Dissolution of crystalline gallium arsenide in aqueous solutions containing complexing agents

Crystalline gallium arsenide (GaAs) was found to dissolve in an aqueous solution containing the inorganic anions, chloride, sulfate, bicarbonate, monohydrogen phosphate, and dihydrogen phosphate, and the organic anions, acetate and citrate. The aqueous solution was made up to resemble lung fluid (Gamble solution) and was maintained at a pH of 7.4. The concentrations of arsenic (As) and gallium (Ga) in solution and the As-GA ratio on the surface of the GaAs increased continuously as the time of contact with the aqueous solution increased. X-ray photoelectron spectroscopic studies of the GaAs surface, at various time intervals, showed that As migrated to the surface and was oxidized to a species resembling As2O3 and, finally, was dissolved. The zinc present in the crystalline GaAs also migrated to the surface.     

Biological monitoring of arsenic exposure of gallium arsenide- and inorganic arsenic-exposed workers by determination of inorganic arsenic and its metabolites in urine and hair

In an attempt to establish a method for biological monitoring of inorganic arsenic exposure, the chemical species of arsenic were measured in the urine and hair of gallium arsenide (GaAs) plant and copper smelter workers. Determination of urinary inorganic arsenic concentration proved sensitive enough to monitor the low-level inorganic arsenic exposure of the GaAs plant workers. The urinary inorganic arsenic concentration in the copper smelter workers was far higher than that of a control group and was associated with high urinary concentrations of the inorganic arsenic metabolites, methylarsonic acid (MAA) and dimethylarsinic acid (DMAA). The results established a method for exposure level-dependent biological monitoring of inorganic arsenic exposure. Low-level exposures could be monitored only by determining urinary inorganic arsenic concentration. High-level exposures clearly produced an increased urinary inorganic arsenic concentration, with an increased sum of urinary concentrations of inorganic arsenic and its metabolites (inorganic arsenic + MAA + DMAA). The determination of urinary arsenobetaine proved to determine specifically the seafood-derived arsenic, allowing this arsenic to be distinguished clearly from the arsenic from occupational exposure. Monitoring arsenic exposure by determining the arsenic in the hair appeared to be of value only when used for environmental monitoring of arsenic contamination rather than for biological monitoring.     

Inhibition of liver, kidney, and erythrocyte delta-aminolevulinic acid dehydratase (porphobilinogen synthase) by gallium in the rat

Selective inhibition of enzymes in the heme biosynthesis pathway with concomitant urinary excretion of heme precursors serve as potentially important biological markers of chemical exposure and cell injury. Intratracheal administration of gallium arsenide particulate suspensions has been shown to result in inhibition of delta-aminolevulinic acid dehydratase (ALAD) in several tissues and increased excretion of the heme precursor aminolevulinic acid (ALA). This study was undertaken to evaluate in vivo the role of gallium alone in ALAD inhibition and increased urinary excretion of ALA. Male CD rats received a single ip injection of Ga2(SO4)3 at doses of 12.5, 25, 50, 100, and 200 mg Ga/kg. A dose-dependent inhibition of ALAD was observed 24 hr later in liver, kidney, and erythrocytes. After injection of 25 mg Ga/kg, maximal inhibition (42 to 49% of control) of ALAD occurred between 6 and 24 hr in liver and kidney with full recovery of activity at 96 hr. In erythrocytes, maximal inhibition (48% of control) occurred between 24 and 48 hr with recovery of activity at 96 hr. Mild to moderate renal proximal tubular necrosis in the pars recta was observed 24 hr after administration of 100 and 200 mg/kg, but no histopathologic changes were evident at lower doses. No consistent changes in urinary excretion of ALA were observed. Lineweaver-Burk analyses of renal and hepatic ALAD activities in the absence and presence of gallium indicated that the inhibition of ALAD by this element is noncompetitive (same Km, decreased Vmax). Gallium was shown to possess an inhibition constant (Ki) of approximately 3 microns for ALAD, similar to the Ki obtained for lead in other studies. Incubation of ALAD in vitro with gallium and lead, an active thiol group inhibitor, resulted in a greater inhibition of the enzyme. Further in vitro studies demonstrated the attenuation of gallium inhibition of hepatic and renal ALAD by zinc, suggesting that the mechanism of gallium action may involve competition for or displacement of zinc from the sulfhydryl group of the enzyme active site. Since ALAD inhibition occurred at doses at which no histopathologic changes were evident, the determination of ALAD activity in various tissues, including blood, may be of potential value as a biomarker of exposure/toxicity to metals such as gallium. The effect of chemical form and route of exposure of gallium and effects of other Group III metals on inhibition of ALAD and excretion of ALA is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulmonary clearance and toxicity of respirable gallium arsenide particulates intratracheally instilled into rats

Gallium arsenide (GaAs) is an intermetallic compound that is recognized as a potential toxicological risk to workers occupationally exposed to its dust. Previous results have shown that rats intratracheally instilled with a fraction of GaAs particulates, characterized with a mean count diameter of 8.30 microns and a mean volume diameter of 12.67 microns, developed signs of systemic arsenic intoxication, pulmonary inflammation, and pneumocyte hyperplasia. The results of the present study confirm these findings and also show that a significantly smaller fraction of GaAs is a relatively more severe pneumotoxicant. Decreasing the particle mean count and mean volume diameter to 1.63 micron and 5.82 microns, respectively, increased the in vivo dissolution rate of GaAs, increased the severity of pulmonary lesions previously associated with GaAs exposure, and resulted in unique pathological sequelae in affected lung tissue. Pulmonary fibrosis, as indicated by analysis of lung 4-hydroxyproline content, was not considered statistically significant although histological examination of lung tissue revealed a mild fibrotic response. These results provide additional evidence that pulmonary exposure to respirable GaAs particulates is a potential health hazard in the semiconductor industry.     

Arsine (arsenic hydride) poisoning in the workplace

The National Institute for Occupational Safety and Health (NIOSH) recommends that appropriate workpractices be implemented to reduce the risk of worker exposure to arsine (AsH3) gas. There is a high potential for the generation of arsine gas when inorganic arsenic is exposed to nascent (freshly formed) hydrogen. This recommendation is based on several reports of worker exposure to arsine resulting in severe toxic effects or death. Most of the reported cases occurred when arsine was accidently generated during an industrial process. NIOSH would like to inform the occupational health community of some of the circumstances in which workers have been poisoned by arsine, with particular emphasis on the underlying mechanisms of generating the gas. We request that producers and distributors of arsenic and materials containing arsenic transmit information to their customers and employees, and that professional associations and unions inform their members. Stibine (SbH3), another toxic gas, if formed when antimony is exposed to nascent hydrogen. In most situations where arsine can be formed if antimony is present. Therefore, similar work practices should be implemented to reduce the risk of worker exposure to stibine.     

新银盐比色法快速测定化妆品中砷元素

利用硼氢化钾片将化妆品中的砷元素还原为砷化氢 ,以新银盐为显色液 ,用便携式测砷仪快速测定化妆品中砷元素。其中 Sb、Bi、Se等元素用二甲基甲酰胺消除。该有色物的最大吸收峰在 40 0 nm处 ,检出下限为 0 .3 3× 1 0 -6,回收率大于 95 % ,且快速简便 ,能满足测定要求     

Synthesis and dopamine transporter binding of 2beta-isopropyl ester analogs of cocaine

A series of 2beta-isopropyl ester analogs of cocaine (7-11) was synthesised and evaluated in an in vitro dopamine transporter (DAT) binding assays. Ecgonine HCl (5) was obtained from (-)-cocaine (1) by hydrolysis using 1 N HCl. Acid catalysed esterification of 5 using 2-propanol and HCl gas afforded 2beta-isopropyl ecgonine (6). Compounds 7-9 were obtained via esterification of the 3beta-hydroxyl group of 6 using the appropriate acid chloride. Compound 10 was obtained via selective hydrolysis and re-esterification of 7 using 2-propanol and HCl gas. Compound 11 was obtained by reduction of 9 using H(2)/Pd-C. Compounds 7, 10 and 11 showed high binding affinity to the DAT (as indicated from the inhibition of the binding of [(3)H]WIN 35,428 (3)) with IC(50) values (mean +/- S.E.M.) 208.5 +/- 9.5, 47.43 +/- 1.79 and 11.25 +/- 3.37 nM, respectively). Compound 7 is comparatively as active as cocaine, 10 is ca. fivefold more active than cocaine and 11 is ca. 20-fold more active than cocaine and even twice more active than the radioligand 3. Compound 11, like its methyl ester analog (2' aminococaine), exhibited the highest affinity to the DAT. These results, along with previous results, emphasise the importance of a hydrogen-bond donor group at the 2'-position of cocaine and its isopropyl ester analogs to enhance binding affinity to the DAT.     

硝酸镓联合抗菌药物抑制洋葱伯克霍尔德菌生物膜形成的研究

目的研究硝酸镓单用及联合头孢他啶或(和)美罗培南对洋葱伯克霍尔德菌生物膜形成的抑制作用。 方法收集2017年1月至12月临床分离到的34株洋葱伯克霍尔德菌,微量肉汤稀释法检测其对硝酸镓及头孢他啶、复方磺胺甲恶唑、左氧氟沙星、哌拉西林/他唑巴坦、替加环素、美罗培南、氯霉素、米诺环素、头孢哌酮/舒巴坦9种抗菌药物的最低抑菌浓度(minimal inhibitory concentration,MIC)。结晶紫染色法定性、定量分析生物膜形成能力,比较不同生物膜形成能力菌株对硝酸镓及这9种抗菌药物的敏感性。将1.0×MIC的硝酸镓和头孢他啶、美罗培南单独应用及联合使用,检测其对洋葱伯克霍尔德生物膜的抑制率。 结果培养48小时34株细菌均能形成稳定的生物膜。其中(弱)阳性10株,占29.4%;强阳性24株,占70.6%,生物膜(弱)阳性和强阳性菌株对头孢哌酮舒巴坦的耐药率差异具有统计学意义。加入硝酸镓前后菌株的生物膜形成光密度(optical density, OD)值、硝酸镓单用与联合头孢他啶后的OD值差异均具有统计学意义,但硝酸镓单用与联合美罗培南后的OD值差异无统计学意义。 结论洋葱伯克霍尔德菌具有较强的生物膜形成能力,硝酸镓单用及联合头孢他啶对菌株生物膜形成具有明显抑制作用。     

氢化物发生-原子荧光光谱法测定居住区大气砷化物

目的建立氢化物原子荧光光谱测定居住区大气中砷化物的方法。方法利用浸渍微孔滤膜采集居住区大气中蒸气态以及气溶胶态砷化物,酸消解或微波消解;活性碳采集居住区大气中气砷化氢以及蒸气态等砷化物,酸性溶液解吸。在最佳仪器、反应条件下测定。结果方法检出限0.16μg/L,方法检测下限0.53μg/L。线性范围0ng/mL～30ng/mL(As),相关系数0.9998。精密度:测试液砷浓度为3.0μg/L、15.0μg/L、27.0μg/L(As)时,7次测定的相对标准偏差(RSD)分别为5.5%、3.9%和1.5%。样品加标回收率在92.7%～101.5%之间。活性碳管采集砷化物的平均采样效率为93.7%(RSD2.7%)、盐酸溶液(2+8)解吸的平均解吸效率为93.1%(RSD2.9%)。浸渍微孔滤膜和活性碳管采集砷化物,在室温下至少可保存7d。结论该方法具有较高的准确度、采样效率和解吸效率,较低的检出限,较好的精密度和稳定性,能满足居住区大气中砷化物浓度的测定要求。     

生活垃圾焚烧发电厂半干式洗烟塔的仿真研究

以天津某垃圾焚烧发电厂的烟气处理系统中的半干式洗烟塔为具体研究对象,建立数学模型并进行了仿真计算.分析了半干式洗烟塔中液滴与烟气之间的传热和传质过程以及反应机理.将半干式洗烟塔模型分为液滴受热蒸发模型和SO2、HCl的反应模型,对液滴受热蒸发模型分4个阶段分析讨论.此模型已用于国内首台垃圾焚烧炉仿真机,仿真计算的结果与实际对象特性符合,可以满足培训的要求.表明仿真建模中所作的主要简化假设能满足工程精度的要求.     

Determination of dibutyltin compounds in polyvinyl chloride resin by capillary gas chromatography

Dibutyltin compounds (DBTC) in polyvinyl chloride resin (PVC) were examined by capillary gas chromatography using a flame photometric detector (FPD). DBTC was extracted with a carbon tetrachloride-methanol (2:1) mixture under reflux. The extract was mixed with a hydrobromic acid solution. Dibutyltin dibromide was converted to dibutyldipentyltin (DBDPeT) by the Grignard reaction with pentylmagnessium bromide and then subjected to gas chromatography. A linear correlation between the amount of tin and peak height was observed in the range of 7.8 to 250 pg of tin on log-log paper. Recoveries of DBTC added to PVC were 92.6-108.1%. The results show that this procedure is more useful and sensitive (the detection limit is 3-4 pg, as tin) than previous methods reported.     

Mechanisms of gastric mucosal protection in peptic ulcer formation

The purpose of this study is to investigate the relationship between gastric mucosal blood flow (GMBF) and hydrogen ion back diffusion (HBD) during the formation of acute gastric mucosal lesion (AGML) induced by intragastric instillation of gastric mucosal barrier breakers such as HCl and/or ethanol in rats. By increasing the concentration of HCl and/or ethanol in the test solution, the decrease in GMBF became evident 5 minutes after the instillation. This decrease was parallel with the simultaneous increase in the HBD and HCO3- secretion together with the increase in AGML in a dose-response manner. These findings indicate that promotion of HBD is in fact related to the decrease of GMBF in AGML induced by HCl and ethanol. Furthermore, to evaluate the mechanism of the cytoprotection, the effects of 16, 16-dimethyl prostaglandin E2 (16, 16-dmPGE2) on decreased GMBF and promoted HBD during impairment of the gastric mucosal barrier were assessed. In addition, the amount of acid (HCl) neutralized by HCO3- secretion, which was included in the decrease in the HBD, was determined. Administration of 16, 16-dmPGE2 markedly inhibited the formation of gastric lesions macroscopically, but had no significant effects on decreased GMBF. Though promotion of HBD was also inhibited dose-dependently, the HBD did not recover to that of the control group not treated by ethanol. HCO3- secretion was increased dose-dependently by administration of 16, 16-dmPGE2, and its maximal secretion was 10% of the decrease in the acid by HBD. These results show that cytoprotection by 16, 16-dmPGE2 is strongly related to factors other than the improvement of GMBF, such as inhibition of HBD and stimulation of HCO3- secretion.     

Magnetometric evaluation of toxicities of chemicals to the lungs and cells

Because the lungs are exposed to airborne hazardous materials, alveolar macrophages (AMs) play a major role in defending against the exposure to various noxious chemical substances. In this study, we reviewed magnetometric investigations of the effects of various chemicals on the lungs and AMs. Magnetometry, using magnetite as an indicator, was used to evaluate the effects of certain chemicals on the lung and AMs. A rapid decrease of the remanent magnetic field after the cessation of external magnetization, a phenomenon called relaxation, was impaired when the lungs and macrophages were exposed to toxic substances. The delayed in vivo relaxation observed in the lungs exposed to magnetite and gallium arsenide was almost identical to the in vitro relaxation observed in the AMs exposed to the same materials. Delayed relaxation was observed in the AMs exposed to silica dust; various fibers, such as chrysotile and some man-made mineral fibers; and toxic arsenic and cadmium compounds. The extracellular release of lactate dehydrogenase activity was found in the AMs exposed to the chemicals. Relaxation is attributed to the cytoskeleton-driven rotation of phagosomes containing magnetite. While the exact mechanism of delayed relaxation due to exposure to harmful chemicals remains to be clarified, cell magnetometry appears to be useful for the safety screening of chemical substances.     

Exposure to cyclic anhydrides in welding: a new allergen-chlorendic anhydride

Respiratory effects associated with welding fumes have been manifested in welders as occupational asthma. Previous studies have concerned mainly the effects of metal fume exposure, although it has also been suggested that asthma may develop as a result of exposure to contaminants generated from painted metals. To determine whether welding fumes contain irritating and sensitizing anhydrides, air samples were collected during the repair welding of forest harvesters, which were painted with chlorinated polyester paint. Samples were collected with an assembly of a spiral glass trap inserted between a filter holder with a Teflon filter and a Tenax sampling tube. Sample analyses were with GC-MS and GC-ECD. Sensitizing anhydrides released from the paint into the air were primarily chlorendic anhydride (<2-44 microg/m(3)) and phthalic anhydride (11-21 microg/m(3)). Hydrogen chloride (HCl) and hexachlorocyclopentadiene were also found. Airborne HCl was measured with Dr?ger tubes. Since paint films are electrical insulators, the film around the welding seam was removed before arc welding. Removal of paint with an abrasive wheel caused the least exposure to HCl (<0.5 ppm) in contrast to burning with a gas fuel torch, (HCl approximately 5 ppm). HCl exposure was the highest (<0.5-20 ppm) during welding. It is recommended that dry paint coating be removed from an area around the seam with an abrasive wheel, not by burning, before welding.     

Evaluation of sampling methods for measuring exposure to volatile inorganic acids in workplace air. Part 1: sampling hydrochloric acid (HCl) and nitric acid (HNO₃) from a test gas atmosphere

Historically, workplace exposure to the volatile inorganic acids hydrochloric acid (HCl) and nitric acid (HNO(3)) has been determined mostly by collection on silica gel sorbent tubes and analysis of the corresponding anions by ion chromatography (IC). However, HCl and HNO(3) can be present in workplace air in the form of mist as well as vapor, so it is important to sample the inhalable fraction of airborne particles. As sorbent tubes exhibit a low sampling efficiency for inhalable particles, a more suitable method was required. This is the first of two articles on "Evaluation of Sampling Methods for Measuring Exposure to Volatile Inorganic Acids in Workplace Air" and describes collaborative sampling exercises carried out to evaluate an alternative method for sampling HCl and HNO(3) using sodium carbonate-impregnated filters. The second article describes sampling capacity and breakthrough tests. The method was found to perform well and a quartz fiber filter impregnated with 500 μL of 1 M Na(2)CO(3) (10% (m/v) Na(2)CO(3)) was found to have sufficient sampling capacity for use in workplace air measurement. A pre-filter is required to remove particulate chlorides and nitrates that when present would otherwise result in a positive interference. A GSP sampler fitted with a plastic cone, a closed face cassette, or a plastic IOM sampler were all found to be suitable for mounting the pre-filter and sampling filter(s), but care has to be taken with the IOM sampler to ensure that the sampler is tightly closed to avoid leaks. HCl and HNO(3) can react with co-sampled particulate matter on the pre-filter, e.g., zinc oxide, leading to low results, and stronger acids can react with particulate chlorides and nitrates removed by the pre-filter to liberate HCl and HNO(3), which are subsequently collected on the sampling filter, leading to high results. However, although there is this potential for both positive and negative interferences in the measurement, these are unavoidable. The method studied has now been published in ISO 21438-2:2009.     

Mechanism of inactivation of bacteriophage deltaA containing single-stranded DNA by ascorbic acid.

The mechanism of inactivation of a single-stranded DNA phage, deltaA of Escherichia coli, by AsA was investigated as a part of the study on the mechanism of inactivation of viruses by AsA. Bubbling air or oxygen gas through the reaction mixture, and the addition of oxidizing agents or transition metals into the reaction mixture enhanced the inactivation of the phage by AsA. In contrast, nitrogen gas bubling, and the addition of reducing agents, chelating agents or radical scavengers prevented inactivation. The rate of inactivation was faster in the AsA solution preincubated for several minutes than in the freshly prepared AsA solution. DAsA, an oxidized form of AsA, demonstrated little effect on the activity of the phage. Concentrations of hydrogen peroxide which were theoretically produced by the autoxidation of AsA had no effect on the phage. The results indicated that the free radical intermediates produced during the course of the autoxidation of AsA participated in the inactivation. The radicals attacked the DNA of the phage to introduce strand scissions in the DNA, which might be mainly responsible for the inactivation.     

Studies on the deodorization by mushroom (Agaricus bisporus) extract of garlic extract-induced oral malodor

The deodorizing effect of the mushroom (Agaricus bisporus) extract on the malodor produced after garlic consumption was investigated using an electronic sensor and sensory evaluation measurements. Comparative gas chromatography analysis revealed that the quantity of methane- and allylthiols that were usually found after garlic solution rinse, significantly fell after mushroom extract rinsing. Furthermore, in-vitro analysis (mixing the garlic solution and mushroom extract) showed that the methanethiol reaction with the mushroom extract proceeded faster than that of the allylthiol. Ab initio calculations implicated an addition reaction as the possible mechanism between the thiol compounds and the polyphenols. In comparison to the methanethiol, the higher activation energy required by allylthiol for a feasible reaction path way with the model acceptor, o-quinone, is expected to contribute to the difference in the rate of the reaction.     

Synthesis, biological activity and HPLC validation of 1,2,3,4-tetrahydroacridine derivatives as acetylcholinesterase inhibitors

The synthesis and biochemical evaluation of new hybrids of tacrine (THA) and 4-fluorobenzoic acid (4-FBA) possessing activity towards acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibition are presented. The compounds of interest were obtained from the reaction of activated 4-FBA and diamino derivatives of 1,2,3,4-tetrahydroacridine. The compounds C6-2KW/HCl, C6-4KW/HCl and C6-3KW/HCl have four-fold higher antiacetylcholinesterase activity than THA. All of the acquired compounds present higher selectivity towards AChE than THA and lower selectivity towards BuChE. In addition, a rapid, selective and stability-indicating HPLC method was developed and validated for the determination of C6-2KW/HCl, C6-3KW/HCl and C6-4KW/HCl. THA and 4-FBA were found to be the main impurities. Chromatographic separation was achieved isocratically on a Waters Symmetry C18 150 × 3.9 mm, 4 μm column with a mobile phase of acetonitrile/buffer (17 mM sodium dodecyl sulphate and 8.3 mM sodium dihydrogen phosphate, 50:50 v/v) (overall pH 4). A 1.5 ml/min flow rate and a 247 nm wavelength were chosen for this method. C6-2KW/HCl, C6-3KW/HCl and C6-4KW/HCl were subjected to acidic and basic hydrolysis, chemical oxidation, thermal exposition at 60 °C and intense UV light. The limits of detection (LOD) and quantification (LOQ) were less than 2 μg/ml and 6 μg/ml for C6-2KW/HCl, C6-3KW/HCl and C6-4KW/HCl, 0.04 μg/ml and 0.12 μg/ml for THA, 0.42 μg/ml and 1.41 μg/ml for 4-FBA, respectively.     

Oxidation kinetics of pentachlorophenol by manganese dioxide

This study examined the abiotic transformation kinetics of pentachlorophenol (PCP) by manganese dioxide (MnO2) at different solution chemistry and initial concentrations of PCP and MnO2. The measured PCP transformation rates were found to be on the order of 1.07 with respect to [PCP] and 0.91 and 0.87 with respect to [MnO2] and [H+], respectively. Dissolved Mn2+ and Ca2+ as background electrolytes considerably decreased the reaction rate because of their adsorption and hence blocking of active sites on MnO2 surfaces. The dechlorination number, 0.59 chloride ions per transformed PCP after a 1-h reaction, suggests that a fraction of the transformed PCP was not dechlorinated and may be coupled directly to dimeric products. Gas chromatography/ mass spectrometry and liquid chromatography/mass spectrometry/mass spectrometry techniques were used to identify two isomeric nonachlorohydroxybiphenylethers as major products and 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol as minor products. Product identification suggested that the reaction may include two parallel reactions to form either dimers or 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol via simultaneous dehydrochlorination and hydroxylation.     

辽宁省一般人群血中镓、铟、 铊水平研究

目的调查辽宁省一般人群血中镓、铟、铊水平,分析其人群分布特点。方法将辽宁省划分为东、中、西部地区,采用多阶段分层整群随机抽样的方法,于2009—2010年从辽宁省东、中、西部地区抽取2105名对象进行问卷调查,并采集血液样品。用电感耦合等离子体质谱法对血样进行镓、铟、铊含量的检测,通过统计分析研究一般人群血液中镓、铟、铊的分布水平。结果辽宁省一般人群血中镓、铟、铊几何均数均小于检出限。结论辽宁省一般人群血中镓、铟、铊几何均数均小于检出限,与全国水平一致。