On the natural fate of maleic hydrazide. Kinetic aspects of the photochemical and microbiological degradation of the herbicide.

Kinetic and mechanistic aspects of the photochemical and microbiological degradation of the herbicide Maleic Hydrazide (MH) have been studied. Riboflavin (Rf, vitamin B2) was employed as a main photosensitizer whereas Humic Acid (HA) was included as a second sensitizer in order to more closely simulate natural environmental conditions. MH quenches excited singlet and triplet states of Rf, with rate constants close to the diffusion limit. The herbicide and dissolved molecular oxygen competitively quench triplet excited Rf. As a consequence the reactive oxygen species (ROS), superoxide radical anion (O2(-·)), hydrogen peroxide (H2O2) and singlet molecular oxygen (O2((1)Δg)) are produced by electron- and energy-transfer processes, respectively, as demonstrated by auxiliary experiments employing selective auxiliary quenchers and the exclusive O2((1)Δg) generator Rose Bengal (RB). As a global result, the photodegradation of Rf is retarded, whereas MH is degraded by the generated ROS. The bacteria Pseudomonas aeruginosa (Ps) and Bacillus subtilis (Bs), recognized as contaminants surface-water and soil and microbial antagonists of phytopathogenic, were used in the microbiological experiments. Results of the individual incubation of both bacteria in in the presence of MH indicate a stimulation on the Ps growth, implying the biodegradation of the herbicide, whereas MH only exerted a bacteriostatic effect on Bs.

Surface-enhanced Raman spectroscopic analysis of maleic hydrazide adsorbed on gold surface.

In this paper, surface-enhanced Raman scattering (SERS) spectra of maleic hydrazide (MH, 6-hydroxy-3(2H)-pyridazinone) were studied by using citrate-reduced gold colloidal nanoparticles. Comparisons between the prominent SERS bands and the precise mode descriptions predicted through density functional theory (DFT) simulations at the B3LYP/6-311++g(d,p) level allowed an in-depth orientation analysis of the adsorbed species on gold surfaces. And main forms of hydrogen bonds in the solid state of MH were also determined to be O-H⋯O. Furthermore, the effects of concentration and pH on the SERS spectra of the molecule were discussed. It is found that with the different adsorbate concentration, the SERS spectra of MH show significant changes in their features, indicating different orientations and adsorption sites of the molecule on the gold colloidal surface. The SERS and absorption spectra under different pH conditions show that a basic environment leads to the deprotonation of N2 and the nearly parallel orientation of the MH molecule on the gold surface. Moreover, the enhanced characteristic bands were observed at MH concentrations down to about 1 ppm with the gold colloids, demonstrating a potential of the technique in the analysis of MH residues.

[Determination of maleic hydrazide residues and its influence on the quality of Atractylodes macrocephala].

OBJECTIVE: To determine maleic hydrazide (MH) residues and discuss its influence on the quality of Atractylodes macrocephala. METHODS: At the bud stage, A. macrocephala different concentration of MH. Then MH residues,the contents of sugar and lactone were determined by HPLC and UV. The quality of A. macrocephala was comprehensively evaluated by independent sample t test and principal component analysis. RESULTS: The range of MH residues was 0.3-2.2 mg/kg. The results of independent sample t test revealed that the trend of the contents of lactone was low-high-low with the increase of MH, and the effect of MH on the content of sugar was barely obvious. Meanwhile, principal component analysis showed that comprehensive evaluation on the quality of A. macrocephala was the best when MH with 75 or 100 times water was applied. CONCLUSION: Proper concentration MH is applied to ensure low concentration MH residues and improve yield and quality of A. macrocephala.

Flow injection chemiluminescence sensor using molecularly imprinted polymers as recognition element for determination of maleic hydrazide.

A novel flow injection chemiluminescence (CL) sensor for the determination of maleic hydrazide (MH) using molecularly imprinted polymer (MIP) as recognition element is reported. The MH-MIP was synthesized by thermal initiated polymerization in methanol, using methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker in the maleic hydrazide template molecule. Molecular modeling was employed to simulate the possible recognition process of the MIP, and to achieve high selectivity. Then the synthesized MH-MIP was employed as recognition element by packing into flow cell to establish a novel flow injection CL sensor. The CL intensity responded linearly to the concentration of MH in the range 3.5x10(-4)-5.0x10(-2) mg/mL with a detection limit of 6.0x10(-5) mg/mL (3sigma), which is lower than that of conventional methods. The relative standard deviation (RSD) for the determination of 1.0 microg/mL of MH was 2.7% (n=11). The sensor is reusable and has a great improvement in sensitivity and selectivity for CL analysis. As a result, the new MIP-CL sensor had been successfully applied to the determination of MH in vegetable samples.

Liquid chromatographic determination of maleic hydrazide in technical and formulated products: collaborative study.

Fourteen collaborating laboratories assayed maleic hydrazide (MH), 6-hydroxypyridazin-3(2H)-one, in technical and formulated products by reversed-phase liquid chromatography (LC) with sulfanilic acid as an internal standard. The active MH in the samples (6 lots) ranged from 16% (expressed as the potassium salt) to 98% (MH in the technical). A small amount of 1 M KOH was added to the technical MH and analytical standards to create the potassium salt of the analyte which is soluble in water. Test samples and standards were extracted with water containing the internal standard before analysis by LC on a C8 column with an ion-pairing eluting solution and UV detection at 254 nm. The concentration of MH was calculated by comparing the peak area response ratios of the analyte and the internal standard with those in the analytical standard solution. Eleven laboratories weighed each test sample twice with single analysis. Three laboratories weighed each sample once and made duplicate injections on the LC system. The data were analyzed using the 11 laboratories' results. A second data analysis was done including all laboratory results using a Youden pair approach, selecting one of 2 duplicate assay values randomly for each laboratory and sample. In the first data analysis, the repeatability standard deviation ranged from 0.07 to 1.39%; reproducibility standard deviation ranged from 0.22 to 1.39%. In the second data analysis (using all laboratory data), repeatability standard deviation ranged from 0.09 to 0.86%; reproducibility standard deviation ranged from 0.22 to 1.31%.

Spectroscopic and thermal studies of chromium(III), molybdenum(VI) and ruthenium(0) complexes of maleic hydrazide.

Interaction of maleic hydrazide (LH(2)) with [Cr(CO)(6)] in air at atmospheric pressure resulted in the formation of the complex [(LH)Cr(mu-O)(2)Cr(LH)] (1). Reaction of LH(2) with [Mo(CO)(6)] in air also gave the complex [(LH(2))O(2)Mo(mu-O)(2)MoO(2)(LH(2))] (2). Under the same conditions, the reaction of LH(2) with [Ru(3)(CO)(12)] resulted in the formation of the tricarbonyl complex [Ru(CO)(3)(LH(2))] (3). The complexes were characterized by elemental analysis, IR, and (1)H NMR spectroscopy. The thermal properties of the complexes were investigated by thermogravimetry technique.

Crystallographic autostereograms.

Perspective drawings of crystal structures can be presented as autostereograms (or single-image stereograms), and their performance for in-depth perception is similar or even more advantageous than of stereopairs. The autostereograms offer a convenient means for realistic insight into crystal structures without excessive size reduction of their drawings, as required when preparing stereopairs; thus structures either as simple as elements or as complex as proteins can be illustrated in enhanced resolution. The mathematical background and guidelines for preparing crystallographic autostereograms are described.

Shake-flask test for determination of biodegradation rates of (14)C-labeled chemicals at low concentrations in surface water systems.

A simple shake-flask surface water biodegradability die away test with (14)C-labeled chemicals added to microgram per liter concentrations (usually 1-100 microg/L) is described and evaluated. The aim was to provide information on biodegradation behavior and kinetic rates at environmental (low) concentrations in surface water systems. The basic principle of measurement was to determine evolved CO(2) indirectly from measurements of total organic activity in subsamples after stripping off their content of CO(2). Used with surface water alone the test simulates a pelagic environment and amended with sediments (0.1-1 dry weight/L) the test is intended to simulate a water environment with suspended solids (e.g., resuspended sediments). A protocol of the test used with the (14)C technique or with specific chemical analysis was recently developed by the International Organization for Standardization. Practical experience with the method is presented for a set of reference substances. These substances could be ranked in five groups of decreasing biodegradability: aniline>p-nitrophenol, 2, 4-dichlorophenoxyacetic acid>4-chloroaniline>maleic hydrazide, pentachlorophenol>atrazine. It was found that degradation rates and lag periods varied considerably among sampling sites and sometimes also among samples from the same site. No significant correlation could be established between degradation rates and microbial biomass estimates. Even small portions of added sediments greatly enhanced biodegradation of the absorbable compound pentachlorophenol, probably by providing sites for microbial attachment. Repeated tests indicated consistent degradation behavior for the readily degradable substances, whereas degradation sometimes stopped or failed with the more recalcitrant substances. A preadaptation step involving regular reinoculation with freshly collected surface water could, however, overcome the problems of false-negative results.

Extraction of maleic hydrazide residues from potato crisps and their determination using high-performance liquid chromatography with UV and atmospheric pressure chemical ionisation mass spectrometric detection.

A method was required for the determination of maleic hydrazide residues in potato crisps. A published method for the extraction of the analyte from onions and potatoes was evaluated and found to be inappropriate due to the inability of the extracting solvent to penetrate the oily matrix. A method was developed to overcome this problem; the resulting recovery data (mean = 92.9%, R.S.D. = 8.3%, n = 16) confirmed its efficiency, and was used to analyse 48 retail potato crisp samples. To confirm possible residues identified by screening with HPLC-UV, an HPLC-atmospheric pressure chemical ionization MS method was developed. There was good agreement between the data obtained from the two detection techniques (R2 = 0.978, slope = 1.11).

A novel heterobifunctional linker for formyl to thiol coupling.

A maleimide hydrazide has been synthesized as a heterobifunctional cross-linking agent for thiol to formyl coupling. This linker has been applied to the coupling of the monoclonal antibody 17-1A, or an Fab' derived therefrom, to polyaldehyde dextran onto which the antineoplastic agent ellipticine has been attached. High binding avidities for the unshed antigen on the SW1116 colorectal tumor cell are retained in these drug-dextran-linker-antibody conjugates.