Determination of nicotine and two major metabolites in serum by solid-phase extraction and high-performance liquid chromatography, and high-performance liquid chromatography-particle beam mass spectrometry

Review of HPLC-MS methods for the analysis of nicotine and its active metabolite cotinine in various biological matrices

In recent years, tobacco smoking is a risk factor for a series of diseases including cardiovascular diseases, cerebrovascular diseases, and cancers. Nicotine, the primary component of tobacco smoke, is mainly transformed to its active metabolite cotinine, which is often used as biomarker for tobacco exposure for its higher blood concentration and longer residence time than nicotine. Various analytical methods have been developed for the determination of nicotine and cotinine in biological matrices. This article reviewed the HPLC-MS based methods for nicotine and/or cotinine analysis in various biological matrices. The sample preparation, mass and chromatographic conditions and method validation results of these methods have been summarized and analyzed. Sample was mainly pretreated by protein precipitation and/or extraction. Separation was achieved using methanol and/or acetonitrile:water (with or without ammonium acetate) on C18 columns, and acetonitrile:water (with formic acid, ammonium acetate/formate) on HILIC columns. Nicotine-d3, nicotine-d4 and cotinine-d3 were commonly used internal standards. Other non-deuterated IS were also used such as ritonavir, N-ethylnorcotinine, and milrinone. For both nicotine and cotinine, the calibration range was 0.005-35000 ng/mL, the matrix effect was 75.96% - 126.8% and the recovery was 53% - 124.5%. The two analytes were stable at room temperature for 1-10 days, at -80 °C for up to 6 months, and after 3-6 freeze-thaw cycles. Comedications did not affect nicotine and cotinine analysis.

Self-Reported Smoking Compared to Serum Cotinine in Bariatric Surgery Patients: Smoking Is Underreported Before the Operation

BACKGROUND

Smoking has been associated with postoperative complications and mortality in bariatric surgery. The evidence for smoking is based on self-report and medical charts, which can lead to misclassification and miscalculation of the associations. Determination of cotinine can objectively define nicotine exposure. We determined the accuracy of self-reported smoking compared to cotinine measurement in three phases of the bariatric surgery trajectory.

METHODS

Patients in the phase of screening (screening), on the day of surgery (surgery), and more than 18 months after surgery (follow-up) were consecutively selected. Self-reported smoking was registered and serum cotinine was measured. We evaluated the accuracy of self-reported smoking compared to cotinine, and the level of agreement between self-report and cotinine for each phase.

RESULTS

In total, 715 patients were included. In the screening, surgery, and follow-up group, 25.6%, 18.0%, and 15.5%, respectively, was smoking based on cotinine. The sensitivity of self-reported smoking was 72.5%, 31.0%, and 93.5% in the screening, surgery, and follow-up group, respectively (p < 0.001). The specificity of self-report was > 95% in all groups (p < 0.02). The level of agreement between self-report and cotinine was 0.778, 0.414, and 0.855 for the screening, surgery, and follow-up group, respectively.

CONCLUSIONS

Underreporting of smoking occurs before bariatric surgery, mainly on the day of surgery. Future studies on effects of smoking and smoking cessation in bariatric surgery should include methods taking into account the issue of underreporting.

Direct quantitative analysis of nicotine alkaloids from biofluid samples using paper spray mass spectrometry

The determination of tobacco derived nicotine alkaloids in biofluid samples is of great importance to testing for tobacco use, tobacco cessation treatment, and studies on exposure to secondhand smoke. Paper spray mass spectrometry (MS) has been adapted for direct, quantitative analysis of tobacco alkaloids from biofluid samples, such as blood, urine, and saliva in liquid and dried form. Limits of quantitation as low as several nanograms per milliliter were obtained for nicotine, cotinine, trans-3'-hydroxycotinine, and anabasine. Direct analysis of fresh blood samples has also been achieved with improved sensitivity using print paper substrates of high density. Quantitation of the cotinine in the blood of a rat was performed with both direct analysis using paper spray and a traditional analysis protocol using liquid chromatography MS. Comparable results were obtained and the precision of the two methods was similar. The paper spray MS method is rapid and shows potential for significantly improved analytical efficiency in clinical laboratories as well as for point-of-care tobacco use assessment.

Development and validation of a hydrophilic interaction chromatography-tandem mass spectrometry for quantification of nicotine and its metabolites in human maternal and cord sera

A selective and sensitive HILIC-MS/MS method for the simultaneous quantification of nicotine and its metabolites in human maternal and cord sera was developed and validated. After solid-phase extraction, LC separation was achieved on a hydrophilic interaction chromatography. The validated method is capable of selective identification as well as accurate and sensitive quantification. Analyte recovery ranged from 86.2 to 107.7% and intra- and inter-day assay precision were less than 15% relative standard deviation. This sensitive HILIC-MS/MS method can be used to determine nicotine and its metabolic profile in smokers. This validated method is useful for the determination of nicotine and its metabolites in human serum in future studies of the effects of nicotine exposure on neonatal outcome.

Nicotine exposure can be detected in cerebrospinal fluid of active and passive smokers

A simple, rapid and sensitive liquid chromatography/mass spectrometry (LC/MS) method has been utilized for the quantitative determination of nicotine and its major metabolite cotinine (COT) in human cerebrospinal fluid (CSF) of active and passive smokers. CSF samples from 18 smokers, 15 non-smokers, 15 children, 15 infants, and 9 neonatal were analyzed for nicotine (NIC) and cotinine content. Cotinine levels in the CSF of smokers ranged from 27.3 to 457.1 ng/ml, whereas nicotine levels were considerably lower (6.0-215.1 ng/ml). Cotinine could be detected in 4 of the 15 CSF samples from non-smokers (3.5-30.4 ng/ml), and a few other passive smokers, including neonates from smoking mothers (15.6-81.1 ng/ml). The concentrations of cotinine in CSF samples suggests that nicotine easily passes into the CSF, which makes it an excellent CSF marker for tobacco-smoke exposure.

CYP2A6 genotype, phenotype, and the use of nicotine metabolites as biomarkers during ad libitum smoking

CYP2A6 inactivates nicotine to cotinine and cotinine to 3-hydroxycotinine. We investigated which of plasma nicotine and metabolites were most related to CYP2A6 genotype and smoking levels. We assessed demographic and smoking histories in 152 Caucasian ad libitum smokers, measured breath carbon monoxide (CO) levels, and determined plasma nicotine, cotinine, and 3-hydroxycotinine by high-performance liquid chromatography and CYP2A6 genotypes by PCR. Cigarettes per day was most closely related to CO (r = 0.60, P < 0.001) followed by plasma cotinine (r = 0.53, P < 0.001), whereas plasma cotinine was most strongly correlated with CO levels (r = 0.74, P < 0.001), confirming that cotinine is a good indicator of smoking levels; this was not limited by CYP2A6 variants. 3-Hydroxycotinine/cotinine is reported to be a good marker of CYP2A6 activity, and we found that the 3-hydroxycotinine/(cotinine + nicotine) ratio was most correlated with CYP2A6 genotype (r = 0.38, P < 0.001). Inclusion of the CYP2A6*12A allele strengthened the correlation (r = 0.46, P < 0.001), suggesting that the identification of novel alleles will continue to improve this relationship. Nicotine metabolism is slower in smokers, and we have shown that CYP2A6 is reduced by nicotine treatment in monkeys. Here, we found that plasma nicotine levels were inversely correlated with CYP2A6 activity (3-hydroxycotinine/cotinine, r = -0.41, P < 0.001) among those without CYP2A6 variants, suggesting a reduction in metabolism with higher nicotine levels. Together, these findings (a) confirm the use of plasma cotinine and CO as indicators of Caucasians' smoking levels, and that this is not limited by CYP2A6 genetic variation; (b) indicate that 3-hydroxycotinine/cotinine and 3-hydroxycotinine/(cotinine + nicotine) are moderately good indicators of the CYP2A6 genotype; and (c) support that nicotine exposure may reduce its own metabolism.

Effect of application sites and multiple doses on nicotine pharmacokinetics in healthy male Japanese smokers following application of the transdermal nicotine patch

The transdermal nicotine patch, which contains 25 mg nicotine per 30 cm(2), is designed to deliver approximately 15 mg nicotine to the blood circulation in 16 hours of application for the treatment of smoking cessation. It was applied to 3 different skin sites (upper arm, abdomen, and back) to examine regional variations in percutaneous nicotine absorption in a single-dose, 3-period, crossover study involving 9 healthy male Japanese smokers. Nicotine pharmacokinetics during once-daily application of the transdermal nicotine patch for 5 days was also investigated in 10 healthy smokers. There were statistically significant effects of application sites on percutaneous nicotine absorption. The ratios (90% confidence intervals) of AUC and C(max) for comparison to the upper arm were 102% (88, 117%) and 106% (95, 119%) for the back and 75% (65, 87%) and 75% (66, 84%) for the abdomen, respectively. These suggest that systemic exposure after application to the upper arm was greater compared with the abdomen but equivalent to the back. Following multiple doses, linear pharmacokinetics and no significant accumulation of nicotine concentrations were observed, and steady state was reached by day 2. Only mild itching and erythema were observed at the application sites. The transdermal nicotine patch was well tolerated in both studies.

Comparison of Nicotine Pharmacokinetics in Healthy Japanese Male Smokers Following Application of the Transdermal Nicotine Patch and Cigarette Smoking

Transdermal nicotine patch (TNP) contains approximately 16.6 and 24.9 mg of nicotine per 20 and 30 cm2 (TNP-20 and TNP-30). The aims of the study are to investigate linearity of nicotine pharmacokinetics after single application of different strengths of TNP and to directly compare plasma nicotine concentrations with those during cigarette smoking. Twelve healthy Japanese male smokers were randomly allocated to 1 of 2 cohorts consisting of 6 subjects each. Cohort 1 subjects received 1 sheet of TNP-20 (TNP-20x1) in period 1, and 2 sheets of TNP-20 (TNP-20x2) in period 3. Cohort 2 subjects were received 1 sheet of TNP-30 (TNP-30x1) in period 2, and smoked a total of 12 cigarettes at 1 h intervals in period 4. Each TNP was applied to the upper arm for 16 h. After TNP-20x1 or TNP-20x2 treatment in cohort 1, the amount of nicotine delivered from TNP (Dose) was proportional to surface area of TNP. Cmax and AUC of nicotine increased with the surface area (Dose), and tmax, t(1/2), CL/F and percentage of dose excreted in urine were almost the same between both treatments. These suggest the linear pharmacokinetics of nicotine in proportion to the surface area and Dose following single application of TNP in identical subjects. In cohort 2, the plasma nicotine concentrations after TNP-30x1 treatment were approximately half those just before each smoking.

Determination of nicotine and cotinine in tobacco harvesters’ urine by solid-phase extraction and liquid chromatography

A solid-phase extraction method using Drug Test-1 column containing chemically modified silica as a solid support for sample clean up and reversed phase ion-paired high-pressure liquid chromatography method have been developed for the simultaneous determination of nicotine and its metabolite cotinine from the urine samples. Mobile phase was consisted of acetate buffer (containing 0.03 M sodium acetate and 0.1 M acetic acid) pH 3.1 and acetonitrile (78:22% (v/v)) containing 0.02 M sodium octanosulfonate as an ion pair agent. pH of the mobile phase was adjusted to 3.6 with triethylamine for better resolution and to prevent peak tailing. The linearity was obtained in the range of 0.5-10 microg/ml concentrations of nicotine and cotinine standards. The correlation coefficients were 0.998 for cotinine and 0.999 for nicotine. The recoveries were obtained in the range of 79-97% with average value of 85% for nicotine and in the range of 82-98% with average value of 88% for cotinine. The limit of detection was 2 ng/ml for cotinine and 5 ng/ml for nicotine with 2 ml urine for extraction, calculated by taking signal to noise ratio 10:3. The intra-day co-efficient of variation (CV) were <4 and 7% and inter-day CV were <9 and 7% for nicotine and cotinine, respectively. The method was applied to the urine samples of tobacco harvesters, who suffer from green tobacco sickness (GTS) to check the absorption of nicotine through dermal route during the various processes of tobacco cultivation due to its good reproducibility and sensitivity.

Determination of Nicotine and Its Major Metabolite Cotinine in Plasma or Serum by Gas Chromatography-Mass Spectrometry Using Ion-Trap Detection

A specific method has been developed for the quantitative determination of nicotine and its major metabolite cotinine in plasma or serum of active and passive smokers. Deuterium-labelled nicotine and cotinine were used as internal standards. The amounts of nicotine and cotinine present in a sample of plasma or serum were extracted with a simple extraction procedure (liquid-liquid or solid-phase extraction). The extracts were analysed by gas chromatography coupled with mass spectrometry using ion-trap detection. The analysis was done in positive chemical ionisation with methanol as the liquid reagent. The method has been demonstrated to be linear up to 1000 microg/l. Limits of quantification for nicotine and cotinine are 10 and 5 microg/l, respectively with liquid-liquid extraction, and 1 microg/l for each of the compounds with solid-phase extraction. The present method has been applied to several real cases.

Simultaneous determination of nicotine and eight nicotine metabolites in urine of smokers using liquid chromatography-tandem mass spectrometry

A method based on liquid chromatography tandem mass spectrometry (LC-MSMS) applying atmospheric pressure chemical ionisation (APCI) in the positive ion mode was developed for the direct determination of nicotine, cotinine, trans-3'-hydroxycotinine, their corresponding glucuronide conjugates as well as cotinine-N-oxide, norcotinine, and nicotine-N'-oxide in the urine of smokers. The assay involves filtration of crude urine, fast liquid chromatography on a reversed-phase column and mass-specific detection using MSMS transitions. Deuterium-labeled nicotine, cotinine, and trans-3'-hydroxycotinine were used as internal standards. Glucuronides used as reference material were either chemically (cotinine-N-glucuronide) or enzymatically synthesized (nicotine-N-glucuronide and trans-3'-hydroxycotinine-O-glucuronide). Precision for the major nicotine analytes at levels observable in urine of smokers was better than 10%. Accuracy expressed in recovery rates in urine matrix for nicotine, cotinine, trans-3'-hydroxycotinine, and cotinine-N-glucuronide ranged from 87 to 113%. Quantitative results for the three glucuronides in urine samples of 15 smokers were compared to an indirect method in which the aglycons were determined with gas chromatography and nitrogen-selective detection (GC-NPD) before and after enzymatic splitting of the conjugates. Good agreement was found for cotinine-N-glucuronide (coefficient of variation, CV: 9%) and trans-3'-hydroxycotinine-O-glucuronide (CV: 20%), whereas the accordance between both methods was moderate for nicotine-N-glucuronide (CV: 33%). The described LC-MSMS method allows the simultaneous determination of nicotine and eight of its major metabolites in urine of smokers with good precision and accuracy. Since the method requires a minimum of sample clean-up and a very short time for chromatography (3 min), it is suitable for determining the nicotine dose in large-scale human biomonitoring studies.

Gender differences in tobacco smoking: higher relative exposure to smoke than nicotine in women

INTRODUCTION

Men and women are thought to regulate their smoking differently and to differ in their susceptibility to nicotine addiction.

METHODS AND MATERIALS

Various measures of smoke exposure were compared between 400 current regular tobacco-dependent (DSM-IV) male and female light (1-15 cigarettes per day) and heavy (>15 cigarettes per day) smokers. Between 2 and 8 PM, blood was collected for nicotine and cotinine analysis, and breath carbon monoxide (CO) was measured. Individuals with genetic variants of the CYP2A6 gene were removed from analysis (n = 25).

RESULTS

No significant difference was found in the number of cigarettes per day or CO levels between the sexes. However, females had significantly lower nicotine levels than males (16.9 +/- 0.6 vs. 21.1 +/- 0.07, p < 0.01). This is only partly explained by the fact that females smoked lower nicotine-containing cigarettes. Female heavy smokers demonstrated higher -log nicotine/CO values (a representation of cost of smoking) compared with male heavy smokers (0.1 +/- 0.02 vs. 0.02 +/- 0.01 mg/L ppm, p < 0.05).

CONCLUSIONS

Thus, gender differences appear to exist in smoking behaviors, nicotine sensitivity, and nicotine requirements. These differences are expected to contribute to gender differences in health risks and cancers associated with smoking.

An in vivo pilot study characterizing the new CYP2A6*7, *8, and *10 alleles

We developed genotyping assays for CYP2A6*7 (Ile471Thr) and CYP2A6*8 (Arg485Leu). We found higher allelic frequencies in Japanese and Chinese versus Caucasians and identified an allele in which both substitutions occur together (CYP2A6*10). We created a homology model for predicting the impact of allelic variants on enzymatic activity and subsequently tested this in vivo in a pilot kinetic study. Consistent with our homology model predictions, we found (i) that CYP2A6*7 produces an enzyme that has decreased (not inactive) activity for metabolizing nicotine and coumarin; (ii) that CYP2A6*8 is unlikely to affect catalytic activity in vivo; and (iii) that having both substitutions together on an allele (CYP2A6*10) dramatically reduces function and may be fully inactive for some substrates. In conclusion, this study identifies, at relatively high frequency in Asians, an allele with decreased activity (may be substrate selective), a fully functional allele, and an allele containing both substitutions in which function is dramatically reduced.

Importance of injection solution composition for LC-MS-MS methods

For the first time, the influence of the injection solution composition on the quality of LC-MS-MS methods, in terms of column efficiency and peak shape, was systematically investigated. Various types of compounds, including polar ionic acidic, polar ionic basic and non-polar neutral compounds, were prepared in different solutions ranging from 100% water to 100% acetonitrile. Different volumes of these solutions were injected onto either C18 or silica columns connected to tandem mass spectrometry. The mobile phases consisted of acetonitrile, water, and small amounts of volatile acid or buffer. On silica columns, the influence of injection solution on the peak shape and column efficiency was straightforward. The sharpest peaks and the highest column efficiency were obtained with 100% acetonitrile as the injection solvent. On C18 columns, this type of influence was less clear due to the dual retention mechanism of the bonded phase and of the residual silanol groups. On C18 column, retention due to residual silanol groups was significant even with a mobile phase containing less than 50% acetonitrile. Poor peak shape was observed when the injection solution had a stronger eluting strength than mobile phase, particularly for early eluting peaks.

Novel liquid chromatographic-tandem mass spectrometric methods using silica columns and aqueous-organic mobile phases for quantitative analysis of polar ionic analytes in biological fluids

Use of silica stationary phase and aqueous-organic mobile phases could significantly enhance LC-MS-MS method sensitivity. The LC conditions were compatible with MS detection. Analytes with basic functional groups were eluted with acidic mobile phases and detected by MS in the positive ion mode. Analytes with acid functional groups were eluted with mobile phases at neutral pH and detected by MS in the negative ion mode. Analytes poorly retained on reversed-phase columns showed good retention on silica columns. Compared with reversed-phase LC-MS-MS, 5-8-fold sensitivity increases were observed for basic polar ionic compounds when using silica columns and aqueous-organic mobile phase. Up to a 20-fold sensitivity increase was observed for acidic polar ionic compounds. Silica columns and aqueous-organic mobile phases were used for assaying nicotine, cotinine, and albuterol in biological fluids.

Determination of nicotine N-1-glucuronide, a quaternary N-glucuronide conjugate, in human biological samples

[Methyl-d3]-N-1-beta-D-glucopyranosyl-(+/-)-nicotinium inner salt ((+/-)-[methyl-d3]nicotine N-1-glucuronide) was synthesized from (+/-)-[methyl-d3]nicotine via reaction with methyl-2,3,4-tri-O-acetyl-1-bromodeoxy-alpha-D-glucopyranouronate, followed by deprotection with 1 M aqueous NaOH and purification by preparative TLC. Nicotine N-glucuronide was identified and determined directly in smokers' urine. A solid phase extraction method was used to partially isolate the material from urine. Subsequent determination was by thermospray-LC/MS using the synthetic d3-labeled nicotine N-glucuronide as internal standard. The identified urinary component had the same retention time as a synthetic standard and gave the same mass spectrum. The thermospray mass spectrum was characterized from the protonated molecular ion (m/z 339) and the protonated aglycone ion (m/z 163). Quantitative results from this direct method were compared with those from an indirect method, which calculated the nicotine glucuronide in the biological sample from the amount of nicotine released following treatment of the sample with the deconjugating enzyme, beta-glucuronidase. On average, the concentration of nicotine N-glucuronide determined by the direct method was 34% greater than that determined by the indirect method. Concentrations of nicotine N-glucuronide in urine ranged from 2.2 to 7.6 nmol/ml with a limit of detection of 1.3 nmol/ml.

Separation of nicotine metabolites by capillary zone electrophoresis and capillary zone electrophoresis/mass spectrometry

The use of capillary zone electrophoresis (CZE) and capillary zone electrophoresis/mass spectrometry (CZE/MS) has been demonstrated, in principle, for the separation of nicotine and nicotine metabolites. The buffer system developed for separation and detection by CZE/UV was modified for use in CZE/MS analysis. Several of the metabolites are isobaric and tandem mass spectrometric (MS/MS) techniques have been used to differentiate such analytes.

Duplications and defects in the CYP2A6 gene: identification, genotyping, and in vivo effects on smoking

In humans, 80% of nicotine is metabolized to the inactive metabolite cotinine by the enzyme CYP2A6, which can also activate tobacco smoke procarcinogens (e.g., 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone). Previously, we demonstrated that individuals who are nicotine-dependent and have defective CYP2A6 alleles (*2, *3) smoked fewer cigarettes; however, we recognize that the genotyping method used for the CYP2A6*3 allele gave a high false-positive rate. In the current study we used improved genotyping methods to examine the effects of the defective CYP2A6*2 and CYP2A6*4 alleles on smoking behavior. We found that those with the defective alleles (N = 14) smoked fewer cigarettes per day than those homozygous (N = 277) for wild-type alleles (19 versus 28 cigarettes per day, P <.001). In addition, we identified a duplicated form of the CYP2A6 gene, corresponding to the gene deletion CYP2A6*4 allele, developed a genotyping assay, assessed the gene copy number, and examined its prevalence in Caucasian smokers (N = 296). We observed an ascending rank order for plasma cotinine and breath carbon monoxide levels (an index of smoke inhalation) in individuals with null (CYP2A6*2 and CYP2A6*4) alleles (N = 14), those homozygous for wild-type (CYP2A6*1/*1) alleles (N = 277), and those with our newly identified CYP2A6 gene duplication (N = 5). The phenotype, as determined by plasma nicotine/cotinine ratios, had a descending rank order for these three genotype groups that did not reach significance. Although further characterization is required for the duplication gene variant, these results extend our previous findings and suggest a substantial influence of CYP2A6 genotype and phenotype on smoking behavior.

High-performance liquid chromatographic determination of cotinine in urine in isocratic mode

A simple procedure for the determination of cotinine, major metabolite of nicotine in urine, is described. The assay involved a liquid-liquid extraction with dichloromethane in alkaline environment. The extract was dried at ambient temperature under a gentle stream of nitrogen. The residue was dissolved in 300 microl of mobile phase and 30 microl aliquot was injected via an automatic sampler into the liquid chromatograph and eluted with the mobile phase (10-9%, v/v methanol and acetonitrile, respectively in potassium dihydrogenphosphate buffer adjusted to pH 3.4) at a flow rate of 1 ml/min on a C8 Symmetry cartridge column (5 microm, 150 mm x 3.9 mm, Waters) at 25 degrees C. The eluate was detected at 260 nm. Internal standard was 2-phenylimidazole. Sensitive and specific, this technique was performed to test urine of diabetic patients (smokers and non-smokers) admitted in an endocrinology service. Urinary cotinine seems to be a better marker of smoking status than thiocyanates.

A simple high performance liquid chromatographic method for the quantification of total cotinine, total 3'-hydroxycotinine and caffeine in the plasma of smokers

A simple isocratic HPLC procedure has been developed for the quantification of caffeine and the nicotine metabolites cotinine, 3'-hydroxycotinine, cotinine glucuronide and 3'-hydroxycotinine glucuronide in the plasma of smokers. The glucuronide conjugates were determined indirectly via initial basic hydrolysis of the analyte sample followed by quantification of the resulting deconjugation product. Plasma was basified, extracted with dichloromethane, evaporated, the residue dissolved water and an aliquot part was analyzed by HPLC. The method utilized a Partisil-10 SCX cation-exchange column and an isocratic mobile phase of sodium phosphate buffer: methanol (92:8 v/v, 0.1 M, adjusted to pH 4.8 with triethylamine) at a flow rate of 1.5 ml/min. UV detection was at 254 nm. All solutes were separated with good resolution, and quantification was determined using an internal standard of N,N-diethylnicotinamide. The retention times were: caffeine 5.1 min, 3'-hydroxycotinine 7.2 min, N,N-diethylnicotinamide 9.5 min, and cotinine 15.5 min. Detection limits for caffeine, 3'-hydroxycotinine, cotinine, and total cotinine were 10 ng/ml; the detection limit for total 3'-hydroxycotinine was 20 ng/ml. The inter-day and intra-day variations for all analytes were between 1 and 8%. This analytical method is suitable for the determination of caffeine and nicotine metabolite levels in large numbers of clinical samples.

Analysis of Nicotine, 3-Hydroxycotinine, Cotinine, and Caffeine in Urine of Passive Smokers by HPLC-Tandem Mass Spectrometry

Background: A method is described for the simultaneous analysis of nicotine and two of its major metabolites, cotinine and 3-hydroxycotinine, as well as for caffeine from urine samples. The method was developed to assess exposure of restaurant and hotel workers to environmental tobacco smoke.

Methods: The method includes sample pretreatment and reversed-phase HPLC separation with tandem mass spectrometric identification and quantification using electrospray ionization on a quadrupole ion trap mass analyzer. Sample pretreatment followed standard protocols, including addition of base before liquid-liquid partitioning against dichloromethane on a solid matrix, evaporation of the organic solvent using gaseous nitrogen, and transferring to HPLC vials using HPLC buffer. HPLC separation was run on-line with the electrospray ionization-tandem mass spectrometric detection.

Results: The detection limits of the procedure were in the 1 μg/L range, except for nicotine (10 μg/L of urine). Still lower detection limits can be achieved with larger sample volumes. Recoveries of the sample treatment varied from 99% (cotinine) to 78% (3-hydroxycotinine).

Conclusions: The method described is straightforward and not labor-intensive and, therefore, permits a high throughput of samples with excellent prospects for automation. The applicability of the method was demonstrated in a small-scale study on restaurant employees.

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Particle counting immunoassay for urinary cotinine. Comparison with chromatography, enzyme-linked immunoassay and fluorescence polarization immunoassay

Urinary cotinine was measured according to its inhibitory activity on the agglutination of cotinine-coated latex particles by anti-cotinine antibodies, the agglutination being measured by optical counting of the remaining non-agglutinated particles (particle counting, PaC). The detection limit was 0.03 microgram/ml and the practical range extended from 0.03 to 3.9 micrograms/ml. The correlation results of 320 urine samples with those of high pressure liquid chromatography, enzyme-linked (Coti-Tracq EIA, Serex Inc., Maywood, NJ, USA), and fluorescence polarization immunoassay (TDX instrument, Abbott, Abbott Park, IL, USA) were r = 0.90, r = 0.69, r = 0.87, respectively, whereas the correlation coefficients between the assays other than particle counting ranged from 0.62 to 0.88. PaC does not require any separation step and can thus be easily automated.

A New Gas Chromatography–Mass Spectrometry Method for Simultaneous Determination of Total and Free trans-3′-Hydroxycotinine and Cotinine in the Urine of Subjects Receiving Transdermal Nicotine

trans-3′-Hydroxycotinine (THOC) has been recognized as the most abundant metabolite of nicotine. In an attempt to assess THOC and cotinine (COT) concentrations during nicotine transdermal therapy, we developed a new quantitative gas chromatography–mass spectrometry (GC–MS) method for simultaneous determination of total and free THOC and COT in human urine. The method utilizes the following: (a) hydrolysis of conjugated THOC and COT by β-glucuronidase; (b) basic extraction of THOC and COT with mixed dichloromethane and n-butyl acetate; (c) derivatization of THOC with bis(trimethylflurosilyl)acetamide; and (d) separation and identification by GC–MS with selective ion monitoring. Lower limits of quantification for the assay were 50 and 20 μg/L for THOC and COT, respectively. The intra- and interassay CVs were 4.4% and 11% for THOC, and 3.9% and 10% for COT at 1000 μg/L. The results from six consecutive 24-h urine collections in 71 subjects administered daily transdermal nicotine doses of 11, 22, and 44 mg showed that, on average, free THOC was 76% of total THOC and free COT was 48% of total COT in all subjects. THOC is the major metabolite of nicotine and constitutes 20% of total nicotine intake at steady state, whereas urinary nicotine and COT excretion were 8% and 17%, respectively. The method is useful for simultaneous determination of free and total THOCand COT and can be used to assess the urinary excretion of these metabolites during transdermal nicotine therapy.

Determination of nicotine, cotinine and caffeine in meconium using high-performance liquid chromatography

A high-performance liquid chromatographic method with diode-array detection for the determination of nicotine and its metabolites, cotinine and caffeine, in meconium is described. This method is suitable to assess foetus exposure to tobacco smoke. The analytes were extracted by solid-phase extraction before chromatography. From among 30 meconium samples 11 were positive for cotinine (20-86 ng/g) and 27 for caffeine (10-45 ng/g). No nicotine was present in the samples because of its rapid metabolism into cotinine.

Hair analysis for nicotine and cotinine: evaluation of extraction procedures, hair treatments, and development of reference material

Analysis of nicotine and cotinine in human hair can provide information on nicotine intake and exposure to environmental tobacco smoke over a long period of time. Nonetheless, to better assess the usefulness of hair analysis to determine smoking habits or exposures, all procedures have to be standardized. Various solvents were tested as washing solvents to eliminate external contamination from nicotine. Dichloromethane was found effective when used for two washes prior to the extraction. Basic and acid digestion of hair followed by solid phase extraction with Extrelut-3 glass column using dichloromethane:isopropyl alcohol (9:1) as eluting mixture both gave good recoveries of nicotine and cotinine, when compared with extractions reported in the literature. The extraction method was free from substances, which could interfere in the chromatographic analysis. Furthermore, the addition of methanolic HCl to the eluting mixture prevented the loss of nicotine during the evaporation step before chromatography. Chromatography was performed using a reversed-phase column and a U.V. detection at 254 nm. Furthermore, hair treatments (dyes, permanent wave, hydrogen peroxide) caused a major decrease in the nicotine content in hair, and a smaller effect on cotinine levels. However, the effect of various treatments was not reproducible. Several attempts to produce reference materials were carried out. Nicotine and cotinine standard solutions at different concentrations were added to blank hair soaked in dimethylsulfoxide, methanol and water.

The analysis of nicotine in infants' hair for measuring exposure to environmental tobacco smoke

Hair samples were collected from 24 infants (3-36 months) exposed and non-exposed to environmental tobacco smoke. Hair was washed in dichloromethane, digested in NaOH, extracted by solid-phase extraction and analyzed by high-performance liquid chromatography to determine the content of nicotine and cotinine. Nicotine concentration in non-exposed infants (1.3 +/- 1.7 ng/mg hair) was significantly different from that in occasionally exposed infants (6.8 +/- 2.1 ng/mg hair) and that in infants passively exposed to smoke (15.4 +/- 6.7 ng/mg hair). Cotinine could be measured only in passive smokers infants. These findings suggest the possibility of monitoring exposure to environmental tobacco smoke in infants by using nicotine measurement in hair rather than in urine, blood or saliva.

Determination of nicotine and cotinine in human plasma by liquid chromatography-tandem mass spectrometry with atmospheric-pressure chemical ionization interface

Here we report a sensitive liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method capable of quantifying nicotine down to 1 ng/ml and cotinine to 10 ng/ml from 1.0 ml of human plasma. The method was validated over linear ranges of 1.0-50.0 ng/ml for nicotine and 10.0-500.0 ng/ml for cotinine, using deuterated internal standards. Compounds were simply extracted from alkalinized human heparinized plasma with methylene chloride, reconstituted into a solution of acetonitrile, methanol and 10 mM ammonium acetate (53:32:15, v/v) after the organic phase was dried down, and analyzed on the LC-MS-MS, which is a PE Sciex API III system equipped with a Keystone BDS Hypersil CI8 column and atmospheric pressure chemical ionization (APCI) interface. The between-run precision and accuracy of the calibration standards were < or = 6.42% relative standard deviation (R.S.D.) and < or = 11.8% relative error (R.E.) for both nicotine and cotinine. The between-run and within-run precision and accuracy of quality controls, (2.5, 15.0, 37.5 ng/ml for nicotine and 25.0, 150.0, 375.0 ng/ml for cotinine), were < or = 6.34% R.S.D. and < or = 7.62% R.E. for both analytes. Sample stabilities in chromatography, in processing and in biological matrix were also investigated. This method has been applied to pharmacokinetic analysis of nicotine and cotinine in human plasma.

Solid-phase extraction of nicotine and its metabolites for high-performance liquid chromatographic determination in urine

A solid-phase extraction, using Extrelut-1 glass columns, has been applied to urine samples of both passive and active smokers for high-performance liquid chromatographic determination of nicotine and its metabolites cotinine and trans-3'-hydroxycotinine. Chromatography was performed using a reversed-phase LC8DB column and a mobile phase consisting of water-acetonitrile (80:9, v/v) containing 5 ml triethylamine, 670 mg/l sodium heptanesulphonate, and 0.034 M each of K2HPO4 and citric acid (pH 4.4), at a flow-rate of 1.6 ml/min. The results obtained indicate that solid-phase extraction is a reliable and quick procedure which can be applied also to other nicotine metabolites.

Variables affecting nicotine metabolism

Nicotine metabolism is exceedingly sensitive to perturbation by numerous host factors. To reduce the large variations and discrepancies in the literature pertaining to nicotine metabolism, investigators in future studies need to recognize and better control these host factors. Recent advances in the understanding of nicotine metabolism have suggested new approaches to elucidating underlying mechanisms of certain toxic effects associated with cigarette smoking.

Determination of nicotine and four metabolites in the serum of smokers by high-performance liquid chromatography with ultraviolet detection

A simple and reliable reversed-phase high-performance liquid chromatographic method with ultraviolet detection is described for the quantitation of nicotine and its metabolites cotinine, trans-3'-hydroxycotinine, norcotinine and cotinine N-oxide in human serum. The analytes and the internal standard, N-ethylnorcotinine, were extracted by solid-phase extraction before chromatography. Two different columns and mobile phases with gradient systems were used. The detection limit of the assay was 10 ng/ml for nicotine, 3 ng/ml for cotinine N-oxide and 5 ng/ml for cotinine, trans-3'-hydroxycotinine and norcotinine. The concentrations of nicotine and its metabolites in the serum of 12 cigarette smokers are reported.