Focusing of alkali earth metals in ligand step gradient.

A capillary electroseparation technique for focusing and selective pre-concentration of metal chelates with subsequent on-line isotachophoresis (ITP) analysis was developed and verified. The ions of alkali earth metals (Mg, Ca, Sr, and Ba) were pre-concentrated from the mixture and analyzed. The focusing of the metals was carried out in a ligand step gradient, which was created by the addition of a convenient ligand agent to the regular stationary pH step gradient. The analytical procedure consisted of three steps. During the first step, the metal ions were electrokinetically continuously dosed into the column where they were selectively trapped on the stationary ligand step gradient in the form of unmoving zones of chelate complexes with effectively zero charge. After a detectable amount of analyte was accumulated, the dosing was stopped. The accumulated zones were mobilized to the analytical column, where they were analyzed by the ITP method with conductivity or photometric detection. The proper electrolyte systems for dosing, mobilizing, and analyzing in isoelectric focusing (IEF), moving boundary electrophoresis (MBE), and ITP modes were consequently developed and put into practice. The trapping selectivity can be regulated by the choice of pH and convenient complexing agents. A mixture of alkali earth metals were used as model analytes. Using a 3000 s dosing time, the proposed method improved the detection limit by 5-29 times in comparison to analysis by ITP with classical injection.

Determination of carbonyl compounds in smoke samples: strategies for sampling and standardization.

There are significant drawbacks to the calibration procedure recommended in the normalized Spanish or American methods used to determine carbonyl compounds in ambient air by quantifying hydrazones that form with 2,4-dinitrophenylhydrazine. The impurities present in 2,4-dinitrophenylhydrazine, as well as the lack of quantitativity and the slow kinetics of some derivatization reactions can lead to considerable errors in quantification. This work proposes two alternative systems for sampling biomass smoke in order to analyze aldehydes and ketones. The standardization process used by both systems requires standard solutions to be reacted with 2,4-dinitrophenylhydrazine under experimental conditions similar to those used to collect the sample. The resulting calibration curve slopes differ between 8% and 74% from the curves used in methods that employ commercial standard hydrazone solutions. The detection limits reached by using the proposed methods are between 0.07 and 0.47 mg L(-1). Both methods are complementary for smoke samples that have significant differences in the concentrations of aldehydes or ketones.

Continuous mode of operation for large volume dosing in analytical carrier ampholyte-free isoelectric focusing of proteins applied to off-line detection of fractions.

Mass spectrometry is being increasingly used for analysis of proteome complex samples. Sample preparation is often necessary to remove matrix interferences and to concentrate analytes prior to MS measurement. A useful method for this purpose is Carrier Ampholyte Free-Isoelectric Focusing (CAF-IEF). In this paper CAF-IEF of ampholytes was performed on a commercial apparatus EA101 (Villa Labeco, Slovakia) equipped with a specially made column for samples of large volume (up to 0.5 mL). A new continuous mode without voltage interruption or electrolyte replacement was developed. In this mode, a low molecular mass pI marker (PIM 7.4) and low concentrations of myoglobin and insulin (16 mg/L), respectively, were concentrated, and then 5-microL fractions collected for off-line analyses. The total time of focusing was 66 minutes. The concentration of PIM 7.4 in the fractions was increased up to 75 times (determined by UV-VIS spectrometry). The concentration in the fractions was increased up to 30 times for myoglobin and 10 times for insulin.