Multiresidue Determination of 27 Sulfonamides in Poultry Feathers and Its Application to a Sulfamethazine Pharmacokinetics Study on Laying Hen Feathers and Sulfonamide Residue Monitoring on Poultry Feathers

A method for the simultaneous determination of 27 sulfonamides in poultry feathers using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established in this study. The samples were extracted using 0.1 mol/L HCl solutions in a 60 °C water bath for 2 h, purified using hydrophilic-lipophilic balance solid-phase extraction, nitrogen-dried, and then reconstituted for UPLC-MS/MS analysis, which was performed with a CSH-C18 column. Linearity, limit of detection, limit of quantification, recovery, and precision were calculated in accordance with Commission Decision 2002/657/EC. For linearity, all standard curves showed a standard coefficient greater than 0.99, and the recoveries and coefficient of variation were 89-115% and <20%, respectively. The limit of detection and limit of quantification were 0.2-5 and 0.5-20 ng/g, respectively. The method was successfully applied to sulfamethazine (SMZ) residue accumulation monitoring in laying hen feathers and sulfonamide residue monitoring on poultry feathers. SMZ residue accumulation in the laying hen feathers was studied after administration with 100 mg/kg of SMZ for 21 consecutive days. SMZ residues were still detected in feathers 14 days after drug administration and persisted for up to 85 days. Results from 42 poultry feather samples showed that the feather is a suitable medium to monitor the illegal use of sulfonamides in poultry production.

Removal of Sulfamethoxazole, Sulfathiazole and Sulfamethazine in their Mixed Solution by UV/H2O2 Process

Sulfamethoxazole (SMZ), sulfathiazole (STZ) and sulfamethazine (SMT) are typical sulfonamides, which are widespread in aqueous environments and have aroused great concern in recent years. In this study, the photochemical oxidation of SMZ, STZ and SMT in their mixed solution using UV/H₂O₂ process was innovatively investigated. The result showed that the sulfonamides could be completely decomposed in the UV/H₂O₂ system, and each contaminant in the co-existence system fitted the pseudo-first-order kinetic model. The removal of sulfonamides was influenced by the initial concentration of the mixed solution, the intensity of UV light irradiation, the dosage of H₂O₂ and the initial pH of the solution. The increase of UV light intensity and H₂O₂ dosage substantially enhanced the decomposition efficiency, while a higher initial concentration of mixed solution heavily suppressed the decomposition rate. The decomposition of SMZ and SMT during the UV/H₂O₂ process was favorable under neutral and acidic conditions. Moreover, the generated intermediates of SMZ, STZ and SMT during the UV/H₂O₂ process were identified in depth, and a corresponding degradation pathway was proposed.

Rapid Detection of the Antibiotic Sulfamethazine in Pig Body Fluids by Paper Spray Mass Spectrometry

We report herein a practical method for nonlethal detection of the antibiotic sulfamethazine in pig body fluids via the combination of simple extraction and paper spray mass spectrometry (PS-MS). This method requires minimal sample preparation while still providing high sensitivities and accuracies in complex matrices including pig whole blood (LOD = 7.9 μg/L; recovery = 95.4-103.7%), pig serum (LOD = 11.5 μg/L; recovery = 103.2-106.2%), and synthetic urine (LOD = 11.2 μg/L; recovery = 99.1-103.2%). Given a known correlation between the level of sulfamethazine in body fluids and edible tissues, this method shows great promise as a practical and nonlethal solution for rapid testing of the drug, which can substantially aid managerial decision in the livestock industry.

Removal mechanism of sulfamethazine and its intermediates from water by a rotating advanced oxidation contactor equipped with TiO2-high-silica zeolite composite sheets

The removal of antibiotic sulfamethazine (SMT) and its intermediates from water was investigated using a rotating advanced oxidation contactor (RAOC) equipped with TiO₂-high-silica zeolite composite sheets. SMT was readily removed from water through adsorption onto high-silica zeolite and photocatalytic decomposition by TiO₂ inside the composite sheet. Some degradation intermediates were retained and photocatalytically decomposed inside the composite sheet. Relatively hydrophobic intermediates such as hydroxylated SMT were captured inside the sheets, whereas hydrophilic intermediates were distributed in water. This was attributed to the hydrophobic interactions in the adsorption mechanism of high-silica zeolite. The time courses of the NH₄⁺, NO₃^-, and SO₄^2- ion concentration during the RAOC treatment of SMT were evaluated. After treatment by RAOC for 24 h, approximately 94% of nitrogen derived from the amino and sulfanilamide groups and 39% of sulfur from the sulfanilamide group were mineralized, which indicated that the mineralization behavior of SMT treated by RAOC was different from that treated by TiO₂ powder. These results strongly suggested that the dissociation of the amino group and cleavage of the sulfonamide group and subsequent dissociation of the amino group preferentially proceeded inside the composite sheets.

Sorptive removal of ionizable antibiotic sulfamethazine from aqueous solution by graphene oxide-coated biochar nanocomposites: Influencing factors and mechanism

Significant concerns have been raised over antibiotics pollution in aquatic environments in recent years. In this study, sorption of sulfamethazine (SMT) by novel graphene oxide-coated biochar nanocomposites (GO-BC) based on graphene oxide (GO) with bamboo sawdust biochar (BC) was investigated. In comparison with the original BC, the sorption capacity of GO-BC for SMT increased by 1.14 times. Sorption of SMT onto GO-BC was proved to be dominantly by chemisorption, and Freundlich isotherm described the sorption adequately. It was found that variation of pH and ionic strength obviously affected the sorption of SMT, and GO-BC had a good sorption effect on SMT at pH 3.0-6.0 and lower ionic strength. Obvious enhancement (by 30%) in sorption of SMT on GO-BC was observed, which might be attributed to the increase of functional groups on the surface of GO-BC. Moreover, the main sorption mechanism for SMT was π-π electron-donor-acceptor interaction, while auxiliary sorption mechanisms were inferred as pore-filling, cation exchange, hydrogen bonding interaction and electrostatic interaction. The results indicated that GO-BC sorption was an efficient way for the removal of SMT.

Synchronized separation, concentration and determination of trace sulfadiazine and sulfamethazine in food and environment by using polyoxyethylene lauryl ether-salt aqueous two-phase system coupled to high-performance liquid chromatography

Polyoxyethylene lauryl ether (POELE10)-Na2C4H4O6 aqueous two-phase extraction system (ATPES) is a novel and green pretreatment technique to trace samples. ATPES coupled with high-performance liquid chromatography (HPLC) is used to analyze synchronously sulfadiazine (SDZ) and sulfamethazine (SMT) in animal by-products (i.e., egg and milk) and environmental water sample. It was found that the extraction efficiency (E%) and the enrichment factor (F) of SDZ and SMT were influenced by the types of salts, the concentration of salt, the concentration of POELE10 and the temperature. The orthogonal experimental design (OED) was adopted in the multi-factor experiment to determine the optimized conditions. The final optimal condition was as following: the concentration of POELE10 is 0.027gmL(-1), the concentration of Na2C4H4O6 is 0.180gmL(-1) and the temperature is 35°C. This POELE10-Na2C4H4O6 ATPS was applied to separate and enrich SDZ and SMT in real samples (i.e., water, egg and milk) under the optimal conditions, and it was found that the recovery of SDZ and SMT was 96.20-99.52% with RSD of 0.35-3.41%. The limit of detection (LOD) of this method for the SDZ and SMT in spiked samples was 2.52-3.64pgmL(-1), and the limit of quantitation (LOQ) of this method for the SDZ and SMT in spiked samples was 8.41-12.15pgmL(-1).

Removal of sulfamethazine antibiotics using CeFe-graphene nanocomposite as catalyst by Fenton-like process

The presence of sulfonamide (SMT) antibiotics in aquatic environments has received increasing attention in recent years, and they are ubiquitous pollutants which cannot be effectively removed by conventional wastewater treatment processes. In this paper, the nanocomposites Ce(0)/Fe(0)-reduced graphene oxide (Ce(0)/Fe(0)-RGO) were synthesized through chemical reduction method, and characterized by Raman and FTIR before and after use. The addition of RGO can prevent the agglomeration of Ce(0) and Fe(0). The elimination of SMT can be divided into adsorption and degradation process. The adsorption of SMT onto the catalyst can enhance its degradation. The effect of pH value, concentration of H2O2, catalyst dosage, temperature and initial SMT concentration on the removal efficiency of SMT was determined. When pH = 7, T = 25 °C, H2O2 = 8 mM, Ce(0)/Fe(0)-RGO = 0.5 g/L, SMT = 20 mg/L, the removal efficiency of SMT and TOC was 99% and 73%, respectively. The stability of the catalysts was evaluated with repeated batch experiments using ethanol, water and acid as solvents to wash the used catalysts, respectively. The surface change of the catalysts after each use was characterized by Raman and FTIR analysis. The intermediates were detected by GC-MS and IC, the possible degradation pathway of SMT was tentatively proposed.

Elimination patterns of worldwide used sulfonamides and tetracyclines during anaerobic fermentation

Antibiotics such as sulfonamides and tetracyclines are frequently used in veterinary medicine. Due to incomplete absorption in the animal gut and/or unmetabolized excretion, the substances can enter the environment by using manure as soil fertilizer. The anaerobic fermentation process of biogas plants is discussed as potential sink for antibiotic compounds. However, negative impacts of antibiotics on the fermentation process are suspected. The elimination of sulfadiazine, sulfamethazine, tetracycline and chlortetracycline in semi-continuous lab-scale fermenters was investigated. Both biogas production and methane yield were not negatively affected by concentrations up to 38 mg per kg for sulfonamides and 7 mg per kg for tetracyclines. All substances were partly eliminated with elimination rates between 14% and 89%. Both matrix and structure of the target molecule influenced the elimination rate. Chlortetracycline was mainly transformed into iso-chlortetracycline. In all other cases, the elimination pathways remained undiscovered; however, sorption processes seem to have a negligible impact.

Enhanced sulfamethazine removal by steam-activated invasive plant-derived biochar

Recent investigations have shown frequent detection of pharmaceuticals in soils and waters posing potential risks to human and ecological health. Here, we report the enhanced removal of sulfamethazine (SMT) from water by physically activated biochar. Specifically, we investigated the effects of steam-activated biochars synthesized from an invasive plant (Sicyos angulatus L.) on the sorption of SMT in water. The properties and sorption capacities of steam-activated biochars were compared with those of conventional non-activated slow pyrolyzed biochars. Sorption exhibited pronounced pH dependence, which was consistent with SMT speciation and biochar charge properties. A linear relationship was observed between sorption parameters and biochar properties such as molar elemental ratios, surface area, and pore volumes. The isotherms data were well described by the Freundlich and Temkin models suggesting favorable chemisorption processes and electrostatic interactions between SMT and biochar. The steam-activated biochar produced at 700 °C showed the highest sorption capacity (37.7 mg g(-1)) at pH 3, with a 55% increase in sorption capacity compared to that of non-activated biochar produced at the same temperature. Therefore, steam activation could potentially enhance the sorption capacities of biochars compared to conventional pyrolysis.

Roles of extracellular polymeric substances (EPS) in the migration and removal of sulfamethazine in activated sludge system

The occurrences, transformation of antibiotics in biological wastewater treatment plants have attracted increasing interests. However, roles of extracellular polymeric substances (EPS) of activated sludge on the fate of antibiotics are not clear. In this study, the roles of EPS in the migration and removal of one typical antibiotic, sulfamethazine (SMZ), in activated sludge process were investigated. The interaction between EPS and SMZ was explored through a combined use of fluorescence spectral analysis, laser light scattering and microcalorimetry techniques. Results show that SMZ interacted with the proteins in EPS mainly with a binding constant of 1.91 × 10(5) L/mol. The binding process proceeded spontaneously, and the driving force was mainly from the hydrophobic interaction. After binding, the structure of EPS was expanded and became loose, which favored the mass transfer and pollution capture. The removal of SMZ was influenced by interaction with EPS. SMZ could be effectively adsorbed on EPS, which accounted for up to 61.8% of total SMZ adsorbed by sludge at the initial adsorption stage and declined to around 35.3% at the subsequent biodegradation stage. The enrichment of SMZ by EPS was beneficial for SMZ removal and acquisition by microbes at the subsequent biodegradation stage.

MCM-48 modified magnetic mesoporous nanocomposite as an attractive adsorbent for the removal of sulfamethazine from water

A novel magnetic mesoporous nanocomposite FeM48 was synthesized and applied to remove sulfamethazine (SMN) from water. The adsorption kinetics could be expressed by the pseudo-second-order model, where external and interfacial diffusions tended to be the rate-limiting step. The adsorption isotherms at varied temperatures were fitted well with Freundlich model, and thermodynamic analysis revealed that SMN adsorption on FeM48 was a spontaneous exothermic process. Solution pH exhibited a remarkable impact on the adsorption process and the maximum adsorbed concentration was obtained at pH 6.3. The effect of co-existing anions and humic acid demonstrated that SMN could be adsorbed selectively by FeM48. Hydrogen bonding between the nitrogen of the aniline, sulfinol or pyrimidine group of SMN and the surface hydroxyl group of FeM48 was the major driving force for adsorption. In addition, the π-π electron-donor-acceptor interaction between SMN (π-electron-acceptor) and MCM-48 (π-electron-donor) also promoted the adsorption process.

Control of the coordination status of the open metal sites in metal-organic frameworks for high performance separation of polar compounds

Metal-organic frameworks (MOFs) with open metal sites have great potential for enhancing adsorption separation of the molecules with different polarities. However, the elution and separation of polar compounds on such MOFs packed columns using nonpolar solvents is difficult due to too strong interaction between polar compounds and the open metal sites. Here, we report the control of the coordination status of the open metal sites in MOFs by adjusting the content of methanol (MeOH) in the mobile phase for fast and high-resolution separation of polar compounds. To this end, high-performance liquid chromatographic separation of nitroaniline, aminophenol and naphthol isomers, sulfadimidine, and sulfanilamide on the column packed with MIL-101(Cr) possessing open metal sites was performed. The interaction between the open metal sites of MIL-101(Cr) and the polar analytes was adjusted by adding an appropriate amount of MeOH to the mobile phase to achieve the effective separation of the polar analytes due to the competition of MeOH with the analytes for the open metal sites. Fourier transform infrared spectra and X-ray photoelectron spectra confirmed the interaction between MeOH and the open metal sites of MIL-101(Cr). Thermodynamic parameters were measured to evaluate the effect of the content of MeOH in the mobile phase on the separation of polar analytes on MIL-101(Cr) packed column. This approach provides reproducible and high performance separation of polar compounds on the open metal sites-containing MOFs.

Biodegradation of sulfamethazine by Trametes versicolor: Removal from sewage sludge and identification of intermediate products by UPLC-QqTOF-MS

Degradation of the sulfonamide sulfamethazine (SMZ) by the white-rot fungus Trametes versicolor was assessed. Elimination was achieved to nearly undetectable levels after 20 h in liquid medium when SMZ was added at 9 mg L(-1). Experiments with purified laccase and laccase-mediators resulted in almost complete removal. On the other hand, inhibition of SMZ degradation was observed when piperonilbutoxide, a cytochrome P450-inhibitor, was added to the fungal cultures. UPLC-QqTOF-MS analysis allowed the identification and confirmation of 4 different SMZ degradation intermediates produced by fungal cultures or purified laccase: desulfo-SMZ, N4-formyl-SMZ, N4-hydroxy-SMZ and desamino-SMZ; nonetheless SMZ mineralization was not demonstrated with the isotopically labeled sulfamethazine-phenyl-13C6 after 7 days. Inoculation of T. versicolor to sterilized sewage sludge in solid-phase systems showed complete elimination of SMZ and also of other sulfonamides (sulfapyridine, sulfathiazole) at real environmental concentrations, making this fungus an interesting candidate for further remediation research.

Determination of sulfonamide antibiotics in wastewater: A comparison of solid phase microextraction and solid phase extraction methods

In recent years, pharmaceutical and personal care products (PPCPs) have been detected in diverse environments (including groundwater, river water, and municipal wastewater). In order to evaluate their environmental impact, PPCPs must first be accurately determined. In this study, we focused on developing methods to accurately determine 10 sulfonamide antibiotics: sulfaguanidine, sulfacetamide, sulfadiazine, sulfathiazine, sulfapyridine, sulfamerazine, sulfamethazine, sulfamethoxazole, sulfadimethoxine, and sulfasalazine. While sulfonamides can easily be determined in pure water, wastewater influent and effluent collected from sewage treatment plants in Burlington and Toronto (Ontario) were found to generate confounding matrix effects. In an effort to overcome these matrix effects, we developed a solid phase microextraction (SPME) method to determine sulfonamides. Of the five different fiber assemblies investigated, the carbowax/divinylbenzene (CW/DVB) fiber produced the optimal response to sulfonamides. The SPME method was further optimized for sorption time (20min), solution salinity (10%, w/v, KCl), pH (4.5), and static desorption time (30min). When compared to solid phase extraction (SPE) using MCX cartridges, we observed that despite having higher MDLs and poorer sensitivity, SPME possessed the advantage of speed and reduced solvent usage. Most importantly, in contrast to SPE, when we applied the SPME method to fortified wastewater samples, we were generally able to accurately determine (i.e., recover) those sulfonamides that were present. Therefore, we conclude that SPME is a viable method for overcoming matrix effects in environmental samples.

Preparation and evaluation of uniform-sized molecularly imprinted polymer beads used for the separation of sulfamethazine

Uniform-sized molecularly imprinted polymer (MIP) beads were prepared using a one-step swelling and polymerization method. The obtained sulfamethazine (SMZ)-imprinted polymer showed high affinity and selectivity toward SMZ and other structurally related sulfonamides in acetonitrile or water-acetonitrile mobile phases, particularly in high aqueous systems. The column performance of the MIPs for SMZ and its analogues could be improved by elevating the column temperature and optimizing the flow rate. The hydrogen-bonding effect plays a significant role in the recognition process of SMZ-imprinted polymer systems in organic media, while the ion-exchange effect, as well as hydrophobic effect, dominates the retention mechanism in aqueous-rich media, in addition to shape recognition.

Supercritical fluid extraction of sulphamethazine and its metabolites from meat tissues

An investigation is reported of factors affecting the supercritical fluid extraction of sulphamethazine and five of its metabolites from spiked meat (swine liver and kidney). The addition of the polar modifier methanol to the carbon dioxide extracting fluid was found to generally enhance recoveries under subcritical and supercritical conditions. Recoveries of the ionic metabolites were increased by up to 72% when employing tetramethylammonium hydroxide for ion pairing in situ with the supercritical fluid extraction. Extraction efficiency is demonstrated to be dependent on the matrix. Extractions of the less polar compounds from the kidney are more successful than from the liver, which corresponds to their partitioning into the supercritical fluid and/or the greater fraction of highly extractable fatty materials. The kidney was more retentive than liver for the relatively more polar compounds, which suggests that the liver offers a less polar environment under the same extraction conditions.

Comparison of supercritical CHF3 and CO2 and methanol-modified CHF3 and CO2 for extraction of sulfonamides from chicken liver

Supercritical CHF3 and methanol-modified CHF3 were compared with supercritical CO2 and methanol-modified CO2 for extraction of sulfonamides from fortified chicken liver admixed with Hydromatrix. Results showed that solvating power and selectivity were higher for supercritical and methanol-modified CHF3 than for supercritical and methanol-modified CO2. Visual observation showed that chicken liver extract obtained with methanol-modified CHF3 was cleaner than that obtained with methanol-modified CO2. Fat precipitated in the solvent trap when CO2 was used as the extraction medium. Also, simple off-line collection of fortified chicken liver extract obtained with CO2 in a solid-phase extraction cartridge (packed with either C18 or alumina) followed by phosphate buffer-methanol (50 + 50) rinse yielded an extract that required no further cleanup for analysis.

Extraction and detection of sulfamethazine in spray-dried milk

Processes that reduce moisture content of fluid milk may result in a high concentration of animal drug residues that are undetectable in the fluid milk on the basis of the same weights. The objectives were to determine the amount of sulfamethazine in spray-dried milk powder manufactured from fluid milk contaminated with sulfamethazine and to determine the effectiveness of supercritical fluid extraction as a means to extract sulfamethazine from dry milk powder. Fluid whole (3.25% fat) and skim milks with sulfamethazine added at concentrations of 5, 10, and 100 ppb were spray-dried. Based on total solids, observed concentrations were 493 and 523 ppb in skim and whole dry milk powders, respectively, compared with fluid milk containing 100 ppb of sulfamethazine as determined by HPLC. The increase in sulfamethazine concentration from fluid to dry milk was also measured quantitatively by a microbial receptor assay and an ELISA. Poor recoveries and variability in data were possibly due to binding of sulfamethazine to undetermined milk components. Dry milk powder with measured concentrations of sulfamethazine was treated with supercritical CO2. Sulfamethazine was not detectable in the extracted dry milk powder by microbial receptor assay or ELISA.

Comparison of matrix solid phase dispersion (MSPD) with a standard solvent extraction method for sulphamethazine in pork muscle using high performance liquid and thin layer chromatography

A rapid and simple extraction/clean-up procedure (matrix solid phase dispersion, MSPD) for the determination of sulphamethazine (SMZ) in pork muscle tissue is compared with a solvent extraction method. Extracts of samples fortified with SMZ or of incurred samples were found to be free from interfering compounds when chromatographed using HPLC or TLC separation systems. Recovery of SMZ from fortified samples is greater than 80% and residue levels of incurred samples found using the MSPD procedure compare favourably with results obtained using the solvent extraction method. Use of aqueous back extraction of SMZ from dichloromethane is also reported as an alternative step to solvent evaporation for ease of use in both the laboratory and in industry (i.e. at slaughter plants).

[Studies on the identification of sulfadimidine in pork by high performance liquid chromatography with photodiode array detector and gas chromatograph-mass spectrometry]

Sulfadimidine (SDD) was detected in pork imported from Mexico by HPLC with gradient elution system. UV spectrum of the peak was measured and confirmed by photodiode array detector, moreover identified by GC/MS after methylation with diazomethane. Content of SDD in the sample was 0.1 ppm and detection limit of SDD by the proposed method was 0.02 ppm. Application of this method to CLP, SMR, SMM, SDM and SQX was studied, and satisfactory results were obtained.

Method for the isolation and liquid chromatographic determination of eight sulfonamides in milk

A method for the isolation and liquid chromatographic determination of eight sulfonamides in milk is presented. Fortified or blank milk samples (0.5 ml) were blended with octadecylsilyl (C18T) derivatized silica (2 g). A column made from the sample C18T matrix was first washed with hexane (8 ml) following which the sulfonamides were eluted with methylene chloride (8 ml). The eluate contained sulfonamide analytes which were free from interferences when analyzed by high-performance liquid chromatography (HPLC) utilizing UV detection (270 nm, photodiode array). Standard curve correlation coefficients (range, 0.998 +/- 0.002 to 0.999 +/- 0.001), average percentage recoveries (73.1 +/- 7.4 to 93.7 +/- 2.7%), and the inter-(3.9-9.6%) and intra-assay (2.2-6.7%) variabilities, were determined for the concentration range examined (62.5-2000 ng/ml) and resulted in a minimal detectable limit of 1.25 ng on column (62.5 ng/ml, 20 microliters injection from a final sample volume of 0.5 ml). Savings in terms of time and solvent make this procedure attractive when compared to classical isolation techniques for sulfonamides.

Evidence for transformation of sulfamethazine to its N4-glucopyranosyl derivative in swine liver during frozen storage

An analytical procedure for determining N4-glucopyranosylsulfamethazine (GPS) in swine livers is described. The sulfamethazine derivative is extracted from the tissues with water. GPS is isolated in sufficient purity for liquid chromatographic determination by a series of adsorption chromatographic procedures. Recovery of the conjugate from spiked swine livers was 82.2% with a coefficient of variation of 4.5%. Evidence is presented suggesting that sulfamethazine in swine livers is transformed to GPS during frozen storage. Two samples of swine liver in which incurred sulfamethazine residues were substantially depleted during frozen storage were analyzed for GPS. The conjugate accounted for 96.2% and 92.2% of the depleted sulfamethazine residues.

Evaluation of three methods for recovery of sulfamethazine metabolites from swine tissue

Recent investigations have clearly established the presence of desaminosulfamethazine (I), N4-acetylsulfamethazine (II), and N4-D-glucosyl sulfamethazine (III) in the tissues of swine which have been dosed with sulfamethazine (V). N4(1-Deoxy-D-glucuronyl) sulfamethazine (IV) has frequently been found in the urine and feces of animals. These metabolites have generally not been investigated in current sulfamethazine methods; therefore, it is not clear to what extent they might be measured by these procedures. Metabolites I, II, III, and IV were synthesized and characterized by several chemical and physical measurements. These metabolites and their parent, V, were added to swine tissue and recoveries were measured by a gas-liquid chromatographic (GLC), a colorimetric, and a gas chromatographic/mass spectrometric method with electron ionization-selected ion monitoring (GC/MS EI-SIM). With modifications of the gas chromatographic parameters, the GLC method can quantitate compounds, I, II, and V simultaneously. If a hydrolysis step is added, all 3 methods can quantitate compound II as V and, in addition, the GC/MS EI-SIM and colorimetric methods can quantitate III as V. In none of these methods do metabolites I, II, III, or IV interfere in the determination of V.