Gas chromatographic determination of acetic acid in industrial atmosphere and waste water.

A gas chromatographic (GC) method is presented for the specific determination of acetic acid in air and total ionic acetate (as acetic acid) in industrial waste water. Atmospheric air samples are collected in fritted midget bubblers containing aqueous sodium carbonate solution; wastewater samples are treated directly with sodium carbonate. Both air and water samples are concentrated by evaporation of water, and the acetic acid is regenerated by the addition of hydrochloric acid. The amount of acetic acid is determined quantitatively on a porous polymer packed column by internal standardization with propionic acid. GC conditions are described for the suppression of "ghosting" and "tailing" caused by adsorption phenomena associated with the GC behavior of organic acids.     

Dissipation of six acid herbicides in water and sediment of two Canadian prairie wetlands

In the present study, an ephemeral (E) and a semipermanent (SP) wetland were divided into halves using a polyvinyl curtain and one-half of each wetland was treated with dicamba (3,6-dichloro-o-anisic acid), bromoxynil (3,5-dibromo-4-hydroxy-benzonitrile), MCPA [(4-chloro-2-methylphenoxy)acetic acid], 2,4-D [(2,4-dichlorophenoxy)acetic acid], mecoprop-P (R)-2-(4-chloro-o-tolyloxy)propionic acid], and dichlorprop [(RS)-2-(2,4-dichlorophenoxy)propionic acid] such that concentrations in the water simulated an overspraying event, thus representing a worst-case scenario for wetland contamination. Water and sediment samples were taken over the 77-d study period to monitor herbicide concentrations. The dissipation of all six herbicides could be described by first-order reaction kinetics. In water, the field half-life (DT50) values ranged from 2.3 d (bromoxynil) to 31 d (dichlorprop). All six herbicides were detected in sediment samples from both wetlands. Overall, the phenoxypropionic acids (mecoprop-P and dichlorprop) were more persistent than the phenoxyacetic acids (2,4-D and MCPA) in both sediment and water. Use of bromide ion as a conservative tracer indicated that infiltration through sediment was an important route of water loss in both wetlands, especially in wetland E. Because strong correlations were found between the mass of each herbicide and bromide ion mass in wetland SP (r(2) = 0.59-0.76) and wetland E (r(2) = 0.80-0.95), it is likely that herbicide dissipation was due, in part, to mass lost by way of infiltration through sediment.     

Catabolism of citrus flavanones by the probiotics Bifidobacterium longum and Lactobacillus rhamnosus

Purpose

Orange juice (OJ) flavanones undergo limited absorption in the upper gastrointestinal tract and reach the colon where they are transformed by the microbiota prior to absorption. This study investigated the ability of two probiotic bacteria, Bifidobacterium longum R0175 and Lactobacillus rhamnosus subsp. Rhamnosus NCTC 10302 to catabolise OJ flavanones.

Methods

The bacteria were incubated with hesperetin-7-O-rutinoside, naringenin-7-O-rutinoside, hesperetin and naringenin, and the culture medium and intracellular cell extracts were collected at intervals over a 48 h of incubation period. The flavanones and their phenolic acid catabolites were identified and quantified by HPLC–HR–MS.

Results

Both probiotics were able to subject hesperetin to ring fission yielding 3-(3′-hydroxy-4′-methoxyphenyl)propionic acid which was subsequently demethylated producing 3-(3′,4′-dihydroxyphenyl)propionic acid and then via successive dehydroxylations converted to 3-(3′-hydroxyphenyl)propionic acid and 3-(phenyl)propionic acid. Incubation of both bacteria with naringenin resulted in its conversion to 3-(4′-hydroxyphenyl)propionic acid which underwent dehydroxylation yielding 3-(phenyl)propionic acid. In addition, only L. rhamnosus exhibited rhamnosidase and glucosidase activity and unlike B. longum, which was able to convert hesperetin-7-O-rutinoside and naringenin-7-O-rutinoside to their respective aglycones. The aglycones were then subjected to ring fission and further catabolised in a similar manner to that described above. The flavanones and their catabolites were found in the culture medium but not accumulated in the bacterial cells.

Conclusions

These findings demonstrate the enzymatic potential of single strains of bifidobacterium and lactobacillus which may be involved in the colonic catabolism of OJ flavanones in vivo.

     

Analysis of urinary metabolites of rats exposed to ethylene oxide

Urinary metabolites of rats exposed to ethylene oxide(EO) were analyzed by gas chromatography-mass spectrometry(GC/MS). Male Wister rats(220-240 g) were exposed to EO for 6 hours. The urine was collected during 18 hours after the exposure and extracted with ethyl acetate. For the water-soluble metabolites, ethanol was added to the urine centrifuged and the supernatant fraction was evaporated to dryness. The residue of the extract was methylated with diazomethane and trimethylsilylated with bis(trimethylsilyl)trifluoroacetamide. Ethylene glycol, 2-hydroxymercapturic acid, 2-methylthioethanol and 2-mercaptoethanol were identified as the metabolites of EO. These results suggest that the inhaled EO was hydrolyzed to ethylene glycol, and conjugated with glutathion to form the mercapturic acid and methylthio metabolite.     

Relative Acute Toxicity of Acid Mine Drainage Water Column and Sediments to Daphnia magna in the Puckett's Creek Watershed, Virginia, USA

Acid mine drainage (AMD) is produced when pyrite (FeS₂) is oxidized on exposure to oxygen and water to form ferric hydroxides and sulfuric acid. If produced in sufficient quantity, iron precipitate, heavy metals (depending on soil mineralogy), and sulfuric acid may contaminate surface and ground water. A previous study of an AMD impacted watershed (Puckett's Creek, Powell River drainage, southwestern Virginia, USA) conducted by these researchers indicated that both water column and sediment toxicity were significantly correlated with benthic macroinvertebrate community impacts. Sites that had toxic water or sediment samples had significantly reduced macroinvertebrate taxon richness. The present study was designed to investigate the relative acute toxicity of acid mine drainage (AMD) water column and sediments to a single test organism (Daphnia magna) and to determine which abiotic factors were the best indicators of toxicity in this system. Nine sampling stations were selected based on proximity to major AMD inputs in the watershed. In 48-h exposures, sediment samples from three stations were acutely toxic to D. magna, causing 64–100% mortality, whereas water samples from five stations caused 100% mortality of test organisms. Forty-eight-hour LC50 values ranged from 35 to 63% for sediment samples and 27 to 69% for water column samples. Sediment iron concentration and several water chemistry parameters were the best predictors of sediment toxicity, and water column pH was the best predictor of water toxicity. Based on these correlations and on the fact that toxic sediments had high percent water content, water chemistry appears to be a more important adverse influence in this system than sediment chemistry. Received: 22 April 1999/Accepted: 21 October 1999     

英蓝超滤直接进样离子色谱法测定生活饮用水中的 二氯乙酸、三氯乙酸和草甘膦

摘要:目的　建立生活饮用水中的二氯乙酸、三氯乙酸、草甘膦的英蓝超滤直接进样离子色谱检测方法。方法　生活饮用水经英蓝超滤装置在线过滤后,引入100 μl至离子色谱仪分析,色谱柱:Metrosep A 7-250,淋洗液:7.2 mmol/L碳酸钠溶液,流速:0.8 ml/min。结果　二氯乙酸在0.05 mg/L～1 mg/L,三氯乙酸在0.05 mg/L～1 mg/L,草甘膦在0.5 mg/L～2 mg/L线性关系良好,线性相关系数r＝0.991～0.999,加标回收率在73%～121%,相对标准偏差（RSD%）在2.6%～13.5%。方法检出限:二氯乙酸0.01 mg/L,三氯乙酸0.03 mg/L,草甘膦0.03 mg/L。结论　本方法操作简单、不污染环境、对操作人员无危害、适合批量检测生活饮用水中的二氯乙酸、三氯乙酸和草甘膦。     

Fate and kinetics of carfentrazone-ethyl herbicide in California, USA, flooded rice fields

Little is known of the environmental fate of the aryltriazolinone herbicide carfentrazone-ethyl (compound I). Rice field applications of Shark 40D commercial formulation to duplicate 5.7 m2 rings (119 g a.i./ha) and 464 m2 commercial basins (224 g a.i./ha) produced pseudo-first-order half-lives (t1/2) of 6.5 to 11.1 h in water and 37.9 to 174 h in sediment. The rapid dissipation from water was due to its hydrolysis to the chloropropionic acid (compound II), which further degraded to its propionic, cinnamic, and benzoic acids. Compound I degraded similarly in soil, but propionic and cinnamic acid levels were higher. Compound I was only weakly adsorbed, but lateral movement of compound II through soil occurred. Laboratory hydrolysis produced quantitative yields of compound II, t1/2 values of 131 h at pH 7 and 3.36 h at pH 9, and slow dissipation at pH 5 (43% at 830 h). Ultraviolet (UV) irradiation of compound I in pH 7 buffer gave dissipation rates similar to those in dark controls (t1/2 113 h vs 128 h), while compound II was comparatively stable to photolysis (t1/2 765 h) and also did not volatilize from water. Ester hydrolysis followed by off-site movement of the acid (compound II) account for the dissipation of compound I.     

薄层色谱法测定食品中牛磺酸

用阴离子交换柱净化液体样品，用阴、阳离子二元交换柱净化固体样品，水浴挥干接收液，水溶解残渣作薄层层析用。以正丙醇—水—冰乙酸—乙醇（５．２＋２＋２＋０．８）和正丁醇—冰乙酸—水（４＋１＋１）作展开剂，１％茚三酮乙醇溶液显色，与标准比较。方法最低检出量为０．２０μｇ，最低检出限为０．０８ｇ／ｋｇ（Ｌ），回收率在９０％以上     

Ionotropic excitatory amino acid receptor ligands. Synthesis and pharmacology of a new amino acid AMPA antagonist

We have previously described the potent and selective (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptor agonist, (RS)-2-amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionic acid (ACPA), and the AMPA receptor antagonist (RS)-2-amino-3-[3-(carboxymethoxy)-5-methyl-4-isoxazolyl]propionic acid (AMOA). Using these AMPA receptor ligands as leads, a series of compounds have been developed as tools for further elucidation of the structural requirements for activation and blockade of AMPA receptors. The synthesized compounds have been tested for activity at ionotropic excitatory amino acid (EAA) receptors using receptor binding and electrophysiological techniques, and for activity at metabotropic EAA receptors using second messenger assays. Compounds 1 and 4 were essentially inactive. (RS)-2-Amino-3-[3-(2-carboxyethyl)-5-methyl-4-isoxazolyl]propionic acid (ACMP, 2), on the other hand, was shown to be a selective AMPA receptor antagonist (IC(50) = 73 microM), more potent in electrophysiological experiments than AMOA (IC(50) = 320 microM). The isomeric analogue of 2, compound 5, did not show AMPA antagonist effects, but was a weak NMDA receptor antagonist (IC(50) = 540 microM). Finally, compound 3, which is an isomer of ACPA, turned out to be a very weak NMDA antagonist, and an AMPA receptor agonist approximately 1000 times weaker than ACPA. None of the compounds showed agonist or antagonist effects at metabotropic EAA receptors.     

Reinvestigation of compound X, a suspected biotin intermediate: identification of N-formyl derivatives of biotin and dethiobiotin

Compound X, reported as an intermediate in the biosynthesis of biotin from dethiobiotin (DTB) (Biochem. Biophys. Res. Commun., 88, 312 (1979)), was found to contain N-formyl DTB and biotin. The methyl ester of N-formyl biotin was considered to be a product from the biotin, which was biosynthesized from DTB by resting cells of E. coli C 124, through treatment with diazomethane in the presence of a trace amount of formic acid after Dowex 1X2 column chromatography. NMR analysis revealed that biotin was formylated at 1'-N. N-Formylated DTB and biotin are new biotin derivatives.     

短链脂肪酸对肠道功效及其机制的研究进展

短链脂肪酸是由不易消化的糖类在结肠中酵解的产物,主要包括乙酸、丙酸和丁酸等。文章综述短链脂肪酸对肠道具有维持水电解质平衡、抗病原微生物和抗炎、调节菌群平衡及改善肠道功能、抗肿瘤和调控基因表达等作用及其机制,以期为临床营养实践提供科学依据。     

Effect of fecal water on an in vitro model of colonic mucosal barrier function

Fecal water (FW) has been shown to exert, in cultured cells, cytotoxic and genotoxic effects that have implications for colorectal cancer (CRC) risk. We have investigated a further biological activity of FW, namely, the ability to affect gap junctions in CACO2 cell monolayers as an index of mucosal barrier function, which is known to be disrupted in cancer. FW samples from healthy, free-living, European subjects that were divided into two broad age groups, adult (40+/-9.7 yr; n=53) and elderly (76+/-7.5 yr; n=55) were tested for effects on gap junction using the transepithelial resistance (TER) assay. Overall, treatment of CACO2 cells with FW samples from adults increased TER (+4%), whereas FW from elderly subjects decreased TER (-5%); the difference between the two groups was significant (P<0.05). We also measured several components of FW potentially associated with modulation of TER, namely, short-chain fatty acid (SCFA) and ammonia. SCFAs (propionic, acetic, and n-butyric) were significantly lower in the elderly population (-30%, -35%, and -21%, respectively, all P A pound 0.01). We consider that FW modulation of in vitro epithelial barrier function is a potentially useful noninvasive biomarker, but it requires further validation to establish its relationship to CRC risk.     

粪便中6种短链脂肪酸的气相色谱快速检测法

目的 建立粪便中乙酸、丙酸、正丁酸、异丁酸、正戊酸和异戊酸等六种短链脂肪酸（SCFAs）的快速提取及气相色谱定量检测方法。方法 粪便样本分别采用纯水和盐酸溶液（pH = 2）提取,静置、离心后,上清液中的SCFAs采用气相色谱法测定。以正丁醇为内标,保留时间定性,峰面积定量。结果 本法线性关系良好,水提取和酸提取的加标回收率分别为78.8%～115%和85.7%～130%,且无统计学差异（P＞0.05）。比较人和鼠的粪便水提法所得SCFAs含量与参考文献检测结果吻合。结论 本法高效、稳定,可应用于大批粪便样本6种短链脂肪酸的快速测定。     

Short-chain fatty acid formation in the hindgut of rats fed oligosaccharides varying in monomeric composition, degree of polymerisation and solubility

The contents of short-chain fatty acids were investigated in rats fed lactitol, lactulose and four fructo-oligosaccharides of different degree of polymerisation and solubility. Fructo-oligosaccharides with a low degree of polymerisation (2-8) generated the highest levels of butyric acid all along the hindgut, whereas fructo-oligosaccharides with a high degree of polymerisation (10-60) generated the highest levels of propionic acid. These specific differences were also generally reflected in the caecal pools and molar proportions of short-chain fatty acids. The lower solubility of the fructo-oligosaccharides was related to a lower degree of caecal fermentation. Lactulose and lactitol yielded high proportions of acetic acid and low proportions of butyric acid. It is concluded that both the degree of polymerisation and the solubility may affect short-chain fatty acid formation, whereas the fructose content per se seem to be of less importance. This may be of interest when designing foods with specific health effects.     

Quantitation of urinary metabolites of toluene,xylene, styrene,ethylbenzene, benzene and phenol by automated high performance liquid chromatography

Summary An automated high performance liquid chromatographic method (HPLC) for the direct determination of urinary concentrations of hippuric acid (HA), and o-, m- and p-methyl hippuric acids (MHAs), metabolites of toluene and o-, m-, and p-xylenes, and of urinary phenyl glyoxylic acid (PGA) and mandelic acid (MA), metabolites of styrene or ethylbenzene, is described. Methanol was added to urine, the mixture was centrifuged and the supernatant was injected into HPLC. A stainless-steel column packed with octadecyl silanized silicate was used and the mobile phase was a mixed solution of 5 mM potassium phosphate monobasic/acetonitrile (90/10). The method is simple and specific. Urine can be analyzed without solvent extraction. Analysis can be performed satisfactorily within 45 min for samples containing HA, MHAs, PGA and MA, and within 15 min for those containing HA, PGA and MA. Another automated HPLC method for the determination of urinary concentrations of phenylsulfate (PhS) and phenylglucuronide (PhG), metabolites of benzene and phenol, is also described. Urine was centrifuged and the supernatant was injected into HPLC. A column packed with octadecyl silicate and a mobile phase of 50 mM of potassium phosphate monobasic/acetonitrile (85/15) were used. The whole analyses and quantitative determination can be performed within 15 min for samples containing PhS and PhG in the worker's urine with a simple mobile phase. The accuracy and precision in the present methods by the use of automated HPLC were satisfactory.     

Simultaneous determination of urinary creatinine and metabolites of toluene,xylene, styrene,ethylbenzene and phenol by automated high performance liquid chromatography

Summary An attempt was made to establish a method for the direct determination of urinary concentrations of creatinine, hippuric acid, methylhippuric acid and mandelic acid by automated high performance liquid chromatography (HPLC). Urine was diluted with distilled water or mobile phase, then the mixture was centrifuged and the supernatant was injected into HPLC. A stainless-steel column packed with octadecyl silanized silicate was used, and the mobile phase was a solution of [20 mM potassium phosphate monobasic containing 3 mM sodium 1-decanesulfonate]/acetonitorile (85/15). Another HPLC method for the determination of urinary concentration of phenol, metabolites of benzene and/or phenol is also described. Phenyl sulfate and phenyl glucuronide in urine were hydrolyzed enzymatically into phenol. The hydrolyzed mixture was injected into HPLC with the ODS column. The mobile phase was a solution of [20 mM potassium phosphate monobasic containing 1 mM sodium 1-decanesulfonate]/acetonitorile (85/15). The ratio of hippuric acid (HA) concentration to creatinine concentration determined by the urine of students after physical exercise was similar to that before exercise. Moreover, the coefficient of correlation found between the toluene concentration in a workshop and the HA concentration in workers' urine, corrected for creatinine, was higher than that obtained between the toluene concentration and the uncorrected HA concentration. For assays on stored urine samples, urine was spotted on filter paper, dried and kept several weeks, and then MA, HA, o-MHA, m-MHA and creatinine in the filter paper were eluted with 50% methanol and their concentrations determined by HPLC.     

The thermo-hand method: evaluation of a new indicator pad for acid permeation of chemical protective gloves

The thermo-hand method was developed to evaluate a new indicator pad for acid permeation through chemical protective gloves under in-use conditions (controlled conditions for the hand's skin temperature, hand movements, and relative humidity inside gloves). An indicator pad was used to detect both organic and inorganic acid permeation through glove materials. Breakthrough times for five types of gloves were determined and found to range from 5 to 308 min for propionic acid, from 4 to 293 min for acrylic acid, and from 15 min to >6 hours for HCl. Quantification was performed for propionic and acrylic acids following solvent desorption and gas chromatography. Both acids exhibited >99% adsorption (including the volume of acid, which reacted with an indicator to contribute the color change) on the pads at a spiking level of 1.8 micro L for each acid. Acid recovery for the system was calculated for each acid, with results ranging from 52-72% (RSD < or =4.0%) for both acids over the spiking range 0.2-1.8 micro L. The quantitative mass of the acids on the pads at the time of breakthrough detection ranged from 253-276 and 270-296 micro g/cm(2) for propionic acid and acrylic acid, respectively. The thermo-hand method and a new acid indicator pad together should be useful in detecting, collecting, and quantitatively analyzing acid permeation samples in the workplace.     

Studies on simultaneous determination of 17 organochlorine and 9 pyrethroid pesticides of agricultural products

A method for simultaneous determination of 17 organochlorine and 9 pyrethroid pesticides in agricultural products by capillary GC with ECD detection was studies. The samples were extracted with acetone under acidic conditions followed by Florisil column clean-up and then injected into a GC-ECD. The organochlorine pesticides used in this study included unstable captan and captafol in the homogenized preparations of fruits and vegetables. Captan and captafol were also found to decompose in rice and wheat samples when the samples were allowed to stand after the addition of water. Addition of phosphoric acid to the samples was effective in preventing the decomposition of captan and captafol. Recovery of the pesticides investigated in this study was not decreased by the addition of phosphoric acid. Addition of phosphoric acid was also effective in removing interfering substances from onion extract. Recovery of organochlorine and pyrethroid pesticides from samples spiked at levels of 0.05-0.25 ppm by the proposed method was 51.4-100.8% for rice and wheat and 60.1-119.0% for vegetables.     

空气中四种羧酸的同时测定

目的 建立工作场所空气中乙酸、丙酸、丙烯酸及甲基丙烯酸4种羧酸同时测定的毛细管柱气相色谱方法.方法 硅胶管吸附空气中乙酸、丙酸、丙烯酸及甲基丙烯酸,用丙酮解吸后毛细管柱气相色谱(FID)测定.结果 乙酸、丙酸、丙烯酸及甲基丙烯酸浓度分别在3.4～500.0、2.1～500.0、2.9～500.0及1.6～500.0 μg/ml范围内线性关系良好;线性方程分别为:y=-4.3+1.46x(r=0.999);y=0.4+2.37x(r=0.999);y=10.4+1.73x(r=0.999);y=-2.3+3.21x(r=0.999);检出限分别为3.4、2.1、2.9及1.6 μg/ml.若采集15 L空气样品,最低检出浓度分别为0.2、0.1、0.2及0.1 mg/m3;平均解吸效率分别为92.2%～92.8%、94.1%～97.4%、94.8%～95.4%及94.1%～98.3%;相对标准偏差分别为1.1%～4.0%、1.2%～7.8%、0.9%～4.0%及1.6%～4.8%.结论 本方法适用于工作场所空气中4种羧酸浓度的同时测定.

Abstract：

Objective Four kinds of acids (acetic acid,propionic acid,acrylic acid and methylacrylic acid) in the air in a workplace were quantitatively determined by gas chromatography synchronously.Methods Four acids in the air were adsorbed by silica gel tube sampling and solvent desorption using acetone,then analyzed by GC with FFAP capillary column.Results To acetic acid,propionic acid,acrylic acid and methylacrylic acid,the linear regression equations were respectively y=-4.3+1.46x (r=0.999),y=0.4+2.37x(r= 0.999),y=10.4+1.73x(r=0.999) and y=-2.3+3.21x(r=0.999).The detection limits were respectively 3.4μg/mL,2.1 μg/mL,2.9 μg/mL and 1.6 μg/mL.The average desorption efficiencies were respectively 92.2%~92.8%,94.1%～97.4%,94.8%～95.4% and 94.1%～98.3%.The relative standard deviations were 1.1%～4.0%,1.2%～ 7.8%,0.9%～4.0% and 1.6%~4.8%.Conclusion The method is suitable to determine four kinds of acids in the air in a workplace.     

Human exposure to styrene

Summary The derivatization of phenylglyoxylic acid (PGA), a urinary styrene metabolite, gives with diazomethane under ordinary reaction conditions secondary products as expected from the behaviour of other -keto acids. Thus reproducible quantitative analysis becomes difficult. It is shown that by proper selection of reaction conditions (low temperature, short reaction time) these secondary transformations can be inhibited and exclusive derivatization to the methylester is obtained. A quantitative determination of urinary PGA can be based on this derivatization procedure. However, this method is not considered suitable for routine monitoring due to the delicate reaction conditions necessary. The results are discussed with reference to a recently published procedure based on an unknown derivative of PGA.