Trichloroacetic Acid Concentration Research Articles

The application of directly suspended droplet microextraction for the evaluation of phthalic acid esters in cow’s milk by gas chromatography mass spectrometry

A simple and rapid method was developed for evaluating 16 phthalic acid esters (PAEs) at the μg/kg level in a complex milk matrix using directly suspended droplet microextraction-gas chromatography mass spectrometry (DSDME-GC–MS). The different parameters for extraction and for the DSDME experiment were optimized, including You are free to submit the revised manuscript at a later date as a new submission.10g/L trichloroacetic acid concentration, 100μL cyclohexane micro-droplet organic solvent, 1100rpm stirring speed, 10min extraction time and no salt amount. Validation experiments showed good linearity (γ>0.9878, 0.002–0.4μg/mL), satisfactory precision (RSD<11%), and good accuracy (relative recovery of 70.2–108%) when analyzing milk samples using the optimized method. The limits of detection (LODs) ranged between 0.001 and 0.2μg/L, and the limits of quantification (LOQs) ranged between 0.003 and 0.7μg/L for 15 PAEs. Dinonyl phthalate (DINP) had a low response and did not have good linearity. The proposed method was successfully applied for the analysis of PAEs in real milk samples.

Application of response surface methodology for modeling and optimization of trichloroacetic acid and turbidity removal using potassium ferrate(VI)

Coagulation/flocculation and oxidation are two of the main processes in treating colloidal and organic substances. Potassium ferrate(VI), a multipurpose chemical, is used in water treatment plants as coagulant and oxidant. In this study, ferrate(VI) was evaluated for the degradation of trichloroacetic acid and turbidity removal in synthetic water. The effects of five independent variables, initial pH of solution (3–9), ferrate(VI) dosage (1–10 mg L−1), contact time (5–60 min), trichloroacetic acid concentration (100–1,000 μg L−1), and initial turbidity (1–10 NTU) were investigated and the process was optimized by means of response surface methodology. Trichloroacetic acid and turbidity removal efficiencies were considered as the process responses. The highest efficiency achieved for trichloroacetic acid removal was 24%, while for turbidity the maximum removal efficiency was in the range 85–95%. The optimum conditions for initial turbidity, pH, and ferrate dosage were 8.89 NTU, 3, and 4.26 mg L−1 as Fe, respectively. Experimentally obtained 89% turbidity removal in the optimum condition confirmed the results predicted by the model. Therefore, it can be concluded that ferrate(VI) can be effectively used in colloidal substances removal, while it is not successful enough in trichloroacetic acid decomposition.

The hemoglobin-modified electrode with chitosan/Fe3O4 nanocomposite for the detection of trichloroacetic acid

A hemoglobin (Hb)-modified electrode based on chitosan/Fe3O4 nanocomposite coated glassy carbon has been constructed for trichloroacetic acid (TCA) detection. The structure of chitosan/Fe3O4 nanocomposite was investigated using energy-dispersive X-ray analysis (EDS) and X-ray diffraction (XRD) patterns. The electron transfer rate constant (ks) of Hb was estimated for as high as 3.12 s−1. The immobilized Hb exhibited excellent electro-catalytic activity toward the reduction of TCA. The response current regressed to the concentration of TCA within the range of 5.70 μM to 205 μM with a detection limit of 1.9 μM (S/N = 3).

CARACTERIZAÇÃO PROTEICA DE LEITE PASTEURIZADO, SORO DE QUEIJO E SUAS MISTURAS PELO USO DO ANALISADOR CEM SPRINT TM

Neste trabalho, o analisador de proteínas SprintTM foi avaliado quanto a sua capacidade de predizer a adição de soro no leite. Este tipo de prática é relativamente comum em laticínios, uma vez que o soro, por se tratar de um componente proteico, pode ser adicionado ao leite com pouca perda do teor de proteínas. Além disso, sua eliminação pela indústria queijeira de maneira incorreta contribui para poluição do meio ambiente. Misturas de leite pasteurizado com soro foram preparadas em diferentes níveis de adição e dois métodos de partição química do leite foram testados. Os resultados indicaram que a concentração de ácido tricloroacético (TCA) do método utilizado não foi adequada para o presente propósito, enquanto o método escolhido usando ácido acético glacial (GAA) apresentou uma melhor separação dos componentes solúveis e insolúveis do leite. Apesar das concentrações de soroproteínas e caseínas serem os parâmetros essenciais na determinação de adição de soro no leite, o uso das leituras de proteínas totais foram importantes para melhorar a linearidade do método, devido ao fato de que as razões soroproteínas/proteínas totais e caseínas/proteínas totais apresentaram os melhores resultados quanto à capacidade de predição de fraude. Portanto, por se tratar de uma plataforma rápida, segura e eficiente, o equipamento pode ser uma alternativa a ser implementada em laboratórios de controle de qualidade de alimentos que realizam ou planejam realizar ensaios para verificar a adição de soro em leite fluido.

Assessment of efficacy and tolerability of different concentrations of trichloroacetic acid vs. carbon dioxide laser in treatment of xanthelasma palpebrarum.

There are numerous methods currently available for the management of xanthelasma. These include surgical excision, laser ablation using a variety of lasers and chemical cauterization. However, each method of treatment is associated with particular limitations and side effects. To assess the clinical efficacy and tolerability of different concentrations of topical trichloroacetic acid (TCA) vs. carbon dioxide laser in the treatment of patients with xanthelasma palpebrarum. Thirty patients with xanthelasma palpebrarum were classified into four groups, treated by TCA 35%, 50%, 70%, and CO2 laser, respectively. Lipid profile was estimated for all patients. Both TCA peeling 70% and carbon dioxide laser ablation showed more significant clinical efficacy and tolerability with least number of sessions in the treatment of xanthelasma palpebrarum than 50% and 35% TCA peeling. Post-therapy erythema and hypopigmentation were more with TCA 70%. Post-therapy hyperpigmentation was more with TCA (50%). There was a significant improvement in patients with normal lipid profile than those with abnormal profile. Both TCA peeling 70% and carbon dioxide laser ablation are highly effective and well tolerated with least number of sessions in the treatment of xanthelasma palpebrarum.

Leuco-crystal-violet micelle gel dosimeters: I. Influence of recipe components and potential sensitizers

Radiochromic leuco crystal violet (LCV) micelle gel dosimeters are promising three-dimensional radiation dosimeters because of their spatial stability and suitability for optical readout. The effects of surfactant type and surfactant concentration on dose sensitivity of LCV micelle gels are tested, demonstrating that dose sensitivity and initial colour of the gel increases with increasing Triton x-100 (Tx100) concentration. Using Cetyl Trimethyl Ammonium Bromide (CTAB) in place of Tx100 produces gels that are nearly colourless prior to irradiation, but reduces the dose sensitivity. The separate effects of Tri-chloro acetic acid concentration and pH are investigated, revealing that controlling the pH near 3.6 is crucial for achieving high dose sensitivity. The sensitizing effect of chlorinated species on dose sensitivity is tested using 2,2,2-trichloroethanol (TCE), chloroform, and 1,1,1-trichloro-2-methyl-2-propanol hemihydrate. TCE gives the largest improvement in dose sensitivity and is recommended for use in micelle gel dosimeters because it is less volatile and safer to use than chloroform. Preliminary experiments on a new gel containing CTAB as the surfactant and TCE show that this new gel gives a dose sensitivity that is 24% higher than that of previous LCV micelle gels and is nearly colourless prior to irradiation.

Direct electrochemistry and electrocatalysis of hemoglobin on three-dimensional graphene modified carbon ionic liquid electrode

In this paper three-dimensional graphene (3D-GR) was directly formed on the surface of carbon ionic liquid electrode (CILE) by electrodeposition. By using 3D-GR/CILE as the substrate electrode, a new electrochemical biosensor was prepared by immobilization of hemoglobin (Hb) on the electrode surface with a chitosan film. Electrochemical investigation indicated that a pair of well-defined redox peaks appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Hb with the underlying electrode. The result can be ascribed to the porous structure of 3D-GR with high conductivity and big surface area. Based on the electrochemical data, the electron transfer coefficient (α) and the apparent heterogeneous electron transfer rate constant (ks) were calculated to be 0.426 and 1.864s−1, respectively. The modified electrode displayed good electrocatalytic activity to the reduction of trichloroacetic acid (TCA), and the catalytic reduction peak current had a good linear relationship to TCA concentration in the range from 0.4 to 26.0mmol/L with the detection limit of 0.133mmol/L (3σ). Therefore a new third-generation electrochemical Hb biosensor based on 3D-GR/CILE was constructed with good stability and reproducibility.

Degradation of trichloroacetic acid by an efficient Fenton/UV/TiO2 hybrid process and investigation of synergetic effect

An efficient hybrid degradation process combined Fenton with TiO2 photocatalytic oxidation for trichloroacetic acid (TCAA) was first investigated, and then the synergetic degradation effect between Fenton reagent and TiO2 photocatalytic oxidation was discussed in this study. The dominant factors, such as dosages of TiO2 and Fe2+, TCAA concentration and pH were researched and optimized. The cooperation effect between Fenton and TiO2 photocatalytic oxidation probably occurred because (1) more OH radicals were produced in the Fe(OH)2+ and H2O2 decomposition reactions irradiated by UV light; and (2) photoinduced electrons voluntarily participated in the reduction from Fe3+ to Fe2+, improving the efficient separation of the photogenerated electrons and holes. Adsorption and degradation were both involved in the removal of TCAA in this hybrid process, and the removal of TCAA followed the Langmuir model and the degradation kinetics accorded with first order degradation kinetics. Toxicity test using a bioluminescent bacterium Photobacterium phosphoreum as the indicator proved that the hybrid process was a safe treatment because the toxicity decreased greatly with the degradation time.

Opportunities for improving the performance of LCV micelle gel dosimeters: I. Preliminary investigation

The effects of the various components of leuco crystal violet (LCV) micelle gels on dose sensitivity and initial colour are tested. Dose sensitivity and gel turbidity are influenced by tri-chloro acetic acid (TCAA) concentration, with the highest dose sensitivity obtained at ~21.5 mM. Increasing Triton x-100 (Txl00) concentration improved dose sensitivity but, unfortunately, increased initial colour of the gel. Using Cetyl Trimethyl Ammonium Bromide (CTAB) in place of Tx100 produces gels that are nearly colourless prior to irradiation, but reduces the dose sensitivity. The effects of chlorinated species on dose sensitivity are tested using 2,2,2-trichloroethanol (TCE), chloroform, and 1,1,1-trichloro-2-methyl-2-propanol hemihydrate (TCMPH). TCE gives the largest improvement in dose sensitivity and is recommended for use in micelle gel dosimeters because it is less volatile and safer to use than chloroform. A new gel containing CTAB as the surfactant and TCE gives improved dose sensitivity compared to previous LCV micelle gels.

Disparity in disinfection byproducts concentration between hot and cold tap water

The quality of water entering a distribution system may differ substantially from the quality at the point of exposure to the consumer. This study investigated temporal variations in the levels of regulated and non-regulated disinfection byproducts (DBPs) in cold and hot tap water in a home on a medium-sized municipal water system. In addition, samples were collected directly from the water plant with some being held in accordance with a simulated distribution system (SDS) test protocol. The location for this work was a system in western Massachusetts, USA that uses free chlorine as a final disinfectant. Very little short term variability of DBPs at the point of entry (POE) was observed. The concentration of DBPs in the time-variable SDS test was similar to concentrations in the cold water tap. For most DBPs, the concentrations continued to increase as the cold water tap sample was held for the time-variable SDS incubation period. However, the impact of heating on DBP levels was compound specific. For example, the concentrations of trihalomethanes (THMs), dichloroacetic acid (DCAA) and chloropicrin (CP) were substantially higher in the hot water tap than in the cold water time-variable SDS samples. In contrast, the concentration of trichloroacetic acid (TCAA) was lower in the heated hot tap water, but about equal to that observed in the cold tap water. The situation was more pronounced for dichloroacetonitrile (DCAN), bromodichloroacetic acid (BDCAA), bromochloroacetic acid (BCAA) and 1,1,1-trichloropropanone (TCP), which all showed lower concentrations in the hot water then in either of the cold water samples (instantaneous or time-variable SDS). The latter was viewed as a clear indication of thermally-induced decomposition. The ratio of unknown total organic halide (UTOX) to TOX was substantially lower in the hot tap water as the THM to TOX ratio became correspondingly larger. The results of this study show that DBP exposure in the home is not well represented by concentrations measured in cold water taps where most compliance monitoring is done.

Seasonal Variation of Urinary Trichloroacetic Acid (TCAA) Concentrations Measured on Multiple Consecutive Days in a Prospective, Pre-Conception Cohort

Seasonal Variation of Urinary Trichloroacetic Acid (TCAA) Concentrations Measured on Multiple Consecutive Days in a Prospective, Pre-Conception CohortAbstract Number:1826 Kyley Cox*, Christina Porucznik, James VanDerslice, Joseph Stanford, Diana Wilkins, Eric Brozek, David Anderson, and Nicole Bailey Kyley Cox* University of Utah Department of Family and Preventive Medicine, United States, E-mail Address: [email protected] Search for more papers by this author , Christina Porucznik University of Utah Department of Family and Preventive Medicine, United States, E-mail Address: [email protected] Search for more papers by this author , James VanDerslice University of Utah Department of Family and Preventive Medicine, United States, E-mail Address: [email protected] Search for more papers by this author , Joseph Stanford University of Utah Department of Family and Preventive Medicine, United States, E-mail Address: [email protected] Search for more papers by this author , Diana Wilkins University of Utah Center for Human Toxicology, United States, E-mail Address: [email protected] Search for more papers by this author , Eric Brozek University of Utah Center for Human Toxicology, United States, E-mail Address: [email protected] Search for more papers by this author , David Anderson University of Utah Center for Human Toxicology, United States, E-mail Address: [email protected] Search for more papers by this author , and Nicole Bailey University of Utah Department of Family and Preventive Medicine, United States, E-mail Address: [email protected] Search for more papers by this author AbstractBackground: Control of bacterial contamination of drinking water by disinfectants leads to the production of disinfection-by-products (DBPs). TCAA is the second most prevalent haloacetic acid in chlorinated water. Urinary TCAA is a validated biomarker of TCAA exposure by ingestion of chlorinated drinking water. Objective: Evaluate variation of urinary TCAA concentrations by season.Methods: A prospective, pre-conception cohort of couples (women 18–35, men 18–40) was recruited in Utah beginning in early 2012. Recruitment is ongoing. Women observed cervical mucus to identify the fertile window. Participants collected first-morning urine samples beginning at the onset of the fertile window, after which men discontinued collecting but women collected for the remainder of the cycle. TCAA was measured in each urine sample using quantitative GC-MS. Geometric means (GM) with 95% confidence intervals (CI) were calculated for each season using STATA ver. 12. Seasons were defined as follows: spring (Mar – May); summer (June – Aug); fall (Sept – Nov); winter (Dec – Feb).Results: The GM for all specimens (n=1521) was 2.42 ng/mL (95% CI 2.32, 2.53). The highest concentrations were observed in specimens collected during spring months (n=212, GM 3.04 ng/mL, 95% CI 2.76, 3.35), followed by fall (n=428, GM 2.69 ng/mL, 95% CI 2.47, 2.93), and summer (n=519, GM 2.53 ng/mL, 95% CI 2.37, 2.69). These levels were significantly higher than the levels observed during winter (n=362, GM 1.76 ng/mL, 95% CI, 1.61, 1.93). Men had slightly higher levels than women (GM 2.64 vs. 2.36 ng/mL) but the difference was not statistically significant.Conclusions: These preliminary findings suggest that TCAA exposures vary seasonally in a pattern similar to the levels of disinfection byproducts in tap water.

Use of urinary trichloroacetic acid as an exposure biomarker of disinfection by-products in cancer studies

Urinary trichloroacetic acid (TCAA) has been proposed as a valid exposure biomarker for ingested disinfection by-products (DBP) for reproductive studies. However, it has never been used in epidemiologic studies on cancer. We investigate the performance of urinary TCAA as a biomarker of DBP exposure in the framework of an epidemiologic study on cancer.We conducted home visits to collect tap water, first morning void urine, and a 48h fluid intake diary among 120 controls from a case-control study of colorectal cancer in Barcelona, Spain. We measured urine TCAA and creatinine, and 9 haloacetic acids and 4 trihalomethanes (THM) in tap water. Lifetime THM exposure was estimated based on residential history since age 18 plus routine monitoring data. Robust linear regressions were used to estimate mean change in urinary TCAA adjusted by covariates.Among the studied group, mean age was 74 years (range 63–85) and 41 (34%) were females. Mean total tap water consumption was 2.2l/48h (standard error, 0.1l/48h). Geometric mean urine TCAA excretion rate was 17.3pmol/min [95%CI: 14.0–21.3], which increased 2% for a 10% increase in TCAA ingestion and decreased with total tap water consumption (−17%/l), water intake outside home (−32%), plasmatic volume (−64%/l), in smokers (−79%), and in users of non-steroidal anti-inflammatory drugs (−50%). Urinary TCAA levels were not associated with lifetime THM exposure.In conclusion, our findings support that urine TCAA is not a valid biomarker in case-control studies of adult cancer given that advanced age, comorbidites and medication use are prevalent and are determinants of urine TCAA levels, apart from ingested TCAA levels. In addition, low TCAA concentrations in drinking water limit the validity of urine TCAA as an exposure biomarker.

Temporal variability in urinary levels of drinking water disinfection byproducts dichloroacetic acid and trichloroacetic acid among men

Urinary haloacetic acids (HAAs), such as dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), have been suggested as potential biomarkers of exposure to drinking water disinfection byproducts (DBPs). However, variable exposure to and the short elimination half-lives of these biomarkers can result in considerable variability in urinary measurements, leading to exposure misclassification. Here we examined the variability of DCAA and TCAA levels in the urine among eleven men who provided urine samples on 8 days over 3 months. The urinary concentrations of DCAA and TCAA were measured by gas chromatography coupled with electron capture detection. We calculated the intraclass correlation coefficients (ICCs) to characterize the within-person and between-person variances and computed the sensitivity and specificity to assess how well single or multiple urine collections accurately determined personal 3-month average DCAA and TCAA levels. The within-person variance was much higher than the between-person variance for all three sample types (spot, first morning, and 24-h urine samples) for DCAA (ICC=0.08–0.37) and TCAA (ICC=0.09–0.23), regardless of the sampling interval. A single-spot urinary sample predicted high (top 33%) 3-month average DCAA and TCAA levels with high specificity (0.79 and 0.78, respectively) but relatively low sensitivity (0.47 and 0.50, respectively). Collecting two or three urine samples from each participant improved the classification. The poor reproducibility of the measured urinary DCAA and TCAA concentrations indicate that a single measurement may not accurately reflect individual long-term exposure. Collection of multiple urine samples from one person is an option for reducing exposure classification errors in studies exploring the effects of DBP exposure on reproductive health.

Disinfection by-product formation from the monochloramination of chironomid larvae

Formation of disinfection by-products (DBPs), including dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), chloroform (TCM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), chloropicrin (TCNM) and chloral hydrate (CH), from monochloramination of chironomid larvae was investigated at different contact times, pH levels and temperatures. Increased monochloramine dosage and prolonged reaction time resulted in an increase in most DBPs. Furthermore, the concentrations of TCAN, DCAN and CH initially increased over time before reaching a plateau. This is because of the hydrolysis of functional groups and the function of NH2Cl. The concentrations of DCAA, TCAA and TCM decreased as pH was increased from 5 to 10, and TCAN, DCAN and CH were not detected when the pH exceeded 8. As for TCNM, their concentration increased as the pH increased from 5 to 7, following a subsequent decrease at higher pH values. High temperatures led to higher DCAN and TCAN concentrations, while low temperatures resulted in higher TCNM and DCAA concentrations. Both high and low temperatures reduced the concentrations of TCAN and CH. Finally, concentrations of the four predominant DBPs (TCM, DCAN of DCAA and TCAA) all decreased as Cl/N ratio declined.

Predictors of urinary trichloroacetic acid and baseline blood trihalomethanes concentrations among men in China

Urinary trichloroacetic acid (TCAA) and baseline blood trihalomethanes (THMs) have been measured as biomarkers of exposure to drinking water disinfection by-products (DBPs) that have been associated with increased risk of cancers and adverse reproductive outcomes. This study aimed to identify predictors of urinary TCAA and baseline blood THMs among men in China. Urine samples, blood samples, and information on socio-demographic factors and water-use activities were collected from 2216 men who participated in a cross-sectional study of exposure to drinking water DBPs and reproductive health during 2011 to 2012. Urinary TCAA and baseline blood THMs including chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM) were analyzed. Multivariable linear regression was used to evaluate predictors of urinary TCAA and baseline blood THM concentrations. Tap water consumption was significantly associated with creatinine-adjusted urinary TCAA concentration (β=0.23μg/g creatinine per log10 unit; 95% CI: 0.12, 0.35). Men with surface water source had 0.13 (95% CI: 0.00, 0.27) higher mean creatinine-adjusted urinary TCAA concentrations than those with ground water source. Smoking was associated with lower concentration of creatinine-adjusted urinary TCAA. Age was significantly associated with baseline blood Br-THM (sum of BDCM, DBCM, and TBM) concentration (β=0.01ng/L per unit; 95% CI: 0.00, 0.02). Increased household income was associated with decreased concentrations of baseline blood BDCM and Br-THMs. Our results suggest that tap water consumption, water source, smoking, age, and household income as the primary determinants of exposure to drinking water DBPs should be considered in exposure assessment.

Essay of Different Extraction Procedures in Capelin Fish Meal for Biogenic Amine Determination by HPLC

This study assesses the effects of different extraction procedures of biogenic amines in capelin fish meal with different concentrations of trichloroacetic acid (TCA) for their determination by high performance liquid chromatography (HPLC). No significant differences were noted between the use of TCA at 7.5 and 10% for the extraction of biogenic amines in E1 and E3 extraction, except for tyramine. The extraction using 7.5% TCA in one step and centrifugation (E1) was a simple and rapid method. This extraction seems to be the most suitable for the extraction of amines in these kinds of samples, compared to the other methods tested. The biogenic amine that presented the highest levels in the fish meal studied was cadaverine (208–226 mg/kg), followed by putrescine and histamine (164–173 and 44–46 mg/kg, respectively). Biogenic amine levels were low when compared to the toxic levels observed in these kinds of products.

Drinking-Water Disinfection By-products and Semen Quality: A Cross-Sectional Study in China

Background: Exposure to disinfection by-products (DBPs) has been demonstrated to impair male reproductive health in animals, but human evidence is limited and inconsistent.Objective: We examined the association between exposure to drinking-water DBPs and semen quality in a Chinese population.Methods: We recruited 2,009 men seeking semen analysis from the Reproductive Center of Tongji Hospital in Wuhan, China, between April 2011 and May 2012. Each man provided a semen sample and a urine sample. Semen samples were analyzed for sperm concentration, sperm motility, and sperm count. As a biomarker of exposure to drinking-water DBPs, trichloroacetic acid (TCAA) was measured in the urine samples.Results: The mean (median) urinary TCAA concentration was 9.58 (7.97) μg/L (interquartile range, 6.01–10.96 μg/L). Compared with men with urine TCAA in the lowest quartile, increased adjusted odds ratios (ORs) were estimated for below-reference sperm concentration in men with TCAA in the second and fourth quartiles (OR = 1.79; 95% CI: 1.19, 2.69 and OR = 1.51; 95% CI: 0.98, 2.31, respectively), for below-reference sperm motility in men with TCAA in the second and third quartiles (OR = 1.46; 95% CI: 1.12, 1.90 and OR = 1.30; 95% CI: 1.00, 1.70, respectively), and for below-reference sperm count in men with TCAA in the second quartile (OR 1.62; 95% CI: 1.04, 2.55). Nonmonotonic associations with TCAA quartiles were also estimated for semen parameters modeled as continuous outcomes, although significant negative associations were estimated for all quartiles above the reference level for sperm motility.Conclusion: Our findings suggest that exposure to drinking-water DBPs may contribute to decreased semen quality in humans.Citation: Zeng Q, Wang YX, Xie SH, Xu L, Chen YZ, Li M, Yue J, Li YF, Liu AL, Lu WQ. 2014. Drinking-water disinfection by-products and semen quality: a cross-sectional study in China. Environ Health Perspect 122:741–746; http://dx.doi.org/10.1289/ehp.1307067

Physical and radiological properties of radiochromic gel as of its composition

In the research, we evaluated the use of leuco crystal violet (LCV) gel as a dosimeter for therapeutic radiation by investigating its optical characteristics at various component concentrations. We also investigated the aging effect of the LCV gel at different beam energies, doserates, and dosing times to evaluate the LCV’s applicability to radiation therapy. We confirmed that the optimal optical wavelength of the LCV gel dosimeter was 600 nm. The dose sensitivity increased with increasing concentration of LCV; however, the optimal concentration was 1 mM LCV because the transparency of the gel dosimeter is important for use in optical CT scanners. However, the dose sensitivity decreased with increasing concentration of trichloroacetic acid (TAA). Moreover, the transparency of LCV rapidly decreased because of the generation of a white precipitate at TAA concentrations below 25 mM. Thus, an optimal TAA concentration of 30 mM was used in this study. Triton X-100 (8 mM) was identified as the optimal reagent for determining the optimum gel transparency and dose sensitivity. Thus, we present an LCV gel dosimeter composed of 4% gelatin by mass, 1 mM LCV, 30 mM TAA, and 8-mM Triton X-100 for use with an optical CT scanner. We showed good dose linearity up to 30 Gy. There was a little doserate dependency at a beam energy of 6 MV while the doserate dependence was more than 4.2% at a beam energy of 10 MV. To evaluate the energy dependence of the LCV gel dosimeter, we irradiated it at 20 Gy by using 6 MV and 10 MV beams. At the high doserate, the difference in the dose energy dependence was relatively small at approximately 1%, but the difference increased to 4.6% at the low doserate. With respect to the radiation absorbance at a photon energy of 6 MV, the absorbance at an electron energy of 6 MeV decreased by 5.4%, and the absorbances at 9, 12, and 15 MeV increased by 3, 18.7, and 12.2%, respectively. Furthermore, the aging effect was larger in the low-dose group then in the high-dose group. Moreover, we observed that the absorbance between 24 and 48 h after irradiation increased by approximately 5% at 5 Gy. For gel groups tested at high doses, the aging effect was reduced by approximately 1%.

Influencing factors of disinfection byproducts formation during chloramination of Cyclops metabolite solutions

Effects of reaction time, chlorine dosage, pH and temperature on the formation of disinfection byproducts (DBPs), were investigated during the chloramination of Cyclops metabolite solutions. The results showed that some species of DBPs like trichloromethane (TCM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) could accumulate to their respective stable values with a progressive elevation in reaction time and monochloramine concentration. And 1,1,1–2-trichloropropanone (1,1,1-TCP) content decreased correspondingly with a continuous increase of reaction time. The amounts of chloral hydrate (CH), chloropicrin (TCNM), 1,1,1-TCP and DCAA firstly increased and then decreased with increasing monochloramine doses. Higher temperature resulted in a decrease of CH, dichloroacetonitrile (DCAN), 1,1-dichloropropanone (1,1-DCP), 1,1,1-TCP, DCAA and TCAA concentration. pH affected the formation of the different DBPs distinctly. TCM accumulateded with the increase of pH under 9, and DCAA, TCAA, CH and 1,1-DCP decreased continuously with increasing pH from 5 to 10, and other DBPs had the maximum concentrations at pH 6–7.

Assessment of Haloacetic Acids in Drinking Water in Bizerte, Tunisia

An investigation into the occurrence of haloacetic acids (HAAs) was conducted during a period of winter and summer seasons of the years 2008–2009 on the drinking water of Bizerte with variable conditions of water quality, pH, water temperature, total organic carbon, and bromide concentrations. The concentrations of HAAs were determined by a fast headspace solid‐phase microextraction GC method, which consists of liquid–liquid extraction, evaporation to dryness of extraction solvent then derivatization of the HAAs to their methyl haloacetates with sulfuric acid and methanol, followed by headspace solid‐phase microextraction with GC and electron capture detection. The results of the analyses show the presence of HAAs in all chlorinated water samples. The most prevalent HAAs were trichloroacetic acid (TCAA), dichloroacetic acid (DCAA), and monochloroacetic acid (MCAA) due to the low concentrations of bromide in the water treatment plant, while other HAAs were detected at low concentrations. The annual means concentrations of TCAA, DCAA and, MCAA varied from 3.9 to 26.25 µg L−1, from 2.76 to 23.19 µg L−1, and from 6.65 to 34.07 µg L−1, respectively. Seasonal variations in HAAs were mainly linked with changes in water temperature and variations of organic precursors, with HAA occurrence at its highest in summer. In all samples the concentrations of HAAs were lower than the maximum level set by the World Health Organization except for MCAA at the network extremity. Finally, a statistically significant (p &lt; 0.05) regression analysis was used to examine the correlation of HAA5 with respect to some water quality parameters. Strong correlations between (total organic carbon, water temperature and chlorine dose) with HAA5 were observed.