A low-cost automated titration system for colorimetric endpoint detection.

An auto titrator system was developed to accurately and precisely detect colorimetric endpoints for spectrochemical titrations. This system was constructed using inexpensive components such as a Raspberry Pi® single-board computer, 3D-printed components, and a commercially available spectral sensor. The auto titrator was evaluated by performing a standard method for determination of water hardness. Regardless of analyst experience, the auto titrator performed better than the traditional titration approach that involves manual dosing of titrant and visual detection of the endpoint. Inter-day, intra-day, inter-instrumental, and intra-instrumental validation studies were performed to establish the accuracy and precision of endpoint detection. The auto titrator eliminates the subjective bias in color perception and produces accurate and precise endpoint results.

A device for fully automated on-site process monitoring and control of trihalomethane concentrations in drinking water.

An instrument designed for fully automated on-line monitoring of trihalomethane concentrations in chlorinated drinking water is presented. The patented capillary membrane sampling device automatically samples directly from a water tap followed by injection of the sample into a gas chromatograph equipped with a nickel-63 electron capture detector. Detailed studies using individual trihalomethane species exhibited method detection limits ranging from 0.01-0.04 µg L(-1). Mean percent recoveries ranged from 77.1 to 86.5% with percent relative standard deviation values ranging from 1.2 to 4.6%. Out of more than 5200 samples analyzed, 95% of the concentration ranges were detectable, 86.5% were quantifiable. The failure rate was less than 2%. Using the data from the instrument, two different treatment processes were optimized so that total trihalomethane concentrations were maintained at acceptable levels while reducing treatment costs significantly. This ongoing trihalomethane monitoring program has been operating for more than ten months and has produced the longest continuous and most finely time-resolved data on trihalomethane concentrations reported in the literature.

A fully-automated analyzer for determining haloacetic acid concentrations in drinking water.

A fully-automated, on-line, real-time analyzer has been developed for preconcentration and analysis of haloacetic acids (HAAs). Preconcentration of HAAs is achieved by sample acidification and solid phase extraction onto a hydrophobic polymeric resin using sequential injection analysis (SIA). The HAAs preconcentrate is then analyzed using post-column reaction-ion chromatography (PCR-IC), which is selective for HAAs. Systematic optimization of SIA preconcentration parameters are described followed by detailed method detection limit (MDL), accuracy, precision, and linearity studies. MDL values for the individual HAA9 species range from 0.4 to 0.9 µg L(-1). Side-by-side comparison studies of HAAs analysis in 14 real-world drinking water samples from Alabama, Arkansas, Kentucky, Minnesota, Missouri, Mississippi, New York, Pennsylvania and Tennessee are presented that compare the optimized SIA-PCR-IC to USEPA Method 552.3. Trace levels of HAAs detected in select samples are reported, and the bias values calculated between the two methods are typically less than 5 µg L(-1) for eight of the nine individual HAAs.

A flow injection analysis system for monitoring silver (I) ion and iodine residuals in recycled water from recovery systems used for spaceflight.

A laboratory-built flow injection analyzer is reported for monitoring the drinking water disinfectants silver (I) ion and iodine in water produced from NASA's water recovery system. This analyzer uses spectrophotometric detection with a custom made 10cm optical flow cell. Optimization and interference studies are discussed for the silver (I) ion configuration. Subsequent results using the silver (I) configuration with minor modifications and alternative reagents gave promising results for iodine determinations as well. The estimated MDL values for Ag(+) and I2 are 52µg L(-1) Ag(+) and 2µg L(-1) I2; the mean percent recoveries were 104% and 96.2% for Ag(+) and I2 respectfully; and percent relative standard deviations were estimated at 1.4% for Ag(+) and 5.7% for I2. The agreement of this potentially multifunctional analyzer to reference methods for each respective water disinfectant is measured using Bland-Altman analysis as well as more traditional estimates.

A single automated instrument for monitoring total trihalomethane and total haloacetic acid concentrations in near real-time.

A single instrument is presented for selectively measuring the concentrations of total trihalomethanes (THM4) and total haloacetic acids (HAA9) directly from drinking water distribution systems. The method is based on the fluorescence reaction of THM4 or HAA5 species with nicotinamide. The method detection limit (MDL) for THM4 was 2.5 microg L(-1) with mean % recovery of 108% and % relative standard deviation (% R.S.D.) of 4%. For HAA5, the MDL was 3.3 microg L(-1) with mean % recovery and % R.S.D. of 102% and 3.5%, respectively. Side-by-side comparisons to United States Environmental Protection Agency methods (Methods 502.2 and 552.3) in chlorinated and chloraminated distribution systems exhibited reproducible biases that ranged from approximately 0.2 to 5 microg L(-1) for THM4 and from approximately -0.7 to -27 microg L(-1) for HAA5. The device provides for automated on-line sampling and analysis of THM4 and HAA9 with hourly sample analysis rates and is effectively a real-time system for drinking water monitoring.

On-line monitoring of nine haloacetic acid species at the microgL(-1) level using post-column reaction-ion chromatography with nicotinamide fluorescence.

A laboratory-built automated instrument is reported for on-line, near real-time monitoring of nine haloacetic acids species (HAA9) in drinking water. The device uses anion-exchange chromatography to separate the HAA9 species, followed by post-column reaction with nicotinamide in basic solution with fluorescence detection. Method detection limits for HAA9 species ranged from 0.6 to 10.1microgL(-1), mean % recovery values ranged from 58 to 161%, and % relative standard deviation ranged from 3.5 to 32% while operating within a factor of 2.5-5 of the method detection limit. The bias between the proposed method and United States Environmental Protection Agency Method 552.3 was measured during two separate on-line studies and using grab samples collected from different distribution systems. In general, the two methods showed good agreement with biases for HAA9 of less than 10microgL(-1).

CYP1B1 is not a major determinant of the disposition of aromatase inhibitors in epithelial cells of invasive ductal carcinoma.

CYP1B1 and CYP19 (aromatase) have been shown to be expressed in breast tumors. Both enzymes are efficient estrogen hydroxylases, indicating the potential for overlapping substrate and inhibitor specificity. We measured the inhibition properties of aromatase inhibitors (AIs) against CYP1B1-catalyzed hydroxylation of 17beta-estradiol (E2) to determine whether CYP1B1 affects the disposition of AIs. In addition, we estimated the frequency of coexpression of these enzymes in breast tumor epithelium. Immunohistochemical analyses of CYP19 and CYP1B1 in a panel of 29 cases of invasive ductal carcinoma of the breast showed epithelial cell staining for CYP19 in 76% and for CYP1B1 in 97% of the samples. Statistical analysis showed no significant correlation (0.33) for positive expression of CYP19 and CYP1B1 (p > 0.07). CYP1B1 inhibition was determined for two steroidal inhibitors: formestane and exemestane and five nonsteroidal inhibitors: aminoglutethimide, fadrozole, anastrozole, letrozole, and vorozole. Of the seven compounds tested, only vorozole exhibited inhibition of CYP1B1 activity with IC(50) values of 17 and 21 microM for 4-hydroxy estradiol and 2-hydroxy estradiol, respectively. The estimated K(i) values of vorozole for E2 4- and 2-hydroxylation were 7.26 and 6.84 microM, respectively. Spectrophotometric studies showed that vorozole was a type II inhibitor of CYP1B1. This study shows that with the exception of vorozole, the aromatase inhibitors are selective for CYP19 relative to CYP1B1. Thus, although both CYP19 and CYP1B1 are expressed in a high percentage of breast cancers, CYP1B1 is not a major determinant of the disposition of AIs.

On-line purge and trap gas chromatography for monitoring of trihalomethanes in drinking water distribution systems.

A method using an automated on-line purge and trap gas chromatograph with a dry electrolytic conductivity detector (DELCD) has been developed for monitoring four regulated trihalomethanes in drinking water distribution systems. This analyzer samples trihalomethanes from drinking water by pervaporation through a silicone capillary membrane contained within a gas extraction cell (GEC) followed by preconcentration using an adsorbent trap. Trihalomethanes are subsequently desorbed from the trap onto a capillary column, separated and detected. The analyzer operates in real-time, samples directly from the drinking water distribution system and is fully automated. The optimization, operation, and evaluation of the analyzer and method are discussed. Method detection limits (MDL) are less than 1.0 microg L(-1) with acceptable estimates for accuracy, and precision. The results from two on-line monitoring studies in chlorinated and chloraminated distribution systems are presented. The performance of the method is compared directly to United Stated Environmental Protection Agency Method 502.2 and shows a very slight, but acceptable bias.

Regioselective 2-hydroxylation of 17beta-estradiol by rat cytochrome P4501B1.

Previous work demonstrated that human cytochrome P4501B1 (CYP1B1) forms predominantly 4-hydroxyestradiol (4-OHE2), a metabolite which is carcinogenic in animal models. Here, we present results from kinetic studies characterizing the formation of 4-OHE2 and 2-hydroxyestradiol (2-OHE2) by rat CYP1B1 using 17beta-estradiol (E2) as a substrate. Km and Kcat values were estimated using the Michaelis-Menten equation. For rat CYP1B1, the apparent Km values for the formation of 4-OHE2 and 2-OHE2 were 0.61+/-0.23 and 1.84+/-0.73 microM; the turnover numbers (Kcat) were 0.23+/-0.02 and 0.46+/-0.05 pmol/min/pmol P450; and the catalytic efficiencies (Kcat/Km) were 0.37 and 0.25, respectively. For human CYP1B1, the apparent Km values for the formation of 4-OHE2 and 2-OHE2 were 1.22+/-0.25 and 1.10+/-0.26; the turnover numbers were 1.23+/-0.06 and 0.33+/-0.02; and the catalytic efficiencies were 1.0 and 0.30, respectively. The turnover number ratio of 4- to 2-hydroxylation was 3.7 for human CYP1B1 and 0.5 for rat CYP1B1. These results indicate that, although rat CYP1B1 is a low Km E2 hydroxylase, its product ratio, unlike the human enzyme, favors 2-hydroxylation. The Ki values of the inhibitor 2,4,3',5'-tetramethoxystilbene (TMS) for E2 4- and 2-hydroxylation by rat CYP1B1 were 0.69 and 0.78 microM, respectively. The Ki values of 7,8-benzoflavone (alpha-NF) for E2 4- and 2-hydroxylation by rat CYP1B1 were 0.01 and 0.02 microM, respectively. The knowledge gained from this study will support the rational design of CYP1B1 inhibitors and clarify results of CYP1B1 related carcinogenesis studies performed in rats.

On-line monitoring of microg/L levels of haloacetic acids using ion chromatography with post-column nicotinamide reaction and fluorescence detection.

A method for measuring the concentrations of the five regulated haloacetic acids (HAA5) in drinking water is reported. This method uses ion chromatography to separate HAA5 species, followed by post-column reaction with nicotinamide and detection of the fluorescent products. The result of method detection limit, accuracy, precision, linearity and interference studies are reported. The on-line monitoring method is compared directly to USEPA 552.3 in Memphis drinking water. Though not meant to replace the USEPA 552.3 for compliance monitoring, the proposed method does offer attractive alternatives considering the ease of automation and application of on-line monitoring directly from drinking water distribution systems.

Measuring the concentrations of drinking water disinfection by-products using capillary membrane sampling-flow injection analysis.

A capillary membrane sampling-flow injection analysis method is presented for selectively measuring the concentrations of total trihalomethanes (THMs) and total haloacetic acids (HAAs) in drinking water. The method is based on the reaction between nicotinamide and THM or HAA species to yield a fluorescent product. Two configurations are presented, one selective for total THMs and another selective for total HAAs. The construction of a capillary membrane sampler is described, and the results of method detection limit, accuracy and precision studies are reported for each method. Interference, selectivity and linearity studies are reported as well as the effect of temperature and ionic strength changes. Drinking water samples were analyzed by each proposed method and the results were compared to USEPA methods 502.2 and 552.3.

Measuring trihalomethane concentrations in water using supported capillary membrane sampling-gas chromatography.

The objective of this study was to develop and evaluate a supported capillary membrane sampling-gas chromatography method for the analysis of trihalomethanes (THMs) in drinking water. The effects of experimental parameters, such as flow rate of carrier gas, water temperature, ionic strengths of solutions and transfer line temperature on the system performance were investigated. The results of method detection limit and accuracy and precision studies are reported.