Multi-residue method for non-steroidal anti-inflammatory drugs in plasma using high-performance liquid chromatography-photodiode-array detection. Method description and comprehensive in-house validation

Measurement uncertainty interval in case of a known relationship between precision and mean

Background: Measurement uncertainty is typically expressed in terms of a symmetric interval y±U, where y denotes the measurement result and U the expanded uncertainty. However, in the case of heteroscedasticity, symmetric uncertainty intervals can be misleading. In this paper, a different approach for the calculation of uncertainty intervals is introduced. Methods: This approach is applicable when a validation study has been conducted with samples with known concentrations. In a first step, test results are obtained at the different known concentration levels. Then, on the basis of precision estimates, a prediction range is calculated. The measurement uncertainty for a given test result can then be obtained by projecting the intersection of the test result with the limits of the prediction range back onto the axis of the known values, now interpreted as representing the measurand. Results: It will be shown how, under certain circumstances, asymmetric uncertainty intervals arise quite naturally and lead to more reliable uncertainty intervals. Conclusions: This article establishes a conceptual framework in which measurement uncertainty can be derived from precision whenever the relationship between the latter and concentration has been characterized. This approach is applicable for different types of distributions. Closed expressions for the limits of the uncertainty interval are provided for the simple case of normally distributed test results and constant relative standard deviation.

Quantification and validation of nine nonsteroidal anti-inflammatory drugs in equine urine using gas chromatography-mass spectrometry for doping control

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used in therapeutic doses in human and veterinary medicine for the treatment of inflammation, pain, and fever. A method for the simultaneous determination of nine NSAIDs, known as therapeutic prohibited substances, in equine urine was developed and fully validated according to the European Commission Decision 2002/657/EC and Association of Official Racing Chemists criteria. The validation was performed for naproxen, flunixin, ketoprofen, diclofenac, eltenac, meclofenamic acid, phenylbutazone, vedaprofen, and carprofen in equine urine in accordance with the International Screening Limits (ISL) regulated by International Federation of Horseracing Authorities. After basic hydrolysis, samples were extracted with a C18 cartridge using automated solid-phase extraction. Several derivatization reagents were investigated, and trimethylphenylammonium hydroxide/methanol (20/80, v/v) was selected. Analyses were carried out using gas chromatography-mass spectrometry with selected ion monitoring mode, but the method can be applied to a large number of analytes. The within-laboratory reproducibility was not more than 12.8% (≤15%), and mean relative recoveries ranged from 91.1% to 104.1% for inter-day and intra-day precision. The decision limits (CCα) and detection capabilities (CCβ) were evaluated at concentrations near the ISL for each therapeutic substance. The validation results demonstrated that the method is highly reproducible, easily applicable, and suitable for the analysis of some NSAIDs in equine urine that have not been previously published. Finally, the method was also applied to known positive samples.

Absorption of ibuprofen orodispersible tablets in early postoperative phase - a pharmacokinetic study

OBJECTIVE

Patient-controlled oral analgesia has gained popularity in postoperative pain management. Anesthesia and surgery delay gastrointestinal tract function and this may therefore decrease bioavailability of drugs taken by mouth. To hasten absorption, an orodispersible ibuprofen tablet has been developed. In this study, we evaluated the pharmacokinetics and feasibility of orodispersible ibuprofen tablets in spine surgery patients.

METHODS

The study design was a prospective clinical trial where each patient served as her/his own control. Fifteen patients aged 19-75 years were given two orodispersible ibuprofen 200 mg tablets the day before surgery and two more tablets immediately after surgery. Blood samples for ibuprofen concentrations were taken at intervals for 6 hours following pre- and postsurgical administration of ibuprofen.

RESULTS

The mean preoperative area under time-concentration curve for ibuprofen (AUC_0-360) was 4806 (SD 1104) min·mg/L, and after surgery it was 2141 (583) min·mg/L (mean difference 2664, 95% CI for difference 2003 to 3325, p < .001). The mean of the maximum preoperative plasma concentration of ibuprofen was three times higher, 26.7 (7.7) mg/L, than the postoperative value of 8.6 (2.1) mg/L (mean diff. 18.1, 95% CI 13.9 to 22.4, p < .001). Times to maximum concentration were similar pre- and postoperatively at 155 (58) minutes and 169 (113) minutes (p = .67). No serious or unexpected adverse events were recorded.

CONCLUSIONS

While orodispersible ibuprofen tablets were feasible, ibuprofen absorption decreased immediately after surgery compared to the day before surgery. Thus, further studies are needed to establish the adequate initial postoperative dose.

Quantification of anthelmintic drug residues in milk and muscle tissues by liquid chromatography coupled to Orbitrap and liquid chromatography coupled to tandem mass spectrometry

A simple method for the determination of some anthelmintic drugs and phenylbutazone residues in milk and muscle was developed. Following a fast and easy extraction and evaporation procedure, the extract was injected into an ultra performance liquid chromatography system coupled to a single stage Orbitrap detector. The high mass resolution of 50,000 full width at half maximum and corresponding narrow mass windows permitted a very selective and sensitive detection of analytes without requiring fragmentation of the observed [M+H](+) or [M+Na](+) ions. This eliminated some difficulties which have plagued the analysis of compounds belonging to the group of avermectins. The analytical method was validated according to the EU commission decision for Orbitrap based, but also for more traditional tandem mass spectrometry based detection and quantification. Equal repeatability but significantly higher sensitivity for critical compounds (avermectins) was obtained for the Orbitrap based detection. A result of this study was the conclusion that analytes with poor fragmentation properties (e.g. sodium-cationized molecules) can be more easily quantified by single stage high resolution mass spectrometry than by tandem mass spectrometry.

Confirmatory identification of sixteen non-steroidal anti-inflammatory drug residues in raw milk by liquid chromatography coupled with ion trap mass spectrometry

The European Council Decision 2002/657/EC established that group B substances detected in foods must be identified and confirmed on the basis of their molecular structure. To this aim, we have developed a panel of methods for unambiguous determination of sixteen non-steroidal anti-inflammatory drugs (NSAIDs) in cattle and buffalo raw milk. A multi-residue reversed-phase high-performance liquid chromatography method with photodiode array detection is described for quantitative screening analysis. For confirmatory purposes, two multi-residue reversed-phase ion trap liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) methods were developed: the former to identify salicylic acid, naproxen, carprofen, flurbiprofen, ibuprofen, meclofenamic acid, niflumic acid, flunixin and its metabolite 5-hydroxyflunixin in the negative ion mode; the latter to identify ketoprofen, suxibutazone, diclofenac, mefenamic acid, tolfenamic acid, phenylbutazone and its metabolite oxyphenbutazone in the positive ion mode. These drugs are representative of different subclasses of NSAIDs not chemically related. The methods were in-house validated, evaluating specificity and calculating the mean recoveries, repeatability, within-laboratory reproducibility, and limits of quantification. For all the NSAIDs, apart from salicylic acid and 5-hydroxyflunixin, mean recoveries ranging between 69.0% and 96.7% were measured. The qualitative identification of all drugs was attained by their MS/MS spectra in the concentration range studied. Similarly, at 5 microg/kg all NSAIDs, apart from flurbiprofen, were unambiguously confirmed.

Determination of gestagens in kidney fat by liquid chromatography tandem mass spectrometry

The use of gestagens in animal fattening is prohibited within the European Union. Recently, the use of spectrometric methods for the detection and confirmation of banned substances was made obligatory. Therefore, conventional high-performance liquid chromatographic (HPLC) methods have been superseded. It has been possible to couple a previously described HPLC method for the determination of acetyl-gestagens in kidney fat to tandem mass spectrometry (LC-MS/MS). The decision limits CCalpha and the detection capability CCbeta are found to be below the minimum required performance limit (MRPL) established for medroxyprogesterone acetate (MPA) at 1 microg kg(-1). The calculated values for CCalpha are as follows: megestrol acetate (MGA)--0.15 microg kg(-1), melengesterol acetate (MLA)--0.15 microg kg(-1), chlormadinone acetate (CMA)--0.37 microg kg(-1) and for medroxyprogesterone acetate (MPA)--0.24 microg kg(-1). The CCbeta values for these compounds have been determined as 0.19, 0.19, 0.47 and 0.32 microg kg(-1), respectively.

Rapid method for the determination of non-steroidal anti-inflammatory drugs in animal tissue by liquid chromatography–mass spectrometry with ion-trap detector

A rapid and new liquid chromatography-mass spectrometry with ion-trap detection method for the determination of meloxicam (MLX), flunixin meglumine (FLU), carprofen (CPF), and tolfenamic acid (TOLF) in animal tissue is described. MRLs between 10 and 500 microg kg(-1) in muscle and between 65 and 1000 microg kg(-1) in liver, from different animal species have been established in the EU for these compounds. After chemical hydrolysis, an organic extraction from homogenised tissue was performed. Final extract was injected in a liquid chromatograph with an ion-trap mass spectrometer with electrospray interface. Four identification points (one precursor and two product ions) and a minimum of one ion ratio was monitored for each compound. For quantitative purposes flunixin-D3 (FLU-D3) was used as internal standard. The method was validated using fortified blank muscle and liver from different animal species according to the 2002/657/EC European decision criteria. The decision limits (CCalpha) and detection capabilities (CCbeta) were determined and their values were at concentrations near the MRL for each substance.

Determination of fourteen non-steroidal anti-inflammatory drugs in animal serum and plasma by liquid chromatography/mass spectrometry

The European Union has regulated the use of non-steroidal anti-inflammatory drugs (NSAIDs) in animal production and requires its member states to detect their residues in different matrices. In this work, a detailed MS and MS/MS study by ion-trap mass spectrometry of fourteen NSAIDs is described. Two multi-residue reversed-phase LC/ESI-MS/MS methods were developed, one for the determination of salicylic acid, naproxen, carprofen, flurbiprofen, ibuprofen, niflumic acid and meclofenamic acid in the negative ion mode, and the other for the determination of ketoprofen, suxibutazone, diclofenac, mefenamic acid, tolfenamic acid, phenylbutazone and its metabolite oxyphenbutazone in the positive ion mode. It was thus possible to confirm up to 14 different NSAID residues in serum and plasma samples of farmed animals, after chromatographic separation by a linear gradient. These substances were chosen as representative of different chemical subclasses of NSAIDs. The two methods were also validated in-house at three contamination levels, evaluating specificity and calculating mean recoveries, repeatability and within-laboratory reproducibility. The MS/MS product ion spectra were successfully used for the qualitative identification of all the drugs tested. All the NSAIDs, apart from salicylic acid, were recovered in high amounts, ranging between 71.6% and 100.9%.

Pharmacokinetic applications of capillary electrophoresis: A review on recent progress

This article covers recent publications from 2003 to 2005 on the subject of pharmacokinetic applications of CE. Many analytical methods were validated and more importantly, they were shown to have sufficient sensitivities to access pharmacokinetic data on different models. Because of unique advantages, such as simplified sample preparation methods, small sample amount required, high separation power, and speedy analysis, CE-based assays were found to gain popularity not only as a second method but also as a major method for many pharmacokinetic studies.

Direct determination of niflumic acid in a pharmaceutical gel by ATR/FTIR spectroscopy and PLS calibration

A simple, rapid and convenient analytical method without sample handling procedure is proposed for the determination of niflumic acid in a pharmaceutical gel with attenuated total reflectance/Fourier transform infrared spectroscopy (ATR/FTIR). A partial least square (PLS) calibration model for the prediction of niflumic acid contents was developed using 81 and 27 spectra of standard gels as training and validation sets, respectively. The used spectral range of niflumic acid for the establishment of this model was 2300-1100 cm(-1). All spectra were obtained in the transmittance mode, then normalized and first derivative transformed. The model yielded a regression coefficient R2 equal to 1 for the training set and a root mean square error of prediction (RMSEP) equal to 0.2 for the validation set. The percentage recoveries of the method for the analysis of Niflugel ranged from 96.60 to 101.02%.

Separation of aceclofenac and diclofenac in human plasma by free zone capillary electrophoresis using N-methyl-D-glucamine as an effective electrolyte additive

Aceclofenac (A) and diclofenac (D) are effective non-steroidal anti-inflammatory drugs (NSAIDs) derived from the phenylacetic acid with pronounced antirheumatic, anti-inflammatory, analgesic and antipyretic properties. Our work proposes a new, fast-free zone capillary electrophoresis method for the simultaneous determination of aceclofenac and diclofenac in human plasma. The effect of increasing concentrations of N-methyl-D-glucamine organic base on borate run buffer was investigated. A good separation was achieved using a 40 cm x 75 microm uncoated silica capillary, 300 mmol/l sodium borate buffer, 200 mmol/l N-methyl-D-glucamine, pH 8.9, in about 3 min. Moreover, the plasma sample pre-treatment procedure was examined: acidic precipitants such as trichloroacetic acid (TCA), metaphosphoric acid (MPA), perchloric acid (PCA) or 5-sulphosalicylic acid (SSA) cause a total loss of analytes while acetonitrile allows a recovery of 97-98% of both compounds. Its simplicity and rapidity and the low analysis costs demonstrate that our method is a reliable and efficient mean for the comprehensive determination of aceclofenac and diclofenac in human plasma when pharmacokinetics studies are required.

Simultaneous determination of ni?umic acid and its prodrug, talni?umate in human plasma by high performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of niflumic acid and its prodrug, talniflumate, in human plasma. Niflumic acid and talniflumate were eluted isocratically with methanol-water (73:27, v/v, adjusted to pH 3.5 by acetic acid) at a fl ow rate of 1 mL/min. Indomethacin was used as an internal standard. Signals were monitored by an UV detector at 288 nm. Retention times of indomethacin, niflumic acid and talniflumate were 5.9, 7.2 and 13.5 min, respectively. Calibration plots were linear over the range 50-5000 ng/mL for niflumic acid and 100-5000 ng/mL for talniflumate. The limits of quantitation were 50 ng/mL for niflumic acid and 100 ng/mL for talniflumate. The intra- and inter-day relative standard deviations (RSD) of niflumic acid and talniflumate were less than 10% and the accuracies were higher than 90%. This method is rapid, sensitive and reproducible for the determination of niflumic acid and talniflumate in human plasma.

Determination by high-performance liquid chromatography of phenylbutazone in samples of plasma from fighting bulls

The purpose of this study was to investigate the possible presence of phenylbutazone in plasma samples from fighting bulls killed in 2nd and 3rd category bullrings in the province of Salamanca (Spain) in 1998, 1999 and 2000. For quantitative and qualitative determination, a high-performance liquid chromatograph was used, equipped with a photodiode-array detector and setting wavelengths at 240, 254 and 284 nm. The mobile phase optimized for the simultaneous detection of dexamethasone, betamethasone, flunixin and phenylbutazone, was 0.01 M acetic acid pH 3 in methanol (35:65 v/v) at a flow rate of 1 ml/min. Plasma samples were deproteinized with 400 microl of acetonitrile and 20 microl of the supernatant were injected directly into the chromatographic system equipped with a Lichrospher 60 RP select B column and guard column. For the quantitative analysis, standard calibration curves were made in a concentration range between 0.25 and 30 microg/ml, using betamethasone as internal standard. The retention time of phenylbutazone was 8.7 +/- 0.2 min and recovery was 83%. The detection and quantification limits were 0.016 and 0.029, respectively for A=240 nm. The study results show that 17 of the 74 samples analyzed in 1998, 18 of those from 1999 and 10 of those from 2000 were positive for phenylbutazone.

Application of f--f luminescence of terbium ion for determination of non-steroidal anti-inflammatory drug-niflumic acid

A simple, rapid and sensitive luminescence method for determination of niflumic acid (NFA) is described. The method is based on the intramolecular energy transfer from niflumic acid to terbium ion (Tb(3+)) in the presence of trioctylphosphine oxide (TOPO). Optimum conditions for the formation of the NFA-Tb(3+)-TOPO ternary complex have been investigated. The calibration graph is linear over the range 0.002--0.02 microg ml(-1). The relative standard deviation is close to 4%. The recoveries obtained by applying the method to the analysis of urine ranged from 94--102%.

Simultaneous determination of aceclofenac and diclofenac in human plasma by narrowbore HPLC using column-switching

A fully automated narrowbore high performance liquid chromatography (HPLC) with column-switching was developed for the simultaneous determination of aceclofenac and diclofenac from human plasma samples. Plasma sample (100 microl) was directly introduced onto a Capcell Pak MF Ph-1 column (20 x 4 mm I.D.) where primary separation was occurred to remove proteins and concentrate target substances using acetonitrile potassium phosphate (pH 7, 0.1 M) (14:86, v/v). The drug molecules eluted from MF Ph-1 column were focused in an intermediate column (35 x 2 mm I.D.) by the valve switching step. The substances enriched in intermediate column were eluted and separated on the narrowbore phenyl hexyl column (100 x 2 mm I.D.) using acetonitrile-potassium phosphate (pH 7, 0.02M) (33:67, v/v) when the valve status was switched back to A position. The method showed excellent sensitivity (detection limit of 10 ng ml(-1)) with small volume of samples (100 microl), good precision and accuracy, and speed (total analysis time 17 min) without any loss in chromatographic efficiency. The response was linear (r2 > or = 0.999) over the concentration range of 50-10,000 ng ml(-1).