapascals at ambient temperature, an amorphous phase is produced whose order can be described as defects in a curved-space crystal.

Properties of IgA myeloma proteins isolated rom sera of patients with the hyperviscosity syndrome.

Sera, purified myeloma proteins, and urinary proteins obtained from eight patients with igA multiple myeloma were studied by physical-chemical and immunochemical methods. In six patients whose serum viscosity was increased, the sedimentation constants of the principal component of myeloma proteins ranged from 9.1 to 10.