Sensitive determination of Fluoxetine and Citalopram antidepressants in urine and wastewater samples by liquid chromatography coupled with photodiode array detector.

A new analyte separation and preconcentration method for the trace determination of antidepressant drugs, Fluoxetine (FLU) and Citalopram (CIT) in urine and wastewaters, was developed based on HPLC-DAD analysis after magnetic solid phase extraction (MSPE). In the proposed method, FLU and CIT were retained on the newly synthetized magnetic sorbent (Fe3O4@PPy-GO) in the presence of buffer (pH 10.0) and then were desorbed into a lower volume of acetonitrile prior to the chromatographic determinations. Before HPLC analysis, all samples were filtered through a 0.45 µm PTFE filter. Experimental parameters such as interaction time, desorption solvent and volume, and pH were studied and optimized in order to establish the detection limit, linearity, enrichment factor and other analytical figures of merit under optimum operation conditions. In the developed method, FLU and CIT were analyzed by diode array detector at the corresponding maximum wavelengths of 227 and 238 nm, respectively, by using an isocratic elution of 60% pH 3.0 buffer, 30% acetonitrile, and 10% methanol. By using the optimum conditions, limit of detections for FLU and CIT were 1.58 and 1.43 ng mL-1, respectively, while the limit of quantifications was 4.82 and 4.71 ng mL-1, respectively. Relative standard deviations (RSD%) for triplicate analyses of model solutions containing 100 ng mL-1 target molecules were found to be less than 5.0 %. Finally, the method was successfully applied to urine (both simulated and real healthy human) and wastewater samples, and quantitative results were obtained in recovery experiments.

Gelatin microsphere coated Fe3O4@graphene quantum dots nanoparticles as a novel magnetic sorbent for ultrasound-assisted dispersive magnetic solid-phase extraction of tricyclic antidepressants in biological samples.

Gelatin microsphere-coated Fe3O4@graphene quantum dots (Fe3O4@GQD@GM) were designed and synthesized as a novel sorbent via ultrasonic-assisted dispersive magnetic solid-phase extraction (UA-DMSPE) method. The synthesized sorbent was identified and confirmed by FT-IR, XRD, VSM, and SEM techniques. UA-DMSPE was combined with corona discharge ion mobility spectrometry for trace determination of desipramine, sertraline, and citalopram. Effective parameters were considered and optimized. The proposed method, under optimal conditions, showed excellent linearity in different concentration ranges (2-700 ng mL-1, R2 > 0.995), repeatability (RSD < 5.1%), good sensitivity (LODs in the range 0.6-1.5 ng mL-1), high preconcentration factor (PF = 207-218), and acceptable relative recoveries (93.5-101.8%). Eventually, this method was used to determine tricyclic antidepressants in various biological samples. Schematic presentation of the microextraction and monitoring of TCAs by ultrasonic-assisted dispersive magnetic solid phase microextraction-ion mobility spectrometry producer.

Urinary selective serotonin reuptake inhibitors across critical windows of pregnancy establishment: a prospective cohort study of fecundability and pregnancy loss.

OBJECTIVE: To prospectively investigate the association of selective serotonin reuptake inhibitor (SSRI) exposure through critical windows of pregnancy establishment with fecundability and pregnancy loss. DESIGN: Prospective cohort study using longitudinal urine measurements of common SSRIs while women are actively trying to conceive. SETTING: Four clinical sites. PATIENT(S): A total of 1,228 women without uncontrolled depression/anxiety, attempting natural conception while participating in a randomized trial of preconception-initiated low-dose aspirin. INTERVENTIONS(S): Not applicable. MAIN OUTCOME MEASURE(S): Urinary SSRIs (fluoxetine, sertraline, escitalopram/citalopram) were measured while trying to conceive and, for women who became pregnant, at weeks 0, 4, and 8 of pregnancy. Fecundability odds ratios and incidence of pregnancy loss and live birth were estimated. RESULT(S): A total of 172 women (14%) were exposed to SSRIs while trying to conceive. SSRI exposure was associated with 24% reduced fecundability, and accordingly, a nonsignificant 9% lower live birth incidence, with significantly lower live birth in fluoxetine-exposed women. SSRI exposure was not associated with subsequent pregnancy loss, whether exposure was before conception or at 0, 4, or 8 weeks of gestation, although estimates varied by specific SSRI drug. CONCLUSION(S): Women using SSRIs may have more difficulty becoming pregnant, and although SSRI exposure overall was not associated with pregnancy loss, fluoxetine deserves caution and future study. CLINICAL TRIAL REGISTRATION NUMBER: NCT00467363.

Capillary Electrophoresis Method for Determination of Escitalopram Oxalate in Urine Samples and Different Dosage Forms.

Application of capillary electrophoresis (CE) has become a rapidly growing analytical technique for the estimation of drugs in pharmaceutical dosage forms and biological fluids. In this study, an effective and sensitive method was developed for the determination of escitalopram oxalate (ESC-OX) by CE with diode-array detection at 200 nm. The separation was achieved by a fused silica capillary with 40 cm effective length (48.5 cm total, 75 µm i.d.). The background electrolyte was composed of 15 mM phosphate buffer (pH 2.5). The applied potential was 22.5 kV, and the samples were injected at 50 mbar pressure for 10 s. Metoprolol was used as an internal standard (IS). The migration time under these optimum conditions was 6.51 ± 0.07 and 6.73 ± 0.08 min for ESC-OX and IS, respectively, with total run time 7 min. The method was validated for linearity, precision, accuracy, specificity and sensitivity. The limit of detection was calculated as 3.85 and 5.07 ng mL-1 for standard and urine samples, respectively. The developed method was employed successfully for the determination of ESC-OX in different pharmaceutical dosage forms and spiked human urine after simple liquid-liquid extraction with good recovery.

Multidimensional Liquid Chromatography Employing a Graphene Oxide Capillary Column as the First Dimension: Determination of Antidepressant and Antiepileptic Drugs in Urine.

Human mental disorders can be currently classified as one of the most relevant health topics. Including in this are depression and anxiety, which can affect us at any stage of life, causing economic and social problems. The treatments involve cognitive psychotherapy, and mainly the oral intake of pharmaceutical antidepressants. Therefore, the development of analytical methods for monitoring the levels of these drugs in biological fluids is critical. Considering the current demand for sensitive and automated analytical methods, the coupling between liquid chromatography and mass spectrometry, combined with suitable sample preparation, becomes a useful way to improve the analytical results even more. Herein we present an automated multidimensional method based on high-performance liquid chromatography-tandem mass spectrometry using a lab-made, graphene-based capillary extraction column connected to a C8 analytical column to determined five pharmaceutical drugs in urine. A method enhancement was performed by considering the chromatographic separation and the variables of the loading phase, loading time, loading flow, and injection volume. Under optimized conditions, the study reports good linearity with R2 > 0.98, and limits of detection in the range of 0.5-20 µg L-1. Afterward, the method was applied to the direct analysis of ten untreated urine samples, reporting traces of citalopram in one of them. The results suggest that the proposed approach could be a promising alternative that provides direct and fully automated analysis of pharmaceutical drugs in complex biological matrices.

Application of LC-ESI-MS/MS Method for Analysis of Escitalopram Oxalate in Human Urine and Pharmaceutical Dosage Forms.

An effective and sensitive liquid chromatographic-electrospray ionization tandem mass-spectrometric (LC-ESI-MS/MS) method was developed and validated for quantification of escitalopram oxalate (ESC-OX), antidepressant drug in spiked human urine and pharmaceutical formulations. In this work, simple liquid-liquid extraction was optimized and used for extraction of cited drug from urine samples. The chromatographic separation was attained within 6 min including re-equilibration time by using gradient elution with 0.1% formic acid in acetonitrile and 0.1% formic acid in water as mobile phase, Zorbax Eclipse RP C18 (50 × 2.1 mm) column was used with a particle size of 1.8 µm; the flow-rate was 0.35 mL min-1. Ion signal m/z 262.0 and 109.0 for ESC-OX product ions were monitored at positive ESI mode. Validation of the method was carried out according to the ICH Q2 (R1) guidelines and EMEA criteria. The method was linear over 79-196,450 pg mL-1 with a regression of 0.9999 and 0.9993 for both standard and urine samples. The LOD was 3.88 and 10.66 pg mL-1 for standard and urine samples, respectively, while lower limit of quantification was 79 pg mL-1.

Comparative performances of a bare graphite-polyurethane composite electrode unmodified and modified with graphene and carbon nanotubes in the electrochemical determination of escitalopram.

A bare composite graphite-polyurethane electrode (EGPU) and two other modified with graphene (EGPU-GR) and functionalized multi-walled carbon nanotubes (EGPU-CNTs) were prepared and compared regarding their voltammetric response to escitalopran (EST). The modifiers were characterized by Raman spectroscopy and the resulting electrode materials by contact angle measurements with a hydrophilicity character in the ascending order for the composites: GPU > GPU-GR > GPU-CNTs and scanning electron microscopy (SEM). The electroactive areas of the EGPU, EGPU-GR, and EGPU-CNTs were 0.065, 0.080, and 0.092cm2, respectively, calculated from the chronocoulometry using K3[Fe(CN)6] as a probe and the Cottrell equation. The cyclic voltammograms obtained for EST indicated irreversible electrochemical behavior, with an anodic peak at ca. +0.80V (νs. SCE). These measurements were carried out with the three electrodes, and comparison of the analytical responses led to the EGPU-GR electrode being selected for use in the subsequent experiments. Under optimal conditions, square wave and differential pulse voltammetry at EGPU-GR presented linear dynamic ranges between 1.5 × 10-6 and 1.2 × 10-5mol L-1, with a detection limit of 2.5 × 10-7molL-1 (SWV) and 1.5 × 10-6 and 1.2 × 10-5molL-1, with a detection limit of 3.2 × 10-7molL-1 (DPV) for EST. The proposed method was applied for the quantification of EST in synthetic urine and cerebrospinal fluid samples, offering advantages including simplicity of fabrication, no requirement for analyte preconcentration and surface renewal, fast response, and selectivity.

An Acute Ocfentanil Fatality: A Case Report with Postmortem Concentrations.

A 24-year-old man known to consume illegal drugs was found dead in his apartment. A reclosable plastic zipper bag containing several hundred milligrams of a brown powder was found close to the dead body and the first assumption of the investigators was death due to heroin intoxication. Therefore, a legal autopsy was ordered. The following toxicological analysis revealed ocfentanil in urine and in the brown powder. Four different approaches for the determination of the ocfentanil concentrations in peripheral whole blood are described. Enrichment of ocfentanil from the powder was realized. With this reference, it was possible to determine the ocfentanil concentration in the seized powder to be 0.91%. Concentrations of ocfentanil were also determined in the sampled body fluids using the standard addition procedure. In peripheral blood 9.1 µg/L, in heart blood 27.9 µg/L and in urine 480 µg/L were measured. In addition, the antidepressant citalopram, the neuroleptic quetiapine and cannabinoids were found in urine and subsequently quantified in peripheral blood.

Enantioselective extraction of (+)-(S)-citalopram and its main metabolites using a tailor-made stir bar chiral imprinted polymer for their LC-ESI-MS/MS quantitation in urine samples.

This paper reports the application of a chiral imprinted polymer (CIP)-coated stir bar for the selective extraction of (+)-(S)-citalopram (SCIT) and its main metabolites, (+)-(S)-desmethylcitalopram (SDCIT) and (+)-(S)-didesmethylcitalopram (SDDCIT), from urine samples. The developed device has been demonstrated to be capable of selectively extracting the three target analytes from urine samples without saturating the imprinted sites. A CIP-coated stir bar sorptive extraction procedure (CIP-SBSE) is proposed for the isolation of SCIT, SDCIT and SDDCIT followed by their subsequent analysis using liquid chromatography ion trap mass spectrometry (LC-ITMS). Deuterated SCIT-d6 was used as an internal standard. The method was validated using a standard procedure, which revealed that a quantification of 5 ng mL(-1) was obtained in urine samples and that the accuracy and precision were within the established values while no matrix effect was observed.

Rapid determination of letrozole, citalopram and their metabolites by high performance liquid chromatography-fluorescence detection in urine: Method validation and application to real samples.

This work reports the validation of a high precision and accuracy method for the simultaneous determination of letrozole, citalopram and their metabolites in urine by high performance liquid chromatography with fluorescence detection. Dilution (urine:mobile phase, 1:2, v/v) was the only sample preparation step. The separation was carried out in a Kromasil C(18) (150mm×4.6mm) column, and the mobile phase was phosphate buffer 80mM (pH 3.0) and acetonitrile (65:35, v/v) at a flow rate of 1.0mL/min. The analytes were detected at 295nm after excitation at 230nm. Linearity was observed in the range of 1.0-1000ng/mL for letrozole and its metabolite and 2.5-1000ng/mL for citalopram and their metabolites, with limits of detection and quantification between 0.09-1.0 and 0.27-1.65ng/mL, respectively. The precisions were satisfactory with RSDs between 0.17 and 5.71%. The accuracy was studied by spiking three urines from healthy female volunteers, and the recoveries were from 85 to 103%. The method was applied to urine samples from women under treatment for breast cancer and depression diseases.

Arrays of SnO2 nanorods as novel solid phase microextraction for trace analysis of antidepressant drugs in body fluids.

The arrays of tin oxide nanorods-solid phase microextraction (ATN-SPME) fibre coupled with the high performance liquid chromatography (HPLC) method was developed for simultaneous determination of selective serotonin reuptake inhibitors (SSRI), citalopram and fluoxetine, in human urine and plasma samples. The variables of interest in the Direct-SPME (D-SPME) were extraction time, pH, ion strength or salt percentage and desorption time of analytes from the fibre. These factors were optimised by using a Box-Behnken design and the response surface equations were developed. The optimal experimental conditions obtained from this statistical evaluation included: the salt percentage (30%, w/v), NaOH volume (6.5 µl from a 1 M solution), extraction time (10 min) and desorption time (30 min) for drugs in the plasma sample and The salt percentage (30%, w/v), NaOH volume (100 µl from a 1 M solution), extraction time (18 min) and desorption time (23 min) for drugs in the urine sample. A satisfactory reproducibility for the extraction from urine and plasma samples (R.S.D.<10%) was obtained. The linearity for urine and plasma ranged from 1 to 5×10(5) ng ml(-1) with a detection limit of 0.2 ng ml(-1) for citalopram and 0.5 ng ml(-1) for fluoxetine, which covered the typical urinary concentrations obtained for citalopram and fluoxetine.

Synthesis of molecularly imprinted polymer as a sorbent for solid phase extraction of citalopram from human serum and urine.

This paper describes a new method for the determination of citalopram in biological fluids using molecularly imprinted solid-phase extraction as the sample cleanup technique combined with high performance liquid chromatography. The molecularly imprinted polymers were prepared using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinker, chloroform as porogen and citalopram hydrobromide as the template molecule. The novel imprinted polymer was used as a solid-phase extraction sorbent for the extraction of citalopram from human serum and urine. Effective parameters on citalopram retention were studied. The optimal conditions for molecularly imprinted solid-phase extraction consisted of conditioning with 1 mL methanol and 1 mL of deionized water at neutral pH, loading of citalopram sample (50 µg L(-1)) at pH 9.0, washing using 1 mL acetone and elution with 3 × 1 mL of 10 % (v/v) acetic acid in methanol. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of citalopram. Results from the HPLC analyses showed that the calibration curve of citalopram using MIP from human serum and urine is linear in the ranges of 1-100 and 2-120 µg L(-1) with good precisions (2.5 and 1.5 % for 10.0 µg L(-1)), and recoveries (between 82-86 and 83-85 %), respectively.

Micellar electrokinetic chromatographic method for the determination of letrozole, citalopram and their metabolites in human urine.

A new micellar electrokinetic chromatographic method has been developed to analyse human urine samples containing a combination of a drug used for the treatment of breast cancer (letrozole), an antidepressant (citalopram) and their main metabolites. Best results were obtained by using 15 mM borate buffer (pH 9.2) containing 20 mM sodium dodecyl sulphate and 12% (v/v) 2-propanol as the background electrolyte. The separation was performed through a fused silica capillary at 40 degrees C with the application of 6s (3.45 kPa) of hydrodynamic injection and 30 kV of separation voltage. Detection wavelength was 240 nm. Under these conditions, the migration times for all the studied compounds were ranged between 3.0 and 8.0 min. Linearity ranges were determined as 0.4-5.0 microg/mL for all the compounds. Detection limits between 12.5 and 25 ng/mL were determined in urine samples. According to the validation study, the developed method has been proven to be accurate, precise, sensitive, specific, rugged and robust. This method has been used to determine letrozole, citalopram and their metabolites in human urine at clinical levels. Prior to determination, the samples are purified and enriched by means of an extraction-preconcentration step with a preconditioned C(18) cartridge and by eluting the compounds with methanol. The developed method was applied to the determination of these analytes in three urine samples from patients undergoing treatment with letrozole or citalopram.

Simultaneous determination of citalopram, fluoxetine and their main metabolites in human urine samples by solid-phase microextraction coupled with high-performance liquid chromatography.

A liquid chromatography method was developed for the determination of some frequently prescribed selective serotonin re-uptake inhibitors (SSRI) - citalopram and fluoxetine - and its main metabolites - demethylcitalopram, didemethylcitalopram and norfluoxetine - in human urine samples, using a previous stage of solid-phase microextraction. All the extraction parameters influencing adsorption (extraction time, temperature, pH, ion strength and organic modifier addition) and desorption (desorption time and desorption solvent mixture composition) of the analytes on the fiber have been studied. A satisfactory reproducibility for extraction from urine samples (R.S.D.<10%) was obtained. The linearity for urine ranged from 0.05 to 2 mg l(-1) with limits of detection close to 0.01 mg l(-1), which cover the typical urinary concentrations obtained for citalopram, fluoxetine and their metabolites.

Escitalopram effects on insula and amygdala BOLD activation during emotional processing.

RATIONALE: The amygdala and insular cortex are integral to the processing of emotionally salient stimuli. We have shown in healthy volunteers that an anxiolytic agent, lorazepam, dose-dependently attenuates activation of limbic structures. OBJECTIVE: The current study investigated whether administration of a selective serotonin reuptake inhibitor (SSRI), escitalopram, alters the activation of limbic structures. We hypothesized that subchronic (21 days) SSRI treatment attenuates the activation of the amygdala and insula during processing of emotional faces. MATERIALS AND METHODS: Thirteen healthy volunteers participated in a double-blind, placebo-controlled, crossover, randomized study. After 21 days of treatment with either escitalopram or placebo, participants underwent functional magnetic resonance imaging (fMRI) during which all subjects completed an emotion face assessment task, which has been shown to elicit amygdala and insula activation. RESULTS: Subjects activated the bilateral insula and amygdala after treatment with both escitalopram and placebo. In subjects who were adherent to the protocol (as evidenced by sufficiently high urine concentrations of escitalopram), a reduction in amygdala activation was seen in the escitalopram condition compared to placebo. CONCLUSION: The current investigation provides further evidence for the mechanism of action of SSRIs through the attenuation of activation in brain regions responsible for emotion processing and provides support for the use of blood oxygenation level-dependent fMRI with pharmacological probes to help identify the specific therapeutic effect of these agents in patients with anxiety and mood disorders.

Rapid on-line extraction and quantification of escitalopram from urine using sol-gel columns and mass spectrometric detection.

A fast and easy way to quantify escitalopram in urine has been developed. A capillary with a silica based monolithic bed inside is used to extract escitalopram from urine and the for mass spectrometry detrimental matrix is washed away by applied pressure. The analyte is eluted by a solution containing organic modifier and directly electrosprayed into a time-of-flight mass spectrometer, ESI-TOF-MS. This method makes it possible to load large volumes of sample onto the column and preconcentrate escitalopram on-line before detection. Standard addition of escitalopram to the urine sample gave a linear calibration curve (R(2)=0.988). The analyzed sample was found to contain an escitalopram concentration of 0.62 ng/ml, well in line with earlier publications. The calculated LOD was 10 pg/ml and LOQ was 34 pg/ml as compared to earlier reports with a LLOQ of 1 ng/ml. The intra day variation of the escitalopram peak area is less than 6.3%.

The effect of CYP2C19 substrate on the metabolism of melatonin in the elderly: A randomized, double-blind, placebo-controlled study.

The metabolism of melatonin to 6-sulphatoxymelatonin (aMT6S) and N-acetylserotonin (NAS) is catalyzed by cytochrome-P450 (CYP) isozymes CYP1A2 and CYP2C19 respectively. We studied the in vivo effect of CYP2C19 substrate (citalopram, omepratzole, or lansopratzole) on the metabolism of endogenous and exogenous melatonin by measuring the excretion of urinary aMT6S, the main metabolite of melatonin, and a reliable estimate of plasma melatonin in 15 insomniac psychogeriatric inpatients. The effect of melatonin treatment on sleep parameters was also assessed. The patients with or without CYP2C19 substrate were treated for 21 days randomly in a double-blind manner with placebo or 2 mg exogenous melatonin orally. aMT6S excretions were measured radioimmunologically from night urine at baseline (day 0), on day 21, and one day after the treatment was discontinued (day 22). Sleep parameters were assessed using the Sleep Assessment Scale and the Sleep Quality Scale. In the control patients receiving only melatonin, aMT6S excretion increased 72-fold and returned to baseline on day 22. In the patients receiving melatonin + CYP2C19 substrate, aMT6S excretion increased 156-fold and was, on day 22, still 6.4-fold higher than at baseline (p = 0.04). The 22/0 day aMT6S excretion ratio was 10-fold higher in the patients treated with melatonin + CYP2C19 substrate when compared with that in the subjects treated with placebo + CYP2C19 substrate (p = 0.02). CYP2C19 substrate did not affect the metabolism of endogenous melatonin. The sleep parameters in the patients on melatonin treatment did not differ from those in the patients treated with placebo. In conclusion, it may be inferred that CYP2C19 substrate slows the metabolism of exogenous melatonin and increases its bioavailability, as shown by the augmented excretion of aMT6S, probably by inhibiting the conversion of melatonin to NAS via CYP2C19 isozyme. Melatonin therapy may not affect the sleep parameters in our psychogeriatric inpatients.

Screening of citalopram, fluoxetine and their metabolites in human urine samples by gas chromatography-mass spectrometry. A global robustness/ruggedness study.

Capillary gas chromatography with mass spectrometry detection in SIM mode (GC-MS-SIM) has been used for the analysis of citalopram (CIT), fluoxetine (FLX), and all of their metabolites in urine samples. The instrumental parameters affecting GC separation and MS-SIM detection were investigated. A validation procedure was performed on urine matrix and a simultaneous robustness/ruggedness evaluation is also presented in this paper. An optimized solid-phase extraction (SPE) has been applied, reaching in this way to limits of detection (LODs) between 0.7 ng L(-1) (CIT) and 33.6 microg L(-1) (CIT-PA). A pharmacokinetic screening in clinical urine samples has been also carried out.

Enantiomeric screening of racemic citalopram and metabolites in human urine by entangled polymer solution capillary electrophoresis: an innovatory robustness/ruggedness study.

Several CE methods have been developed to achieve the chiral separation of citalopram (CIT) and its metabolites demethylcitalopram (DCIT), didemethylcitalopram (DDCIT), and citalopram N-oxide (CIT-NO). All of these compounds were present as racemic mixtures. The best method, which led to the first ever chiral screening of CIT, DCIT, DDCIT, and CIT-NO, involved the use of carboxymethyl-gamma-CD (CM-gamma-CD) and the entangled polymer hydroxypropylmethylcellulose (HPMC) as chiral and selectivity additives, respectively, in the buffer system. In an effort to improve the selectivity and sensitivity of the method, the chemical and instrumental parameters were optimized. The best conditions were short-end anodic hydrodynamic injection (6 s, 0.7 psi); as BGE pH 5, 20 mM phosphate buffer, 0.2% w/v CM-gamma-CD, 0.05% w/v HPMC; voltage of 28 kV with a ramp applied (0.4 s); cartridge temperature of 20 degrees C; detection at 205 nm. In addition, a simple and rapid achiral CE method for the determination of citalopram propionic acid (CIT-PA, the only anionic metabolite of CIT) is also reported for the first time. Prior to the electrophoretic procedure it was necessary to apply an extraction and preconcentration step to obtain analytes from the human urine samples. This was achieved using an optimized SPE process. Moreover, an innovatory experimental and statistical design approach, which involves the simultaneous evaluation of the global robustness and ruggedness effects, was applied. Both of the proposed methods proved to be very useful in the chiral pharmacokinetic screening of CIT and related metabolites in clinical human urine samples.

A comparison of methods for alignment of NMR peaks in the context of cluster analysis.

This paper compares the performance of two recently developed algorithms and methods for peak alignment of first-order NMR data of complex biological samples. The NMR spectra of such samples exhibit variations in peak position and peak shape due to variations in the sample matrix and to instrumental instabilities. The first method comprises an alignment of spectral segments with linear interpolation and shift correction to accommodate correspondence between a target and a test spectrum by a beam search or genetic algorithm. The second method is based on peak picking and needle vector representation of the NMR data with subsequent breadth-first search to establish shift corrections between the target and the test spectrum. The two proposed peak alignment methods and their respective merits are discussed for a real metabonomics application. Both alignment methods have been shown to enhance the interpretability of the resulting multivariate models, thereby increasing the prospect of detecting and following the onset of subtle biological changes reflected in the NMR data.