Determination of Total Organic Carbon in Water by Thermal Combustion-Ion Chromatography

A high-throughput atomic emission analyzer for simultaneous field detection of dissolved inorganic and organic carbon in seawater and lake water

Dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) are two important indicators of global carbon cycle. However, there are no portable analyzers available to simultaneously accomplish high-throughput field detection of them in the same sample. Herein, a simple analyzer comprising a dual-mode reactor to accomplish both chemical vapor generation and headspace sampling, and a miniature point discharge optical emission spectrometer (μPD-OES) was developed for simultaneous and high-throughput detection of DIC and DOC in seawater and lake water. Phosphoric acid and persulfate were successively injected into sample solutions to convert DIC and DOC to CO₂ under the conditions of magnetic stirring and UV irradiation, respectively. Subsequently, the generated CO₂ was swept into the μPD-OES for quantitation of DIC and DOC via monitoring carbon atomic emission at 193.0 nm. Under optimal conditions, limits of detection for DIC and DOC (as C) were both 0.01 mg L^-1 with relative standard deviations (n = 20) better than 5% and sample throughput of 80 samples per hour. Compared to conventional analyzers, the proposed instrument provides the advantages of high throughput, compactness, low energy consumption and eliminates expensive instruments. The accuracy of the system was validated by simultaneous determination of DIC and DOC in various water samples in laboratory and field environments.

A New Setup for the Measurement of Total Organic Carbon in Ultrapure Water Systems

With the increasing demand for ultrapure water in the pharmaceutical and semiconductor industry, the need for precise measuring instruments for those applications is also growing. One critical parameter of water quality is the amount of total organic carbon (TOC). This work presents a system that uses the advantage of the increased oxidation power achieved with UV/O3 advanced oxidation process (AOP) for TOC measurement in combination with a significant miniaturization compared to the state of the art. The miniaturization is achieved by using polymer-electrolyte membrane (PEM) electrolysis cells for ozone generation in combination with UV-LEDs for irradiation of the measuring solution, as both components are significantly smaller than standard equipment. Conductivity measurement after oxidation is the measuring principle and measurements were carried out in the TOC range between 10 and 1000 ppb TOC. The suitability of the system for TOC measurement is demonstrated using the oxidation by ozonation combined with UV irradiation of defined concentrations of isopropyl alcohol (IPA).

Miniaturized TOC analyzer using dielectric barrier discharge for catalytic oxidation vapor generation and point discharge optical emission spectrometry

Total organic carbon (TOC) is an important parameter describing organic pollution degree of waters. Due to the increasing need of field analysis and drawbacks of conventional TOC analytical instruments, miniaturized TOC analyzers are still demanding. In this work, a dielectric barrier discharge (DBD) microplasma was utilized for catalytic oxidation vapor generation (COVG) of organic compounds into CO₂, and a point discharge (PD) microplasma was employed to excite the carbon atomic emission spectra for quantification. Sample solution with phosphoric acid and persulfate solution was injected into the DBD-COVG reactor by a syringe to convert organic compounds into CO₂ efficiently and quickly, which was subsequently transported into the point discharge optical emission spectrometer (PD-OES) for detecting carbon at 193.09 nm. Under optimal experimental conditions, high oxidation efficiencies for several organic compounds were achieved, i.e., 96.4%, 95.1% and 94.3% for 50 mg L^-1 potassium hydrogen phthalate (KHP), sodium laurylsulfonate and phenol, respectively. A limit of detection (LOD) of 0.02 mg L^-1 (as C) was obtained, with a precision of 3.9% (relative standard deviation, RSD) at 15 mg L^-1 TOC standard (as C). The possible catalytic oxidation mechanism was proposed with the characteristic results of electron paramagnetic resonance (EPR). Its potential environmental application was demonstrated by successfully analyzing TOC in underground water, surface river water and surface sedimentary water samples from oil fields, with analytical results agreed well with those obtained by the commercial high-temperature combustion coupled nondispersive infrared absorption (HTC-NDIR) technique.

Machine learning for total organic carbon analysis of environmental water samples using high-throughput colorimetric sensors

Process of total organic carbon (TOC) prediction using colorimetric sensors and machine learning (ML).

Continuous and Inexpensive Monitoring of Nonpurgeable Organic Carbon by Coupling High-Efficiency Photo-oxidation Vapor Generation with Miniaturized Point-Discharge Optical Emission Spectrometry

Currently, no applicable analyzers are available to accomplish online continuous monitoring of organic pollution, which is one of the most important factors contributing to water shortages around the world, particularly in developing countries. In this work, a sensitive, miniaturized, inexpensive, and online nonpurgeable organic carbon (NPOC) analysis system was developed for continuous monitoring of such organic pollution. This system consists of a specially designed high-efficiency UV photo-oxidation vapor generation (HE-POVG) reactor and a miniaturized, low-power (7 W) point-discharge microplasma optical emission spectrometer (PD-OES). Organics present in sample or standard solutions are pumped to the HE-POVG and efficiently converted into CO₂, which is separated and further transported to the PD-OES for NPOC analysis via highly sensitive detection of carbon atomic emission at 193.0 nm. Under optimal conditions, a limit of detection of 0.05 mg·L^-1 (as C) is obtained, with precision better than 5.0% (relative standard deviation) at 5 mg·L^-1. This system overcomes many shortcomings associated with conventional chemical oxygen demand or total organic carbon analyzers such as long analysis time, use of expensive and toxic chemicals, production of secondary toxic waste, requirement of large, power consuming and expensive instrumentation and difficulties implementing continuous online monitoring. The system was successfully applied to sensitive and accurate determination of NPOC in various water samples and for continuous monitoring of such organic pollution in tap water.

Flow-injection analysis for the determination of total inorganic carbon and total organic carbon in water using the H2O2–luminol–uranine chemiluminescent reaction

In the presence of carbonate and uranine, the chemiluminescent intensity from the reaction of luminol with hydrogen peroxide was dramatically enhanced in a basic medium. Based on this fact and coupled with the technique of flow-injection analysis, a highly sensitive method was developed for the determination of carbonate with a wide linear range. The method provided the determination of carbonate with a wide linear range of 1.0 x 10(-10)-5.0 x 10(-6) mol L(-1) and a low detection limit (S/N = 3) of carbonate of 1.2 x 10(-11) mol L(-1). The average relative standard deviation for 1.0 x 10(-9)-9.0 x 10(-7) mol L(-1) of carbonate was 3.7% (n = 11). Combined with the wet oxidation of potassium persulfate, the method was applied to the simultaneous determination of total inorganic carbon (TIC) and total organic carbon (TOC) in water. The linear ranges for TIC and TOC were 1.2 x 10(-6)-6.0 x 10(-2) mg L(-1) and 0.08-30 mg L(-1) carbon, respectively. Recoveries of 97.4-106.4% for TIC and 96.0-98.5% for TOC were obtained by adding 5 or 50 mg L(-1) of carbon to the water samples. The relative standard deviations (RSDs) were 2.6-4.8% for TIC and 4.6-6.6% for TOC (n = 5). The mechanism of the chemiluminescent reaction was also explored and a reasonable explanation about chemical energy transfer from luminol to uranine was proposed.

Determination of carbon dioxide and acid components in exhaust gas by suppressed ion chromatography

Although anions are usually determined by suppressed ion chromatography (IC), carbonate and bicarbonate ions can not be determined, because a mixed solution of sodium carbonate and sodium hydrogencarbonate is used as the eluent. This paper describes an IC method for the determination of carbonate ion and common anions using an IonPac AG17/AS17 column, an EG 40 eluent generator and a conductivity detector. The proposed IC method could determine carbonate ion and anions within 6 min. The relative standard deviations (n = 5) for chloride (0.4 mg L(-1)), nitrite (0.8 mg L(-1)), carbonate (100 mg L(-1)), nitrate (1.0 mg L(-1)) and sulfate (2.0 mg L(-1)) ions were 5.1%, 1.1%, 4.2%, 5.1% and 1.1%, respectively. In addition, the absorbing solution of carbon dioxide was examined, and 2-amino-2-methyl-1-propanol was found to be a good absorbing solution. The proposed IC method was applied to the determination of carbon dioxide and acid components in flue gas and automobile exhaust gas.

Advances in the determination of inorganic anions by ion chromatography

The time period covered for this review includes articles published from 1997 to 1999, with the addition of a few classic references. The purpose of the review is to include the most relevant works from each topic area of the determination of inorganic anions by ion chromatography, including new sample pretreatments, new separation methods, new detection systems and the latest applications in the field of environmental, water, foods, etc. samples. Experimental conditions such as stationary phase, eluent, detection mode, as well as matrix are summarized in a table.

Applications of anion chromatography in terrestrial environmental research

Ion chromatography can be applied to characterise single samples for a wide range of ionic species, at elevated or trace concentrations, or with automation may be used to determine many of the common ions on several thousand samples per year. It has been applied to a wide range of sample types of environmental interest. Examples of applications are given for the common sample types, i.e. atmospheric gases and particulates, water, biological materials and soil. The recent literature in the field of anion chromatography, as applied to environmental research, is reviewed (102 references). Suppressed and non-suppressed systems are covered, as are comparisons with other methods of analysis. Development of sample preparation methods, stationary and mobile phases, detection systems and techniques are also discussed.