Tissue distribution, metabolism, and residue depletion study in Atlantic salmon following oral administration of [3H]emamectin benzoate

Atlantic salmon (approximately 1.3 kg) maintained in tanks of seawater at 5 +/- 1 degrees C were dosed with [3H]emamectin B1 benzoate in feed at a nominal rate of 50 microg of emamectin benzoate/kg/day for 7 consecutive days. Tissues, blood, and bile were collected from 10 fish each at 3 and 12 h and at 1, 3, 7, 15, 30, 45, 60, and 90 days post final dose. Feces were collected daily from the tanks beginning just prior to dosing to 90 days post final dose. The total radioactive residues (TRR) of the daily feces samples during dosing were 0.25 ppm maximal, and >97% of the TRR in pooled feces covering the dosing period was emamectin B1a. Feces TRR then rapidly declined to approximately 0.05 ppm by 1 day post final dose. The ranges of mean TRR for tissues over the 90 days post dose period were as follows: kidney, 1.4-3 ppm; liver, 1.0-2.3 ppm; skin, 0.04-0.09 ppm; muscle, 0.02-0.06 ppm; and bone, <0.01 ppm. The residue components of liver, kidney, muscle, and skin samples pooled by post dose interval were emamectin B1a (81-100% TRR) and desmethylemamectin B1a (0-17% TRR) with N-formylemamectin B1a seen in trace amounts (<2%) in some muscle samples. The marker residue selected for regulatory surveillance of emamectin residues was emamectin B1a. The emamectin B1a level was quantified in individual samples of skin and muscle using HPLC-fluorometry and was below 85 ppb in all samples analyzed (3 h to 30 days post dose).     

Freshwater Fish Mercury Concentrations in a Regionally High Mercury Deposition Area

We sampled and analyzed individually, edible dorsal muscle from largemouth bass (LMB), Micropterus salmoides (n?=?138) and yellow perch (YP), Perca flavescens (n?=?97) from 15 lakes to investigate potential local impacts of mercury emission point sources in northeastern Massachusetts (MA), USA. This area was identified in three separate modeling exercises as a mercury deposition hotspot. In 1995, 55% of mercury emissions to the environment from all MA sources came from three municipal solid waste combustors (trash incinerators) and one large regional medical waste incinerator in the study area. We determined the mercury accumulation history in sediments of a lake centrally located in the study area. Recent maximum mercury accumulation rates in the sediment of the lake of ~ 88 μg/m²/year were highly elevated on a watershed area adjusted basis compared to other lakes in the Northeast and Minnesota. Fish from the study area lakes had significantly (p?=?0.05) greater total mercury concentrations than fish from 24 more rural, non-source-impacted lakes in other regions of the state (LMB n?=?238, YP n?=?381) (LMB: 1.5–2.5 x; YP: 1.5 x). The integration of this extensive fish tissue data set, depositional modeling projections, historical record of mercury accumulation in sediments of a lake in the area, and knowledge of substantial mercury emissions to the atmosphere in the area support designation of this area as a mercury depositional and biological concentration hotspot in the late 1990s, and provides further evidence that major mercury point sources may be associated with significant local impacts on fisheries resources.     

Tissue distribution, elimination, and metabolism of sodium [36Cl]perchlorate in lactating goats

Perchlorate has contaminated water sources throughout the United States but particularly in the arid Southwest, an area containing large numbers of people and few water sources. Recent studies have demonstrated that perchlorate is present in alfalfa and that perchlorate is secreted into the milk of cows. Studies in lactating cows have indicated that only a small portion of a perchlorate dose could be accounted for by elimination in milk, feces, or urine. It was hypothesized that the remainder of the perchlorate dose was excreted as chloride ion. The purpose of this study was to determine the fate and disposition of (36)Cl-perchlorate in lactating dairy goats. Two goats (60 kg) were each orally administered 3.5 mg (16.5 muCi) of (36)Cl-perchlorate, a dose selected to approximate environmental perchlorate exposure but that would allow for adequate detection of radioactive residues after a 72 h withdrawal period. Blood, milk, urine, and feces were collected incrementally until slaughter at 72 h. Total radioactive residue (TRR) and perchlorate concentrations were measured using radiochemical techniques and liquid chromatography mass spectrometry (LC-MS-MS). Peak blood levels of TRR occurred at 12 h ( approximately 195 ppb) postdose; peak levels of parent perchlorate, however, occurred after only 2 h, suggesting that perchlorate metabolism occurred rapidly in the rumen. The serum half-life of perchlorate was estimated to be 2.3 h. After 24 h, perchlorate was not detectable in blood serum but TRR remained elevated (160 ppb) through 72 h. Milk perchlorate levels peaked at 12 h (155 ppb) and were no longer detectable by 36 h, even though TRRs were readily detected through 72 h. Perchlorate was not detectable in skeletal muscle or liver at slaughter (72 h). Chlorite and chlorate were not detected in any matrix. The only radioactive residues observed were perchlorate and chloride ion. Bioavailability of perchlorate was poor in lactating goats, but the perchlorate that was absorbed intact was rapidly eliminated in milk and urine.     

Determination of albendazole and its major metabolites in the muscle tissues of Atlantic salmon,tilapia, and rainbow trout by high performance liquid chromatography with fluorometric detection

A liquid chromatographic procedure for the determination of albendazole ([5-(propylthio)-1H-benzimidazol-2yl]carbamic acid methyl ester) and its major metabolites, albendazole sulfoxide, albendazole sulfone, and albendazole-2- aminosulfone in rainbow trout, tilapia, and salmon muscle with adhering skin tissue is described. The muscle tissue samples are made alkaline with potassium carbonate and extracted with ethyl acetate. The extracts are further subjected to cleanup by utilizing a number of liquid-liquid extraction steps. After solvent evaporation, the residue is reconstituted in mobile phase and chromatographed. The chromatography is carried out on a reversed phase Luna C(18) column, using acetonitrile/methanol/buffer as a mobile phase and a fluorescence detector. The average recoveries from the fortified muscle tissue of the three fish species for albendazole (25-100 ppb), albendazole sulfoxide (15.5-62 ppb), albendazole sulfone (1-10 ppb), and albendazole-2- aminosulfone (10-100 ppb) were 94, 77, 82, and 67%, respectively. The average CV for each compound was < or =10%. The procedure was validated and then applied to the determination of albendazole and its three major metabolites in the muscle tissue of the three fish species obtained after orally dosing with albendazole.     

Distribution of total 14C residue in egg yolk, albumen, and tissues following oral [14C]sulfamethazine administration to hens

The distribution of total 14C residues was studied in egg yolk and albumen after administration of either single or multiple oral dosages of [14C]sulfamethazine (SMZ). One day after a single dose of [14C]SMZ (121 mg of sulfamethazine, 2.42 x 10(7) dpm), the 14C residue concentration peaked in egg albumen and egg yolk with the concentration in the former >4-fold greater than in the latter. Three days postdose, the 14C residue concentration in the yolk was approximately 7-fold higher than in the egg albumen. A multiple dose of [14C]SMZ containing sulfamethazine mass equivalent of an average therapeutic dose (282 mg, 2.9 x 10(7) dpm) for chickens was also administered orally for six consecutive days to hens. A significantly reduced level of egg production was observed during the medication, and most of the hens stopped laying eggs after the last dose. The 14C residue concentrations peaked on the last day (sixth) of medication in egg albumen and yolk. The 14C residue concentrations were also measured in liver, muscle, blood, and plasma of chickens sacrificed at 1, 24, 48, and 72 h after the last dose. Highest concentrations of 14C residue were accumulated in liver followed by, in decreasing order, blood, plasma, and muscle.     

Liquid chromatographic analysis of incurred amoxicillin residues in catfish muscle following oral administration of the drug

Improper application of antibiotic chemicals to livestock and aquaculture species may lead to the occurrence of residues in food supplies. An appropriate depletion period is needed after the administration of drugs to animals for ensuring that residues in edible tissues are below established tolerance levels. This study was conducted to determine incurred amoxicillin residues in catfish muscle following oral administration. Dosed fish were harvested after four depletion periods, and muscle fillets were analyzed for amoxicillin residues using an HPLC method with precolumn derivatization and fluorescence detection. The residue levels in fish after a 6-h depletion ranged from 40 to 64 ng/g with one exception at 297 ng/g. Average residue levels decreased to 5.4 and 2. 8 ng/g after 24- and 48-h depletions, respectively. Residue levels after a 72-h depletion decreased to below the method's limit of quantitation (1.2 ng/g). An LC-MS/MS confirmatory method was developed. Confirmation of the presence of amoxicillin was demonstrated in incurred fish samples containing residues at approximately 50-300 ng/g.     

Liquid chromatographic monitoring of the depletion of carbadox and its metabolite desoxycarbadox in swine tissues

A liquid chromatographic method was used to monitor a depletion study of carbadox (and its most important metabolite, desoxycarbadox) in young pigs fed carbadox-treated rations for 1 week. Carbadox was found in blood (20 ppb), blood serum (26 ppb), and muscle tissue 24 h after withdrawal from treated ration; residues were reduced to a trace (less than 2 ppb) in 48 h, and eliminated by 72 h. Desoxycarbadox, although not detected in blood, was found in muscle (17 ppb) 24 h after withdrawal; it was reduced to 9 ppb at 48 h and to a trace by 72 h. Although no carbadox was detected in liver 24 h after withdrawal, appreciable desoxycarbadox (125 ppb) was found in liver 24 h after withdrawal; it was reduced to 17 ppb at 48 h and to a trace by 72 h. Whereas only a trace of carbadox was found in kidney 24 h after withdrawal, 186 ppb desoxycarbadox was found in kidney at 24 h, 34 ppb at 48 h, and a trace at 72 h. No metabolite of carbadox other than desoxycarbadox was found in extracts of swine tissues during this medicated feed trial, and no metabolite was found in blood extracts by using the established methodology. The effect of tissue storage (aging) at -20 degrees C on levels of the drug and its metabolite was a modest alteration of residue levels. The inadvertent use of feed adulterated with furazolidone and initially medicated with chlortetracycline, sulfamethazine, and penicillin G, did not affect the uptake of carbadox in this depletion study or interfere with the analytical methodology.     

Residue depletion of nitrofuran drugs and their tissue-bound metabolites in channel catfish (Ictalurus punctatus) after oral dosing

The depletion of the nitrofuran drugs furazolidone, nitrofurazone, furaltadone, and nitrofurantoin and their tissue-bound metabolites [3-amino-2-oxazolidinone (AOZ), semicarbazide (SC), 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), and 1-aminohydantoin (AH), respectively] were examined in the muscle of channel catfish following oral dosing (1 mg/kg body weight). Parent drugs were measurable in muscle within 2 h. Peak levels were found at 4 h for furazolidone (30.4 ng/g) and at 12 h for nitrofurazone, furaltadone, and nitrofurantoin (104, 35.2, and 9.8 ng/g respectively). Parent drugs were rapidly eliminated from muscle, and tissue concentrations fell below the limit of detection (1 ng/g) at 96 h. Peak levels of tissue-bound AMOZ and AOZ (46.8 and 33.7 ng/g respectively) were measured at 12 h, and of SC and AH (31.1 and 9.1 ng/g, respectively) at 24 h. Tissue-bound metabolites were measurable for up to 56 days postdose. These results support the use of tissue-bound metabolites as target analytes for monitoring nitrofuran drugs in channel catfish.     

Dimetridazole residues in pork tissue. II. Application of liquid chromatographic method to monitor elimination of drug and its major metabolite

A study was conducted to monitor the elimination of dimetridazole (DMZ) and its major metabolite 2-hydroxymethyl-1-methyl-5-nitroimidazole (HMMNI) in swine plasma and tissue, using a liquid chromatographic method with electrochemical detector sensitive to 0.5 ppb. The study consisted of 2 experiments. In the preliminary experiment, one young female piglet was fed medicated ration containing 125 ppm dimetridazole (DMZ) for 2 weeks, followed by a withdrawal period using regular ration for 5 days. Another, control, piglet was given regular diet throughout. Plasma concentrations of DMZ and its most important residue, HMMNI, were measured daily at 2 h after the morning feeding and, on days 8 and 15, several times during the day. The 2 h concentrations after 3 days loading ranged from 47 to 77 ppb for DMZ and 424 to 1081 ppb for HMMNI. A daily cycle in the plasma levels was seen for both substances. Upon withdrawal of medication, elimination of drug and metabolite was biexponential with a terminal half-life of 6.7 h. In the second experiment, 5 piglets were medicated as above and slaughtered 2, 6, 12, 25, and 49 h after withdrawal of the medication; the concentration of DMZ and HMMNI was measured in plasma, muscle, kidney, and liver. DMZ in the plasma amounted to 22 and 1.8 ppb at 2 and 6 h, while HMMNI declined from 535 ppb at 2 h to 0.75 ppb at 25 h. Most values for both substances found in muscle were close to those in the plasma; in kidney they amounted to 9-17% of the plasma levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bioaccumulation of ivermectin from natural and artificial sediments in the benthic organism <Emphasis Type="Italic">Lumbriculus variegatus</Emphasis>

Purpose  

Although ivermectin is a widely used lipophilic parasiticide, data on its potential bioaccumulation in aquatic invertebrates are scarce. In this study, bioaccumulation patterns of radiolabeled ³H-ivermectin from sediments into tissues of the sediment-dwelling worm Lumbriculus variegatus were investigated and assessed.     

Flunixin residues in milk after intravenous treatment of dairy cattle with (14)C-flunixin

Flunixin meglumine is used in veterinary medicine as an alternative to narcotic analgesics and as an antiinflammatory agent. Eight Holstein dairy cows were dosed intravenously once daily on three consecutive days with (14)C-flunixin meglumine at approximately 2.2 mg of flunixin free acid/kg of body weight. Milk was collected twice daily to determine the decline of the total radioactive residues (TRR) in milk and to identify or characterize residue components. TRR in milk declined rapidly and averaged 66, 20, and 14 ppb, respectively, for the first, second, and third milkings after administration of the last dose. Milk was extracted, and the extracts were examined for radioactive residues. Mean extractability of milk TRR was always greater than 80%. Flunixin and 5-hydroxyflunixin were identified by coelution with analytical standards using reverse phase HPLC. These two residues were the main radioactive residues found in milk and together accounted for 64, 37, and 44% of the extractable residues, for the first, second, and third milkings, respectively, after administration of the last dose. The presence of 5-OH flunixin in milk was confirmed by HPLC/MS/MS.     

Determination of gentian violet, its demethylated metabolites, and leucogentian violet in chicken tissue by liquid chromatography with electrochemical detection

A method is presented for determination of residues of gentian violet (GV), its demethylated metabolites (pentamethyl and tetramethyl), and leucogentian violet (LGV) in chicken tissue. The analytes are extracted from tissue with acetonitrile/buffer and partitioned into methylene chloride. Polar lipids are removed on an alumina column followed by partitioning into methylene chloride from a citrate buffer. The compounds of interest are isolated on a disposable carboxylic acid cation exchange column and then eluted with 0.02% HCl in methanol. GV, its metabolites, and LGV are determined by liquid chromatography using isocratic elution with a buffered mobile phase from a cyano column and amperometric electrochemical detection at +1.000 V. Average recoveries of GV and LGV from commercially purchased chicken liver fortified with 20 ppb of each compound were 92% [standard deviation (SD) = 7, coefficient of variation (CV) = 7.6%] and 86% (SD = 7, CV = 8.1%), respectively. Average recoveries of GV, LGV, the pentamethyl metabolite, and 1 of the tetramethyl metabolites from control chicken liver (provided by the Center for Veterinary Medicine) fortified with 20 ppb of each compound were 80% (SD = 7, CV = 8.8%), 76% (SD = 3, CV = 3.9%), 83% (SD = 6, CV = 7.2%), and 76% (SD = 8, CV = 10.5%), respectively. Mean results from 10 analyses of residue-incurred chicken liver were 31 ppb GV (SD = 3, CV = 9.7%), 34 ppb pentamethyl metabolite (SD = 3, CV = 8.8%), and 40 ppb tetramethyl metabolite(s) (SD = 2, CV = 5.0%), for an average value of 105 ppb total residues (SD = 6, CV = 5.7%); no LGV was found. Data are also presented to show applicability of the method to muscle tissue.     

Gas chromatographic determination of incurred dimetridazole residues in swine tissues

A gas chromatographic method for determination of 2-hydroxymethyl-1-methyl-5-nitroimidazole (DMZOH), the hydroxy metabolite of dimetridazole, in swime muscle has been developed. The method uses cleanup steps similar to those of an earlier polarographic method. The present method is capable of quantitating levels as low as 2 ppb and detecting less than 1 ppb. Recoveries from 30 control tissues spiked at 1, 2, or 4 ppb averaged 80.4%. Performance of the method in incurred tissue was documented and limited data on the depletion of the metabolite in muscle were generated. The muscle of swine given 150 ppm dimetridazole in feed for 14 days contained less than 1 ppb DMZOH at 12 h withdrawal time.     

Extraction, gas-liquid chromatographic detection, and quantitation of hexachlorophene residues from plant tissues high in lipid content

A method has been developed for the extraction, cleanup, derivatization, detection, and quantitation of hexachlorophene (HCP) residues from 2 types of plant storage tissue high in lipid content. Wet soybean or peanut tissue was homogenized and extracted with ethyl ether and chromatographed on silica gel to remove the neutral lipids. The cleaned up sample was methylated with diazomethane and the dimethoxyhexachlorophene was eluted from a second silical gel column and chromatographed on a 6' glass column packed with 3% OV-1 or 3% SE-30 on Gas-Chrom Q. The instrument detection limit for the 63Ni electron capture detector was less than 0.1 ng for dimethoxyhexachlorophene and about 1 ppb HCP residue in plant issue. Recovery of 10-420 ppb HCP added to tissue averaged 90.9 +/- 5.7%. Interfering substances were removed, column life was increased, peak sharpness was increased, and tailing of the parent compound was decreased by using appropriate column chromatography.     

田间管理对华北平原冬小麦产量土壤碳及温室气体排放的影响

选取华北平原冬小麦为研究对象,针对（1）秸秆移除;（2）秸秆表覆;（3）免耕;（4）秸秆深施;（5）施农家肥这5种典型的田间管理,使用农田自动温室气体测定系统对冬小麦农田全生育期进行了原位长期观测,并采用^13C自然丰度法对土壤碳的转化进行了监测,同时对冬小麦产量及生物量、土壤有机碳的变化进行了监测。结果表明,冬小麦产量及生物量高低顺序为施农家肥、秸秆深施、秸秆表覆、秸秆移除和免耕,而且土壤有机碳的更新也有同样的趋势;施农家肥能显著增加土壤有机碳而秸秆移除和免耕则会导致土壤有机碳的轻微下降;冬小麦甲烷的排放或吸收只占总增温潜势的不到1％,在进行统计总排放当量时基本可以忽略,N2O在总排放当量中的比例在2．55％-11．62％范围内;N2O的大量排放主要来自于拔节期及开花期,秸秆移除、施农家肥和秸秆深施会导致N2O排放在总当量中的份额增加至10％左右,而秸秆覆盖和免耕N2O排放在总排放当量中的份额只有3％左右,冬小麦农田总的温室气体排放88％以上来自于CO2的排放,特别是秸秆表覆和免耕95％以上来自土壤碳的损失而释放的CO2。总体来看,秸秆深施能保证较高的产量,减少碳的损失,增加土壤碳并产生相对较少的总温室气体排放量,是较好的固碳减排方式。     

Residue depletion of tilmicosin in chicken tissues

A high-performance liquid chromatography (HPLC) method with detection at 290 nm was modified and validated for the determination of tilmicosin residues in broiler chicken tissues. The limits of detection (LOD) of the method were 0.01 microg/g for muscle and 0.025 microg/g for liver and kidney. Average recoveries ranged from 80.4 to 88.3%. Relative standard deviation values ranged from 5.2 to 12.1%. Residue depletion of tilmicosin in broiler chickens was examined after dosing over a 5-day period by incorporation of the drug into drinking water at 37.5 and 75.0 mg/L. Tilmicosin concentrations in liver and kidney were highest on day 3 of medication and on day 5 in muscle, in both low- and high-dose groups. The residue levels in both groups were significantly higher in liver than in kidney or muscle. A minimum withdrawal time of 9 days was indicated for residue levels in muscle, liver, and kidney tissues below the maximum residue level (MRL).     

Acidification effects on larval striped bass,Morone saxatilis in Chesapeake Bay tributaries: A review

Reduced striped bass populations along the East Coast of the United States have prompted numerous studies to assess various factors contributing to the decline. Available data from in-situ, on-site and laboratory studies with striped bass in conjunction with water quality and contaminants data confirm that the eastern shore rivers of the Chesapeake Bay (Choptank, Nanticoke, and Pocomoke Rivers) are susceptible to acidic conditions. The Choptank and Nanticoke Rivers are significant striped bass spawning areas. Acidification conditions (low pH, Al, low hardness) were documented in these systems in 1984 at levels reported to cause high mortality to striped bass larvae. Striped bass populations in several western shore tributaries such as the Mattaponi, Pamunkey, Patuxent, and Rappahannock Rivers also appear to be vulnerable to acidic pH conditions. In-situ toxicity studies documenting actual striped bass larval mortality are lacking in these systems; however, based on laboratory data it appears that potentially toxic acidic conditions can exist. Although certain Chesapeake Bay spawning tributaries do exhibit acidic conditions during spawning periods, other systems are resistant to acidification. The Chesapeake and Delaware Canal (C & D Canal), Elk River and Susquehanna River of the Upper Chesapeake Bay and the Potomac River on the western shore appear to be resistant to reductions in pH. The upper Chesapeake Bay and Potomac River are major striped bass spawning areas. Therefore, reduced striped bass production in these systems may be related to factors other than acidification.     

Mercury and polychlorinated biphenyls in striped bass (Morons saxatilis) from two nova Scotia Rivers

Striped bass (Morone saxatilis) collected from the Annapolis and Shubenacadie Rivers in Nova Scotia, Canada, were analyzed for Hg in four tissues and for PCB's in two tissues. Average Hg concentrations in the muscle, liver, kidney, and gonad of 3.9 kg fish from Annapolis River were 0.77, 0.79, 0.26, and 0.07 μg g^?1, respectively, and the corresponding values for the much smaller, 1.5 kg, fish from the Shubenacadie River were 0.51, 0.27, 0.24, and 0.06 μg g^?1. The PCB concentrations in the muscle tissues of fish from Annapolis and Shubenacadie Rivers are 0.02 and 0.01 μg g^?1, respectively, while the concentrations in gonads are 1.4 and 0.04 μg g^?1 The observed lack of recruitment of striped bass in the Annapolis River may be related to high PCB concentrations in the gonad tissue.     

Liquid chromatographic determination of carbadox, desoxycarbadox, and nitrofurazones in pork tissues

A liquid chromatographic (LC) method has been developed for the determination of carbadox, desoxycarbadox, and nitrofurazones in the 10-40 ppb range in pork muscle, liver, and kidney tissues. Tissues were homogenized in absolute ethanol, and the homogenates were treated with metaphosphoric acid and reduced in volume by rotovaporization. Hexane was added to the concentrates, which were then centrifuged to remove fat. After addition of KH2PO4 to the aqueous phase and extraction with ethyl acetate, the extracts were passed through alumina columns before analysis by reverse phase LC. Overall average recoveries (10-40 ppb range) for carbadox and desoxycarbadox from spiked tissues were 53% +/- 13.6 and 61% +/- 7.2, respectively; overall average recoveries for nitrofurazone and furazolidone were 43% +/- 7.3 and 77% +/- 10.9, respectively. Before these optimum determinations, degradation by even minimal incandescent light was found to reduce recovery especially of desoxycarbadox. The results of this photochemical degradation are reported and briefly discussed.     

Determination of flunixin in edible bovine tissues using liquid chromatography coupled with tandem mass spectrometry

An accurate, reliable, and reproducible assay was developed and validated to determine flunixin in bovine liver, kidney, muscle, and fat. The overall recovery and percent coefficient of variation (%CV) of twenty-eight determinations in each tissue for flunixin free acid were 85.9% (5.9% CV) for liver, 94.6% (9.9% CV) for kidney, 87.4% (4.7% CV) for muscle, and 87.6% (4.4% CV) for fat. The theoretical limit of detection was 0.1 microg/kg (ppb, ng/g) for liver and kidney, and 0.2 ppb for muscle and fat. The theoretical limit of quantitation was 0.3, 0.2, 0.6, and 0.4 ppb for liver, kidney, muscle, and fat, respectively. The validated lower limit of quantitation was 1 ppb for edible tissues with the upper limit of 400 ppb for liver and kidney, 100 ppb for fat, and 40 ppb for muscle. Accuracy, precision, linearity, specificity, ruggedness, and storage stability were demonstrated. Briefly, the method involves an initial acid hydrolysis, followed by pH adjustment ( approximately 9.5) and partitioning with ethyl acetate. A portion of the ethyl acetate extract was purified by solid-phase extraction using a strong cation exchange cartridge. The eluate was then evaporated to dryness, reconstituted, and analyzed using LC/MS/MS. The validated method is sensitive and specific for flunixin in edible bovine tissue.