液相色谱-电喷雾串联质谱法同时检测鸡组织中5种抗病毒类药物的残留量

建立了鸡组织中抗病毒类药物多残留检测的液相色谱-电喷雾串联质谱法(LC-ESI-MS/MS)。采用三氯乙酸-乙腈溶液提取鸡组织中的金刚烷胺、金刚乙胺、美金刚、咪喹莫特和吗啉胍,离心过滤后经强阳离子交换柱(SCX)净化,色谱柱Xamide(100 mm×2.1 mm, 5 μm)分离,多反应监测(MRM)正离子扫描方式进行质谱检测。结果表明,鸡组织与鸡肝中5种药物的检出限为0.06～0.30 μg/kg,定量限为0.2～1.0 μg/kg。当5种药物的添加水平为0.2～10.0 μg/kg时,在鸡肉中的平均回收率为72.3%～94.2%,相对标准偏差(RSD)(n=6)为3.5%～11.3%;在鸡肝中的平均回收率为70.8%～92.7%, RSD(n=6)为5.3%～12.6%。该方法选择性好,抗干扰能力强,可作为鸡肉和鸡肝中抗病毒药物残留检测的确证方法。     

Simultaneous determination of niacin and pyridoxine at trace levels by using diode array high‐performance liquid chromatography and liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry

A highly sensitive and simple diode‐array high‐performance liquid chromatography and liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry method was developed for the simultaneous determination of niacin and pyridoxine in pharmaceutical drugs, tap water, and wastewater samples. To determine the in vivo behavior of niacin and pyridoxine, analytes were subjected to simulated gastric conditions. The calibration plots of the diode‐array high‐performance liquid chromatography and liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry method showed good linearity over a wide concentration range with close to 1.0 correlation coefficients for both analytes. The limit of detection/limit of quantitation values for liquid chromatography quadrupole time‐of‐flight tandem mass spectrometry analysis were 1.98/6.59 and 1.3/4.4 μg/L for niacin and pyridoxine, respectively, while limit of detection/limit of quantitation values for niacin and pyridoxine in high‐performance liquid chromatography analysis were 3.7/12.3 and 5.7/18.9 μg/L, respectively. Recovery studies were also performed to show the applicability of the developed methods, and percentage recovery values were found to be 90–105% in tap water and 94–97% in wastewater for both analytes. The method was also successfully applied for the qualitative and quantitative determination of niacin and pyridoxine in drug samples.     

High‐performance liquid chromatography with diode array detection method for the simultaneous determination of seven selected phosphodiesterase‐5 inhibitors and serotonin reuptake inhibitors used as male sexual enhancers

This work presents a simple, sensitive and generic high‐performance liquid chromatography with diode array detection method for the simultaneous determination of seven drugs prescribed for the treatment of erectile dysfunction and premature ejaculation. Investigated drugs include the phosphodiesterase‐5 inhibitors: sildenafil, tadalafil, and vardenafil, in addition to the selective serotonin reuptake inhibitors: dapoxetine, duloxetine, fluoxetine, and paroxetine. The drugs were separated using a Waters C8 column (4.6 × 250 mm, 5 μm) with the mobile phase consisting of phosphate buffer pH 3, acetonitrile and methanol in the ratio 60:33:7. The flow rate was 1.2 mL/min, and quantification was based on measuring peak areas at 225 nm. Peaks were perfectly resolved with retention times 3.3, 3.9, 6.4, 7.5, 9.5, 10.7, and 13.4 min for vardenafil, sildenafil, paroxetine, duloxetine, dapoxetine, fluoxetine, and tadalafil, respectively. The developed method was validated with respect to system suitability, linearity, ranges, accuracy, precision, robustness, and limits of detection and quantification. The proposed method showed good linearity in the ranges 5–500, 2–200, 2–200, 3–300, 1.5–150, 2–200, and 2–200 μg/mL for sildenafil, tadalafil, vardenafil, dapoxetine, duloxetine fluoxetine, and paroxetine, respectively. The limits of detection were 0.18–0.38 μg/mL for the analyzed compounds. The applicability of the proposed method to real life situations was assessed through the analysis of commercial tablets, and satisfactory results were obtained.     

Chromatography column comparison and rapid pretreatment for the simultaneous analysis of amantadine,rimantadine, acyclovir,ribavirin, and moroxydine in chicken muscle by ultra high performance liquid chromatography and tandem mass spectrometry

In this work, a chromatography column comparison and rapid pretreatment development were carried out. A multi‐class method was built based on the quick, easy, cheap, effective, rugged, and safe pretreatment method with hydrophilic interaction ultra high performance liquid chromatography and tandem mass spectrometry for the high‐throughput analysis of five antivirals in chicken muscle. The HSS T3 column, BEH HILIC column and BEH Amide column were studied, and their chemical functionalities and chromatographic separation effectiveness were compared. The BEH Amide column was selected to perform the mass spectrometry analysis under the hydrophilic interaction chromatography mode. First, a different strategy without adding MgSO₄ and NaCl into the muscle samples was considered. Then, different concentrations of formic acid, acetic acid, and ammonia in acetonitrile were compared for better extraction efficiency. Nine sorbents (C₁₈, PSA, NH₂, Florisil, Alumina‐B, Alumina‐N, PestiCarb, NANO, and NANO‐NH₂) were studied. The optimized procedure consisted of the use of 10% acetic acid in acetonitrile for the extraction solvent and NANO‐NH₂ for clean‐up. NANO‐NH₂ had not been applied in other matrix and pollutants so far. The developed method provided favorable trueness, precision, and acceptable matrix effect. Meanwhile, the method was sensitive, the limits of detection of amantadine, rimantadine, acyclovir, ribavirin, and moroxydine achieved were 0.56, 0.50, 0.30, 2.22, and 0.51 μg/kg, respectively, and were successfully applied for the routine detection of antivirals in the chicken samples.     

Determination of a metabolite of nifursol in foodstuffs of animal origin by liquid–liquid extraction and liquid chromatography with tandem mass spectrometry

An analytical method has been developed for the detection of a metabolite of nifursol, 3,5‐dinitrosalicylic acid hydrazide, in foodstuffs of animal origin (chicken liver, pork liver, lobster, shrimp, eel, sausage, and honey). The method combines liquid chromatography and tandem mass spectrometry with liquid–liquid extraction. Samples were hydrolyzed with hydrochloric acid and derivatized with 2‐nitrobenzaldehyde at 37°C for 16 h. The solutions of derivatives were adjusted to pH 7.0−7.5, and the metabolite was extracted with ethyl acetate. 3,5‐Dinitrosalicylic acid hydrazide determination was performed in the negative electrospray ionization method. Both isotope‐labeled internal standard and matrix‐matched calibration solutions were used to correct the matrix effects. Limits of quantification were 0.5 μg/kg for all samples. The average recoveries, measured at three concentration levels (0.5, 2.0, and 10 μg/kg) were in the range of 75.8–108.4% with relative standard deviations below 9.8%. The developed method exhibits a high sensitivity and selectivity for the routine determination and confirmation of the presence of a metabolite of nifursol in foodstuffs of animal origin.     

Immunoaffinity Chromatography Clean-Up and LC for Analysis of Salinomycin and Narasin in Chicken Muscle

A method has been developed for simultaneous analysis of salinomycin and narasin in chicken muscle. Muscle samples were extracted with acetonitrile. Clean-up of the extracts on an immunoaffinity chromatography column was followed by liquid chromatography with postcolumn derivatisation and UV–visible detection at 520 nm. The immunoaffinity columns were prepared by coupling the anti-salinomycin monoclonal antibody to CNBr-activated Sepharose 4B. When chicken muscle fortified at 5, 25, and 50 ng g^?1 was analyzed, intra-assay mean recoveries of salinomycin and narasin were in the ranges 87.5–93.1 and 86.2–94.3%, respectively, with relative standard deviation (RSD) of 4.7–6.2 and 2.4–5.7%. Inter-assay mean recoveries were 86.0–93.0 and 86.0–92.1%, respectively, with RSD of 4.8–6.5 and 5.8–7.4%. The limit of detection of the method was 2.5 ng g^?1 for both drugs in chicken muscle.     

Ultra high performance liquid chromatography with photodiode array detector and quadrupole time‐of‐flight tandem mass spectrometry coupled with discriminant analysis to evaluate Angelicae pubescentis radix from different regions

A rapid and effective method was developed for the qualitative and quantitative analysis of the major chemical constituents in Angelicae pubescentis radix by ultra high performance liquid chromatography with photodiode array detection and quadrupole time‐of‐flight tandem mass spectrometry. The chromatographic separation was achieved on an ACQUITY UHPLC BEH C₁₈ column (2.1 × 100 mm, 1.7 μm). Nine phenolic acids, 30 coumarins, bisabolangelone, and adenosine were identified by quadrupole time‐of‐flight tandem mass spectrometry. All calibration curves exhibited good linearity (r > 0.9996) within the linear ranges. The relative standard deviation calculated for intraday and interday precision, stability, and accuracy were <5%. The mean recovery ranged from 95.8 to 106%. The overall limits of detection and quantification were 0.025–0.160 and 0.100–0.560 μg/mL, respectively. Discriminant analysis was investigated as a method for evaluating the quality of the samples with 100% correction in their classification. The results demonstrated that the developed method could successfully be used to differentiate samples from different regions and could be a helpful tool for detection and confirmation of the quality of traditional Chinese medicines.     

A fast and accurate isotope dilution GC‐IT‐MS/MS method for determination of eugenol in different tissues of fish: Application to a depletion study in mandarin fish

An accurate, rapid and effective method was established for determination of eugenol in plasma, muscle, skin, liver, kidney and gill of fish using gas chromatography–ion trap tandem mass spectrometry. Samples of muscle, skin, liver, kidney and gill were prepared using the modified QuEChERS (quick, easy, cheap, effective, rugged and safe) procedure, and a plasma sample was prepared by a liquid–liquid extraction procedure. Eugenol was monitored in <7 min using an electron‐ionization source in MS/MS mode and quantified by an internal standard of eugenol‐d₃. The limit of detection was 5.0 μg/kg, and the limit of quantification was 10.0 μg/kg. The calibration curve was linear in the range of 5–1000 μg/L (R² = 0.9996). Intra‐ and inter‐day precisions of eugenol expressed as relative standard deviation were within 9.74%, and the accuracy exhibited a relative error ranging from −2.20 to 8.89%. The developed method was successfully used to study the elimination regularity of eugenol in mandarin fish.     

超高效液相色谱-电喷雾串联质谱法同时分析鸡肉中7种氟喹诺酮类药物残留

建立了一种同时测定鸡肉中7种氟喹诺酮类药物残留的超高效液相色谱-电喷雾串联质谱确证分析方法(UPLC-ESI-MS/MS)。样品经酸化乙腈提取、正己烷脱脂和HLB固相萃取柱净化,采用ACQUITY UPLCTM BEH C18色谱柱(50 mm×2.1 mm,1.7 μm)分离,以0.1%甲酸水溶液和乙腈作为流动相进行梯度洗脱,电喷雾质谱检测,正离子多反应监测模式进行定性和定量分析。7种药物在5～100 μg/kg范围内线性关系良好,相关系数(r2)均大于0.99;以5,25,50 μg/kg3个浓度水平进行添加回收试验,7种药物的平均回收率在79.2%～108.6%之间,相对标准偏差为4.2%～8.9%,方法的检出限(LOD)为0.2～1.4 μg/kg。方法重现性好、灵敏度高、分析时间短、确证能力强,适用于鸡肉中氟喹诺酮类药物多残留的确证检测。     

Liquid chromatography–tandem MS/MS method for simultaneous quantification of paracetamol,chlorzoxazone and aceclofenac in human plasma: An application to a clinical pharmacokinetic study

A facile, fast and specific method based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the simultaneous quantitation of paracetamol, chlorzoxazone and aceclofenac in human plasma was developed and validated. Sample preparation was achieved by liquid–liquid extraction. The analysis was performed on a reversed‐phase C₁₈ HPLC column (5 μm, 4.6 × 50 mm) using acetonitrile–10 mM ammonium formate pH 3.0 (65:35, v/v) as the mobile phase where atrovastatin was used as an internal standard. A very small injection volume (3 μL) was applied and the run time was 2.0 min. The detection was carried out by electrospray positive and negative ionization mass spectrometry in the multiple‐reaction monitoring mode. The developed method was capable of determining the analytes over the concentration ranges of 0.03–30.0, 0.015–15.00 and 0.15–15.00 μg/mL for paracetamol, chlorzoxazone and aceclofenac, respectively. Intraday and interday precisions (as coefficient of variation) were found to be ≤12.3% with an accuracy (as relative error) of ±5.0%. The method was successfully applied to a pharmacokinetic study of the three analytes after being orally administered to six healthy volunteers.     

Assay and stability‐indicating micellar electrokinetic chromatography method for the simultaneous determination of valacyclovir,acyclovir and their major impurity guanine in pharmaceutical formulations

A micellar electrokinetic chromatography (MEKC) method for the simultaneous determination of the antiviral drugs acyclovir and valacyclovir and their major impurity, guanine, was developed. The influences of several factors (surfactant and buffer concentration, pH, applied voltage, capillary temperature and injection time) were studied. Using tyramine hydrochloride as internal standard, the analytes were all separated in about 4 min. The separation was carried out in reversed polarity mode at 28°C, 25 kV and using hydrodynamic injection (15 s). The separation was effected in a fused‐silica capillary 100 μm × 56 cm and a background electrolyte of 20 mM citric acid–1 M Tris solution (pH 2.75), containing 125 mM sodium dodecyl sulphate and detection at 254 nm. The method was validated with respect to linearity, limit of detection and quantification, accuracy, precision and selectivity. Calibration curves were linear over the range 0.1–1 μg/mL (guanine) and from 0.1 to 120 μg/mL for both valacyclovir and acyclovir. The relative standard deviations of intra‐ and inter‐day migration times and corrected peak areas were less than 5.0%. The proposed method was successfully applied to the determination of the analytes in tablets and creams. From the previous study it is concluded that the stability‐indicating method developed for acyclovir and valacyclovir can be used for analysis of the drug in various stability samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of tetracycline antibiotics in fatty food samples by selective pressurized liquid extraction coupled with high‐performance liquid chromatography and tandem mass spectrometry

For the determination of trace residues of tetracycline antibiotics in fatty food samples, selective pressurized liquid extraction coupled with high‐performance liquid chromatography and tandem mass spectrometry was applied in this study. Copper(II) isonicotinate was first used as online cleanup adsorbent in the selective pressurized liquid extraction process. The adsorbent to sample ratio, extraction temperature, extraction time, and recycle times, etc. were optimized. The tetracyclines in food samples of pork, chicken meat, and clam meat were detected by liquid chromatography with tandem mass spectrometry. Tetracycline was found at levels of 0.32 and 0.53 μg/g and oxytetracycline was found at 0.14 and 0.21 μg/g in chicken meat and clam meat, respectively, while chlorotetracycline and deoxytetracycline were below the detection limit. The detection limit (S/N = 3) for these four tetracyclines were from 0.2 to 3.3 ng/g, the recoveries were from 75.8 to 110.5%, and relative standard deviations were from 5.5 to 13.6%. Copper(II) isonicotinate showed a higher purification capacity than other cleanup adsorbents for extraction of antibiotics in fatty food and the recovery showed predominance compared with a pressurized liquid extraction method without adsorbent. The study demonstrated that copper(II) isonicotinate would be a promising cleanup adsorbent in pressurized liquid extraction for the analysis of trace organic pollutants in complicated samples.     

Validation of a high-performance chromatographic method for determination of cefotaxime in biological samples

An analytical method for detecting and quantifying cefotaxime in plasma and several tissues is described. The method was developed and validated using plasma and tissues of rats. The samples were analyzed by reversed phase liquid chromatography (HPLC) with UV detection (254 nm). Calibration graphs showed a linear correlation (r > 0.999) over the concentration ranges of 0.5–200 μg/mL and 1.25–25 μg/g for plasma and tissues, respectively. The recovery of cefotaxime from plasma standards prepared at the concentrations of 25 μg/mL and 100 μg/mL was 98.5 ± 3.5% and 101.8 ± 2.2%, respectively. The recovery of cefotaxime from tissue standards of liver, fat and muscle, prepared at the concentration of 10 μg/g was: 89.8 ± 1.2% (liver), 103.9 ± 6.5% (fat) and 97.8 ± 2.1% (muscle). The detection (LOD) and quantitation (LOQ) limits for plasma samples were established at 0.11 μg/mL and 0.49 μg/mL, respectively. The values of these limits for tissues samples were approximately 2.5 times higher: 0.3 μg/g (LOD) and 1.25 μg/g (LOQ). For plasma samples, the deviation of the observed concentration from the nominal concentration was less than 5% and the coefficient of variation for within-day and between-day assays was less than 6% and 12%, respectively. The method was used in a pharmacokinetic study of cefotaxime in the rat and the mean values of the pharmacokinetic parameters are given.     

Development and validation of LC‐MS/MS method for simultaneous determination of sofosbuvir and daclatasvir in human Plasma: Application to pharmacokinetic study

A simple and highly sensitive liquid chromatography–tandem mass spectrometry (LC‐MS/MS) bioanalytical method was developed and fully validated for the first time for the simultaneous determination of newly discovered antiviral drugs, namely sofosbuvir (SOF) and daclatasvir (DAC) in human plasma. Tadalafil (TAD) was used as internal standard (IS). SOF, DAC and TAD (IS) were extracted from plasma using liquid–liquid extraction technique with methyl tert‐butyl ether. The chromatographic separation was carried out using ZorbaxSB‐C₁₈ column (4.6 × 50 mm,5 μm) and 5 mm ammonium formate buffer (pH 3.5)–acetonitrile (50:50, v/v) as mobile phase in an isocratic elution mode pumped at a flow rate 0.7 mL min⁻¹. The quantitation was performed on API4500 triple quadrupole tandem mass spectrometer with positive electrospray ionization interface in multiple reaction monitoring mode. Validation was applied according to US Food and Drug Administration guidelines for bio‐analytical methodswith respect to linearity, precision, accuracy, selectivity, carry‐over, stability and dilution integrity. Linearity was obtained over concentration ranges of 0.3–3000 and 3–3000 ng mL⁻¹ for SOF and DAC, respectively, by applying a weighted least‐squares linear regression method (1/x²). The proposed method could be applied successfully in bioequivalence and/or clinical studies for therapeutic drug monitoring of patients undergoing dual combination therapy as the latter combination proved more efficacious and powerful tool for the complete treatment of hepatitis C genotype 3 within 16 weeks. The suggested method has been applied successfully to pharmacokinetic studies with excellent assay ruggedness and reproducibility.     

Cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction and HPLC–DAD analysis of ezetimibe and simvastatin in human plasma and urine

A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L^?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L^?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L^?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L^?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs.     

A validated stability‐indicating ultra performance liquid chromatography method for the determination of potential process‐related impurities in eplerenone

A simple, sensitive, and accurate stability‐indicating analytical method has been developed and validated using ultra high performance liquid chromatography. The developed method is used to evaluate the related substances of eplerenone (EP). The degradation behavior of EP under stress conditions was determined, and the major degradants were identified by ultra high performance liquid chromatography with tandem mass spectrometry. The chromatographic conditions were optimized using an impurity‐spiked solution, and the samples, generated from forced degradation studies. The resolution of EP, its potential impurities, and its degradation products was performed on a Waters UPLC BEH C₁₈ column (50 × 2.1 mm, 1.7 μm) by linear gradient elution using a mobile phase consisting of 10 mmol/L ammonium acetate adjusted to pH 4.5, methanol and acetonitrile. A photo‐diode array detector set at 245 nm was used for detection. The flow rate was set at 0.3 mL/min. The procedure had good specificity, linearity (0.02–3.14 μg/mL), recovery (96.1–103.9%), limit of detection (0.01–0.02 μg/mL), limit of quantitation (0.03–0.05 μg/mL), and robustness. The correction factors of the process‐related substances were calculated.     

分散固相萃取/液相色谱串联质谱法测定鸡肉中二硝托胺及其代谢产物残留量

建立了同时测定鸡肉中二硝托胺及其代谢产物3-氨基-5-硝基邻甲苯酰胺(3-ANOT)的分散固相萃取/液相色谱串联质谱(LC-MS/MS)分析方法。样品用乙腈提取,离心后吸取2 mL上清液,进行分散固相萃取净化,净化液以1∶4的比例用0.1%甲酸溶液混合稀释,混匀后过滤膜即可进行LC-MS/MS分析。采用Acquity BEH C18色谱柱,以0.1%甲酸溶液和乙腈为流动相进行梯度洗脱;电喷雾正负离子切换多反应监测模式检测,外标法定量。二硝托胺和3-ANOT的峰面积与其质量浓度均在1～500μg.L-1范围内呈良好线性,线性系数分别为0.999 5和0.999 4。在50～4 500μg.kg-1加标范围内,二硝托胺和ANOT的加标回收率为81%～94%,批内相对标准偏差(RSD)为2.1%～5.3%,批间RSD为4.3%～6.2%。二硝托胺和3-ANOT的检出限分别为10、14μg.kg-1,定量下限均为50μg.kg-1。该方法能满足鸡肉中二硝托胺及其代谢产物残留分析的要求。     

Simultaneous extraction and quantification of albendazole and triclabendazole using vortex‐assisted hollow‐fiber liquid‐phase microextraction combined with high‐performance liquid chromatography

A novel, simple, and rapid vortex‐assisted hollow‐fiber liquid‐phase microextraction method was developed for the simultaneous extraction of albendazole and triclabendazole from various matrices before their determination by high‐performance liquid chromatography with fluorescence detection. Several factors influencing the microextraction efficiency including sample pH, nature and volume of extraction solvent, ionic strength, vortex time, and sample volume were investigated and optimized. Under the optimal conditions, the limits of detection were 0.08 and 0.12 μg/L for albendazole and triclabendazole, respectively. The calibration curves were linear in the concentration ranges of 0.3–50.0 and 0.4–50.0 μg/L with the coefficients of determination of 0.9999 and 0.9995 for albendazole and triclabendazole, respectively. The interday and intraday relative standard deviations for albendazole and triclabendazole at three concentration levels (1.0, 10.0, and 30.0 μg/L) were in the range of 6.0–11.0 and 5.0–7.9%, respectively. The developed method was successfully applied to determine albendazole and triclabendazole in water, milk, honey, and urine samples.     

Liquid chromatography tandem mass spectrometry for the simultaneous determination of mequindox and its metabolites in porcine tissues

A rapid liquid chromatography tandem mass spectrometric method was developed for the simultaneous determination of mequindox and its five metabolites (2-isoethanol mequindox, 2-isoethanol 1-desoxymequindox, 1-desoxymequindox, 1,4-bisdesoxymequindox, and 2-isoethanol bisdesoxymequindox) in porcine muscle, liver, and kidney, fulfilling confirmation criteria with two transitions for each compound with acceptable relative ion intensities. The method involved acid hydrolysis, purification by solid-phase extraction, and subsequent analysis with liquid chromatography tandem mass spectrometry using electrospray ionization operated in positive polarity with a total run time of 15 min. The decision limit values of five analytes in porcine tissues ranged from 0.6 to 2.9 μg/kg, and the detection capability values ranged from 1.2 to 5.7 μg/kg. The results of the inter-day study, which was performed by fortifying porcine muscle (2, 4, and 8 μg/kg), liver, and kidney (10, 20, and 40 μg/kg) samples on three separate days, showed that the accuracy of the method for the various analytes ranged between 75.3 and 107.2% with relative standard deviation less than 12% for each analyte.     

Determination of cefoperazone and sulbactam in serum by HPLC‐MS/MS: An adapted method for therapeutic drug monitoring in children

A rapid, accurate and specific high‐performance liquid chromatography–tandem mass spectrometry method has been validated for the simultaneous determination of cefoperazone and sulbactam in a small volume sample for children. A Shim‐pack XR‐ODS C₁₈ column with gradient elution of water (0.1% formic acid) and acetonitrile (0.1% formic acid) solution was used for separation at a flow rate of 0.3 mL/min. The calibration curves of two analytes in serum showed excellent linearity over the concentration ranges of 0.03–10 μg/mL for cefoperazone, and 0.01–3 μg/mL for sulbactam, respectively. This method involves simple sample preparation steps and was validated according to standard US Food and Drug Administration and European Medicines Agency guidelines in terms of selectivity, linearity, detection limits, matrix effects, accuracy, precision, recovery and stability. This assay can be easily implemented in clinical practice to determine concentrations of cefoperazone and sulbactam in children.