Stir bar sorptive extraction for trace analysis

Before the injection--modern methods of sample preparation for separation techniques.

Stir-bar sorptive extraction: A view on method optimisation, novel applications, limitations and potential solutions.

Pressurized liquid extraction in the analysis of food and biological samples.

Sample preparation techniques for the determination of trace residues and contaminants in foods.

An analytical scheme for the determination of several organochlorine pesticides like hexachlorocyclohexanes (HCHs) and DDX compounds (p,p'-DDE, p,p'-DDD, and p,p'-DDT) as well as chlorobenzenes in strawberries has been developed. The procedure is based on aqueous accelerated solvent extraction (ASE) followed by solid-phase microextraction (SPME) or stir bar sorptive extraction (SBSE) and subsequent thermodesorption-gas chromatography/mass spectrometry analysis. A 65 microm polydimethylsiloxane/ divinylbenzene fiber was chosen for the SPME experiments. Significant SPME and ASE parameters were optimized using spiked water and strawberry samples. For the ASE of the organochlorine compounds, a water-acetone mixture (90 + 10, v/v) as the extraction solvent, an extraction temperature of 120 degrees C, and 2 cycles of 10 min extraction proved optimal. The developed method was evaluated with respect to precision and limits of detection (LOD). The relative standard deviations of replicate ASE-SPME determinations (n = 5) were in the range of 4-24%. LOD values between 1 and 10 microg/kg were achieved with the exception of DDT and DDE (40 microg/kg). Using SBSE, the LOD of these compounds could be improved (2 and 5 microg/kg). The main advantages of this method are the avoidance of cleanup and concentration procedures as well as the significant reduction of the required volume of organic solvents. The described method was applied to the determination of the pollutants in strawberry samples collected from different allotment gardens in a potentially polluted area, the Bitterfeld-Wolfen region (Germany).

Determination of organochlorine pesticides and chlorobenzenes in strawberries by using accelerated solvent extraction combined with sorptive enrichment and gas chromatography/mass spectrometry.

Comparison of ELISA and capillary electrophoresis with laser-induced fluorescence detection in the analysis of Ochratoxin A in low volumes of human blood serum.

Determination of Ochratoxin A in small volumes of human blood serum.

A sensitive method for the analysis of Ochratoxin A (OA) in house dust is described using capillary zone electrophoresis coupled to laser-induced fluorescence. The method’s sensitivity makes it suitable for determining OA from just 500 mg house dust. The house dust is extracted with acetonitrile. The extract is purified in a two-step sample clean-up. The first step is liquid-liquid extraction with dichloromethane followed by normal-phase solid phase extraction. The estimated recovery of OA exceeds 82%. Capillary electrophoresis with a developed sample stacking procedure with reversed polarity provides a low limit of detection of 0.2 ng g−1 in house dust. The buffer system and the injected volume are optimized. To enhance reproducibility and ensure proper peak identification, an internal standard was added to the method.

A New Method for the Sensitive Analysis of Ochratoxin A in House Dust

The concentration of calprotectin in feces (fCal) is a clinically useful marker of chronic gastrointestinal inflammation in humans and dogs. No commercial assay is widely available to measure fCal in small animal medicine, to date. Thus, we verified the immunoturbidimetric fCAL turbo assay (Bühlmann) of fCal for canine and feline fecal extracts by determining linearity, spiking and recovery, and intra-assay and inter-assay variability. We determined RIs, temporal variation over 3 mo, and effect of vaccination and NSAID treatment. Observed:expected (O:E) ratios (x̄ ± SD) for serial dilutions of feces were 89–131% (106 ± 9%) in dogs and 77–122% (100 ± 12%) in cats. For spiking and recovery, the O:E ratios were 90–118% (102 ± 11%) in dogs and 83–235% (129 ± 42%) in cats. Intra- and inter-assay CVs for canine samples were ≤19% and ≤7%, and for feline samples ≤22% and ≤21%. Single-sample RIs were <41 μg/g for dogs and <64 μg/g for cats. With low reciprocal individuality indices, using population-based fCal RIs is appropriate, and moderate fCal changes between measurements (dogs 44.0%; cats: 43.2%) are considered relevant. Cats had significant (but unlikely relevant) fCal increases post-vaccination. Despite individual fCal spikes, no differences were seen during NSAID treatment. The fCAL turbidimetric assay is linear, precise, reproducible, and sufficiently accurate for measuring fCal in dogs and cats. Careful interpretation of fCal concentrations is warranted in both species during the peri-vaccination period and for some patients receiving NSAID treatment.

G. Köller

Papers

Determination of organochlorine pesticides and chlorobenzenes in strawberries by using accelerated solvent extraction combined with sorptive enrichment and gas chromatography/mass spectrometry.

Comparison of ELISA and capillary electrophoresis with laser-induced fluorescence detection in the analysis of Ochratoxin A in low volumes of human blood serum.

Determination of Ochratoxin A in small volumes of human blood serum.

A New Method for the Sensitive Analysis of Ochratoxin A in House Dust

Verification of the fCAL turbo immunoturbidimetric assay for measurement of the fecal calprotectin concentration in dogs and cats