The determination of six taste and odour compounds in water using Ambersorb 572 and high resolution mass spectrometry.

A method for the analysis of six taste and odour causing compounds in aqueous samples using the granular adsorbent, Ambersorb 572, and gas chromatography-high resolution mass spectrometry (GC-HRMS) has been developed. This method for the determination of geosmin, 2-methylisoborneol (2-MIB), 2-isopropyl-3-methoxypyrazine (IPMP), 2-isobutyl-3-methoxypyrazine (IBMP), 2,3,6-trichloroanisole (236-TCA) and 2,4,6-trichloroanisole (246-TCA) is highly productive [up to 40 samples per day + 23 quality control (QC) samples] and provides rapid (24-48 h) turnaround times. The analytes are extracted from water by the addition of Ambersorb 572 to the sample bottle and rolling for 1 h. The adsorbent is isolated by filtration and allowed to air dry for 1 h. The Ambersorb 572 is transferred to an autosampler vial and the analytes are desorbed into dichloromethane. The extract is analysed by GC-HRMS at 7000 resolving power (RP). Quantification is performed by isotope dilution and internal standard techniques utilizing d3-geosmin, d3-2-MIB, d5-246-TCA and 2-sec-butyl-3-methoxypyrazine (s-BMP). Method precisions of 3.5-5.8% and accuracies of +/- 5.7-8.9% were obtained. Reporting detection limits (RDLs) of 1.0 ng L-1 were obtained for 2-MIB, geosmin, IPMP and IBMP, while RDLs of 2.0 ng L-1 were obtained for 236-TCA and 246-TCA.

Structural elucidation of disinfection by-products in treated drinking water.

Two unusual disinfection by-products have been detected periodically in the gas chromatography/mass spectrometry (GC/MS) characterization analyses of semi-volatile organics in treated drinking water. The electron ionization (EI) mass spectra contained mono-chlorinated and mono-brominated ions at m/z 107/109 and 151/153, respectively. Library searching techniques suggested mono-halogenated butanol structures but no matches could be found. Positive ion chemical ionization (CI) spectra contained mono-chlorinated and mono-brominated ions at m/z 105/107 and 149/151, respectively. No [M + H]+ ions were initially observed. Accurate mass measurements confirmed the empirical formulae for the significant ions in the EI spectra and the mono-halogenated butanol structures. Further CI experiments with other reagent gases and instruments revealed possible molecular weights of 139 and 183 Da, respectively. Tandem mass spectrometry (MS/MS) experiments in EI and CI were used to elucidate the fragmentation schemes. The two compounds have been tentatively identified as 1-aminoxy-1-chlorobutan-2-ol and 1-aminoxy-1-bromobutan-2-ol, respectively.

Characterization of nonyl phenol ethoxylates in sewage treatment plants by combined precursor ion scanning and multiple reaction monitoring.

A novel rapid screening technique for the profiling of nonyl phenol ethoxylates (NPEs) in sewage treatment plant (STP) influent/effluent was developed using flow injection with atmospheric pressure ionization coupled to mass spectrometric analysis by combined precursor ion scanning and multiple reaction monitoring. The technique allows for total NPE concentrations as low as 50 parts-per-trillion to be detected in STP samples.

Determination of diquat and paraquat in water by liquid chromatography-(electrospray ionization) mass spectrometry.

A method for the determination of the herbicides diquat and paraquat in water was developed using liquid chromatography-(electrospray ionization) mass spectrometry [LC-(ESI)MS]. The analytes were isolated on an ENVI-8 DSK solid phase extraction (SPE) disk and eluted with 5-M trifluoroacetic acid (TFA). The eluate was evaporated to dryness and the analytes were redissolved in the mobile phase (7% methanol/93% water/25-mM TFA). The extract was analyzed by liquid chromatography (C1 column) with postcolumn addition of propionic acid/methanol followed by (ESI)MS. Diquat was detected using the [M(2+)-H+] ion (M2+ = dication) at m/z 183, whereas paraquat was detected using the mono-trifluoroacetate ion pair [M2 +/- OOCCF3] at m/z 299. Quantitation was done by isotope dilution mass spectrometry using d4-diquat and d8-paraquat and the corresponding ions [M(2+)-D+] and [M2 +/- OOCCF3] at m/z 186 and m/z 307, respectively. Detection limits of 0.1 and 0.2 microgram/L, respectively (based on the dications), were adequate to meet the Ontario Drinking Water Objectives of 70 and 10 micrograms/L, respectively, and the Ontario Provincial Water Quality Objective for diquat of 0.5 microgram/L. Precision and accuracy were 14% and 6% for diquat and 12% and 3% for paraquat.

N-nitrosodimethylamine in drinking water using a rapid, solid-phase extraction method.

A simple, rapid method for the extraction of N-nitrosodimethylamine (NDMA) from drinking and surface waters was developed using Ambersorb 572. Development of an alternative method to classical liquid-liquid extraction techniques was necessary to handle the workload presented by implementation of a provincial guideline of 9 ppt for drinking water and a regulatory level of 200 ppt for effluents. A granular adsorbent, Ambersorb 572, was used to extract the NDMA from the water in the sample bottle. The NDMA was extracted from the Ambersorb 572 with dichloromethane in the autosampler vial. Method characteristics include a precision of 4 % for replicate analyses, an accuracy of 6 % at 10 ppt and a detection limit of 1.0 ppt NDMA in water. Comparative data between the Ambersorb 572 method and liquid-liquid extraction showed excellent agreement (average difference of 12 %). With the Ambersorb 572 method, dichloromethane use has been reduced by a factor of 1,000 and productivity has been increased by a factor of 3-4. Monitoring of a drinking water supply showed rapidly changing concentrations of NDMA from day to day.

Determination of drug stability in aspirin tablet formulations by high-pressure liquid chromatography.

Salicylic acid and aspirin were resolved from the other salicylates in thermally degraded multicomponent tablets and determined quantitatively. The analytical method involved wetting the powdered tablet with acetic acid and diluting with chloroform to extract the drug components. Automated high-pressure liquid chromatographic analyses of filtered extracts were performed on a silica column with a mobile phase of acetic acid in heptane. The method was capable of resolving the major thermally induced transformation products in tablet formulations. It was sensitive to approximately 0.1 mg of salicylic acid/tablet. Good agreement with the compendial method for free salicylic acid was obtained.