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A convenient method has been developed for the separation and determination of beeswax in propolis from beehives located in the Netherlands. The method is based on differences in specific density and involves the adding of water and microwave heating of a propolis sample. After cooling to room temperature, the resulting three phase system provides a full separation of the beeswax from the propolis in the upper layer. This layer can easily be collected to quantify the authentic beeswax content of the raw propolis sample. Confirmation of the identity of beeswax isolated from propolis with this procedure, was obtained using Near Infrared Spectroscopy (NIR).

Restricted access media (RAM) columns in the column mode and column switching (LC/LC) configuration represent a powerful approach for the analysis of acidic compounds in water samples with high levels of organic matter. This was gleaned from a study aimed at determining their performance in decreasing the humic acid interference in the trace analysis of acidic herbicides in water samples during the use of reversed-phase liquid chromatography with UV detection. The use of RAM columns permits the development of a rapid, sensitive and selective multiresidue procedure for the screening of a heterogeneous group of acidic herbicides.

This study investigated the potential of restricted access media (RAM) columns used as a first column in coupled-column LC hyphenated to thermospray tandem mass spectrometry (LC/LC-TSP/MS/MS) for the fast, selective, and sensitive determination of target drugs in serum samples. Because of their wide range in polarity, salbutamol and clenbuterol were chosen as model compounds and representatives of the class of [[Beta].sub.2]-agonists. Three types of RAM columns were tested: (i) Pinkerton ISRP (internal surface reversed phase, 5 [[micro]meter]), (ii) SPS (semipermeable surface, 5 [[micro]meter] C18), and (iii) RP-18 ADS (alkyl-diol silica, 25 [[micro]meter]). A 3-[[micro]meter] C18 column (50 mm x 4.6 mm i.d.) was chosen as the second column. Tandem mass spectrometric detection was carried out in the selected reaction monitoring (one parent[right arrow]one daughter) mode. With regard to retention and, moreover, the peak elution volume of the analytes, the ISRP material was found to perform best: a 50-mm x 4.6-mm i.d. ISRP column in combination with a 100% aqueous buffer (pH of 7.0 [+ or -] 0.2) allowed the injection of large volumes (up to 200 [[micro]liter]) of sample without additional band broadening of the analytes and provided sufficient preseparation between analytes and large-molecule serum constituents. Under the selected conditions, both analytes could be determined in serum samples up to a limit of quantification (LOQ) of 0.5 ng/mL, with a sample throughput of 7 and 5 [h.sup.-1] for salbutamol and clenbuterol, respectively. Method validation was carried out by analyzing, in the course of several days, calf and human serum samples spiked with the analytes. In the case of salbutamol, the overall recovery from serum samples spiked at levels between 0.5 and 50 ppb (n = 33) was 103.4%, with a repeatability of 12.7% and reproducibility of 14.3%. The overall recovery for clenbuterol was 99.6% (n = 15, spiked level 0.5-5 ppb), with a repeatability of 15.2% and reproducibility of 16.4%. The adopted LC/LC-TSP/MS/MS analyzer appeared to be very robust under the selected conditions, and, after the period of analysis involving the processing of more than 100 mL of serum, neither loss of chromatographic performance nor pressure increase of columns or of the interface was observed.

Focuses on the development of column switching in liquid chromatography (LC) in many configurations. Discrimination of precolumn switching from coupled-column; Packing of precolumns with materials of larger particle size; Evidence of the high separation power of the analytical column of LC.