Capillary electrophoretic fingerprint investigation of gel pen inks.

In this study, two capillary electrophoresis modes, capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC), were employed for the examination of gel ink fingerprints. The optimized CZE conditions were as follows: running buffer, 0.2M boric acid and 0.05M sodium tetraborate; pH, 6.47; detection, 214 nm; separation voltage, 20 kV MEKC conditions were as follows: 20 mM sodium tetraborate-20 mM sodium dodecyl sulphate; detection, 214 nm; separation voltage, 20 kV. The CZE and MEKC fingerprints of 18 el pen inks from Beijing markets were analyzed and the inks were classified according to the fingerprints of the two CE modes.

Enantioseletive bioaccumulation and metabolization of diniconazole in earthworms (Eiseniafetida) in an artificial soil.

Degradation and enantioselective bioaccumulation of diniconazole in earthworms (Eiseniafetida) in artificial soil was investigated using liquid chromatography-tandem mass spectrometry (LC-MS/MS) method under laboratory condition. Three exposure concentrations (1 mg/kg, 10 mg/kg and 25 mg/kg) of diniconazole in soil (dry weight) to earthworms were used. The uptake kinetics fitted the first-order kinetics well. The bioaccumulation factors (BAF) of R, S isomers were 6.6046 and 8.5115 in 25 mg/kg dose exposure, 2.6409 and 2.9835 in 10mg/kg dose exposure, 1.7784 and 2.0437 in 1 mg/kg dose exposure, respectively. Bioaccumulation of diniconazole in earthworm tissues was enantioselective with a preferential accumulation of S-diniconazole and the enantiomer fractions were about 0.45-0.50 in all three level dose exposures. In addition, it was obvious that both R-diniconazole and S-diniconazole had bioaccumulation effect in earthworm. Diniconazole was metabolized to 1,2,4-triazole, (E)-3-(1H-1,2,4-triazol-1-yl) acrylaldehyde, (E, S)-4-(2, 4-dichlorophenyl)-2, 2-dimethyl-5-(1H-1,2,4-triazol-1-yl)pent-4-ene-1,3-diol, and (E)-4-(2, 4-dichlorophenyl)-3-hydroxy-2,2-dimethyl-5-(1H-1,2,4-triazol-1-yl) pent-4-enoic acid in earthworms; the metabolites of 1,2,4-triazole and (E)-3-(1H-1,2,4-triazol-1-yl)acrylaldehyde could be detected in soil as well.

The enantioselective pharmacokinetics metabolism of diniconazole in quail (Coturnix coturnixs japonica).

The pharmacokinetics of diniconazole enantiomers in quail (Coturnix coturnix japonica) were investigated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Quails were exposed to racemic diniconazole in capsule by oral at dose of 10 mg/kg (body weight). The maximal concentrations observed in blood, heart, liver, and kidney were 3.18, 11.35, 12.32, 15.03 µg/g for S-diniconazole, and 1.13, 3.70, 6.00, 2.60 µg/g for R-diniconazole. The elimination of enantiomers all met the one-compartment model in blood, heart, liver, and kidney well. The elimination half-lives (T1/2) of S-diniconazole were 2.87, 3.85, 5.29, and 4.42 h in blood, heart, liver, and kidney, respectively; the T1/2 of R-diniconazole were 2.44, 3.42, 146.23, and 74.02 h in blood, heart, liver, and kidney, respectively. The enantiomer fractions (EFs) steadily increased from 0.50 to 0.92 in blood samples and 0.91 in heart samples. Meanwhile, the values increased to 0.70 and 0.80 in liver and kidney initially, and then decreased to 0.33 and 0.44 at the end of the experiment. Metabolism was examined as well and it was found that diniconazole was metabolized to 1, 2, 4-triazole, (E)-3-(1H-1, 2, 4-triazol-1-yl) acrylaldehyde, (E, S)-(R, S)-4-(2, 4-dichlorophenyl)-2, 2-dimethyl-5-(1H-1, 2, 4-triazol-1-yl) pent-4-ene-1, 3-diol, (E)-4-(2, 4-dichlorophenyl)-3-hydroxy-2, 2-dimethyl-5-(1H-1, 2, 4-triazol-1-yl) pent-4-enoic acid, and 1, 3-dichlorobenzen in all samples of quail.

Enantioselective bioaccumulation of diniconazole in Tenebrio molitor larvae.

The enantioselective bioaccumulation of diniconazole in Tenebrio molitor Linne larva was investigated with liquid chromatography tandem mass spectrometry based on the ChiralcelOD-3R[cellulose tri-(3,5-dimethylphenyl carbamate)] column. In this study we documented the effects of dietary supplementation with wheat bran contaminated by racemic diniconazole at two dose levels of 20 mg kg(-1) and 2 mg kg(-1) (dry weight) in Tenebrio molitor. The results showed that both doses of diniconazole were taken up by Tenebrio molitor rapidly in the first few days, the concentrations of R-enantiomer and S-enantiomer at high doses reached the highest level of 0.55 mg kg(-1) and 0.48 mg kg(-1) , respectively, on the 1(st) d, and the concentrations of them obtained a maxima of 0.129 mg kg(-1) and 0.128 mg kg(-1) at low dose, respectively, on the 3(rd) d, which means that the concentration of diniconazole was proportional to the time of achieving the highest accumulated level. It afterwards attained equilibrium after a sharp decline at both 20 mg kg(-1) and 2 mg kg(-1) of diniconazole. The determination results from the feces of Tenebrio molitor demonstrated that the extraction recovery (ER) values of the high dose group were higher than that of the low dose group and the values were all above 1; therefore, it could be inferred that enantiomerization existed in Tenebrio molitor. Additionally, the biota accumulation factor was used to evaluate the bioaccumulation of diniconazole enantiomers, showing that the bioaccumulation of diniconazole in Tenebrio molitor was enantioselective with preferential accumulation of S-enantiomer.

Determination and safety evaluation of difenoconazole residues in apples and soils.

Difenoconazole was a triazole fungicide with proven bio-efficacy which leads to morphological and functional changes in the fungal cell membrane. In this work, field trials were conducted in three apple orchards. Sampling methods were improved in both the terminal residual and dissipation experiments. Residual data were analyzed and results showed that, at both recommended rates with 3 times applications and 1.5-folds of recommended rates with 4 times applications, the preharvest intervals (PHIs) of difenoconazole in apples were 6-7 days. The DT50 of difenoconazole in apples and soils were 6.3-10.2 and 9.6-68.4 days, respectively. The DT90 them were 26.2-40.6 and 45.6-216.3 days, respectively.

Citrinin selective molecularly imprinted polymers for SPE.

Molecularly imprinted polymers (MIPs) for citrinin (Cit) with 1-hydroxy-2-naphthoic acid (HNA) as mimic template were prepared and the molecularly imprinted SPE method was developed for the detection of Cit in rice with HPLC. The adsorption properties of HNA and Cit on the MIPs and nonimprinted polymers were investigated. It proved that MIPs showed higher selectivity adsorption to HNA and Cit than nonimprinted polymers were. The recoveries of Cit in rice were in the range of 86.7-97.7%. The spiked rice samples and five rice samples in Beijing market were detected using molecularly imprinted SPE method and satisfied results were obtained as discussed in this article.

The study of the interactions between heavy metals with sulfonylurea herbicides using ACE.

The affinity capillary electrophoresis method was used in the study of interactions between heavy metals (Pb, Mn, La, Cd, and Ni) and the sulfonylurea herbicides (thifensulfuron, nicosulfuron and sulfometuron). A buffer of 50 mM acetate (pH 5.85) was employed in the study. The results proved that there are two binding sites in the herbicides when chelating with the heavy metals. Binding constants of the high chelating ability sites between them were in the range of 10(3) to 10(5), and the other were in the range of 10 to 10(3). Thifensulfuron is the most powerful chelator among the three herbicides. Ni is of the weaker chelators, within the herbicides than Pb, Mn, La, and Cd. The binding abilities were proven to be increased with the pH value among the investigated range.

Ultra-high concentration of amylose for chiral separations in capillary electrophoresis.

In the present study, a capillary electrophoresis method using high concentration of amylose solutions as separation medium has been developed with the aid of dimethyl sulfoxide (DMSO) as co-solvent. The best buffer conditions for primaquine, trihexyphenidyl (THP), sulconazole and cetirizine enantiomers were optimized as 20mM sodium phosphate buffer with DMSO/water (40/60, v/v) as solvent at a pH of 3.0, containing 10% (w/v) amylose. Partial-filling and semi-permanent coating techniques were used considering the influences of DMSO on UV detection. High chiral resolution for THP enantiomers was obtained showing good chiral separation capacity of this method. The method showed good linearity (R(2) > 0.998) over the concentration range of 0.50 and 2.00 mg L(-1) for all the enantiomers. The detection limits for the tested enantiomers were in the range from 0.05 to 0.12 mg L(-1). The linear calibration models were proven to be adequate for the experimental data by lack-of-fit test. The intra-assay precision, inter-day precision and accuracy were all evaluated to be acceptable. Separation and determination of THP enantiomers in rabbit blood were also carried out.

Enantioseparation of esbiothrin by cyclodextrin-modified microemulsion and micellar electrokinetic chromatography.

A comparison between chiral cyclodextrin-modified microemulsion electrokinetic chromatography (CD-MEEKC) and cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) for the enantiomeric separation of esbiothrin was carried out. For both methods, the separation conditions were optimized by varying CD types and concentration, running buffer pH and compositions, organic modifiers, and temperature. The optimal CD-MEEKC conditions were 0.8% n-heptane, 2.3% SDS, 6.6% n-butanol, 90.3% 10 mM sodium tetraborate containing 3% (w/v, the ratio of CD mass to microemulsion volume) methyl-beta-cyclodextrin, pH 10, 25 degrees C. The optimized CD-MEKC conditions were 3.3% SDS, 96.7% 10 mM sodium tetraborate containing 5% (w/v) beta-CD, pH 10, 25 degrees C. The difference in physicochemical properties of the buffer and CDs resulted in different optimal CD type. The competitive distribution between the microemulsion (or micelle) and chiral CD contributed to the chiral separation. Both methods provided excellent separation (R(s) approximately 3) with similar migration time (ca. 15 min). CD-MEEKC provided higher separation efficiencies (>300000) than CD-MEKC (>200000). The LODs for CD-MEEKC and CD-MEKC were 4.7 microg/mL and 3.2 microg/mL, respectively. The RSDs of migration time and peak area for CD-MEEKC were slightly higher than for CD-MEKC. Both the demonstrated CD-MEEKC and CD-MEKC methods provided high efficiencies, low LODs, and reproducible enantioseparations of esbiothrin.

Simultaneous determination of inorganic anions and cations in explosive residues by ion chromatography.

A non-suppressed ion chromatographic method by connecting anion-exchange and cation-exchange columns directly was developed for the separation and determination of five inorganic anions (sulfate, nitrate, chloride, nitrite, and chlorate) and three cations (sodium, ammonium, and potassium) simultaneously in explosive residues. The mobile phase was composed of 3.5mM phthalic acid with 2% acetonitrile and water at flow rate of 0.2 mL/min. Under the optimal conditions, the eight inorganic ions were completely separated and detected simultaneously within 16 min. The limits of detection (S/N=3) of the anions and cations were in the range of 50-100 microg/L and 150-320 microg/L, respectively, the linear correlation coefficients were 0.9941-0.9996, and the R.S.D. of retention time and peak area were 0.10-0.29% and 5.65-8.12%, respectively. The method was applied successfully to the analysis of the explosive samples with satisfactory results.

Study of low-molecular weight organic acids in maize roots under the stress of cadmium using capillary zone electrophoresis.

An indirect CE method was developed for the study of low-molecular weight organic acids (LMWOAs) in maize under the stress of cadmium. The influences of indirect reagents (phthalate, salicylic acid, and benzoic acid), coion concentration, and pH were studied. A buffer composed of 15 mmol/L benzoate and 0.2 mmol/L CTAB (pH 5.7) was used in the organic acid determination. The detection limit ranged between 0.5 and 6 micromol/L. The RSD (n = 14) of the method was found to be in the range of 0.11-0.49% for migration time and 1.25-4.72% for peak area. In the maize roots, obvious increases of LMWOAs were observed when the plants were under the stress of cadmium and/or organic acids. The recovery of standard organic acids added in real samples ranged from 85 to 116%.

Studies on degradation of imazalil enantiomers in soil using capillary electrophoresis.

A scheme was demonstrated to elucidate the degradation behaviors of the two enantiomers of the fungicide imazalil in soil using cyclodextrin-modified capillary zone electrophoresis. The separation buffer was 50 mmol/L NaH2PO4, 5 mmol/L (NH4)H2PO4, and 5 mmol/L beta-cyclodextrin (pH 3.0). The limits of detection of this CE method were 0.24 and 0.26 microg/mL for (-)- and (+)-imazalil, respectively. Five different soil conditions were investigated in laboratory microcosms: under sunlight; in darkness; under UV irradiation; in sterilized soil; and in soil with wheat planted in it. Radiation, microorganisms, and uptake by wheat benefited the degradation of imazalil in this study. The half-lives (t1/2) of imazalil in soil under the above conditions were 20, 30.5, 11, 27.5, and 21.5 days, respectively. The degradation rate of imazalil in soil under the five different sets of conditions decreased in the order: UV irradiation > sunlight > soil with wheat planted in it > sterilized soil > soil kept in darkness. Imazalil in soil (pH 8.2, slightly alkaline) collected in the suburbs showed non-enantioselective degradation.

Separation and determination of phthalates by micellar electrokinetic chromatography.

A method has been developed for the separation and determination of dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DnOP) by micellar electrokinetic chromatography (MEKC). The baseline separation of phthalates was achieved by using a buffer of 100 mM sodium cholate, 50 mM borate and 15% methanol (pH 8.5). The optimized MEKC method was used to quantify the concentrations of phthalates in 11 soil samples from different regions of China. The contents of DEP, DBP and DEHP in soils were ranged 0-0.42, 0-1.43, and 0.24-2.35 mg/kg, respectively, and no DMP and DnOP was detected. The limits of detection for DMP, DEP, DBP, DEHP, and DnOP were found to be 0.050, 0.051, 0.052, 0.054, and 0.063 mg/kg, respectively. The results obtained by the MEKC method were compared with those obtained by gas chromatography with flame ionization detector (GC-FID), and a good agreement was achieved.

Separation and determination of phospholipids in plant seeds by nonaqueous capillary electrophoresis.

A method has been developed for the separation and determination of phospholipids by nonaqueous capillary electrophoresis in a separation medium of acetonitrile-2-proponol (3:2, v/v), 0.3% acetic acid and 60 mM ammonium acetate. To optimize the separation conditions, the composition of separation medium including alcohols, acetic acid, n-hexane and ammonium acetate was studied. The solvation interaction and ion-dipole interaction were also investigated. The contents of phospholipids in soybean, sunflower, peanut, apricot kernel, filbert and walnut were determined by the recommended method. The results obtained by the nonaqueous capillary electrophoreses were in good agreement with those determined by micellar electrokinetic chromatography.