LC-MS-MS Determination of Cyclo{(2S)-2-amino-8-[(aminocarbonyl)hydrazono] decanoyl-1-l-tryptophyl-l-isoleucyl-(2R)-2-piperidinecarbonyl} a Novel Histone Deacetylase Inhibitor in Rat Serum

A rapid and sensitive liquid chromatography-tandem mass spectrometry assay was developed for the determination of a novel histone deacetylase inhibitor, cyclo{(2S)-2-amino-8-[(aminocarbonyl)hydrazono]decanoyl-1-l-tryptophyl-l-isoleucyl-(2R)-2-piperidinecarbonyl} (SD-2007), in rat serum. The mobile phase consisted of acetonitrile and ammonium formate (10 mM) (85:15 v/v), and the flow rate was 0.25 mL min⁻¹. Chromatographic separations were achieved by isocratic elution on a C₁₈ column. Multiple reaction monitoring was based on the transition of m/z = 681.8 → 83.6 for SD-2007 and 372.1 → 176.1 for trazodone (internal standard). A linearity was observed over a concentration range from 2 to 1,000 ng mL⁻¹ (r ² > 0.999), with the lower limit of quantification at 2 ng mL⁻¹ with 100 μL of rat serum. The mean intra- and inter-day assay accuracy ranged from 98.5–109.7% to 95.2–102.7%, respectively, and the mean intra- and inter-day precision was between 4.3–11.3% and 2.9–13.3%. The developed assay was applied to a pharmacokinetic study of SD-2007 in rats after intravenous injection (dose 4 mg kg⁻¹).     

LC–MS–MS Assay for Simultaneous Quantification of Fexofenadine and Pseudoephedrine in Human Plasma

A rapid, sensitive, and simple HPLC–MS–MS method, with electro-spray ionization and cetirizine as internal standard (IS), has been developed and validated for simultaneous quantification of fexofenadine and pseudoephedrine in human plasma. The analytes were isolated from plasma by solid-phase extraction (SPE) on Oasis HLB cartridges. The compounds were chromatographed on an RP 18 column with a mixture of ammonium acetate (10 mm, pH 6.4) and methanol as mobile phase. Quantification of the analytes was based on multiple reaction monitoring (MRM) of precursor-to-product ion pairs m/z 502 → 466 for fexofenadine, m/z 166 → 148 for pseudoephedrine, and m/z 389 → 201 for cetirizine. The linear calibration range for both analytes was 2–1,700 ng mL⁻¹ (r = 0.995), based on analysis of 0.1 mL plasma. Extraction recovery was 91.5 and 80.88% for fexofenadine and pseudoephedrine, respectively. The method was suitable for analysis of human plasma samples obtained 72 h after administration of a drug containing both fexofenadine and pseudoephedrine.     

LC–ESI–MS for Rapid and Sensitive Determination of Aripiprazole in Human Plasma

A rapid, sensitive, and accurate high-performance liquid-chromatographic–mass spectrometric (HPLC–MS) method, with estazolam as internal standard, has been developed and validated for determination of aripiprazole in human plasma. After liquid–liquid extraction the compound was analyzed by HPLC on a C₁₈ column, with acetonitrile—30 mm ammonium acetate containing 0.1% formic acid, 58:42 (v/v), as mobile phase, coupled with electrospray ionization mass spectrometry (ESI-MS). The protonated analyte was quantified by selected-ion recording (SIR) with a quadrupole mass spectrometer in positive-ion mode. Calibration plots were linear over the concentration range 19.9–1119.6 ng mL⁻¹. Intra-day and inter-day precision (CV%) and accuracy (RE%) for quality-control samples (37.3, 124.4, and 622.0 ng mL⁻¹) ranged between 2.5 and 9.0% and between 1.3 and 3.5%, respectively. Extraction recovery of aripiprazole from plasma was in the range 75.8–84.1%. The method enables rapid, sensitive, precise, and accurate measurement of the concentration of aripiprazole in human plasma.     

Quantitative analysis of eletriptan in human plasma by HPLC-MS/MS and its application to pharmacokinetic study

Authors developed a simple, sensitive, selective, rapid, rugged, and reproducible liquid chromatography–tandem mass spectrometry method for the quantification of eletriptan (EP) in human plasma using naratriptan (NP) as an internal standard (IS). Chromatographic separation was performed on Ascentis Express C18, 50 × 4.6 mm, 2.7 μm column. Mobile phase was composed of 0.1% formic acid: methanol (40:60 v/v), with 0.5 mL/min flow rate. Drug and IS were extracted by liquid–liquid extraction. EP and NP were detected with proton adducts at m/z 383.2→84.3 and 336.2→97.8 in multiple reaction monitoring (MRM) positive mode, respectively. The method was validated with the correlation coefficients of (r ²) ≥ 0.9963 over a linear concentration range of 0.5–250.0 ng/mL. This method demonstrated intra- and inter-day precision within 1.4–9.2% and 4.4–5.5% and accuracy within 96.8–103% and 98.5–99.8% for EP. This method is successfully applied in the bioequivalence study of 24 human volunteers.     

Simultaneous Determination of Tramadol and Acetaminophen in Human Plasma by LC–ESI–MS

This study presents a high-performance liquid chromatography–electrospray ionization–mass spectrometric (LC–ESI–MS) method for the simultaneous determination of tramadol and acetaminophen in human plasma using phenacetinum as the internal standard. After alkalization with saturated sodium bicarbonate, both compounds were extracted from human plasma with ethyl acetate and were separated by HPLC on a Hanbon LiChrospher CN column with a mobile phase of 10 mM ammonium acetate buffer containing 0.5% formic acid–methanol (40:60, v/v) at a flow rate of 1 mL min⁻¹. Analytes were determined using electrospray ionization in a single quadrupole mass spectrometer. LC–ESI–MS was performed in the positive selected-ion monitoring (SIM) mode using target ions at [M+H]⁺ m/z 264.3 for tramadol, [M+H]⁺ m/z 152.2 for acetaminophen and [M+H]⁺ m/z 180.2 for phenacetinum. Calibration curves were linear over the range of 5–600 ng mL⁻¹ for tramadol and 0.03–16 μg mL⁻¹ for acetaminophen. The inter-run relative standard deviations were less than 14.4% for tramadol and 12.3% for acetaminophen. The intra-run relative standard deviations were less than 9.3% for tramadol and 7.9% for acetaminophen. The mean plasma extraction recovery for tramadol and acetaminophen were in the ranges of 82.7–85.9 and 83.6–85.3%. The method was applied to study the pharmacokinetics of a new formulation of tramadol/acetaminophen tablet in healthy Chinese volunteers.     

A sensitive liquid chromatography–mass spectrometry method for simultaneous determination of alisol A and alisol A 24-acetate from <Emphasis Type="Italic">Alisma orientale</Emphasis> (Sam.) Juz. in rat plasma

A liquid chromatography–mass spectrometry (LC-MS) method was developed and validated for the simultaneous determination of alisol A and alisol A 24-acetate from Alisma orientale (Sam.) Juz. in rat plasma using diazepam as an internal standard. A 200-μl plasma sample was extracted by methyl tert-butyl ether and the separation was performed on Kromasil C₁₈ column (150 × 4.6 mm, 5 μm) with the mobile phase of acetonitrile (containing 0.1% of formic acid)–water (73:27, v/v) at a flow rate of 0.8 ml/min in a run time of 10 min. The two analytes were monitored with positive electrospray ionization by selected ion monitoring mode. The lower limit of quantitation for both alisol A and alisol A 24-acetate were 10 ng/ml. The calibration curves were linear in the measured range 10–1,000 ng/ml for alisol A and 10–500 ng/ml for alisol A 24-acetate. The mean extraction recoveries were above 74.7% for alisol A and above 72.4% for alisol A 24-acetate from biological matrixes. The intra- and inter-day precision for all concentrations of quality controls was lower than 14.1% (RSD %) for each analyte. The accuracy ranged from −12.3% to 9.8% (RE %) for alisol A, and −8.6% to 14.2% (RE %) for alisol A 24-acetate. The method was successfully applied to the study on the pharmacokinetics of alisol A and alisol A 24-acetate in rat plasma.     

Determination and Pharmacokinetic Study of 10-O-Dimethylaminoethylginkgolide B in Rat Plasma by LC–MS

To evaluate the pharmacokinetics of a novel analogue of ginkgolide B, 10-O-dimethylaminoethylginkgolide B (XQ-1) in rat plasma in pre-clinical studies, a sensitive and specific liquid chromatographic method with electrospray ionization mass spectrometry detection (LC–ESI–MS) was developed and validated. After a simple extraction with ethyl acetate, XQ-1 was analyzed on a Shim-pack C18 column with a mobile phase of a mixture of 1 μmol L⁻¹ ammonium acetate containing 0.02% formic acid and methanol (55:45, v/v) at a flowrate of 0.3 mL min⁻¹. Detection was performed in selected ion monitoring (SIM) mode using target ions at [M + H]⁺ m/z 496.05 for XQ-1 and m/z 432.10 for the internal standard (lafutidine). Linearity was established for the concentration range from 2 to 1,000 ng mL⁻¹ . The extraction recoveries ranged from 86.0 to 89.9% in plasma at concentrations of 5, 50, and 500 ng mL⁻¹. The lower limit of quantification was 2 ng mL⁻¹ with 100 μL plasma. The validated method was successfully applied to a pharmacokinetic study after intragastic administration of XQ-1 mesylate in rats at a dose of 20 mg kg⁻¹.     

UPLC-MS/MS determination of doxazosine in human plasma

A sensitive, selective and rapid method for the analysis of doxazosine (DOX) in human plasma based on ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) is described. DOX and tamsulosin, used as an internal standard (IS), were extracted by liquid-liquid extraction, and the chromatography was performed on a C18 UPLC column packed with 1.7 μm particles. The total run time was 2 min. Detection was achieved by the multiple reaction monitoring of the following transitions: m/z 452→344 and m/z 409→228 for DOX and IS, respectively. Transitions of m/z 452→247 and m/z 409→271 were also collected for confirmation purposes. The calibration curve based on peak area ratio was linear up to at least 100 ng ml⁻¹, with a detection limit of 0.02 ng ml⁻¹ (a signal-to-noise ratio of 3). The method showed satisfactory reproducibility, and the short-term stability of the analyte was assessed. The method was successfully applied to the analysis of DOX in human plasma.     

Determination and Pharmacokinetic Study of Calycosin-7-O-β-d-glucoside in Rat Plasma After Intravenous Administration of Aidi Lyophilizer

Aidi injection is a clinical medicine used in China for the treatment of cancer. Calycosin-7-O-β-d-glucoside is the main effective components of the formulas. In this study, a high performance liquid chromatographic (LC) method was developed to quantify calycosin-7-O-β-d-glucoside in rat plasma using a liquid–liquid extraction and ultraviolet (UV) absorbance detection. LC analysis was performed on a Diamonsil C₁₈ column (200 × 4.6 mm i.d., 5 μm particle size) with isocratic mobile phase consisting of acetonitrile–0.05% phosphoric acid (19.5:80.5, v/v) of a flow rate of 1.0 mL min⁻¹. The linear range was 0.11–17.6 μg mL⁻¹ and the low quantification limit was 0.11 μg mL⁻¹ (S/N = 10). The intra- and inter-day relative standard deviations (RSD) in the measurement of quality control (QC) samples 0.11, 0.22, 1.32 and 8.80 μg mL⁻¹ ranged from 4.1 to 6.3 and 4.3 to 6.2%, respectively. The accuracy was from −6.7 to 4.3% in terms of relative error (RE). Calycosin-7-O-β-d-glucoside was stable in storage at −20 °C for 2 weeks and stable after three freeze–thaw cycles in rat plasma. This method was validated for specificity, accuracy, precision and was successfully applied to pharmacokinetic study of calycosin-7-O-β-d-glucoside in rat plasma after intravenous administration of Aidi lyophilizer.     

A sensitive liquid chromatographic-mass spectrometric method for simultaneous determination of dehydroevodiamine and limonin from Evodia rutaecarpa in rat plasma

A liquid chromatographic–mass spectrometric (LC–MS) method has been developed and validated for simultaneous determination of dehydroevodiamine and limonin from Evodia rutaecarpa in rat plasma. After addition of the internal standard, domperidone, plasma samples were extracted by liquid–liquid extraction with ethyl acetate and separated on an Apollo C₁₈ column (250 mm × 4.6 mm, 5 μm), with methanol–0.01% formic acid water (60:40, v/v) as mobile phase, within a runtime of 12.0 min. The analytes were detected without interference in the selected ion monitoring (SIM) mode with positive electrospray ionization. The linear range was 1.0–500 ng mL⁻¹ for dehydroevodiamine and 2.0–1,000 ng mL⁻¹ for limonin, with lower limits of quantitation of 1.0 and 2.0 ng mL⁻¹, respectively. Intra-day and inter-day precision were within 6.0% and 10.9%, respectively, for both analytes, and the accuracy (relative error, RE, %) was less than 4.8% and 6.5%, respectively. The validated method was successfully applied to a comparative pharmacokinetic study of dehydroevodiamine and limonin in rat plasma after oral administration of dehydroevodiamine, limonin, and an aqueous extract of Evodiae fructus. The results indicated there were obvious differences between the pharmacokinetic behavior after oral administration of an aqueous extract of Evodiae fructus compared with single substances.     

Simultaneous Determination of Enalapril and Enalaprilat in Human Plasma by LC-MS: Application to a Bioequivalence Study

A rapid, simple and specific liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for the simultaneous determination of enalapril and its major active metabolite enalaprilat in human plasma. Benazepril hydrochloride was used as the internal standard. Plasma was deproteinized with acetone and centrifuged. The supernatant was transferred and evaporated to dryness and the residue dissolved in mobile phase. Samples were separated on a C18 column with a mobile phase of methanol–20 mM ammonium acetate (53:47, v/v) containing 0.15% trifluoracetic acid (v/v) with a pH of 3.0. Enalapril, enalaprilat and the internal standard were measured by electrospray positive selective ion monitoring mode. The method was validated over a linear range of 1.56–400 ng mL⁻¹ and the limits of quantification were 1.56 ng mL⁻¹ for both enalapril and enalaprilat using 0.1 mL plasma. Extraction efficiency was more than 84% and recoveries were in range of 93.65–101.17%. The intra-day relative standard deviations (RSD) were less than 8.16 and 7.05% and inter-day RSDs were within 8.42 and 5.72% for enalapril and enalaprilat, respectively. The storage stability of QC samples was investigated under various conditions. The method was successfully applied for the evaluation of the pharmacokinetics and bioequivalence of enalapril and enalaprilat in 20 healthy volunteers after an oral dose of 20 mg enalapril maleate.     

LC–ESI–MS Determination of Lovastatin in Human Plasma

A convenient, selective and sensitive liquid chromatographic-electrospary ionization mass spectrometry (LC–ESI–MS) method was developed and validated to determine lovastatin in human plasma. The analyte was extracted from human plasma samples by typical liquid–liquid extraction, separated on a C₁₈ column by using the mobile phase consisting of water–methanol (13:87, v/v). Simvastatin was used as the internal standard (IS). The method was linear within the range of 0.1–20 ng mL⁻¹. The lower limit of quantification (LLOQ) was 0.1 ng mL⁻¹. The intra- and inter-run precision, calculated from quality control (QC) samples was less than 10.2%. The accuracy as determined from QC samples was in the range of 99.3–102.9% for the analyte. The mean recoveries for lovastatin and IS were 84.8 and 88.0%, respectively. The method was successfully applied for evaluation of the pharmacokinetic of lovastatin in healthy volunteers.     

Simple Liquid Chromatographic Determination of Minocycline in Brain and Plasma

A new high-performance liquid chromatography assay was developed for the determination of minocycline in plasma and brain. A solid–liquid extraction procedure was coupled with a reversed-phase HPLC system. The system requires a mobile phase consisting of acetonitrile:water:perchloric acid (26:74:0.25, v/v/v) adjusted to pH 2.5 with 5 M sodium hydroxide for elution through a RP8 column (250 × 3.0 mm, i.d.) with UV detection set at 350 nm. The method proved to be accurate, precise (RSD < 20%) and linear between 0.15–20 μg mL⁻¹ in plasma and 1–20 μg mg⁻¹ in brain. The method was successfully applied to a blood-brain barrier minocycline transport study.     

Determination of (E)-3,5,4′-Trimethoxystilbene in Rat Plasma by LC with ESI-MS

(E)-3,5,4′-trimethoxystilbene (BTM-0512) is a resveratrol analog with a variety of pharmacological action, including anti-cancer properties, anti-allergic activity, estrogenic activity, antiangiogenic activity, and vascular-targeting activity against microtubule-destabilization. There is, however, no validated analytical method for quantification of (E)-3,5,4′-trimethoxystilbene in biological matrices, so pharmacokinetic data and suitable methods for determination of the compound in plasma are currently lacking. A rapid and sensitive liquid chromatographic–mass spectrometric method for determination of (E)-3,5,4′-trimethoxystilbene in rat plasma, using carbamazepine as internal standard, has been developed and validated. Plasma samples were treated with acetonitrile to precipitate proteins. Samples were then analyzed by HPLC on a 250mm × 4.6 mm i.d., 5-μm particle, C₁₈ column with methanol–water, 80:20 (v/v), containing 10 mm ammonium acetate and 0.2% formic acid (pH 3.0), as mobile phase, delivered at 0.85 mL min⁻¹. A single-quadrupole mass spectrometer with an electrospray interface operated in selected-ion monitoring mode was used to detect [M + H]⁺ ions at m/z 271.3 for (E)-3,5,4′-trimethoxystilbene and m/z 237.5 for the internal standard. (E)-3,5,4′-trimethoxystilbene and the internal standard eluted as sharp, symmetrical peaks with retention times of 8.9 and 4 min, respectively. Calibration plots for (E)-3,5,4′-trimethoxystilbene in rat plasma at concentrations ranging from 0.01 to 5.0 μg mL⁻¹ were highly linear. Intra-day and inter-day precision, as RSD, was <12.9%, and accuracy was in the range 94.8–104.7%. The limit of detection in plasma was 0.005 μg mL⁻¹. The method was successfully used to determine the concentration of (E)-3,5,4′-trimethoxystilbene after oral administration of 86 mg kg⁻¹ of the drug to Sprague–Dawley rats and can be used to investigate the pharmacokinetics of the compound.     

Development and Validation of LC–MS Method for the Determination of Hydroxyzine Hydrochloride in Human Plasma and Subsequent Application in a Bioequivalence Study

A rapid, simple and specific liquid chromatography-electrospray ionization mass spectrometry method has been developed and validated for the determination of hydroxyzine hydrochloride in human plasma. Samples were separated using a Thermo Hypersil-HyPURITYC18 reversed-phase column (150 mm × 2.1 mm i.d., 5 μm). The mobile phase consisted of 50 mM ammonium acetate (pH 4.0)–methanol–acetonitrile (45:36:19, v/v). Hydroxyzine and its internal standard were measured by electrospray ion source in positive selective ion monitoring mode. The method was validated with a linear range of 1.56–200.0 ng mL⁻¹ and the lowest limit of quantification was 1.56 ng mL⁻¹ for hydroxyzine hydrochloride (r ²= 0.9991). The extraction efficiencies were about 70% and recoveries of the method were in the range of 93.5–104.4%. The intra-day relative standard deviation (RSD) was less than 8.0% and inter-day RSD was within 7.4%. QC samples were stable when kept at ambient temperature for 12 h at −20 °C for 30 days and after four freeze–thaw cycles. The method has been successfully applied to the evaluation of pharmacokinetics and bioequivalence of two hydroxyzine hydrochloride formulations in 12 healthy Chinese volunteers after an oral dose of 25 mg.     

Quantitative estimation of riluzole in human plasma by LC-ESI-MS/MS and its application to a bioequivalence study

A novel simple, sensitive, selective, and rapid high-performance liquid chromatography coupled with tandem mass spectrometry method was developed and validated for quantification of riluzole in human plasma. The chromatography was performed by using a Zorbax-SB-C18 (4.6 × 75 mm, 3.5 μm) column , isocratic mobile phase 0.1% formic acid/acetonitrile (10:90 v/v), and an isotope-labeled internal standard (IS), [¹³C,¹⁵N₂]riluzole. The extraction of drug and internal standard was performed by liquid–liquid extraction and analyzed by MS in the multiple reaction monitoring (MRM) mode using the respective [M+H]⁺ ions, m/z 235.0/165.9 for riluzole and m/z 238.1/169.0 for the IS. The calibration curve was linear over the concentration range 0.5–500.0 ng/ml for riluzole in human plasma. The limit of quantification (LOQ) was demonstrated at 0.5 ng/ml. The within-batch and between-batch precision were 0.6–2.3% and 1.4–5.7%, and accuracy was 97.1–101.1% and 98.8–101.2% for riluzole respectively. Drug and IS were eluted within 3.0 min. The validated method was successfully applied in a bioequivalence study of riluzole in human plasma.     

Determination of clozapine in human plasma by solid-phase extraction and liquid chromatography with amperometric detection

Summary A sensitive and selective high-performance liquid chromatographic method has been developed for monitoring clozapine levels in human plasma. Chromatography was performed on a reversed-phase column (C₈, 150 mm×4.6 mm i.d., 5 μm) with acetonitrile-aqueous sodium acetate solution, 88∶12 (v/v), as mobile phase; the flow rate was 1 mL min⁻¹. Clozapine oxidation at +800 mV was detected amperometrically. Response was linearly dependent on concentration over the range 50–1500 ng mL⁻¹ clozapine in plasma. Sample preparation by solid-phase extraction before HPLC analysis gave high extraction yield (94%). The accuracy and precision of the method were both very good (recovery: 97%;RSD<3.3%).     

HPLC Determination of DCJW in Rat Plasma and Its Application to Pharmacokinetics Studies

A high-performance liquid chromatography–UV method for determining DCJW concentration in rat plasma was developed. The method described was applied to a pharmacokinetics study of intramuscular injection in rats. The plasma samples were deproteinized with acetonitrile in a one-step extraction. The HPLC assay was carried out using a VP-ODS column and the mobile phase consisting of acetonitrile–water (80:20, v/v) was used at a flow rate of 1.0 mL min⁻¹ for the effective eluting DCJW. The detection of the analyte peak area was achieved by setting a UV detector at 314 nm with no interfering plasma peak. The method was fully validated with the following validation parameters: linearity range 0.06–10 μg mL⁻¹ (r > 0.999); absolute recoveries of DCJW were 97.44–103.46% from rat plasma; limit of quantification, 0.06 μg mL⁻¹ and limit of detection, 0.02 μg mL⁻¹. The method was further used to determine the concentration–time profiles of DCJW in the rat plasma following intramuscular injection of DCJW solution at a dose of 1.2 mg kg⁻¹. Maximum plasma concentration (C _max) and area under the plasma concentration–time curve (AUC) for DCJW were 140.20 ng mL⁻¹ and 2405.28 ng h mL⁻¹.     

Determination of Apigenin by LC with Electrochemical Detection

A rapid, sensitive, and specific method for quantification of olmesartan, the prodrug of olmesartan medoxomil, in human plasma, using zidovudine as internal standard, is described. Sample preparation involved a simple solid-phase extraction procedure. The extract was analyzed by high-performance liquid chromatography coupled to electrospray tandem mass spectrometry (LC–MS–MS). Chromatography was performed isocratically on a 5 μm C₁₈ analytical column (50 mm × 4.6 mm i.d.) with water–acetonitrile–formic acid 20:80:0.1 (v/v) as mobile phase. The response to olmesartan was a linear function of concentration over the range 4.82–1,928 ng mL⁻¹. The lower limit of quantification in plasma was 4.82 ng mL⁻¹. The method was successfully applied in a bioequivalence study of an olmesartan formulation after administration as a single oral dose.     

Determination of 6-Benzyladenine in Bean Sprout by LC–ESI-IT-MS–MS

A rapid and sensitive method has been developed and validated to determine 6-benzyladenine (6-BA) residues in bean sprout using high-performance liquid chromatography coupled with electrospray ionization ion trap tandem mass spectrometry. Liquid–liquid extraction, using acidified methanol, was used to isolate 6-BA from the sample matrix. The separation was carried out on a Zorbax SB C₁₈ column (150 mm × 4.6 mm i.d., 5 μm) with 0.1% acetic acid/methanol (25:75 v/v) as mobile phase in isocratic mode. The quantitation of 6-BA was based on fragmentation of the molecular ion at m/z 226.1 to a product ion at m/z 91.1. In addition, the recoveries of three extraction solvents by ultrasound extraction and conventional extraction method were compared, and it was found that acidified methanol as the extraction solvent was the best. The calibration curve was linear (r ² > 0.997) in the concentration range of 0.04–10.0 ng mL⁻¹ with a lower limit of quantification of 0.5 ng g⁻¹ for 6-BA in bean sprout. Intra-day and inter-day relative standard deviations (RSDs) were less than 7.1 and 9.8%. Recoveries of 6-BA were between 85.0 and 88.5%. This assay has been successfully applied to the determination of trace 6-BA residues in bean sprout and monitoring the market in Ningbo, China.