Multiple response optimization of a QuEChERS extraction and HPLC analysis of diclazuril, nicarbazin and lasalocid in chicken liver.

A method for the simultaneous determination of three commonly used coccidiostats in chicken liver was developed, comprising a multi-residue QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction step, and a liquid chromatography-ultra violet-fluorescence (HPLC-UV/FL) analysis. The QuEChERS extraction was optimized using an experimental design approach that includes a screening step to obtain the critical variables, an optimization step using multiple response surface analysis and the calculation of a desirability parameter. The optimized method was validated with fortified samples, reaching an average recovery of 91% and an overall precision of 5.5% (mean of three analytes at three levels). Limits of detection calculated on fortified samples were 20 µg kg-1 for lasalocid, 15 µg kg-1 for nicarbazin and 120 µg kg-1 for diclazuril. These values resulted at least one order of magnitude lower than the maximum allowed residue limit (MRL) of the studied coccidiostats for chicken liver.

Continuous method to determine the trypsin inhibitor activity in soybean flour.

The determination of trypsin inhibitor (TI) activity is of importance to evaluate the nutritional value of soybean flours. An analytical method, which involves a continuous spectrophotometric rate determination for trypsin activity against the substrate N-benzoyl-DL-arginine p-nitroanilide, is proposed as an alternative to the standard discontinuous assay. Stopping the reaction with acetic acid and a centrifugation/filtration step to decrease turbidity are not required, thus reducing costs and sample preparation time. The TI activity of different flour samples, determined by both assays, demonstrated to be statistically comparable, irrespective of the TI concentration level. The coefficients of variation of the novel method did not exceed 8% at any concentration level. The curves of progress reaction showed a non-linear behavior in samples without TI. A reduction of incubation time from 10min to 2min increased the method sensitivity and extended its linear range. A more economical, faster and simpler assay was developed.

Achieving second order advantage with multi-way partial least squares and residual bi-linearization with total synchronous fluorescence data of monohydroxy-polycyclic aromatic hydrocarbons in urine samples.

An attractive approach to handle matrix interference in samples of unknown composition is to generate second- or higher-order data formats and process them with appropriate chemometric algorithms. Several strategies exist to generate high-order data in fluorescence spectroscopy, including wavelength time matrices, excitation-emission matrices and time-resolved excitation-emission matrices. This article tackles a different aspect of generating high-order fluorescence data as it focuses on total synchronous fluorescence spectroscopy. This approach refers to recording synchronous fluorescence spectra at various wavelength offsets. Analogous to the concept of an excitation-emission data format, total synchronous data arrays fit into the category of second-order data. The main difference between them is the non-bilinear behavior of synchronous fluorescence data. Synchronous spectral profiles change with the wavelength offset used for sample excitation. The work presented here reports the first application of total synchronous fluorescence spectroscopy to the analysis of monohydroxy-polycyclic aromatic hydrocarbons in urine samples of unknown composition. Matrix interference is appropriately handled by processing the data either with unfolded-partial least squares and multi-way partial least squares, both followed by residual bi-linearization.

Determination of polycyclic aromatic hydrocarbon metabolites in milk by a quick, easy, cheap, effective, rugged and safe extraction and capillary electrophoresis.

We describe the first application of a quick, easy, cheap, effective, rugged and safe extraction technique to the CZE analysis of monohydroxylated metabolites of polycyclic aromatic hydrocarbons in milk. Complete resolution of 2-hydroxyfluorenene, 1-hydroxynaphthalene, 2-hydroxynaphthalene, 3-hydroxyphenanthrene, and 9-hydroxyphenanthrene was accomplished in 4 min of electrophoretic run. Limits of detection at the parts-per-billion were obtained with a single solvent (acetonitrile) for metabolite extraction and sample stacking. The small sample volume (1.2 mL) and the conservative usage of chemicals provided a simple and rapid procedure for the simultaneous extraction of numerous samples. Adding 4 min of electrophoretic run per sample, it should be possible to screen ten samples in approximately 1 h of analysis time. The nanoliter extract volume required for sample injection allows for further chromatographic usage and confirmation of positive samples. The unique electrophoretic pattern of the studied metabolites demonstrates the potential for the unambiguous determination of positional isomers with very similar chromatographic behaviors and undistinguishable mass fragmentation patterns.

Solid-phase extraction, sample stacking and capillary zone electrophoresis for the analysis of urinary polycyclic aromatic hydrocarbon metabolites.

A capillary zone electrophoresis method is presented for the analysis of six biomarkers of polycyclic aromatic hydrocarbons in urine samples. Baseline resolution of 2-hydroxyfluorene, 2-hydroxynaphthalene, 1-hydroxypyrene, 9-hydroxyphenanthrene, 3-hydroxybenzo[a]pyrene, 4-hydroxybenzo[a]pyrene and 5-hydroxybenzo[a]pyrene was achieved in approximately 17 min with a 20 mM borate buffer prepared in 50% methanol-water (volume/volume). Competitive limits of detection were obtained for all the studied metabolites using commercial instrumentation equipped with an ultraviolet-visible absorption detector. Detection at the sub-parts-per-billion concentration levels was made possible via sample pre-concentration based on solid-phase extraction and sample stacking. Solid-phase extraction was performed with the aid of a twelve port vacuum manifold. Sample stacking was carried out in methanol, i.e. the eluting solvent from the solid-phase extraction procedure. To the extent of our literature search, this is the first application of sample stacking to the analysis of monohydroxy-polycyclic aromatic hydrocarbons in urine samples. Metabolite recoveries varied from 93.2 ± 7.7% (5-hydroxybenzo[a]pyrene) to 108.7 ± 7.8% (2-hydroxynaphthalene). Limits of detection were at the trace level ranging from 0.99 ng mL(-1) (3-hydroxybenzo[a]pyrene) to 8.54 ng mL(-1) (2-hydroxynaphthalene). The new method was found to be free of interference from four pharmacological drugs - naproxen, ibuprofen, diclofenac and amoxicillin - that might be found in urine samples of unhealthy individuals.

Gold nanoparticles deposited capillaries for in-capillary microextraction capillary zone electrophoresis of monohydroxy-polycyclic aromatic hydrocarbons.

This article presents the first application of gold nanoparticles deposited capillaries as pre-concentration devices for in-capillary microextraction CZE and their use for the analysis of monohydroxy-polycyclic aromatic hydrocarbons in synthetic urine samples. The successful separation of 1-hydroxypyrene, 9-hydroxyphenanthrene, 3-hydroxybenzo[a]pyrene (3-OHbap), 4-hydroxybenzo[a]pyrene and 5-hydroxybenzo[a]pyrene under a single set of electrophoretic conditions is demonstrated as well as the feasibility to obtain competitive ultraviolet absorption LOD with commercial instrumentation. Enrichment factors ranging from 87 (9-OHphe) to 100 (3-OHbap) made it possible to obtain LOD ranging from 9 ng/mL (9-OHphe and 3-OHbap) to 14 ng/mL (4-hydroxybenzo[a]pyrene).