Determination of ceftiofur metabolite desfuroylceftiofur cysteine disulfide in bovine tissues using liquid chromatography-tandem mass spectrometry as a surrogate marker residue for ceftiofur.

Ceftiofur is a widely used cephalosporin ß-lactam antibiotic with frequently reported residue violations. This paper reports a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determining a ceftiofur metabolite, desfuroylceftiofur cysteine disulfide (DCCD), in bovine kidney, liver, and muscle tissues. Incurred tissue samples were obtained from dosed animals and analyzed to evaluate the utility of the method. For kidney, the target tissue, the method utilized a simple extraction with phosphate buffer followed by solid phase extraction (SPE) cleanup. For liver and muscle, acetonitrile and hexane were used to remove most proteins and fat from the initial buffer extract before the SPE cleanup. Method accuracy was between 97 and 107%, and the coefficient of variation was between 3.4 and 11.0% for all three types of tissues. The relationship between the new and regulatory methods for bovine kidney was established. It was concluded that DCCD is a suitable surrogate marker residue for ceftiofur in bovine kidney.

Evaluation of spot urine as an alternative to 24h urine collection for determination of biomarkers of exposure to cigarette smoke in adult smokers.

OBJECTIVE: Exposure to cigarette smoke in adult smokers (SM) can be determined by measuring urinary excretion of selected smoke constituents or metabolites. Complete 24h urine collections are difficult to achieve in ambulatory clinical studies; therefore spot urine (SU) might be a useful alternative. The objective of this study was to evaluate the optimum time for SU collections, and to predict 24h urine biomarker excretion from SU collections. METHODS: SU samples were collected at three time points (early morning, post-lunch and evening) along with 24h collections in 37 healthy adult smokers. Nicotine and its five metabolites (nicotine equivalents, NE), metabolites of NNK (NNAL), pyrene (1-OHP), acrolein (HPMA), benzene (S-PMA) and butadiene (MHBMA) were measured in 24h and SU samples. Correlation and agreement between creatinine-adjusted SU and 24h urine collections were determined from the Pearson product-moment correlation, Bland-Altman and Lin's concordance correlation analyses. A random effect regression model was used to calculate the 24h biomarker excretion from SU collections. RESULTS: There were no significant differences (p>0.05) between the three SU collections for the selected biomarkers of exposure except for 3-HPMA, which showed a diurnal variation. Good correlation and statistical agreements were observed for creatinine-adjusted SU (all three time points) and 24h for most of the selected biomarkers. 24h biomarker excretion could be estimated for most of the biomarkers based on the regression model, with the early morning SU collections giving the best results for tobacco specific biomarkers NE (R(2)=0.66) and NNAL (R(2)=0.6). CONCLUSIONS: SU is a useful alternative to 24h urine collections for most of the selected biomarkers of exposure to cigarette smoke. The early morning SU appears to be the most feasible and practical option as an alternative to 24h collections.

A determinative and confirmatory method for ceftiofur metabolite desfuroylceftiofur cysteine disulfide in bovine kidney by LC-MS/MS.

Ceftiofur is a cephalosporin ß-lactam antibiotic widely used for treating certain bacterial infections in beef and dairy cattle. The regulatory HPLC-UV method for ceftiofur residues in animal tissues is time consuming and non-specific. Additionally, because the regulatory method involves chemical reactions to convert the metabolites into a single moiety, it is virtually impossible to incorporate the procedure into a multi-residue method. Ceftiofur residue violations in beef and dairy cattle have been frequently reported and therefore an improved method is needed. Herein we report a rapid and sensitive LC-MS/MS method for the determination and confirmation of ceftiofur metabolite, desfuroylceftiofur cysteine disulfide (DCCD), in bovine kidney tissue. The new method utilizes a simple extraction with phosphate buffer followed by SPE cleanup. A deuterated internal standard was synthesized and used for quantitation. The matrix-based calibration curve was linear from 25 to 2000 ng/g. The average accuracy for control kidney samples from six different sources fortified at 50-1000 ng/g was 97.7-100.2% with CV ≤ 10.1%. The limit of confirmation was 50 ng/g.

Biomarkers of potential harm among adult smokers and nonsmokers in the total exposure study.

INTRODUCTION: There is overwhelming medical and scientific consensus that cigarette smoking causes lung cancer, heart disease, emphysema, and other serious diseases in smokers. In the Total Exposure Study, 29 biomarkers of potential harm (BOPH) were measured in a cross-sectional sample of 3,585 adult smokers (AS) and 1,077 nonsmokers (NS). The BOPH included markers of oxidative stress, inflammation, platelet activation, endothelial function, lipid metabolism, hematology, metabolism, the cardiovascular system, lung function, kidney function, and liver function. METHODS: Multiple stepwise regression was used to examine the effect of demographic factors (age, gender, body mass index [BMI], and race) and smoking (number of cigarettes smoked per day or nicotine equivalents [NE] per 24 hr and smoking duration) on each BOPH. RESULTS: As compared with NS, AS had >10% higher levels of 8-epi-prostaglandin F(2α) (8-epi-PG F(2α), 42%), 11-dehydrothromboxane B2 (11-DHTB, 29%), white blood cell (WBC) count (19%), high-sensitivity C-reactive protein (15%), triglycerides (16%), and alkaline phosphatase (11%) and had 18% lower total bilirubin. Multiple stepwise regression revealed that although NE (milligrams per 24 hours) was statistically significant for 18 of the 29 BOPH, it was the most important factor only for WBCs and 11-DHTB. Smoking duration was the most important factor for forced expiratory volume in 1 second. In contrast, BMI was the most important factor for 12 BOPH. CONCLUSIONS: These results contribute to the understanding of the relationship between tobacco smoking and potential biological effects.

Determination of methyl-, 2-hydroxyethyl- and 2-cyanoethylmercapturic acids as biomarkers of exposure to alkylating agents in cigarette smoke.

Alkylating agents occur in the environment and are formed endogenously. Tobacco smoke contains a variety of alkylating agents or precursors including, among others, N-nitrosodimethylamine (NDMA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), acrylonitrile and ethylene oxide. We developed and validated a method for the simultaneous determination of methylmercapturic acid (MMA, biomarker for methylating agents such as NDMA and NNK), 2-hydroxyethylmercapturic acid (HEMA, biomarker for ethylene oxide) and 2-cyanoethylmercapturic acid (CEMA, biomarker for acrylonitrile) in human urine using deuterated internal standards of each compound. The method involves liquid/liquid extraction of the urine sample, solid phase extraction on anion exchange cartridges, derivatization with pentafluorobenzyl bromide (PFBBr), liquid/liquid extraction of the reaction mixture and LC-MS/MS analysis with positive electrospray ionization. The method was linear in the ranges of 5.00-600, 1.00-50.0 and 1.50-900 ng/ml for MMA, HEMA and CEMA, respectively. The method was applied to two clinical studies in adult smokers of conventional cigarettes who either continued smoking conventional cigarettes, were switched to test cigarettes consisting of either an electrically heated cigarette smoking system (EHCSS) or having a highly activated carbon granule filter that were shown to have reduced exposure to specific smoke constituents, or stopped smoking. Urinary excretion of MMA was found to be unaffected by switching to the test cigarettes or stop smoking. Urinary HEMA excretion decreased by 46 to 54% after switching to test cigarettes and by approximately 74% when stopping smoking. Urinary CEMA excretion decreased by 74-77% when switching to test cigarettes and by approximately 90% when stopping smoking. This validated method for urinary alkylmercapturic acids is suitable to distinguish differences in exposure not only between smokers and nonsmokers but also between smoking of conventional and the two test cigarettes investigated in this study.

Evaluation of biomarkers of exposure in adult cigarette smokers using Marlboro snus.

INTRODUCTION: It has been reported that adult smokers (AS) may be considering smokeless tobacco products as an alternative to smoking. The objective of this study was to evaluate the change in exposure in AS using Marlboro snus (MSNUS) (a tobacco pouch product in test market in June 2007). METHODS: AS were randomized into the following groups--CS: subjects (n = 30) continue smoking their own brand; DU: subjects (n = 60) reduced their daily cigarette consumption by >or=50% and were allowed to use MSNUS; SN: subjects (n = 15) stopped smoking their cigarettes but were allowed to use MSNUS; NT: subjects (n = 15) were not allowed to use any tobacco products for the entire duration of the 8-day study. Biomarkers of smoke exposure (BOE) measured at baseline and postbaseline were 24-hr urinary excretion of metabolites of N-nitrosamines, nicotine (urine and plasma), aromatic amines, benzene, and polycyclic aromatic hydrocarbon; urine mutagenicity; and carboxyhemoglobin at various timepoints. RESULTS: Statistically significant (p < .05) reductions in all the urinary BOE were observed in the DU group compared with the CS group. After correcting for the residual effect, a proportionate reduction (approximately 50%) in most of the biomarkers was observed. Even larger reductions, similar to the NT group, were observed in the SN group. DISCUSSION: The proportionate reduction in exposure when reducing the number of cigarettes by 50% and using MSNUS, under the consumption patterns observed, suggest that the AS did not appear to alter their smoking behavior. The added exposure from MSNUS usage in this group was minimal. The AS sustained substantial reductions in exposure when using MSNUS exclusively.

Quantitation of N'-nitrosonornicotine (NNN) in smokers' urine by liquid chromatography-tandem mass spectrometry.

The tobacco-specific nitrosamine N'-nitrosonornicotine (NNN) is carcinogenic to humans (IARC Group 1). Assessing the tobacco smoke-related exposure to NNN by suitable biomarkers is of interest for risk evaluation. Recently, NNN and NNN-N-glucuronide have been quantified in urine of smokers. However, it is unknown what percentage of the absorbed dose of NNN is excreted as total NNN (sum of free and conjugated NNN) in urine of smokers. We developed a sensitive method based on liquid chromatography with tandem mass spectrometry with deuterium-labeled internal standard for the determination of total NNN in human urine. The limit of quantitation of the method was 2 pg/mL with a calibration line linear up to 256 pg/mL. In a study with 16 smokers in which the respiratory retention of NNN was measured through controlled smoking, we found that on average about 1% of the pulmonary NNN dose was excreted in 24 h urine as total NNN.

Population estimates for biomarkers of exposure to cigarette smoke in adult U.S. cigarette smokers.

INTRODUCTION: There are about 4,800 different chemical constituents in cigarette smoke. Therefore, the total systemic exposure evaluation of the population of smokers to cigarette smoke is challenging. Measurement of biomarkers as surrogates of cigarette smoke constituents is a realistic approach to assess exposure. OBJECTIVE: To estimate cigarette smoke exposure of the U.S. smoker population. METHODS: Stratified, cross-sectional, multicenter design (39 sites in 31 states); 3,585 adult cigarette smokers and 1,077 nonsmokers. Biomarkers were determined from 24-hr urine collections or blood samples. Population estimates were generated by weighting sample data with weights from a large U.S. probability sample (Behavioral Risk Factor Surveillance System). RESULTS: The adult smoker population estimates for tobacco-specific biomarkers were nicotine equivalents 13.3 mg/24 hr (SE 0.14), serum cotinine 184 ng/ml (1.8), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol 439 ng/24 hr (5.5). The population estimates for smokers and nonsmokers for nontobacco-specific biomarkers were 1-hydroxypyrene 317 (6.8) and 110 (7.1) ng/24 hr, 4-aminobiphenyl Hb adducts 43.1 (1.04) and 11.4 (1.5) pg/g Hb, carboxyhemoglobin 5.26(0.04) in percent of hemoglobin saturation and 1.45(0.02), 3-hydroxypropylmercapturic acid 2,030 (24) and 458 (17) microg/24 hr, monohydroxy-butenyl-mercapturic acid 3.61 (0.1) and 0.30 (0.02) microg/24 hr, and dihydroxy-butyl-mercapturic acid 556 (4.9) and 391 (5.5) microg/24 hr. On average, young adult smokers had lower exposure than older smokers; female smokers had lower exposure than males, and Black smokers had lower exposure than Whites. DISCUSSION: This study estimated the population exposure to cigarette smoke constituents in adult U.S. smokers and identified significant differences between subpopulations. The data may serve as a reference for monitoring the impact of changes in cigarette consumption and the introduction of potentially reduced exposure cigarettes.

Synthesis and evaluation of dihydroartemisinin and dihydroartemisitene acetal dimers showing anticancer and antiprotozoal activity.

Twelve artemisinin acetal dimers were synthesized and tested for antitumor activity in the National Cancer Institute (NCI) in vitro human tumor 60 cell line assay, producing a mean GI(50) concentration between 8.7 (least active) and 0.019 microM (most active). The significant activity of the compounds in this preliminary screen led to additional in vitro antitumor and antiangiogenesis studies. Several active dimers were also evaluated in the in vivo NCI hollow fiber assay followed by a preliminary xenograft study. The title compounds were found to be active against solid tumor-derived cell lines and showed good correlation with other artemisinin-based molecules in the NCI database. The dimers were also evaluated for their antimalarial and antileishmanial activities. The antimalarial activity ranged from 0.3 to 32 nM (IC(50)), compared to 9.9 nM for artemisinin.

Evaluation of biomarkers of exposure to selected cigarette smoke constituents in adult smokers switched to carbon-filtered cigarettes in short-term and long-term clinical studies.

Cigarette smoke is a complex aerosol that includes a gas vapor phase and a particulate phase. Inclusion of activated carbon in the cigarette filter can reduce some of the gas-phase smoke constituents implicated as toxicologically relevant. The present study evaluated exposure to selected gas-phase constituents when adult smokers switched to prototype cigarettes with a highly activated carbon filter. Smokers (N = 160) in two separate studies were randomized to continue to smoke conventional cigarettes (either a 6-mg or 11-mg FTC tar product), to smoke test cigarettes containing carbon filters (comparable tar levels), or to stop smoking. After completing 8 days in controlled smoking conditions (short-term studies), smokers had the option to continue in 24-week long-term ambulatory studies with unrestricted smoking. Urinary excretion of mercapturic acid metabolites of 1,3-butadiene, acrolein, and benzene; nicotine and five of its metabolites, total NNAL, and 1-hydroxypyrene were measured at baseline in the conventional cigarette group, in all groups in the short-term studies, and every 4 weeks in the long-term studies. In the short-term studies, statistically significant reductions (>70%, p<.001) in gas-phase biomarker levels were observed in the test cigarette group for both tar level products compared with the conventional cigarette group. These reductions were similar to those observed in the stop-smoking groups. The reductions continued consistently (p<.001) throughout the long-term studies. Switching to test cigarettes minimally affected the particulate-phase biomarkers. Statistically significant and consistent reductions in selected gas vapor phase biomarkers were observed when smokers switched to activated carbon filter cigarettes.

12-week clinical exposure evaluation of a third-generation electrically heated cigarette smoking system (EHCSS) in adult smokers.

This randomized, controlled, forced-switching, open-label, parallel-group, single-center study in 90 male and female adult smokers evaluated six biomarkers of tobacco smoke exposure over a 12-week period of unrestricted smoking in the participants' normal life setting. Baseline biomarker levels were measured, then participants were randomly assigned to switch to an electrically heated cigarette smoking system (EHCSS, Series K) or to continue smoking a conventional cigarette (CC) of similar tar yield (Federal Trade Commission method) for 12 weeks. Compared to Baseline, adult smokers who switched to the EHCSS for 12 weeks in their normal life setting had significantly reduced nicotine equivalents (-33%), total NNAL (a biomarker for NNK, -63%), 1-OHP (a surrogate biomarker for polycyclic aromatic hydrocarbons, -38%), carboxyhemoglobin (a biomarker for carbon monoxide, -23%), 3-HPMA (a biomarker for acrolein, -25%) and S-PMA (a biomarker for benzene, -49%), whereas exposure was stable in the CC control group.

Short-term clinical exposure evaluation of a third-generation electrically heated cigarette smoking system (EHCSS) in adult smokers.

This randomized, controlled, forced-switching, open-label, parallel-group, single-center study in 100 male and female adult smokers evaluated 12 biomarkers of tobacco smoke exposure. We measured exposure to the following smoke constituents: nicotine, pyrene, tobacco-specific nitrosamines, three aromatic amines, carbon monoxide, benzene, acrolein, crotonaldehyde, and 1,3-butadiene. After baseline exposure determination, adult smokers of a conventional cigarette (CC) were switched to an electrically heated cigarette smoking system (EHCSS, Series K), continued smoking the CC, or stopped smoking (No-smoking) for 8 days in a controlled, confined, clinical setting. In the EHCSS group, the mean decrease from Baseline to Day 8 in the biomarkers of exposure ranged from 16% to 77% at Day 8 compared to Baseline. After adjusting for the residual effect (carryover effects due to long elimination half-life and non-tobacco confounding sources of exposure), the mean percent decrease from Baseline for all 12 biomarkers ranged from 47% to 90%. In conclusion, switching for 8 days from a conventional cigarette to the EHCSS substantially reduced exposure of adult smokers to several constituents of both the particulate and gas phases of cigarette smoke.

A randomized, controlled exposure study in adult smokers of full flavor Marlboro cigarettes switching to Marlboro Lights or Marlboro Ultra Lights cigarettes.

Rationale. To date no state-of-the-art clinical study has been conducted to address the question as to whether switching to lower tar cigarettes reduces exposure to smoke constituents in humans. Methods. Randomized, controlled, forced switching study in 225 adult smokers of full flavor Marlboro (MFF) cigarettes for 8 days with a 24-week follow-up. Subjects smoked MFF (a 15-mg Federal Trade Commission (FTC) tar cigarette) at baseline and were randomized to smoke 11-mg Marlboro Lights (ML) or 6-mg Marlboro Ultra Lights (MUL) cigarettes. Biomarkers of exposure to nicotine, 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), pyrene, CO, benzene, acrolein, and mutagenic substances were measured. Results. In the short-term phase, switching from MFF to ML showed statistically significant decreases in nicotine exposure (-13%) and non-significant increases in CO exposure (+6%), while switching from MFF to MUL showed statistically significant decreases in nicotine (-27%) and CO (-13%) exposure. Both nicotine and CO biomarkers trended similarly in the 24-week follow-up as in the short-term phase. The other biomarkers of cigarette smoke constituents followed the same trend as nicotine at the end of the 24-week follow-up. Conclusions. Switching smokers to lower FTC tar yield cigarettes, on average, reduces nicotine and other biomarkers considered surrogates of tar exposure.

A 12-month, randomized, controlled study to evaluate exposure and cardiovascular risk factors in adult smokers switching from conventional cigarettes to a second-generation electrically heated cigarette smoking system.

This randomized, controlled, forced-switching, open-label, parallel-group study in 97 adult male and female smokers of conventional cigarettes evaluated biomarkers of tobacco smoke exposure and cardiovascular risk factors. After baseline measurements, smokers were either switched to a second-generation electrically heated cigarette smoking system (EHCSS) or continued smoking conventional cigarettes for 12 months. Biomarkers of exposure and cardiovascular risk factors were measured at 0.5, 1, 2, 3, 4, 5, 6, 9, and 12 months. There was a rapid and sustained reduction in all biomarkers of exposure after switching to the EHCSS, with statistically significant reductions from baseline in nicotine equivalents (-18%), plasma cotinine (-16%), total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (-73%), total 1-hydroxypyrene (-53%), urine mutagenicity (-52%), 4-aminobiphenyl hemoglobin adducts (-43%), carboxyhemoglobin AUC7-23 h (-80%), and 3-hydroxypropylmercapturic acid (-35%). These reductions in exposure in the EHCSS group were associated with statistically significant and pathophysiologically favorable changes in several cardiovascular risk factors, including white blood cell count (-0.78 x 10(3)/microL), hemoglobin (-0.16 g/dL), hematocrit (-0.44%), urine 11-dehydrothromboxane B2 (-374 ng/24 h), and high-density lipoprotein cholesterol (+5 mg/dL).

Respiratory retention of nicotine and urinary excretion of nicotine and its five major metabolites in adult male smokers.

Urinary excretion of nicotine and its five major metabolites (nicotine-N-glucuronide, cotinine, cotinine-N-glucuronide, trans-3'-hydroxycotinine, and trans-3'-hydroxycotinine-O-glucuronide), expressed as nicotine equivalents (NE), has been used as a biomarker of smoking-related nicotine exposure. In this open-label, single center study, we investigated the relationship between nicotine retention from smoking and urinary excretion of NE in adult smokers. After a 4-day washout period, 16 adult male smokers smoked 6 cigarettes per day for four consecutive days according to three predefined smoking patterns: no inhalation (Pattern A), normal inhalation (Pattern B), and deep inhalation (Pattern C). The amount of nicotine retained in the respiratory tract during smoking was estimated from the difference between the amounts of nicotine delivered and exhaled. The daily excretion of urinary NE was measured in 24h urine samples by LC-MS/MS. The mean (+/-S.D.) amount of nicotine retained was 0.126+/-0.167, 0.960+/-0.214, and 1.070+/-0.223mg/cig for Patterns A, B, and C, respectively. The mean (+/-S.D.) relative retention (the amount retained relative to the amount delivered) was 11.2+/-14.7%, 98.0+/-1.6%, and 99.6+/-0.3% for Patterns A, B, and C, respectively. On the fourth day of smoking, an average of 86+/-20% of the total daily amount of retained nicotine was recovered as NE in 24h urine. Nicotine equivalents was treated as a single component and the data was described by a first-order elimination pharmacokinetic model which assumed instantaneous input and distribution. Based on this model, the elimination half-life of NE was 19.4+/-2.6h, and the NE excretion had reached approximately 96% of the steady state levels by Day 4. Our results suggest that most of the nicotine inhaled from a cigarette is retained (> or =98%) in the lung, and at steady state, daily urine NE excretion reflects approximately 90% of the retained nicotine dose from cigarette smoking.

Short-term clinical exposure evaluation of a second-generation electrically heated cigarette smoking system.

This randomized, controlled, forced-switching, open-label, parallel-group study in 100 adult male and female smokers of conventional cigarettes evaluated 8 biomarkers of tobacco smoke exposure. After baseline exposure determinations, adult smokers were switched to a second-generation electrically heated cigarette smoking system (EHCSS) for 8 days in a clinical setting. After 8 days of smoking the EHCSS biomarkers of exposure decreased by 43% to 85% compared to baseline. After correction for residual effects (carryover effects due to long elimination half-life and non-tobacco-confounding sources of exposure), reductions in exposure ranged from 59% to 97%. Results from this short-term clinical exposure study indicate that switching from a conventional cigarette to a second-generation electrically heated cigarette smoking system substantially reduced the exposure to several measured potentially harmful constituents of tobacco smoke.

A new method for estimating the retention of selected smoke constituents in the respiratory tract of smokers during cigarette smoking.

This report describes a new method for estimating the retention of selected mainstream smoke constituents in the respiratory tract of adult smokers during cigarette smoking. Both particulate-phase (PP) constituents including nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and N'-nitrosonornicotine (NNN), two tobacco-specific nitrosamines (TSNA), and gas-vapor-phase (GVP) constituents including carbon monoxide (CO), isoprene (IP), acetaldehyde (AA), and ethylene, were studied. To estimate the amounts of smoke constituents delivered during smoking, we used predetermined linear relationships between the measured cigarette filter solanesol content and machine-generated mainstream deliveries of these selected compounds. To determine the amounts of smoke constituents exhaled, the expired breath was directed through a Cambridge filter pad (CFP) attached to an infrared spectrometer. PP compounds were trapped on the CFP for later analysis and GVP compounds were analyzed in near real time. The smokers' respiratory parameters during smoking, such as inhalation/exhalation volume and time, were monitored using LifeShirt(R), a respiratory inductive plethysmography (RIP) device. The retention of each smoke constituent, expressed as a percentage, was then calculated as the difference between the amount delivered (estimated) and the amount exhaled relative to the amount delivered. We studied 16 adult male smokers who smoked cigarettes according to 3 predefined smoking patterns: no inhalation (pattern A), normal inhalation (pattern B), and deep inhalation (pattern C). For the three PP constituents, the mean retentions for pattern A ranged between 10 and 20%; and while the mean retentions of the two TSNAs were significantly higher for pattern C (84% for NNK and 97% for NNN) than those for pattern B (63% for NNK and 84% for NNN), the mean retentions of nicotine were basically the same between patterns B and C, which were both greater than 98%. For the GVP constituents, the retentions were similar between pattern B and pattern C, although different constituents were retained to different degrees (average values of 33%, 52%, 79%, and 99% for ethylene, IP, CO, and AA, respectively). The differences in the retention between different constituents could be interpreted in terms of each constituent's physical properties such as volatility and solubility. In conclusion, the method described is suitable for studying the retention of selected mainstream smoke constituents in the respiratory tract of smokers.

Testing equivalence between two laboratories or two methods using paired-sample analysis and interval hypothesis testing.

A modified interval hypothesis testing procedure based on paired-sample analysis is described, as well as its application in testing equivalence between two bioanalytical laboratories or two methods. This testing procedure has the advantage of reducing the risk of wrongly concluding equivalence when in fact two laboratories or two methods are not equivalent. The advantage of using paired-sample analysis is that the test is less confounded by the intersample variability than unpaired-sample analysis when incurred biological samples with a wide range of concentrations are included in the experiments. Practical aspects including experimental design, sample size calculation and power estimation are also discussed through examples.

Hydrolysis of conjugated metabolites of buprenorphine II. The quantitative enzymatic hydrolysis of norbuprenorphine-3-beta-D-glucuronide in human urine.

In gas chromatographic-mass spectroscopic analysis of buprenorphine metabolites, the urine specimen must be first hydrolyzed to release buprenorphine and norbuprenorphine from their glucuronide conjugates. For evaluation of existing hydrolysis methods and to find out the optimal hydrolysis conditions, buprenorphine-3-beta-D-glucuronide (B3G) and norbuprenorphine-3-beta-D-glucuronide (NB3G) were synthesized. In a previous communication we reported on the optimum conditions for hydrolysis of B3G. Because we have previously shown that no hydrolysis was achieved under basic conditions and that acid hydrolysis resulted in extensive degradation, only enzymatic hydrolysis was examined for NB3G. This study therefore reports on the optimum enzymatic conditions for the hydrolysis of NB3G. Urine fortified with synthetic NB3G was hydrolyzed with beta-glucuronidases from different source species, including Helix pomatia, Escherichia coli, and Patella vulgata. Glusulase, a preparation containing both the beta-glucuronidase (H. pomatia) and sulfatase, was also tested. It was found that marked differences exist in the reactivity of these enzymes. Incubation with glucuronidases from H. pomatia or E. coli at 37 degrees C for 16 h resulted in quantitative hydrolysis of NB3G. At 60 degrees C, complete hydrolysis was achieved with 1000 units of H. pomatia in 4 h and after only 1 h with glusulase. On the other hand, incubation at 60 degrees C for 4 h with Patella vulgata resulted in only 14.7% hydrolysis.