Hydrothermal conversion of toilet waste: effect of processing conditions on gas phase emissions.

Globally, many populations suffer from a lack of access to basic sanitation facilities. This is partly caused by a combination of water resource shortages and the high cost of conventional centralised treatment systems. A novel decentralised treatment technology based on sub-critical hydrothermal processing of organic wastes at toilet-scale, contributes to addressing these economic and resource limitations. To be effective, this technology needs to satisfy a broad range of environmental and safety considerations, including the nature and quantity of formed gas products. We investigated the impact of four process parameters (temperature; O2: COD ratio (λ); time; feed solids content) on off-gas composition by quantifying volatile organic compounds (VOCs), CO, H2 and CO2 in factorial experiments. Temperature and λ influenced VOCs generation greatly. The lowest VOC emissions occurred at 200% λ and 300 °C. Aldehydes and ketones were mostly generated at 200% λ and intermediate temperatures, sulphur compounds in the absence of oxygen, and aromatics, furans, and pyrroles at intermediate oxygen levels and elevated temperatures. Most CO was created at 300 °C but its concentration decreased at longer processing times. Processing conditions have complex impacts and require careful consideration when designing for real world deployment.

[Letter to the Editor] NaOH concentration and streptavidin bead type are key factors for optimal DNA aptamer strand separation and isolation.

Address correspondence to Geoffrey K. Kilili or Christine M. Karbiwnyk, Winchester Engineering and Analytical Center, US Food and Drug Administration, Winchester, MA, 01890. E-mail: Geoffrey.Kilili@fda.hhs.gov or Christine.Karbiwnyk@fda.hhs.gov.

Bioaccumulation of melamine in catfish muscle following continuous, low-dose, oral administration.

In this study, catfish muscle was analyzed for melamine (MEL) and cyanuric acid (CYA) residues following experimental feeding with low doses of MEL and MEL and CYA (MEL+CYA) and with the insoluble melamine-cyanurate complex (MEL=CYA). Catfish were daily fed 0.1 mg/kg BW of MEL for 15, 28, or 42 days, 0.1 mg/kg BW of MEL+CYA for 28 days, 2.5 mg/kg BW of MEL+CYA for 14 days, or 400 mg/kg BW of MEL=CYA for 3 days. Residues in the tissue were determined by LC-MS/MS. MEL was extracted with acidic acetonitrile, followed by defatting with dichloromethane, and isolated with cation exchange solid phase extraction (SPE). For CYA analysis, fish were extracted with dilute acetic acid, defatted with hexane, and cleaned up with a graphitic carbon SPE. Catfish fed 0.1 mg/kg BW of MEL reached a maximum muscle residue concentration of 0.33 ± 0.04 mg/kg (ppm) after 28 days of continuous feeding. The same concentration was found for MEL+CYA feeding at the 0.1 mg/kg BW level for 28 days. Feeding at 2.5 mg/kg BW of MEL+CYA yielded muscle concentrations above the 2.5 mg/kg level of concern for most of the study fish. Finally, catfish fed high levels of the MEL=CYA complex (400 mg/kg BW) accumulated relatively little MEL in the muscle (0.14 ± 0.07 mg/kg) and, unlike treatment with MEL+CYA, did not form renal melamine-cyanurate crystals. Appreciable concentrations of CYA were not detected in any of the muscles tested. These studies provide data to model the bioaccumulation of triazine residues into edible fish tissue as a result of the continuous consumption of adulterated feed.

Bioaccumulation of cyanuric acid in edible tissues of shrimp following experimental feeding.

Due to concerns that cyanuric acid (CYA)-contaminated feed had been used in aquaculture and could enter the human food chain, a method to quantify CYA residues in the edible tissues of fish and shrimp was previously developed and validated. This paper provides further data on the deliberate feeding of CYA to shrimp to determine the extent of residue accumulation in edible tissue. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed for the analysis of CYA in shrimp tissue. Edible tissue of shrimp fed 1666 or 3333 mg kg⁻¹ CYA in their diet (approximately 55 and 124 mg kg⁻¹ body weight) contained 0.767 and 0.406 mg kg⁻¹ CYA, respectively. The residue levels are below the World Health Organization (WHO) tolerable daily intake level for CYA and are generally considered unlikely to pose a human health risk.

Analysis of aminoglycoside residues in bovine milk by liquid chromatography electrospray ion trap mass spectrometry after derivatization with phenyl isocyanate.

A derivatization procedure using phenyl isocyanate was adapted to liquid chromatography ion trap mass spectrometry (LC-MS(n)) for confirmation and quantification of aminoglycoside residues in milk. Aminoglycoside residues were extracted from milk with acid and isolated from the matrix with a weak cation exchange solid-phase extraction cartridge. After isolating the compounds from the milk, derivatives of gentamicin, neomycin, and tobramycin were formed by reacting the drugs with phenyl isocyanate in the presence of triethylamine. The analytes were separated using a dilute formic acid/acetonitrile gradient on a reversed-phase LC column. The derivatized compounds were analyzed using positive ion electrospray LC-MS(n) with ion trap detection. Product ion spectra were generated from the derivatized protonated molecules. Specific ion transitions were evaluated for quantitative determination and qualitative confirmation of residues in milk. Using this procedure, residues were qualitatively confirmed in milk samples fortified with gentamicin and neomycin at levels ranging from 15 to 300 ng mL(-1). Gentamicin has four major components that were successfully separated and confirmed independently; for quantitative determination the peak areas from the four analogs were summed. Tobramycin was added as an internal standard for quantitation to mitigate the effects of matrix ion suppression and variable recoveries. Overall recoveries for this method ranged from 80% to 120% with relative standard deviations of less than 25%. The method detection limits are 9.8 ng mL(-1) for NEO and 12.8 ng mL(-1) for total GEN residues.

Determination of cyanuric acid residues in catfish, trout, tilapia, salmon and shrimp by liquid chromatography-tandem mass spectrometry.

In May 2007, investigators discovered that waste material from the pet food manufacturing process contaminated with melamine (MEL) and/or cyanuric acid (CYA) had been added to hog and chicken feeds. At this time, investigators also learned that adulterated wheat gluten had been used in the manufacture of aquaculture feeds. Concern that the contaminated feed had been used in aquaculture and could enter the human food supply prompted the development of a method for the determination of CYA residues in the edible tissues of fish and shrimp. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed as a sensitive technique for the analysis of CYA in catfish, tilapia, salmon, trout and shrimp tissue. CYA was extracted from ground fish or shrimp with an acetic acid solution, defatted with hexane, and isolated with a graphitic carbon black solid-phase extraction column. Residues were separated from matrix components using a porous graphitic carbon LC column, and then analyzed with electrospray ionization in negative ion mode on a triple quadrupole mass spectrometer. Selective reaction monitoring was performed on the [M-H](-)m/z 128 ion resulting in the product ions m/z 85 and 42. Recoveries from catfish, tilapia and trout fortified with 10-100 microgkg(-1) of CYA averaged 67% with a relative standard deviation (R.S.D.) of 18% (n=107). The average method detection limit (MDL) for catfish, tilapia and trout is 3.5 microgkg(-1). An internal standard, (13)C(3)-labeled CYA, was used in the salmon and shrimp extractions. Average recovery of CYA from salmon was 91% (R.S.D.=15%, n=18) with an MDL of 7.4 microgkg(-1). Average recovery of CYA from shrimp was 85% (R.S.D.=10%, n=13) with an MDL of 3.5 microgkg(-1).

Multiresidue method for the triphenylmethane dyes in fish: Malachite green, crystal (gentian) violet, and brilliant green.

Liquid chromatographic methods are presented for the quantitative and confirmatory determination of crystal violet (CV; also known as gentian violet), leucocrystal violet (LCV), brilliant green (BG), and leucobrilliant green (LBG) in catfish. LCV and LBG were oxidized to the chromic CV and BG by reaction with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, and residues were measured as the combined CV+/-LCV and BG+/-LBG. These methods are extensions of published methods for malachite green (MG) analysis to allow simultaneous determination of MG, CV, and BG. Residues were extracted from muscle with ammonium acetate buffer and acetonitrile, and extracts cleaned up using dichloromethane partitioning and solid-phase extraction. Extracts were analyzed by liquid chromatography with visible detection (LC-VIS). The method was validated for catfish fortified with LCV over the range 0.25-10 ngg(-1) and CV at 2 ngg(-1). Average recoveries were 90.6% (+/-8.1% R.S.D., n=45) for LCV and 84.4% (+/-4.2% R.S.D., n=6) for CV. The average recovery for samples fortified with BG or LBG over the range 0.5-10 ngg(-1) was 67.2% (+/-14.8% R.S.D., n=31). CV and BG were confirmed in fish extracts by ion trap LC-mass spectrometry (LC-MS(n)) with no discharge-atmospheric pressure chemical ionization. Average LC-MS(n) recoveries were 96.5, 96.6, and 70.2% for samples fortified with CV, LCV, and BG or LBG. The limits of detection for CV, BG, and MG were in the range of 0.07-0.24 ngg(-1) (ppb) for the two different instrumental methods. This methodology was applied to the analysis of catfish treated with CV and BG.

Evaluation of the renal effects of experimental feeding of melamine and cyanuric acid to fish and pigs.

OBJECTIVE: To determine whether renal crystals can be experimentally induced in animals fed melamine or the related triazine compound cyanuric acid, separately or in combination, and to compare experimentally induced crystals with those from a cat with triazine-related renal failure. ANIMALS: 75 fish (21 tilapia, 24 rainbow trout, 15 channel catfish, and 15 Atlantic salmon), 4 pigs, and 1 cat that was euthanatized because of renal failure. PROCEDURES: Fish and pigs were fed a target dosage of melamine (400 mg/kg), cyanuric acid (400 mg/kg), or melamine and cyanuric acid (400 mg of each compound/kg) daily for 3 days and were euthanatized 1, 3, 6, 10, or 14 days after administration ceased. Fresh, frozen, and formalin-fixed kidneys were examined for crystals. Edible tissues were collected for residue analysis. Crystals were examined for composition via Raman spectroscopy and hydrophilic-interaction liquid chromatography-tandem mass spectrometry. RESULTS: All animals fed the combination of melamine and cyanuric acid developed goldbrown renal crystals arranged in radial spheres (spherulites), similar to those detected in the cat. Spectral analyses of crystals from the cat, pigs, and fish were consistent with melamine-cyanurate complex crystals. Melamine and cyanuric acid residues were identified in edible tissues of fish. CONCLUSIONS AND CLINICAL RELEVANCE: Although melamine and cyanuric acid appeared to have low toxicity when administered separately, they induced extensive renal crystal formation when administered together. The subsequent renal failure may be similar to acute uric acid nephropathy in humans, in which crystal spherulites obstruct renal tubules.

Determination of oxytocin in a dilute IV solution by LC-MS(n).

The most common drug prescribed to induce labor in the United States is oxytocin, a peptide hormone composed of nine amino acids. Oxytocin is often reconstituted in intravenous (IV) saline solutions at less than 0.05 units ml(-1) (125 ng ml(-1)) to be delivered at 1-4 drops per minute. Existing LC-UV methods for oxytocin do not have sufficient detection limits to quantitate and/or confirm oxytocin in IV solutions without sample concentration. A determinative and confirmatory method for oxytocin was developed using an LC-MS(n) ion trap instrument with an electrospray ionization (ESI) interface in positive ion mode. Separation was achieved on a C-18 column using an isocratic elution of water with 50% acetonitrile (v/v) and water with 0.05% formic acid (v/v) at a flow rate of 250 microl min(-1). Data was acquired from the selected ion monitoring (SIM) of the precursor ion (m/z 1007.3) and MS(2) scans from the collision induced dissociation of m/z 1007.3 at 30% collision energy. In this method, MS(2) full scans were utilized to obtain three structurally significant ions for the unambiguous identification of oxytocin. Calibration standards, prepared in de-ionized water from 0.006 to 0.046 units ml(-1), were linear with an R(2) value of 0.9983. The methods LOD and LOQ were 0.00084 and 0.0029 units ml(-1) (2 and 7 ng ml(-1)), respectively. This LC-MS(n) method was used to determine the amount of oxytocin in a 0.04 units ml(-1) clinical sample that was prepared in 0.9% sodium chloride IV solution.

Determination and confirmation of melamine residues in catfish, trout, tilapia, salmon, and shrimp by liquid chromatography with tandem mass spectrometry.

Pet and food animal (hogs, chicken, and fish) feeds were recently found to be contaminated with melamine (MEL). A quantitative and confirmatory method is presented to determine MEL residues in edible tissues from fish fed this contaminant. Edible tissues were extracted with acidic acetonitrile, defatted with dichloromethane, and cleaned up using mixed-mode cation exchange solid-phase extraction cartridges. Extracts were analyzed by liquid chromatography with tandem mass spectrometry with hydrophilic interaction chromatography and electrospray ionization in positive ion mode. Fish and shrimp tissues were fortified with 10-500 microg/kg (ppb) of MEL with an average recovery of 63.8% (21.5% relative standard deviation, n = 121). Incurred fish tissues were generated by feeding fish up to 400 mg/kg of MEL or a combination of MEL and the related triazine cyanuric acid (CYA). MEL and CYA are known to form an insoluble complex in the kidneys, which may lead to renal failure. Fifty-five treated catfish, trout, tilapia, and salmon were analyzed after withdrawal times of 1-14 days. MEL residues were found in edible tissues from all of the fish with concentrations ranging from 0.011 to 210 mg/kg (ppm). Incurred shrimp and a survey of market seafood products were also analyzed as part of this study.

Multi-class, multi-residue liquid chromatography/tandem mass spectrometry screening and confirmation methods for drug residues in milk.

This paper describes the development and optimization of a multi-residue veterinary drug screening method for whole milk. The drug residues of regulatory interest in milk include beta-lactams, sulfonamides, tetracyclines, fluoroquinolones, and macrolides. Milk samples were extracted with acetonitrile and the samples were then subjected to a clean-up procedure using a bonded solid-phase extraction cartridge and a molecular weight cut-off filter. Liquid chromatography/tandem mass spectrometry (LC/MS/MS) triple quadrupole electrospray methods were developed to monitor for the drugs in milk. Since established tolerance levels are set for most of these drugs in milk, the initial screening procedure was semi-quantitative, where samples were compared to the response of a positive control. The positive control, consisting of an extract from a portion of milk fortified with the drugs at half their allowed levels, was used to set the laboratory's minimum response criteria for unknown samples. Confirmatory analyses, with additional ion transitions for each residue, were performed on the same extracts.

Determination of quinolone residues in shrimp using liquid chromatography with fluorescence detection and residue confirmation by mass spectrometry.

The quinolones, oxolinic acid (OXO), flumequine (FLU), and nalidixic acid (NAL), are antibacterial drugs effective against gram-negative bacteria. Quinolones are used in both human and veterinary medicine, but are currently not approved by the U.S. Food and Drug Administration for use in food fish. A liquid chromatography-fluorescence (LC-FL) method was developed to determine OXO, FLU, and NAL residues in shrimp. An additional liquid chromatography-mass spectrometry (LC-MS(n)) method was created to confirm these residues using the same sample extract. Samples were prepared with a simple ethyl acetate extraction followed by solvent exchange into 0.2% formic acid and cleaned-up with hexane. Reverse phase chromatography was used to separate the three compounds in both procedures. For the LC-FL determinative method, fluorescence emission was monitored at 369 nm with excitation at 327 nm. With electrospray ionization, the three most abundant ions from the MS3 product ion spectrum were used to identify OXO, FLU, and NAL in the confirmation procedure. Shrimp samples fortified at levels ranging from 7.5 to 100 ng g(-1) were used to validate both methods.

Confirmation of diminazene diaceturate in bovine plasma using electrospray liquid chromatography-mass spectrometry.

Diminazene diaceturate is used as a trypanocide for cattle in tropical regions. This paper describes a LC-MS(n) method to confirm the presence of diminazene in bovine plasma. Bound diminazene in plasma samples was freed with dilute phosphoric acid, then concentrated on a bonded C(18) SPE cartridge. The LC-MS(n) method utilized electrospray ionization coupled with an ion trap mass spectrometer. Ions observed in MS(2) and MS(3) product ion spectra, as well as those from the MS(1) spectrum, were monitored. The method was validated with plasma samples fortified with diminazene diaceturate (4-100ng/mL). Diminazene was confirmed in samples fortified with diminazene diaceturate at levels of 6.4ng/mL or higher.

No-discharge atmospheric pressure chemical ionization: evaluation and application to the analysis of animal drug residues in complex matrices.

Alternative ionization methods are increasingly being utilized to increase the versatility and selectivity of liquid chromatography/mass spectrometry (LC/MS). One such technique is the practice of using commercially available atmospheric pressure chemical ionization (APCI) sources with the corona discharge turned off, a process termed no-discharge APCI (ND-APCI). The relative LC/MS responses for several different classes of veterinary drugs were obtained by using ND-APCI, electrospray ionization (ESI), and APCI. While the ND-APCI-MS and -MSn spectra for these compounds were comparable with ESI, ND-APCI provided advantages in sensitivity and selectivity for some compounds. Drugs that were charged in solution as cations or sodium adducts responded particularly well with this technique. Instrumental parameters such as temperatures, gas and liquid flow rates, and source design were investigated to determine their effect on the process of ND-APCI. This paper explores advantages of using ND-APCI for the determination and confirmation of drug residues that might be found in food matrices, including malachite green residues in fish tissue and avermectin residues in milk.

Use of chloroflurocarbons as internal standards for the measurement of atmospheric non-methane volatile organic compounds sampled onto solid adsorbent cartridges.

Solid adsorbents have proven useful for determining the vertical profiles of volatile organic compounds (VOCs) using sampling platforms such as balloons, kites, and light aircraft, and those profiles provide valuable information about the sources, sinks, transformations, and transport of atmospheric VOCs. One of the largest contributions to error in VOC concentrations is the estimation of the volume of air sampled on the adsorbent cartridge. These errors arise from different sources, such as variations in pumping flow rates from changes in ambient temperature and pressure with altitude, and decrease in the sampling pump battery power. Another significant source for sampling rate variations are differences in the flow resistance of individual sampling cartridges. To improve the accuracy and precision of VOC measurements, the use of ambient chlorofluorocarbons (CFCs) as internal standards was investigated. A multibed solid adsorbent, AirToxic (Supelco), was chosen for its wide sampling range (C3-C12). Analysis was accomplished by thermal desorption and dual detection GC/FID/ECD, resulting in sensitive and selective detection of both VOCs and CFCs in the same sample. Long-lived chlorinated compounds (CFC-11, CFC-12, CFC-113, CCl4 and CH3CCl3) banned by the Montreal Protocol and subsequent amendments were studied for their ability to predict sample volumes using both ground-based and vertical profiling platforms through the boundary layer and free troposphere. Of these compounds, CFC-113 and CCl4 were found to yield the greatest accuracy and precision for sampling volume determination. Use of ambient CFC-113 and CCl4 as internal standards resulted in accuracy and precision of generally better than 10% for the prediction of sample volumes in ground-, balloon-, and aircraft-based measurements. Consequently, use of CFCs as reference compounds can yield a significant improvement of accuracy and precision for ambient VOC measurements in situations where accurate flow control is troublesome.

Minimization of water vapor interference in the analysis of non-methane volatile organic compounds by solid adsorbent sampling.

Water vapor can be a significant interference in the analysis of air for non-methane volatile organic compounds (NMVOCs) using solid-adsorbent sampling techniques. The adsorbent materials used in sampling cartridges have different hydrophobic characteristics, and it is therefore necessary to characterize solid-adsorbent cartridges over a wide range of humidity. Controlled humidity experiments were performed to assess the extent of water vapor interference when samples are collected onto AirToxics solid-adsorbent cartridges. It was found that elevating the temperature of the cartridge to 10 degrees C above the temperature of the air sample greatly reduced water vapor adsorption and interferences and resulted in > or = 90% recovery of NMVOCs, biogenic VOCs and chlorofluorocarbons. Similar collection efficiencies were obtained at ambient temperature by reducing the relative humidity to > or = 60% in the sample by dilution with dry, scrubbed ambient air. A procedure also was developed and optimized for dry-purging cartridges prior to analysis. However, under optimized conditions, significant losses of C3-C5 compounds still occurred under highly humid conditions. It was determined that these losses were due to reduced retention during sampling rather than loss during the dry purge procedure. The dry purge method was shown to be adequate at high humidities for sampling NMVOCs with retention indices greater than 500.