Elution System Research Articles

Development of a mixed-mode chromatography with tandem mass spectrometry method for the quantitative analysis of 23 underivatized amino acids in human serum

In this study, a robust, selective and simplified method was developed and validated for the simultaneous quantitative analysis of 23 underivatized amino acids in human serum using mixed-mode chromatography with tandem mass spectrometry (LC–MS/MS). Serum samples were deproteinized with acetonitrile and subjected to LC–MS/MS analysis. The chromatographic separation of amino acids was achieved using a mixed-mode column (150×3mm, 3μm) with a gradient elution system; the mobile phase consisted of 50mM ammonium formate and 0.1% formic acid in acetonitrile. The total run time was 22min. Eluted compounds were detected in the electrospray ionization-positive mode with multiple reaction monitoring. The validation study evaluated linearity, repeatability, intra and inter-day accuracy and precision, and matrix effect. The validation results were satisfactory in all the tested parameters. This method was successfully applied to the analysis of amino acids in the clinical sample of human serum.

Analyzing crude/processed root of Polygonum multiflorum from different habitats by UPLC fingerprint and mode identification methods

To establish a content determination method for 2,3,5,4'-tetrahydroxy stilbene-2-O-β-D-glucoside (TSG) of the crude/processed root of Polygonum multiflorum from different habitats in China and set up the fingerprint by using UPLC. Various samples were pretreated by macro-porous resin. Then UPLC analysis was performed on Waters ACQUITY UPLC@BEH C18 chromatographic column (2.1 mm×50 mm, 1.7 μm) at (25±5) ℃. A binary gradient elution system was composed of acetonitrile (phase A) and 0.5% acetic acid solution (phase B). Detection was performed at the wavelength of 254 nm, and the mobile flow rate was set at 0.3 mL•min⁻¹. Results showed that the yield of extraction of the 2,3,5,4'-tetrahydroxy stilbene-2-O-β-D-glucoside from root of P. multiflorum was all over 25.0% after macro-porous resin separation; an exclusive UPLC fingerprint method of the crude/processed root of P. multiflorum from different habitats was successfully set up and 17 chromatographic peaks were calibrated. Cluster analysis can not entirely distinguish the crude one from the processed one, while principal component analysis absolutely can. 2,3,5,4'-tetrahydroxy stilbene-2-O-β-D-glucoside is the composition that has largest differences in variable importance in projection (VIP) between crude and processed root of P. multiflorum. The separating method can gain high-purity 2,3,5,4'-tetrahydroxy stilbene-2-O-β-D-glucoside, and the determination method is simple, sensitive, reliable and can be used in fast identifying the crude/processed root of P. multiflorum or as a method for overall quality control of root of P. multiflorum.

HPLC-MS/MS determination of residual amount of 4 plant growth retardants in 6 dried root and Rhizome Herbs

HPLC-MS/MS was applied to the determination of residual amount of plant growth retardant such as paclobutrazol, daminozide, chlormequat and mepiquat chloride in dried root and rhizome herbs. The sample was extracted twice with acetonitrile containing 0.1% formic acid. The separation was performed on a Waters Atlantis HILIC column with an elution system consisting of acetonitrile-5 mmol•L⁻¹ ammonium acetate solution with 0.1% formic acid, methanol and acetonitrile. The MS spectrum was acquired in positive mode with multiple reactions monitoring (MRM). The linear range was 6-1 500 μg•kg⁻¹, and the optimized method offered a good linear correlation (r>0.997 8), excellent precision (RSD<11%) and acceptable recovery (from 79.3% to 103.3%). Four kinds of plant growth retardant have detected in some ofhenise herbs like Ophiopogonis Radix, Angelicae Sinensis Radix, Achyranthis Bidentatae Radix, Alismatis Rhizoma, Chuanxiong Rhizama and Notoginseng Radix et Rhizama, is among the more severe cases, dwarf lilyturf, multi-effect azole detection quantity is 63.4~1 351.66 μg•kg⁻¹, and Daminozide was detected in Ophiopogonis Radix, Angelicae Sinensis Radix, Chuanxiong Rhizama, Alismatis Rhizoma.

A multidimensional liquid chromatography–tandem mass spectrometry platform to improve protein identification in high-throughput shotgun proteomics

A new on-line multidimensional system for sequential trapping and individual elution and separation of peptides based on their molecular weight is described. By sequentially using two chemically different trapping columns, a polymethacrylate monolith and a packed C18 one, peptides from complex samples can be on-line trapped and divided into two fractions, containing respectively mainly medium-large peptides and smaller peptides. Then, by means of two switching valves working in parallel, the two fractions were individually separated by reversed phase chromatography. The whole gradient consisted of two subgradients, with the first one dedicated to the separation of smaller peptides and the second one to the separation of larger peptides. Such configuration allowed to identify up to 1476 proteins in a standard E. coli tryptic digest, with improved performance, increased average sequence coverage and reduced single unique peptide identifications compared to a conventional shotgun proteomics configuration comprising only the C18 trapping column and the analytical column.

Characterization of peak capacity of microbore liquid chromatography columns using gradient kinetic plots

The performance of micro-liquid chromatography columns with an inner diameter of 0.3mm was investigated on a dedicated micro-LC system for gradient elution. Core-shell as well as fully porous particle packed columns were compared on the basis of peak capacity and gradient kinetic plot limits. The results for peak capacity showed the superior performance of columns packed with sub-2μm fully porous particles compared to 3.0μm fully porous and 2.7μm core-shell particles within a range of different gradient time to column void time ratios. For ultra-fast chromatography a maximum peak capacity of 16 can be obtained using a 30s gradient for the sub-2μm fully porous particle packed column. A maximum peak capacity of 121 can be achieved using a 5min gradient. In addition, the influence of an alternative detector cell on the basis of optical waveguide technology and contributing less to system variance was investigated showing an increased peak capacity for all applied gradient time/column void time ratios. Finally, the influence of pressure was evaluated indicating increased peak capacity for maximum performance whereas a limited benefit for ultra-fast chromatography with gradient times below 30s was observed.

Quantitative Determination of Bakkenolide D in Petasites japonicus and Farfugium japonicum by HPLC/UV

A quantitative analysis of bakkenolide D in the different parts of Petasites japonicus and Farfugium japonicum was performed by HPLC. A gradient HPLC elution system with a mobile phase consisting of water: acetonitrile solution (20:80 to 0:100 for 45 min) was followed and an INNO C18 column was used for the chromatographic separation. The injection volume, flow rate, and UV detection were 10 μL, 1 mL/min, and 290 nm, respectively. Results show that both species showed the highest amount of bakkenolide D in the roots being 107.203 and 166.103 mg/g for P. japonicas and F. japonicum, respectively. Content analysis on the different parts of both plants displayed remarkably lower values which ranged from 0.403 - 4.419 and 7.252 - 32.614 mg/g for P. japonicas and F. japonicum, respectively. The results show that the roots of both plants are rich in bakkenolide D showing a promising use in the development of nutraceuticals and industrial application of the compound.

超高效液相色谱法测定Ex4c的有关物质

目的：建立超高效液相色谱法(UPLC)测定聚乙二醇化促胰岛素分泌肽类似物原料Ex4c有关物质的方法。方法：采用Waters ACQUITY UPLC® Peptide CSH™C18 column (130 A, 2.1 × 150 mm, 1.7 mm)为色谱柱；以0.05%三氟乙酸水溶液-四氢呋喃(9:1)为流动相A，0.05%三氟乙酸乙腈溶液-四氢呋喃(9:1)为流动相B；进行梯度洗脱。柱温45℃，检测波长为214 nm，进样量为2 ml，流速为0.3 mL∙min−1。结果：杂质A、B、C、D线性良好，相关系数r均 ≥ 0.995；4种杂质的检测限范围为4.0~5.6 ng；平均回收率为96.3%~101.1%。结论：经方法学验证，所建立的方法简便、准确、重复性好，可用于测定聚乙二醇化促胰岛素分泌肽类似物原料Ex4c的有关物质，有效地控制药品质量。 Objective: To establish a method for the determination of related substances in Ex4c (the raw ma-terial of the pegylation of glucagon-like peptide-1) by UPLC. Methods: The UPLC method was de-veloped by using a Waters ACQUITY UPLC® Peptide CSH™C18 column (130 A, 2.1 × 150 mm, 1.7 mm) with a gradient elution system. The mobile phase A was 0.05% trifluoroacetic acid aqueous solution/tetrahydrofuran (9:1), and the mobile phase B was 0.05% trifluoroacetic acid in acetoni-trile/tetrahydrofuran (9:1). The column temperature was maintained at 45˚C while the detection wavelength setting at 214 nm. Furthermore, the sample injection was 2 ml via keeping a flow rate of 0.3 mL∙min−1. The developed method was validated. Results: The resolution between Ex4c and adjacent impurities, between Ex4C and the known impurities were greater than 1.5. All four known impurities exhibited good linear relationships with their related coefficients ≥ 0.995. And their detection limits ranged from 4.0 ng to 5.6 ng, comprising 96.3%~101.1% of recovered material. Conclusion: The validation results showed that the established method was simple, accurate and reproducible. It is capable of determinating impurities in Ex4c (the raw material of the pegylation of glucagon-like peptide-1) and can be effectively used for quality control of this drug.

Simultaneous determination of four compounds, campesterol, emodin8-O-β-D-Glucopyranoside, quercetin, and isoquercitrin in Reynoutria sachalinensis by high-performance liquid chromatography-diode array detector

Background:Reynoutria sachalinensis is a well-known and used herbal medicine to treatment of arthralgia, jaundice, amenorrhea, coughs, carbuncles, and sores.Objective:We have developed high-performance liquid chromatography analysis method for simultaneous determination of isolated four compounds, campesterol, emodin8-O-β-D-glucopyranoside, quercetin, and isoquercitrin from R. sachalinensis is.Materials and Methods:The four compounds were separated on Shiseido C18 column (S-5 μm, 4.6 mm I.D. ×250 mm) at a column temperature of 25°C. The mobile phase composed of water and methanol with gradient elution system, and flow rate is 1.0 ml/min. The detection wavelength was set at 205 nm.Results:Validation of this analytical method was evaluated by linearity, precision, and accuracy test. This established method had good linearity (R2 > 0.997). The relative standard deviation values of intra- and inter-day testing were indicated that <2%, and accuracy is 91.66%–103.31% at intraday and 91.69%–103.31% at intraday. The results of recovery test were 92.60%–108.99%.Conclusion:In these results, developed method was accurate and reliable to the quality evaluation of campesterol, emodin 8-O-β-D-glucopyranoside, quercetin, and isoquercitrin isolated from R. sachalinensis.SUMMARY We have developed high-performance liquid analysis method for simultaneous determination of 4 compounds of Reynoutria sachalinensis. Abbreviations used: HPLC: High-performance liquid chromatography, DAD: Diode array detector, LOD: Limit of detection, LOQ: Limit of quantitation, ICH: International Conference on Harmonisation.

Identification and Structure Elucidation of Forced Degradation Products of the Novel Propionic acid Derivative Loxoprofen: Development of Stability-Indicating Chromatographic Methods Validated as per ICH Guidelines.

Loxoprofen sodium (LOX) is a recently developed novel propionic acid derivative. Owing to its instability under both hydrolytic and oxidative conditions, the development of simple, rapid and sensitive methods for its determination in the presence of its possible forced degradation products becomes essential. Two simple chromatographic methods, high-performance thin layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC), were developed associated with ultraviolet (UV) detection. In HPTLC-densitometric method, the separation of LOX from its degradation products was achieved using silica gel F254 plates and toluene:acetone:acetic acid (1.8:1.0:0.1, v/v/v) as the developing system followed by densitometric scanning at 220 nm. In the HPLC-UV method, the separation was performed using isocratic elution system with acetonitrile: 0.15% triethylamine (pH 2.2) (50:50, v/v) on C18 analytical column. The flow rate was optimized at 1.0 mL·min-1 and UV detection was achieved at 220 nm. Validation was performed in accordance with the International Conference on Harmonization guidelines and the method was perfectly applied for determination of LOX in its pharmaceutical preparation. The results obtained were statistically compared to those obtained after application of the official HPLC method, where no significant difference was found incompliance with precision and accuracy. Identification and characterization of the possible hydrolytic degradation product under alkaline conditions and that produced during oxidative degradation using hydrogen peroxide were structurally elucidated using infrared and mass spectrometry analyses.

Discrimination of red and white rice bran from Indonesia using HPLC fingerprint analysis combined with chemometrics.

HPLC fingerprint analysis combined with chemometrics was developed to discriminate between the red and the white rice bran grown in Indonesia. The major component in rice bran is γ-oryzanol which consisted of 4 main compounds, namely cycloartenol ferulate, cyclobranol ferulate, campesterol ferulate and β-sitosterol ferulate. Separation of these four compounds along with other compounds was performed using C18 and methanol-acetonitrile with gradient elution system. By using these intensity variations, principal component and discriminant analysis were performed to discriminate the two samples. Discriminant analysis was successfully discriminated the red from the white rice bran with predictive ability of the model showed a satisfactory classification for the test samples. The results of this study indicated that the developed method was suitable as quality control method for rice bran in terms of identification and discrimination of the red and the white rice bran.

Selective RP-HPLC method for determination of quetiapine in presence of coadministered drugs: Application for long-term stability study of quetiapine in whole blood

Incidence of suicidal attempts presents an explanation for the high prevalence of quetiapine (QTI) in forensic cases. Thus, the interpretation of its concentrations in biological specimens is needed, but in forensic toxicology, potential postmortem changes such as instability of the target drugs should be taken in consideration. High-performance liquid chromatography (HPLC) method has been developed for determination of QTI. This method was based on reversed phase (RP)-HPLC separation of QTI on a C-18 column (150 mm × 4.6 mm, 5 μm) with elution system of acetonitrile—methanol—0.025 M phosphate buffer (pH 2.5), containing 1 mL TEA in each 250 mL, in a ratio of 40:30:30%, v/v, at the flow rate of 1.2 mL min−1 using mirtazapine as internal standard (IS). The proposed method was applied to the determination of QTI in plasma in presence of coadministered drugs. The application of the proposed method was extended for long-term stability study of two different concentration levels of QTI in the whole blood.

Development and Validation of New RP-HPLC Method for Simultaneous Determination of Methyl and Propyl Parabens with Levetiracetam in Pure Form and Pharmaceutical Formulation

A simple and robust high-performance liquid chromatography (HPLC) method is described for the assay for levetiracetam (LTC), methyl paraben (MHB), and propyl paraben (PHB) either in their pure form or in commercial Levepsy® syrup. The method is selective and stability indicating and all chromatographic conditions were studied to obtain adequate separation of LTC, MHB, and PHB from their degradation products and from excipients. The HPLC separation was carried out on a RP C18 Hypersil BDS analytical column (150 mm × 4.6 mm ID) using gradient elution system. The mobile phase flow rate was 1.5 mLmin−1 and the column temperature was kept at 40°C. Complete separation of the studied components was obtained within a cycle time of 8 min. LTC, MHB, and PHB were eluted at 1.56, 5.86, and 7.85 min, respectively. Detection was carried out at 240 nm using a dual wavelength detector. The method has been validated for linearity, accuracy, precision, specificity, limit of detection, limit of quantitation, robustness, and ruggedness. The proposed method was successfully applied for the determination of LTC in the presence of parabens in Levepsy syrup.

Simple isocratic method for simultaneous determination of caffeine and catechins in tea products by HPLC.

Tea is a popular beverage almost all over the world. Many studies show that tea consumption is closely associated with positive health impact. Most of the HPLC methods used for the determination of tea constituents include gradient elution systems which involve expensive instrumentation. The objective of this study was to develop a simple, rapid precise and low cost HPLC method for the separation and quantification of catechins and caffeine in tea (Camellia sinensis). The method utilizes a phenyl column (2.1 × 150 mm) with a UV-detector (280 nm) where excellent chromatographic separation of tea components i.e. gallic acid (GA), caffeine (Caf), epicatechin (EC) and (−)-epigallocatechin gallate (EGCG) was achieved. The isocratic elution system of acetonitrile, glacial acetic acid and deionized water (8:1:91 v/v/v) at a flow rate of 0.5 mL/min was involved. This method produced excellent accuracy and precision. Within run and between run precision was less than 7.5 %. The equations for calibration curves were y = 0.117 (±0.010)x + 0.173 (±0.024), y = 0.100 (±0.003)x + 0.045 (±0.019), y = 0.016 (±0.001)x + 0.006 (±0.004), y = 0.025 (±0.001)x−0.025 (±0.007) for GA, Caf, EC and EGCG respectively. The method validation parameters prove that the method is efficient, a simple and adequate for the quantitative determination of principal components in tea samples.

Anthocyanin Profiling Method Based on Isocratic Elution for Comparable Speed, Reproducibility, and Quantitation with Gradient Elution

The present work aims at developing a simple and rapid method for the quantification of anthocyanins irrespective of acylation present or not. The proposed analytical approach is based on isocratic elution mode in order to avoid the complexity of gradient elution system. The optimal conditions for the separation of anthocyanins were obtained as 14 % acetonitrile in water containing 2 % trifluroacetic acid with a flow rate of 0.6 ml min−1 when analyzed in Syzygium cumini (Jamun) anthocyanins. The method was successfully separated eight anthocyanins present in Jamun using C18 column as a stationary phase. Anthocyanins characterization was done by using electrospray ionization mass spectrometry (ESI-MS). LOD and LOQ value was calculated based on signal-to-noise ratio (S/N ratio) and ordinary least square regression (OLSR) approaches. LOD were obtained as 0.9, 0.4, and 0.3 μg ml−1 by S/N ratio method and 0.27, 1.2, and 1.0 μg ml−1unit by OLSR method for M3-G, C3-G and D3-G, respectively. In the isocratic elution mode, critical pair resolution was 1.95 whereas it was 0.85 under the gradient elution mode. Interestingly, ratio of peak area and peak height in gradient and isocratic elution was virtually same for almost all the evaluated peaks. More importantly, the method was validated with other three sources of anthocyanins (black carrot, red cabbage, and berry) and found variable resolution and response. After analyzing all the data, it may be concluded that the proposed method is useful for separation and identification of anthocyanin irrespective of acylation present in it when the number of anthocyanin is ≤10.

Anesthetic constituents of Zanthoxylum bungeanum Maxim.: A pharmacokinetic study.

A sensitive and selective ultra high performance liquid chromatography with tandem mass spectrometry method was established and validated for the simultaneous determination of hydroxy-α-sanshool, hydroxy-β-sanshool, and hydroxy-γ-sanshool in rat plasma after the subcutaneous and intravenous administration of an extract of the pericarp of Zanthoxylum bungeanum Maxim. Piperine was used as the internal standard. The analytes were extracted from rat plasma by liquid-liquid extraction with ethyl acetate and separated on a Thermo Hypersil GOLD C18 column (2.1 mm × 50 mm, 1.9 μm) with a gradient elution system at a flow rate of 0.4 mL/min. The mobile phase consisted of acetonitrile/0.05% formic acid in water and the total analysis time was 4 min. Positive electrospray ionization was performed using multiple reaction monitoring mode for the analytes. The calibration curves of the three analytes were linear over the tested concentration range. The intra- and interday precision was no more than 13.6%. Extraction recovery, matrix effect, and stability were satisfactory in rat plasma. The developed and validated method was suitable for the quantification of hydroxy-α-sanshool, hydroxy-β-sanshool, and hydroxy-γ-sanshool and successfully applied to a pharmacokinetic study of these analytes after subcutaneous and intravenous administration to rats.

Robust design space development for HPLC analysis of five chemical components in Panax notoginseng saponins

ABSTRACTThe present work describes the systematic development of a robust, precise, and rapid reversed-phase liquid chromatography method for the simultaneous analysis of five chemical components in Panax notoginseng saponins (PNS) using quality by design (QbD). The method was developed in two main phases: screening and optimization. During the screening phase, the most suitable stationary phase, column temperature, and flow rate were identified, while the secondary influential parameters, such as the gradient slope, the initial concentration of acetonitrile, and the initial isocratic hold of the gradient elution system were fine-tuned in the later optimization phase. In this phase, a 17-run experiment was used to examine multifactorial effects of these parameters on the critical resolution, analysis time, and peak symmetry. The Monte Carlo simulation method was successfully used to build the chromatographic design space and the process capability index Cp was introduced to evaluate the robustness of the design space. At last, the verification experiment was performed within the working design space by the accuracy profile methodology and model was found to be accurate. A robust combination of separation conditions predicted in the design space was obtained with the gradient slope of 1.6% · min−1, the initial concentration of acetonitrile of 20%, and the initial isocratic hold of 20 min, and the total analysis time was no more than 40 min. The results demonstrated that rapid separation of five components of PNS herbal extract could be achieved on the chromatographic column packed with narrow size particles at backpressures available in ordinary high performance liquid chromatography (HPLC) instruments.

Validation of an HPLC-UV method for the identification and quantification of bioactive amines in chicken meat

ABSTRACT A high-performance liquid chromatography with ultraviolet detection (HPLC-UV) method was validated for the study of bioactive amines in chicken meat. A gradient elution system with an ultraviolet detector was used after extraction with trichloroacetic acid and pre-column derivatization with dansyl chloride. Putrescine, cadaverine, histamine, tyramine, spermidine, and spermine standards were used for the evaluation of the following performance parameters: selectivity, linearity, precision, recovery, limits of detection, limits of quantification and ruggedness. The results indicated excellent selectivity, separation of all amines, a coefficient of determination greater than 0.99 and recovery from 92.25 to 102.25% at the concentration of 47.2mg.kg-1, with a limit of detection at 0.3mg.kg-1 and a limit of quantification at 0.9mg.kg-1 for all amines, with the exception of histamine, which exhibited the limit of quantification, of 1mg.kg-1. In conclusion, the performance parameters demonstrated adequacy of the method for the detection and quantification of bioactive amines in chicken meat.

Rapid quantitative method for the detection of phenylalanine and tyrosine in human plasma using pillar array columns and gradient elution.

This study reports a fast and quantitative determination method for phenylalanine (Phe) and tyrosine (Tyr) in human plasma using on-chip pressure-driven liquid chromatography. A pillar array column with low-dispersion turns and a gradient elution system was used. The separation of fluorescent derivatives of Phe, Tyr, and other hydrophobic amino acids was successfully performed within 140s. Under the optimized conditions, Phe and Tyr in human plasma were quantified. The developed method is promising for rapid diagnosis in the clinical field.

English

The present study evaluates the in vitro antioxidant activity of the leaves and stem-barks extracts and fractions of Ochna schweinfurthiana. To this effect, the different extracts were obtained by maceration in four solvents namely ethyl acetate, methanol, acetone and water- ethanol mixture (20-80). The methanol extract which exhibited the best antioxidant activity was partitioned in hexane and ethyl acetate. The ethyl acetate fraction was fractionated by column chromatography with the aid of methyl dichloride/methanol (a€–CHa€—_2 a€–Cla€—_2/ MeOH) solvent system at different polarities. The antioxidant activity of the extracts and fractions was assessed by the 2,2-diphenyl-1-picrilhidrazil (DPPH), ferric reducing antioxidant power assay (FRAP) and the total polyphenol content was evaluated using the Folin-Ciocalteu reagent. The results were analyzed using SPSS 20 presented as mean ± standard deviation. The results phytochemical screening confirmed the abundance of flavonoids and catechic tannins in the methanol and water-ethanol extracts whose content vary between 37.83 ± 1.6 mg ascorbic acid equivalent (EAA)/g dry weight (dw) and 96.4 ±2.33 mg EAA/g dw. The leaves methanol extract possess the best antiradical power (AP) of 0.00114 ± 0.00001 g/mg and the best ferric reducing antioxidant power (542.33±16.51 mg EAA/g dw). The F3 fraction obtained usinga€– CHa€—_2 a€–Cla€—_2/MeOH 5/1 elution system possess the best AP of 0.00125 ± 0.00001 g/mg identical to that of ascorbic acid (AP = 0.00125 ± 0.00002 g/mg) and the strongest ferric reducing antioxidant power (508.66 ± 18 mg EAA/g dw). A positive correlation between the two antioxidant tests and the polyphenols content was obtained. Thus, Ochna schweinfurthiana could be used by the population to prevent some diseases caused by oxidative stress, due to its high antioxidant effect. Key words: Ochna schweinfurthiana, extracts, fractions, antioxidant activity.

Sirolimus-loaded CaP coating on Co-Cr alloy for drug-eluting stent.

To achieve polymer-free and controllable drug-eluting system, there have been many efforts to modify the surface composition and topography of metal stent. Recently, calcium phosphate is commonly applied to metallic implants as a coating material for fast fixation and firm-implant bone attachment on the account of its demonstrated bioactive and osteoconductive properties. In the present study, the release of sirolimus could be controllable because of immobilization of sirolimus during the process of biomimetic CaP coating forming. A completely new concept is the drug carrier of biomimetic CaP coating with sirolimus for an absorbable drug eluting system, which in turn can serve as a drug reservoir. We here describe the characteristic, mechanisms and drug release in vitro of new drug-eluting system in comparison to conventional system equivalent. Nano-structured calcium phosphate (CaP) coating was formed on the cobalt–chromium (Co-Cr) alloy substrate. By immersing coated sample in solution with sirolimus (rapamycin), the sirolimus could be immobilized in the newly formed CaP layer. The morphology, composition and formation process of the coating were studied with scanning electron microscopy, energy dispersive spectrometer, X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that a uniform CaP coating incorporated with sirolimus was observed on Co-Cr alloy.