Simple and selective determination of arsenite and arsenate by electrospray ionization mass spectrometry

Arsenic pollution of public water supplies has been reported in various regions of the world. Recently, some cancer patients are treated with arsenite (As^III); most Japanese people consume seafoods containing large amounts of negligibly toxic arsenic compounds. Some of these arsenic species are metabolized, but some remain intact. For the determination of toxic As^III, a simple, rapid and sensitive method has been developed using electrospray ionization mass spectrometry (ESI-MS). As^III was reacted with a chelating agent, pyrrolidinedithiocarbamate (PDC, C₄H₈NCSS^-) and tripyrrolidinedithiocarbamate-arsine, As(PDC)₃, extracted with methyl isobutyl ketone (MIBK). A 1 μL aliquot of MIBK layer was directly injected into ESI-MS instrument without chromatographic separation, and was detected within 1 min. Arsenate (As^V) was reduced to As^III with thiosulfate, and then the total inorganic As was quantified as As^III. This method was validated for the analysis of urine samples. The limit of detection of As was 0.22 μg L⁻¹ using 10 μL of sample solution, and it is far below the permissible limit of As in drinking water, 10 μg L⁻¹, recommended by the WHO. Results were obtained in < 10 min with a linear calibration range of 1-100 μg L⁻¹. Several organic arsenic compounds in urine did not interfere with As^III detection, and the inorganic As in the reference materials SRM 2670a and 1643e were quantified after the reduction of As^V to As^III.     

HPLC profile of captopril disulfide that undergoes reversible cis-trans conversion among three isomers.

Peculiarly shaped chromatograms of some compounds that consist of two reversible isomers have been reported. Those of a compound that consists of three reversible isomers are described here. Because disulfide of captopril has two cis-trans convertible bonds, it exists in three forms of cis-cis, cis-trans and trans-trans isomers. The disulfide has produced various HPLC-UV profiles under various conditions, such as three split peaks, three peaks with bridging plateaus and one broad peak. The effect of the column temperature and the eluent flow rate on the profile was investigated and explained by interconversion among three isomers. A profile analysis could provide some kinetic constants of this reaction.     

Synthesis and photophysical properties of Rhodamine B dye‐bearing poly(isobutyl methacrylate‐co‐2,2,2‐trifluoroethyl methacrylate) as a temperature‐sensing polymer film

To develop a novel temperature‐sensitive paint, methacrylamide monomers bearing Rhodamine B dye (two regioisomers, 3a and 3b ) were synthesized and polymerized with isobutyl methacrylate and 2,2,2‐trifluoroethyl methacrylate to afford Rhodamine B‐pendant polymers 4a and 4b . The methacrylamide monomers 3a and 3b showed photophysical properties almost identical with those of Rhodamine B. The temperature sensitivity of the luminescence intensity of 3a and 3b was also similar to that of Rhodamine B. The polymers 4a and 4b have excellent solubility in nonpolar organic solvents and are suitable for application as paint. Films of polymers 4a and 4b showed temperature‐dependent luminescence, which is applicable for temperature‐sensing. The temperature sensitivity of the film of 4a was estimated to be ?0.37% °C^?1, and was independent of pressure. The film of 4b showed higher temperature sensitivity, but its temperature sensitivity was slightly pressure‐dependent. Hence, polymer 4a is expected to be superior for practical use in paints having temperature‐sensing functionality. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2876–2885, 2007     

Simultaneous analysis of cardiac glycosides in blood and urine by thermoresponsive LC-MS-MS

A new thermoresponsive polymer separation column was applied to simultaneous analysis of four cardiac glycosides (CGs) being widely used for the treatment of arrhythmias and heart failure in human blood and urine. This column is composed of an N-isopropylacrylamide polymer, the surface of which undergoes a reversible alteration from hydrophilic to hydrophobic by changing temperature. The chromatographic separation and retention times can be easily be controlled by adjusting the column temperature. As the column temperature was changed from 50 to 10 °C over 8 min, five CGs, including deslanoside, digoxin, methyldigoxin, digitoxin, and digitoxigenin (internal standard) were better resolved. Using these LC conditions, we analyzed four CGs in human whole blood and urine simultaneously by liquid chromatography-tandem mass spectrometry (LC-MS-MS). Validation data as functions of recovery rates, linearity, accuracy, and precision were carefully tested; all were generally satisfactory. The detection limits for the four CGs in both matrices were 0.2–0.3 ng/mL. The method was applied to analysis of methyldigoxin and its main metabolite digoxin in whole blood and urine samples obtained from a deceased person in actual autopsy case. To our knowledge, this is the first report describing an LC-MS-MS method using a thermoresponsive column for analysis of drug(s). The inclusion of the thermoresponsive column in an LC-MS-MS technique seems to extend the possibility for simultaneous analysis of compounds of different properties, such as hydrophobic precursors and their hydrophilic metabolites in biological samples within limited analysis times.     

The effect of water on the stability of C<Subscript>60</Subscript> fullerene nanowhiskers

The morphology of C₆₀ precipitates synthesized by using isopropyl alcohol (IPA) added with water was investigated in order to know the effect of water on the growth of C₆₀ nanowhiskers (C₆₀NWs) in C₆₀–toluene–IPA solution systems. The stability of C₆₀NWs decreased and granular crystals of C₆₀ were formed in the solutions when IPA added with an excess amount of water was used in the liquid–liquid interfacial precipitation method. The C₆₀NWs were found to be destabilized with time in the solutions added with water. The C₆₀NWs dried in air showed similar Raman profiles irrespective of the use of IPA with and without water addition. The Raman profiles of granular C₆₀ single crystals showed the base lines much flatter than those of C₆₀NWs, indicating that C₆₀NWs possess a disordered crystal structure. By optimizing the growth condition, short C₆₀NWs with aspect ratios ranging from 3 to 10 and an average length of about 1.8 μm were successfully fabricated. The short C₆₀NWs are expected to be applicable for electrodes of organic thick film solar cells.     

Enzymatic hydrolysis of cellulose hydrates

We prepared two cellulose hydrates, Na-cellulose IV and cellulose II hydrate, along with their respective anhydrous forms, cellulose II and II′, from microcrystalline cellulose. X-ray diffractometry analysis showed that the structure of the hydrophobic stacking sheet was conserved in the samples, but the distance between the sheets was in the order: cellulose II hydrate > Na-cellulose IV > cellulose II and II′. The hydrates exhibited an expanded structure compared with the anhydrous form from the incorporation of hydrate water, and cellulose II hydrate contained more hydrate water than Na-cellulose IV. Enzymatic hydrolysis of the samples was carried out at 37 °C using solutions comprising a mixture of cellulase and β-glucosidase. The hydrates were hydrolyzed more efficiently than the anhydrous forms, and cellulose II hydrate showed a more efficient hydrolysis than Na-cellulose IV. This result also agrees well with the enzymatic adsorption properties of each sample, where the samples that adsorbed the greater amount of enzyme showed a higher degradability. The results obtained in this study provide useful knowledge on controlling the biodegradability of cellulose by converting its structure.     

A novel and concise synthesis of spirodienone alkaloids using hypervalent iodine(III) reagents

Intramolecular oxidative coupling reaction of N-protected benzyltetrahydroisoquinoline derivatives using hypervalent iodine(III) reagents was investigated. The use of remarkable combination of phenyliodine bis (trifluoroacetate) (PIFA) and heteropoly acid (HPA) in wet acetonitrile smoothly afforded morphinandienone alkaloids, while neospirinedienone alkaloids were obtained in high yield under anhydrous conditions.