Field investigations on the snow chemistry in central and southern california—II. Carbonyls and carboxylic acids

A new sensitive method for the quantification of glyoxal and methylglyoxal in snow and ice by stir bar sorptive extraction and liquid desorption-HPLC-ESI-MS

In this study, the development of a new sensitive method for the analysis of alpha-dicarbonyls glyoxal (G) and methylglyoxal (MG) in environmental ice and snow is presented. Stir bar sorptive extraction with in situ derivatization and liquid desorption (SBSE-LD) was used for sample extraction, enrichment, and derivatization. Measurements were carried out using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). As part of the method development, SBSE-LD parameters such as extraction time, derivatization reagent, desorption time and solvent, and the effect of NaCl addition on the SBSE efficiency as well as measurement parameters of HPLC-ESI-MS/MS were evaluated. Calibration was performed in the range of 1-60 ng/mL using spiked ultrapure water samples, thus incorporating the complete SBSE and derivatization process. 4-Fluorobenzaldehyde was applied as internal standard. Inter-batch precision was <12 % RSD. Recoveries were determined by means of spiked snow samples and were 78.9 ± 5.6 % for G and 82.7 ± 7.5 % for MG, respectively. Instrumental detection limits of 0.242 and 0.213 ng/mL for G and MG were achieved using the multiple reaction monitoring mode. Relative detection limits referred to a sample volume of 15 mL were 0.016 ng/mL for G and 0.014 ng/mL for MG. The optimized method was applied for the analysis of snow samples from Mount Hohenpeissenberg (close to the Meteorological Observatory Hohenpeissenberg, Germany) and samples from an ice core from Upper Grenzgletscher (Monte Rosa massif, Switzerland). Resulting concentrations were 0.085-16.3 ng/mL for G and 0.126-3.6 ng/mL for MG. Concentrations of G and MG in snow were 1-2 orders of magnitude higher than in ice core samples. The described method represents a simple, green, and sensitive analytical approach to measure G and MG in aqueous environmental samples.

Degradation of atrazine photoinduced by Fe(III)-pyruvate complexes in the aqueous solution

The composition and photochemical properties of the Fe(III)-Pyr complexes in the aqueous solution was studied in this work. Fe(III) was complexed by Pyr in the ratio of 1:3. The photochemical processes occurred in the Fe(III)-Pyr system was studied in detail. Fe(II) was the main intermediate product. DMPO was used as scavenger to determine the active radicals, such as *OH, CO3*-, CO2*-, H and RCO2* by ESR. Photodegradation of atrazine induced by the photolysis of Fe(III)-Pyr was studied and the reaction kinetics fitted the first order reaction. Parameters such as pH, the initial concentrations of Fe(III), pyruvate (Pyr) and atrazine were all investigated. Photoproducts were detected by the LC-MS and the photodegradation scheme was proposed. *OH radical was the main pathway of atrazine degradation.

Cross determination of the vapor liquid equilibrium of formaldehyde aqueous solutions by quadrupole mass spectrometry and infrared diode laser spectroscopy

Quantitative measurements of the partial vapor pressure of formaldehyde are performed above aqueous H2CO solutions of different concentrations (from 10(-5) to 0.3 molar fraction) using mass spectrometry and IR diode laser spectroscopy. Both experimental techniques allow direct probing of the gas phase concentration collected at equilibrium above the aqueous solutions. A correlation is observed between the polymerization processes occurring in the solution and the partial pressure of H2CO measured at vapor liquid equilibrium (VLE). A similar correlation is observed from total pressure measurements for which the equilibrium vapor pressure decreases as [VLE XH2CO]liq is increased. A saturation regime of the H2CO partial pressure is reached as the dissolved fraction of formaldehyde increases above approximately 0.15 mol frac. Henry's law constants are derived at 295K for the diluted solutions.