Analysis of 10 ß-agonists in pork meat using automated dispersive pipette extraction and LC-MS/MS.

An analytical procedure for the analysis of 10 ß-adrenergic agonists (cimaterol, terbutaline, salbutamol, isoxsuprine, ractopamine, cimbuterol, clenbuterol, brombuterol, mabuterol and mapenterol) in pork meat was developed and validated using LC-MS/MS. An automated dispersive pipette extraction (DPX) was employed on a Hamilton Microlab® NIMBUS96® platform to extract the analytes of interest prior to LC-MS/MS analysis. The extraction time was <20 min with a total LC-MS/MS run time of 9.6 min. The method was fully validated in accordance with the international guidelines (European Commission Decision 2002/657/EC and National Standards of People's Republic of China, GB/T 22286-2008) for limit of detection, limit of quantitation, carryover, extraction efficiency, matrix effects, linearity, and within and between-run precision. The proposed method can be successfully used in the routine determination of 10 ß-adrenergic agonists in pork and as a potential solution for compliance monitoring in regulatory laboratories.

Variations in enzymatic hydrolysis efficiencies for amitriptyline and cyclobenzaprine in urine.

A collaborative study was conducted to investigate discrepancies in recoveries of two commonly prescribed compounds, amitriptyline and cyclobenzaprine, in patient urine samples when hydrolyzed with different enzymes from different sources. A 2- to 10-fold increase in analyte recoveries was seen for patient samples hydrolyzed using a recombinant ß-glucuronidase (IMCSzyme™) over samples hydrolyzed with ß-glucuronidase from Haliotis rufescens We report outcomes from four commercially available ß-glucuronidase enzymes (IMCSzyme™, Patella vulgata, Helix pomatia and H. rufescens) on patient samples that tested positive for amitriptyline and cyclobenzaprine. Our results confirm reduced hydrolysis of glucuronides by ß-glucuronidases isolated from mollusks, but near complete conversion when using the recombinant enzyme. Our premise is that systematic differences in hydrolysis efficiencies due to varying substrate affinity among enzyme subtypes potentially impacts accuracy and reliability of measurements.

Automated QuEChERS tips for analysis of pesticide residues in fruits and vegetables by GC-MS.

This paper reports the development of an automated method of QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) using pipet tips fitted with filtration screens and containing primary-secondary amine, magnesium sulfate, and graphitized carbon black. These tips are referred to as "QuEChERS Tips". Using loosely contained sorbent, dispersive solid phase extraction (dSPE) cleanup was performed with the QuEChERS Tips and automation. The main advantage of the QuEChERS Tips is that they are readily automated because this dSPE method does not require centrifugation. High recoveries (70-117%) and good reproducibilities (<12%) are shown for over 200 pesticides using automated QuEChERS Tips and GC-MS in various sample matrices.

Multiresidue analysis of pesticides in fruits and vegetables using disposable pipette extraction (DPX) and micro-luke method.

Simple and rapid methods for the analysis of pesticides in produce samples have been developed. The current study involves analysis of nonpolar and polar pesticides using GC-ECD and GC-NPD, respectively. The nonpolar pesticides were extracted using disposable pipette extraction (DPX) following a preliminary acetone extraction based on the Luke method. Recoveries of the fortified pesticides ranged between 70.5 and 110.0%, with relative standard deviations (% RSD) below 10% for most target analytes. From calibration plots, the limits of detection (LOD) were determined to be <0.05 ppm for most studied pesticides with coefficients of determination (r(2)) >0.99. A micro-Luke method was adapted and used for the analysis of polar pesticides, which greatly reduces the volumes of solvent and time for sample preparation. This new method of analysis, combining DPX and micro-Luke, was compared directly with the modified Luke method for analysis of pesticides in produce samples over a 9 week period. This study validates the suitability for routine analysis of pesticides in acetone extract of fruits and vegetables using the proposed DPX and micro-Luke method.

Disposable pipette extraction for the analysis of pesticides in fruit and vegetables using gas chromatography/mass spectrometry.

Organochlorine, organophosphate pesticides and fungicides in fruits and vegetables were analyzed using disposable pipette extraction (DPX) followed by gas chromatography-mass spectrometry-selective ion monitoring (GC/MS-SIM). The intrinsic rapid mixing capabilities of DPX result in fast and efficient extractions, and eluates are concentrated by using minimal elution solvent volumes rather than solvent evaporation methods. Matrix-matched calibrations were performed with reversed phase mechanisms (DPX-RP), and the limits of detection (LOD) were determined to be lower than 0.1 microg/mL for all targeted pesticides in carrot and orange sample matrices. Coefficients of determination (r(2)) were greater than 0.995 for most studied pesticides. DPX-RP exhibited recoveries between 72 and 116% for nonpolar and slightly polar pesticides (logP>2) with most of the recoveries over 88%. Only very polar pesticides (e.g., acephate, mathamidophos) were not extracted well using DPX-RP.

New approach to multiresidue pesticide determination in foods with high fat content using disposable pipette extraction (DPX) and gas chromatography-mass spectrometry (GC-MS).

Organochlorine and organophosphate pesticides in corn muffin mix and cocoa beans were analyzed using disposable pipette extraction (DPX) for rapid cleanup followed by gas chromatography-mass spectrometry (GC-MS). The DPX method in this study used weak anion exchange (WAX) mechanisms to remove the major sample matrix interferences, fatty acids, from the chromatographic analyses. The limits of detection (LOD) were determined to be <10 ppb for all studied pesticides in corn muffin. DPX-WAX exhibited average recoveries reaching 100% for most targeted pesticides, with relative standard deviations below 10%. These results indicate that DPX with weak anion exchange sorbent is effective at eliminating fatty acid interferences in foods of high fat content prior to multiresidue pesticide analysis. Furthermore, the DPX cleanup method takes approximately 2 min to perform. In addition, removal of fatty acids from cocoa beans demonstrates the high capacity of this extraction method for samples containing up to 50% fat.

Comprehensive analysis of drugs of abuse in urine using disposable pipette extraction.

The extraction of basic, acidic, and neutral drugs of abuse from a low volume of urine (0.2 mL) using disposable pipette extraction (DPX) is described. DPX is a solid-phase extraction device that uses loosely contained sorbent inside a pipette tip fitted with a screen. This device provides faster extraction times because conditioning steps are not required. In this study, the DPX used a modified divinyl benzene sorbent containing both cation-exchange and reversed-phase mechanisms that facilitates the retention of basic and acidic/neutral drugs, respectively. With this device, a comprehensive method of analysis was developed for a diverse group of drugs and drug classes in urine including amphetamines, opiates, cocaine and its metabolites, tetrahydrocannabinol metabolite, tricyclic antidepressants, meperidine, methadone, and phencyclidine. Recoveries of the majority of drugs analyzed were 90% or greater with relative standard deviations of less than 10%. Additional validation involved the analysis of urine specimens previously analyzed by a local forensic toxicology laboratory.

The analysis of delta9-tetrahydrocannabinol and metabolite in whole blood and 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in urine using disposable pipette extraction with confirmation and quantification by gas chromatography-mass spectrometry.

Essential to forensic laboratories is the desire to find a more sensitive, rapid method of analyzing Delta9-tetrahydrocannabinol (THC) and metabolite in biological specimens. Disposable pipette extraction (DPX) is a valuable method in extracting THC and 11-nor-Delta9-tetrahydrocannabinol-9-carboxylic acid (THCc) in blood and THCc in urine. Less waste and solvent usage; smaller specimen volume; clean chromatograms; and utilization of lowcost equipment and consumables were achieved using this method. Differing from traditional solid-phase extraction devices, DPX uses loosely packed sorbent allowing thorough mixing with the specimen without requiring vacuum for elution. Prior to extraction, urine specimens were hydrolyzed and proteins precipitated from blood. Specimen volume requirements were 1 mL of blood and 0.2 mL of urine. The limits of quantitation for THC and THCc in blood were 1 and 2 ng/mL, respectively, and 3 ng/mL for THCc in urine. With R2 values > or = 0.99, blood calibration curves were linear from 1 to 200 ng/mL and 2 to 500 ng/mL for THC and THCc, respectively, with urine THCc linear from 3 to 2000 ng/mL.