Highly sensitive and selective catalytic determination of formaldehyde and acetaldehyde

A highly sensitive, simple and selective kinetic method was developed for the determination of ultra-trace levels of formaldehyde and acetaldehyde based on their catalytic effect on the oxidation of N,N-diethyl-p-phenylenediamine (DPD) with hydrogen peroxide. The reaction was monitored spectrophotometrically by tracing the formation of the red-colored oxidized product of DPD at 510nm, within 30s of mixing the reagents. The optimum reaction conditions were: 20mmolL(-1) DPD, 250mmolL(-1) H(2)O(2), 150mmolL(-1) phosphate, 150mmolL(-1) citrate and pH 6.60+/-0.05 at 25 degrees C. Following the recommended procedure, formaldehyde and acetaldehyde could be determined with linear calibration graphs up to 0.50 and 1.4microg mL(-1) and detection limits, based on the 3S(b)-criterion, of 0.015 and 0.035microg mL(-1), respectively. In addition, analytical data for other 10 aldehydes were also presented. The high sensitivity and selectivity of the proposed method allowed its successful application to rain water, mainstream smoke (MSS) and disposed tips of smoked cigarettes (DTSC). A sample aliquot was directly analyzed for its total water-soluble aldehyde content. A second sample aliquot was heated at 80 degrees C for 10min to expel acetaldehyde and the aliquot was analyzed for its content of other water-soluble aldehydes (expressed as formaldehyde equivalent), and acetaldehyde was determined by difference. The analytical results were in excellent agreements with those obtained following the standard HPLC method based on pre-column derivatization with 2,4-dinitrophenylhydrazine. Moreover, published catalytic-spectrophotometric methods for the determination of aldehydes were reviewed.     

The effect of a functional group in penicillin derivatives on the interaction with bile salt micelles studied by micellar electrokinetic chromatography.

A capillary electrophoresis method is developed and validated for the characterization of the affinity and the interaction between aminopenicillanic acid (APS-H) and its derivatives with bile salt micelles. The micellar systems studied contained sodium taurocholate (NaTC) and sodium deoxycholate (NaDC). Using the retention factor k', functional group selectivity, gammaG, is defined as the ratio of the retention factor of a substituted aminopenicillanic acid (APS-R) over the capacity factor of APS-H and the difference in free energy (deltadeltaG degrees) can be used for the characterization of the affinity and interaction between drugs and micelles. The functional group selectivity is a direct measure of the interaction of the functional group with micelles. The calculated deltadeltaG degrees value gives information on the partition equilibrium and interaction between drugs and micelles. A positive deltadeltaG degrees value means that the interaction of a functional group gammaG to the APS-H leads to a decrease in the interaction with the micelles. A negative deltadeltaG degrees value, on the other hand, has the opposite meaning. The results obtained in this study exhibited that these APS-R compounds have smaller affinity to the micelles compared to unsubstituted APS-H. Furthermore, the log k' of the drugs in these systems were correlated with the log Pow in the n-octanol/water system and with log P(G) (permeation coefficient).