High-pH mobile phase in reversed-phase liquid chromatography-tandem mass spectrometry to improve the separation efficiency of aminoglycoside isomers

In chromatography, the use of extreme conditions can often lead to unique separation selectivity. In this study, a highly basic mobile phase (pH > 11), which is not typically employed for reversed-phase liquid chromatography (RPLC), was utilized in RPLC-tandem mass spectrometry (MS/MS) to achieve effective separation between electrically neutral bases of aminoglycosides (AGs). A mixture of AGs was simultaneously analyzed using 500 mmol L-1 ammonia aqueous solution (pH 11.8) as the mobile phase. A total of 11 AGs, including 2 stereoisomers of neomycin (B and C) and 5 structurally similar components of gentamicin (C1, C1a, C2, C2a, and C2b), were completely separated for the first time. The high separation performance for AGs was mainly due to two factors: First, slight differences in hydrophobicity among the AGs were significantly enhanced at a high pH by the complete acid dissociation of amines. Second, the high pH of the mobile phase minimized any electrostatic interactions between the AGs and residual silanol groups in the stationary phase, resulting in extremely sharp peaks for the AGs. The sensitivity of spectinomycin decreased by more than 20% when using the highly basic mobile phase (pH 11.8) due to its degradation, therefore, a mixture of 10 AGs was analyzed with 250 mmol L-1 ammonia aqueous solution (pH 11.5) with less degradation as the optimum condition. The developed analytical method could be used to determine the concentrations of trace AGs in milk with high accuracy and precision. Thus, RPLC-MS/MS using a high-pH mobile phase has great potential for the efficient separation of basic compounds containing amino sugars such as AGs.

Residue analysis of 10 aminoglycoside antibiotics in aquatic products by multiwalled carbon nanotubes combined with mixed-mode ion exchange liquid chromatography-tandem mass spectrometry

An ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed for simultaneous determination of 10 kinds of aminoglycosides in edible parts of aquatic products. The samples were extracted with 10 mmol/L potassium dihydrogen phosphate buffer solution, then the pH value of the extract was adjusted to neutral by sodium hydroxide. Half volume of the extract was loaded onto multiwalled carbon nanotubes cartridge. All the target compounds were separated on a mixed-mode ion exchange column and detected by ultra-high-performance liquid chromatography-tandem mass spectrometry with electrospray in the positive ionization mode. Under optimized conditions, this method had a good linearity with a squared correlation coefficient > 0.999. For neomycin, the limit of detection and limit of quantification were 5.0 μg/kg and 10.0 μg/kg, respectively; for hygromycin B and apramycin, values were 2.0 μg/kg and 5.0 μg/kg, respectively; for the other seven kinds of aminoglycosides, values were 1.0 μg/kg and 2.0 μg/kg, respectively. The average recoveries presented 75.8%-107.2% with intra- and interday reproducibility ranging between 3.8% and 12.5%. The method was rapid with good separation and sharp peak shapes, had the characteristicsis of high accuracy and good precision, and was suitable for simultaneous determination of 10 kinds of aminoglycosides in aquatic products.

An optimized method for the detection and spatial distribution of aminoglycoside and vancomycin antibiotics in tissue sections by mass spectrometry imaging

Suboptimal antibiotic dosing has been identified as one of the key drivers in the development of multidrug-resistant (MDR) bacteria that have become a global health concern. Aminoglycosides and vancomycin are broad-spectrum antibiotics used to treat critically ill patients infected by a variety of MDR bacterial species. Resistance to these antibiotics is becoming more prevalent. In order to design proper antibiotic regimens that maximize efficacy and minimize the development of resistance, it is pivotal to obtain the in situ pharmacokinetic-pharmacodynamic profiles at the sites of infection. Mass spectrometry imaging (MSI) is the ideal technique to achieve this. Aminoglycosides, due to their structure, suffer from poor ionization efficiency. Additionally, ion suppression effects by endogenous molecules greatly inhibit the detection of aminoglycosides and vancomycin at therapeutic levels. In the current study, an optimized method was developed that enabled the detection of these antibiotics by MSI. Tissue spotting experiments demonstrated a 5-, 15-, 35-, and 54-fold increase in detection sensitivity in the washed samples for kanamycin, amikacin, streptomycin, and vancomycin, respectively. Tissue mimetic models were utilized to optimize the washing time and matrix additive concentration. These studies determined the improved limit of detection was 40 to 5 μg/g of tissue for vancomycin and streptomycin, and 40 to 10 μg/g of tissue for kanamycin and amikacin. The optimized protocol was applied to lung sections from mice dosed with therapeutic levels of kanamycin and vancomycin. The washing protocol enabled the first drug distribution investigations of aminoglycosides and vancomycin by MSI, paving the way for site-of-disease antibiotic penetration studies.

Aptamer-based ellipsometric sensor for ultrasensitive determination of aminoglycoside group antibiotics from dairy products

BACKGROUND

Residual antibiotics taken along with food consumed through the food chain are the main cause of the super-bacteria and may damage organs such as liver and kidney. Therefore, monitoring residual antibiotic levels of products in the food chain is both important and a requirement. Maximum residual limits for kanamycin and neomycin are 150 ng mL^-1 and 500 ng mL^-1 respectively, which are challenging for most sensor platforms. In this paper, a novel method is presented for the determination of antibiotics residues in animal-derived foods.

RESULTS

Aptamer-based kanamycin and neomycin biosensors based on the spectroscopic ellipsometer and the surface plasmon resonance-enhanced total internal reflection ellipsometer methods as transducing element were developed. Detection limits of both sensor platforms were in the 0.1-1 nmol L^-1 ranges, and the detection range was between the detection limit and 1000 nmol L^-1 .

CONCLUSION

Both ellipsometry-based aptasensors can be used as an alternative to the existing enzyme-linked immunosorbent assay-based method in terms of assay time (10 min), detection limit (0.22 ng mL^-1 for neomycin and 0.048 ng mL^-1 for kanamycin), and detection range. © 2020 Society of Chemical Industry.

Simultaneous Determination of 11 Aminoglycoside Residues in Honey, Milk, and Pork by Liquid Chromatography with Tandem Mass Spectrometry and Molecularly Imprinted Polymer Solid Phase Extraction

An analytical method was developed for the simultaneous determination of 11 aminoglycoside (AG) antibiotics, including amikacin, paromomycin, dihydrostreptomycin, gentamicin C1a, hygromycin, kanamycin, netilmicin, spectinomycin, sisomicin, streptomycin, and tobramycin in honey, milk, and pork samples by LC with tandem MS and molecularly imprinted polymer (MIP) SPE. The AG antibiotics in milk and homogenated meat samples were extracted with a solution composed of 10 mmol/L potassium dihydrogen phosphate, 0.4 mmol/L EDTA-Na2, and 2% trichloroacetic acid. For honey samples, the extractant was 50 mmol/L potassium dihydrogen phosphate. The extracts were cleaned up with MIP SPE cartridges. The separation was performed on a zwitter ionic-HILIC column (50 × 2.1 mm, 3.5 μm), with the mobile phase consisting of methanol, 0.3% formic acid, and 175 mmol/L ammonium formate at 0.50 mL/min in gradient elution. A triple-quadrupole mass spectrometer equipped with an electrospray ionization source, which was operated in positive mode, was used for detection. The quantification was based on matrix-matched calibration curves. The method was applied to real samples with three different matrixes. The LODs of the method were 2–30 μg/kg and the LOQs were 7–100 μg/kg; the average recovery ranged from 78.2 to 94.8%; intraday RSDs and interday RSDs were ≤15 and ≤18%, respectively; and the absolute values of matrix effect for all AGs were RSDs ≤23%.

Study of matrix effects for liquid chromatography-electrospray ionization tandem mass spectrometric analysis of 4 aminoglycosides residues in milk

Matrix effect (ME) is always a major issue for the development of LC-MS/MS method. ME resulting from co-eluting residual matrix components can affect the ionization efficiency of target analytes, leading to quantification errors of the analytes of interest. The present work evaluates MEs of milk samples on simultaneous analysis of four aminoglycosides residues via LC-ESI/MS/MS including streptomycin, dihydrostreptomycin, spectinomycin and kanamycin. Approaches to reduce MEs were examined: optimization of the sample preparation, sample dilution and lower flow rate used. Three commercial sorbents were tested including Oasis MCX, Oasis HLB and Oasis WCX. WCX behaved better for all analytes, but high MEs (80.8-134.9%) were obtained. Therefore, a consecutive SPE of tC18-WCX was found to effectively reduce ME. Milk samples from different manufacturers were analyzed and low MEs (85.6-112.9%) were obtained.

Development of spectrofluorimetric method for determination of certain aminoglycoside drugs in dosage forms and human plasma through condensation with ninhydrin and phenyl acetaldehyde

A simple and sensitive spectrofluorimetric method has been developed and validated for determination of amikacin sulfate, neomycin sulfate and tobramycin in pure forms, pharmaceutical formulations and human plasma. The method was based on condensation reaction of cited drugs with ninhydrin and phenylacetaldehyde in buffered medium (pH 6) resulting in formation of fluorescent products which exhibit excitation and emission maxima at 395 and 470nm, respectively. The different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized. The calibration plots were constructed with good correlation coefficients (0.9993 for tobramycin and 0.9996 for both neomycin and amikacin). The proposed method was successfully applied for the analysis of cited drugs in dosage forms with high accuracy (98.33-101.7)±(0.80-1.26)%. The results show an excellent agreement with the reference method, indicating no significant difference in accuracy and precision. Due to its high sensitivity, the proposed method was applied successfully for determination of amikacin in real human plasma.

Validated spectrofluorimetric method for determination of selected aminoglycosides

New, sensitive, and selective spectrofluorimetric method was developed for determination of three aminoglycoside drugs in different dosage forms, namely; neomycin sulfate (NEO), tobramycin (TOB) and kanamycin sulfate (KAN). The method is based on Hantzsch condensation reaction between the primary amino group of aminoglycosides with acetylacetone and formaldehyde in pH 2.7 yielding highly yellow fluorescent derivatives measured emission (471 nm) and excitation (410 nm) wavelengths. The fluorescence intensity was directly proportional to the concentration over the range 10-60, 40-100 and 5-50 ng/mL for NEO, TOB and KAN respectively. The proposed method was applied successfully for determination of these drugs in their pharmaceutical dosage forms.

[Inducible specific lux-biosensors for the detection of antibiotics: construction and main parameters]

Based on Escherichia coli, highly sensitive specific lux-biosensors for the detection of tetracycline and beta-lactam antibiotics, quinolones, and aminoglycosides have been obtained. To make biosensors, bacteria were used that contained fungal plasmids pTetA'::lux, pAmpC'::lux, pColD'::lux, and plbpA'::lux, in which transcription of the reporter Photorhabdus luminescens luxCDABE genes occurred from the inducible promoters of the tetA, ampC, cda, and ibpA genes, respectively. The main parameters (threshold sensitivity and response time) of lux-biosensors were measured. The high specificity of biosensors responding only to antibiotics of a certain type was demonstrated.

DNA-aptamers binding aminoglycoside antibiotics

Aptamers are short, single stranded DNA or RNA oligonucleotides that are able to bind specifically and with high affinity to their non-nucleic acid target molecules. This binding reaction enables their application as biorecognition elements in biosensors and assays. As antibiotic residues pose a problem contributing to the emergence of antibiotic-resistant pathogens and thereby reducing the effectiveness of the drug to fight human infections, we selected aptamers targeted against the aminoglycoside antibiotic kanamycin A with the aim of constructing a robust and functional assay that can be used for water analysis. With this work we show that aptamers that were derived from a Capture-SELEX procedure targeting against kanamycin A also display binding to related aminoglycoside antibiotics. The binding patterns differ among all tested aptamers so that there are highly substance specific aptamers and more group specific aptamers binding to a different variety of aminoglycoside antibiotics. Also the region of the aminoglycoside antibiotics responsible for aptamer binding can be estimated. Affinities of the different aptamers for their target substance, kanamycin A, are measured with different approaches and are in the micromolar range. Finally, the proof of principle of an assay for detection of kanamycin A in a real water sample is given.

Residues and dynamics of kasugamycin in chilli and soil

A simple and efficient method for determination of kasugamycin in chilli and soil was developed, and the fate of kasugamycin in chilli field ecosystem was also studied. Kasugamycin residues were extracted from sample, cleaned up by solid phase extraction and chromatographic column and then determined by ultra performance liquid chromatography with tandem mass spectrometry detection. The method got recoveries ranged from 77.82% to 83.35% with relative standard deviations of 2.20%-6.54%. As far as the accuracy and precision was concerned, the method met certain standard. The LODs of kasugamycin calculated as a sample concentration (S/N ratio of 3) was 2.50 μg kg(-1). The degradation of kasugamycin in chilli and soil was determined. The results showed that kasugamycin degradation in chilli plant and soil followed the first-order kinetics. The half-lives of kasugamycin in chilli and soil was 2.76-3.77 and 3.07-3.91 days, respectively. The final kasugamycin residues in chilli and soil were undetectable at levels of recommended and 1.5 times recommended dosage with an interval of 21 days.

Sensitive fluorescence detection of etimicin based on derivatives of formaldehyde and acetylacetone

A novel fluorescence method for the determination of etimicin is described. Etimicin reacts with acetylacetone and formaldehyde in pH 4.0 Britton-Robinson (B.R.) buffer solution to from a fluorescent substance [I]. Emission spectra of [I] and the reagent blank were overlapped, so the arithmetic emission spectra of the fluorescent substance were obtained by subtracted form the spectra of [I] to the spectra of the reagent blank using the Fluorescence Data Software. There is a linear relationship between the intensity of the arithmetic emission spectra and the concentration of etimicin. Effects of pH, amount of acetylacetone-formaldehyde, and heating time on the determination of etimicin have been examined. Etimicin can be determined over the concentration range of 1.0 to 10.0 μg mL(-1) with a correlation coefficient of 0.9991. The relative standard deviation (RSD) for 11 repetitive determinations of 5.0 μg mL(-1) etimicin is 0.22%. The utility of this method was demonstrated by determining etimicin in commercial samples.

Toggled RNA aptamers against aminoglycosides allowing facile detection of antibiotics using gold nanoparticle assays

We have used systematic evolution of ligands by exponential enrichment (SELEX) to isolate RNA aptamers against aminoglycoside antibiotics. The SELEX rounds were toggled against four pairs of aminoglycosides with the goal of isolating reagents that recognize conserved structural features. The resulting aptamers bind both of their selection targets with nanomolar affinities. They also bind the less structurally related targets, although they show clear specificity for this class of antibiotics. We show that this lack of aminoglycoside specificity is a common property of aptamers previously selected against single compounds and described as "specific". Broad target specificity aptamers would be ideal for sensors detecting the entire class of aminoglycosides. We have used ligand-induced aggregation of gold-nanoparticles coated with our aptamers as a rapid and sensitive assay for these compounds. In contrast to DNA aptamers, unmodified RNA aptamers cannot be used as the recognition ligand in this assay, whereas 2'-fluoro-pyrimidine derivatives work reliably. We discuss the possible application of these reagents as sensors for drug residues and the challenges for understanding the structural basis of aminoglycoside-aptamer recognition highlighted by the SELEX results.

Multiresidue analysis of antibiotics in food of animal origin using liquid chromatography-mass spectrometry

Antibiotics are the most important drugs administered in veterinary medicine. Their use in food-producing animals may result in antibiotic residues in edible tissues, which are monitored to protect human and animal health, support the enforcement of regulations, provide toxicological assessment data, and resolve international trade issues. This chapter provides basic characterization of the most important classes of antibiotics used in food-producing animals (aminoglycosides, amphenicols, β-lactams, macrolides and lincosamides, nitrofurans, quinolones, sulfonamides, and tetracyclines), along with examples of practical liquid chromatographic-(tandem) mass spectrometric methods for analysis of their residues in food matrices of animal origin. The focus is on multiresidue methods that are favored by regulatory and other food testing laboratories for their ability to analyze residues of multiple compounds in a time- and cost-effective way.

Analysis of antibiotic fungicide kasugamycin in irrigation water by high performance liquid chromatography

A high performance liquid chromatographic (HPLC) analysis method with an ultraviolet (UV) detector and an Aqua C18 (250 x 4.6 mm, Phenomenex) column were applied to analyze the antibiotic fungicide kasugamycin in water. An aromatic sulfonic acid spe column (Backerbond, J. T. Backer) was used to remove the interfering materials from irrigation water. A good linear relation existed between the concentration of the fungicide and the peak area, and correlation coefficient of linearity from 0.1 to 10.2 microg/mL was 0.998. The accuracies expressed as the recoveries of kasugamycin from irrigation water ranged from 112.2 to 111.7 %. The precisions expressed as relative standard deviations (RSD) were found to be below 7.0 %. The quantitative detection limit (LOQ) of kasugamycin in irrigation water was set at 2.2 microg/mL which was 2-times higher than the method detection limit (MDL) 1.03 microg/mL. Electrospray ionization-mass (ESI-MS) and fast-atom bombardment-mass (FAB-MS) were applied to compare the ability of identifying the component of the eluent peak from HPLC, and the result indicated that electrospray ionization-mass (ESI-MS) was more sensitive than fast-atom bombardment-mass (FAB-MS) in the detection of kasugamycin. There was no kasugamycin residue detected in irrigation water samples collected from paddyfields at Wufong, indicated that the residues of kasugamycin in water were less than 2.2 microg/mL, and the risk of water contamination was very low.

Multiclass, multiresidue drug analysis, including aminoglycosides, in animal tissue using liquid chromatography coupled to tandem mass spectrometry

A multiresidue, multiclass semiquantitative screening analysis of 39 drug residues covering 8 drug classes, including aminoglycosides in veal muscle, based on a single multiresidue extraction routine and using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS), is presented. Sample preparation involves extraction of a 5 g diced tissue sample with 10 mL of acetonitrile/ water (86:14), incubated at 60 degrees C for 1 h, and then cooled for 10 min in ice. Formic acid is added to the suspension, then mixed, and centrifuged. The supernatant is retained, and the pellet is extracted with 10 mL of water for aminoglycosides and again centrifuged. Approximately 9.5 mL of each of the supernatants from both extracts is combined and diluted with water to 25 mL. The final solution is then defatted with 20 mL of hexane prior to analysis. Liquid chromatography for the aminoglycosides is carried out with ZIC-HILIC and for the remainder of the compounds with an Atlantis dC18 minicolumn. LC-ESI-MS/MS in positive and negative ionization modes (three injections total) is carried out, and two ion transitions per analyte are monitored. The method provides semiquantitative analysis to identify incurred positive drug classes in a rapid and cost-effective manner. Of particular interest is the detection of numerous compounds in the low nanograms per gram concentration range, which are not typically detected using receptor-based screening methods. All identified drugs were confirmed using internationally recognized regulatory methods, with no apparent false positives.

Immunoassays for the rapid detection of gentamicin and micronomicin in swine muscle

A monoclonal antibody (mAb)-based ELISA and strip test for gentamicin (GEN) and its analogue micronomicin (MIN), are reported in this study. The conjugate gentamicin-glutaraldehyde-bovine serum albumin (GEN-GDA-BSA) was used as an immunogen. The produced anti-GEN mAB exhibited high cross-reactivity with micronomicin (MIN; 131.2%) and slight or negligible crossreactivity with other aminoglycosides. Based on this mAB, an ELISA and a strip test for GEN and MIN were developed and evaluated. The ELISA showed a 50% inhibition concentration (IC50) of 0.75 ng/mL for GEN and 0.58 ng/mL for MIN. For GEN, the average recoveries at 25-200 microg/kg ranged from 73 to 91%, with intraday CVs of 9-16% and interday CVs of 8-15%. For MIN, the average recoveries ranged from 108 to 131%, with intraday CVs of 10-16% and interday CVs of 8-15%. In contrast, the strip test for GEN or MIN had a detection limit of 5 ng/mL in phosphate-buffered saline and 50 microg/kg in muscle (n=24), and the results could be judged within 10 min. The detection results of incurred samples analyzed by the strip test, ELISA, and HPLC indicated that the two immunoassays correlated well with the HPLC method and could be used as convenient tools for the rapid screening of GEN and MIN residues in swine muscle.

Resonance Rayleigh scattering and resonance non-linear scattering method for the determination of aminoglycoside antibiotics with water solubility CdS quantum dots as probe

In pH 6.6 Britton-Robinson buffer medium, the CdS quantum dots capped by thioglycolic acid could react with aminoglycoside (AGs) antibiotics such as neomycin sulfate (NEO) and streptomycin sulfate (STP) to form the large aggregates by virtue of electrostatic attraction and the hydrophobic force, which resulted in a great enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum scattering peak was located at 310 nm for RRS, 568 nm for SOS and 390 nm for FDS, respectively. The enhancements of scattering intensity (DeltaI) were directly proportional to the concentration of AGs in a certain ranges. A new method for the determination of trace NEO and STP using CdS quantum dots probe was developed. The detection limits (3 sigma) were 1.7 ng mL(-1) (NEO) and 4.4 ng mL(-1) (STP) by RRS method, were 5.2 ng mL(-1) (NEO) and 20.9 ng mL(-1) (STP) by SOS method and were 4.4 ng mL(-1) (NEO) and 25.7 ng mL(-1) (STP) by FDS method, respectively. The sensitivity of RRS method was the highest. The optimum conditions and influence factors were investigated. In addition, the reaction mechanism was discussed.

Simultaneous identification and quantitative determination of selected aminoglycoside antibiotics by thin-layer chromatography and densitometry

A TLC-densitometric method has been developed for simultaneous identification and quantitative determination of amikacin, gentamicin, kanamycin, neomycin, netilmicin, and tobramycin. This separation of antibiotics was achieved on silica gel TLC plates without a fluorescent indicator and with methanol-25% ammonia-chloroform (3 + 2 + 1, v/v/v) as the mobile phase. The densitometric measurements were made at 500 nm after detection with a 0.2% ninhydrin solution in ethanol. Under these conditions, good separation of the chosen aminoglycosides was obtained. The method is distinguished by high sensitivity, with the LOD from 0.25 microg for amikacin to 1.00 microg for gentamicin and the LOQ from 0.5 microg for amikacin to 1.65 microg for gentamicin, and a wide linearity range 0.75-6.25 microg/spot for amikacin and netilmicin and 1.5-12.50 microg/spot for other antibiotics. The precision of the determination was very good; RSD varied in the range 0.3-0.6%.

sanN encoding a dehydrogenase is essential for Nikkomycin biosynthesis in Streptomyces ansochromogenes

Nikkomycins are a group of peptidyl nucleoside antibiotics with potent fungicidal, insecticidal, and acaricidal activities. sanN was cloned from the partial genomic library of Streptomyces ansochromogenes 7100. Gene disruption and complementation analysis demonstrated that sanN is essential for nikkomycin biosynthesis in S. ansochromogenes. Primer extension assay indicated that sanN is transcribed from two promoters (sanN-P1 and sanN-P2), and sanN-P2 plays a more important role in nikkomycin biosynthesis. Purified recombinant SanN acts as a dehydrogenase to convert benzoate-CoA to benzaldehyde in a random-order mechanism in vitro, with respective Kcat/Km values of 3.8 mM-1s-1 and 12.0 mM-1s-1 toward benzoate-CoA and NADH, suggesting that SanN catalyzes the formation of picolinaldehyde during biosynthesis of nikkomycin X and Z components in the wild-type stain. These data would facilitate us to understand the biosynthetic pathway of nikkomycins and to consider the combinatorial synthesis of novel antibiotic derivatives.

Micellar electrokinetic chromatography of aminoglycosides

The components of the aminoglycosides, e.g., gentamicin, sisomicin, netilmicin, kanamycin, amikacin, and tobramycin, and related impurities of these antibiotics can be separated by means of micellar electrokinetic chromatography (MEKC). Derivatization with o-phthaldialdehyde and thioglycolic acid is found to be appropriate for all antibiotics. The background electrolyte was composed of sodium tetraborate (100 mM), sodium deoxycholate (20 mM), and beta-cyclodextrin (15 mM) and has a pH value of 10.0. This method is valid for evaluation of gentamicin, kanamycin, and tobramycin. It has yet to be adopted for amikacin, paramomycin, neomycin, and netilmicin.

Analytical Profiling of Biosynthetic Intermediates Involved in the Gentamicin Pathway of Micromonospora echinospora by High-Performance Liquid Chromatography Using Electrospray Ionization Mass Spectrometric Detection

In the present study, we developed a sensitive and highly selective method of detecting the biosynthetic intermediates involved in the gentamicin pathway from a cell culture of Micromonospora echinospora. A novel extraction method utilizing a dual solid-phase extraction (SPE) technique was employed to purify and recover all of the gentamicin-related components from the cell culture broth, and high-performance liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS/MS) was used to analyze the extractant for gentamicin intermediates. The pH of the culture broth was adjusted to an acidic condition of pH 2 prior to the extraction. The samples were first cleaned with a reversed-phase AccuBOND C(18) cartridge, and then the aminoglycosidic components were purified using a cationic exchanger OASIS MCX cartridge. The detection limit of a gentamicin standard spiked in blank medium processed by this method was found to be approximately 5 ng for each component of the gentamicin C complex, and the mean recovery for each component of standard gentamicin was above 91% when analyzed by HPLC-ESI-MS/MS. We further demonstrated that this method enables the analytical profiling of the gentamicin-related compounds produced by wild-type M. echinospora ATCC 15835, which mainly produces the gentamicin C complex, and the UV-induced mutant strain KCTC 10506BP, which produces gentamicin B as the major product. Seven intermediates (paromamine, gentamicin A2, B, X2, A, JI-20A, and JI-20B) besides the gentamicin C complex were detected in the culture broth of both M. echinospora strains when analyzed by MS/MS for the distinct fragmentation patterns of each gentamicin component. This report displays the first example of the HPLC profiling in a wide range of structurally related biosynthetic intermediates involved in the gentamicin pathway.

Impact of workflow-integrated corollary orders on aminoglycoside monitoring in children

Computerized provider order entry (CPOE) and clinical decision support improve medication prescribing safety in adults. However, effective therapy for children requires dosing based on circulating medication levels. We examined the introduction of a computerized corollary order for aminoglycoside blood level monitoring. The study was divided into baseline (BP) and corollary order (CP) periods. In the CP, we implemented a workflow-integrated reminder to order blood levels and presented this to the clinician during each aminoglycoside ordering session. Appropriate laboratory monitoring was 128/159 (80.5%) courses in the BP and 146/177 (82.5%) courses in the CP. Thus introduction of the order did not significantly improve laboratory monitoring rates, nor did it result in a reduction in the rate of either toxic or subtherapeutic levels. However, aminoglycoside corollary orders may have an important role in institutions where pharmacists are not actively involved in monitoring therapy.

Determination of neomycin sulfate and impurities using high-performance anion-exchange chromatography with integrated pulsed amperometric detection

Neomycin B is one of a class of aminoglycoside antibiotics that lack a good chromophore, and is therefore difficult to determine using reversed-phase HPLC with absorbance detection. This is especially true for determining the quantity of each impurity. We show that neomycin sulfate and its major impurities, including neamine (neomycin A), can be separated on a strong anion-exchange column using a weak potassium hydroxide eluent (2.40 mM) at a column temperature of 30 degrees C, and directly detected by integrated pulsed amperometric detection (IPAD). The resolution (United States Pharmacopeia (USP) definition) between neomycin B and the closest major impurity ranged from 6.56 and 7.45 over 10 days of consecutive analysis (7.24+/-0.10, n=836 injections). Due to the difficulty of producing weak hydroxide eluents of the required purity (i.e. carbonate-free), this method depends on automatic eluent generation to ensure method ruggedness. This method exhibited good long-term (10 days, 822 injections) retention time stability with a R.S.D. of 0.6%. Peak area R.S.D. (10 microM) was 1.3%. Method robustness was evaluated by intentionally varying the flow rate, eluent concentration, column temperature, and column. The spike recoveries of neomycin B from extractions of three different topical ointments and cream formulations ranged from 95 to 100%. The measured concentration of neomycin B in these formulations ranged from 119 to 154% of the label concentration. The R.S.D. for the measured concentration of one of the formulations tested over three separate days, n=11 extracts, was 3.2%. Based on the results of these evaluations, we believe this method can be used for neomycin sulfate identity, assay, and purity.

Electrochemical detection of tobramycin or gentamicin according to the European Pharmacopoeia analytical method

Tobramycin and gentamicin are two aminoglycosidic antibiotics used in lung infection, ophthalmic treatments as well as in skin infections. Pharmaceutical companies which produce remedies containing tobramycin and gentamicin need an analytical method for their internal quality control. For several years a simple chromatographic method based on anion exchange separation coupled with amperometric detection was proposed for aminoglycosides. This analytical approach was partially used in the last edition of the European Pharmacopoeia (EP) for tobramycin and gentamicin analysis. In fact they use integrated pulsed amperometric detection (IPAD) on a gold electrode while the separation is obtained on a polymeric wide pore reversed phase instead of anion exchange in alkaline conditions. Such coupling seems to be cumbersome and not so easy to realize and to reproduce from one laboratory to another. Besides, the described method lacks some of the details as important as the waveform steps duration. Unfortunately the quality control (QC) laboratories have to use exactly the method described in the EP, so they complained about the troubles. Therefore, the EP authors published recently a paper regarding the guidelines for good practice in the method application, but the suggestion was not yet resolutive. In our work we evaluated the eluent composition and the kind of amperometric cell, work electrode diameter and cell volume. Mainly we optimized the amperometric waveform. In addition, for tobramycin analysis another chromatographic phase was explored in order to achieve better efficiency and to separate all the impurities confirming the effectiveness of the detection. The conditions described in the paper seem to allow the analyst to operate in conformity with the EP method.

Trace analysis of aminoglycoside antibiotics in bovine milk by MEKC with LIF detection

This work describes a straightforward and sensitive method for the multi-residue analysis of aminoglycoside antibiotics (kanamycin B, amikacin, neomycin B and paromomycin I) in bovine milk samples. The method involves the pre-capillary derivatization of antibiotics with sulfoindocyanine succinimidyl ester (Cy5) and their separation and determination by MEKC with LIF detection. The optimum procedure includes a derivatization step of the antibiotics at 25 degrees C for 30 min and direct injection for MEKC analysis, which is performed in about 20 min by using borate buffer (35 mM; pH 9.2) with 55 mM SDS as an anionic surfactant and 20% ACN as the organic modifier. Under these conditions, dynamic ranges of 10-500 microg/L and RSDs (within-day precision) from 3.8 to 5.3% were obtained. These results indicate that the proposed MEKC-LIF method is useful as a selective and sensitive tool for the determination of these antibiotics and surpasses other reported electrophoretic alternatives. Finally, the method was successfully applied to bovine milk samples after a simple solid-phase extraction clean-up and preconcentration procedure. The aminoglycosides were readily detected at 0.5-1.5 microg/kg levels with average recoveries ranging from 89.4 to 93.3%.

Determination of vertilmicin sulfate and its related substances by HPLC-ELSD and HPLC-MS2

A new and simple high-performance liquid chromatography (HPLC)-evaporative light scattering detection (ELSD) method for the determination of vertilmicin sulfate and its related substances is developed. The column is an Agilent SB-C(18) (250 x 4.6 mm, 5 microm). The mobile phase is 0.05 mol/L trifluoroacetic acid-methanol (85:15). Good separation of vertilmicin from the main related substances is achieved. The standard curve is rectilinear in the range of 270-1350 microg/mL (r = 0.9998). The average recovery is 99.8%. The limit of detection is 10 microg/mL. The HPLC-mass spectrometry-mass spectrometry (MS(2)) method is used to characterize the structures of vertilmicin sulfate and its related substances. In positive mode, vertilmicin sulfate and its related substances are elucidated by use of electrospray ion trap MS in the multi-stage MS full scan mode. The possible structure of an unknown impurity in vertilmicin is deduced based on the HPLC-MS(2) data.

On-line concentration of neomycin and screening aminoglycosides in milk by short capillary column and tandem mass spectrometry

An MS-MS method was established for the trace analysis of neomycin and screening aminoglycoside antibiotics (such as amikacin, gentamicin, kanamycin, and tobramycin) in a milk sample. The extraction and purification are based on ion-pair SPE technology on a short fused-silica capillary RP C18 column. The capillary SPE column provided the stationary phase to retain aminoglycoside antibiotics and MS-MS compatible organic acid heptafluorobutyric acid (HFBA) was used as protein precipitation and ion-pair reagent. Aminoglycosides were extracted in this short column and directly eluted to MS-MS without evaporating to dryness and reconstituted with MS-MS compatible solvent after SPE. The LOQ was 0.1 microg/mL and the calibration curve was linear up to 6.4 microg/mL. A small amount of milk product, 10 microL, is sufficient for the analysis and application of this method as the trace analysis of neomycin in the biological matrix proved simple and workable.

Evaporative light scattering detection (ELSD): a tool for improved quality control of drug substances

Thanks to the recent technological advancements, evaporative light-scattering detection (ELSD) is regarded as a valuable alternative to UV detection for liquid chromatographic analysis of substances that do not contain a chromophore. In the field of substances for pharmaceutical use, LC-ELSD appears to be suitable for aminoglycosides, most of which (for ex. gentamicin) are presently controlled in the Ph. Eur. by pulsed amperometric detection. Other substances (ex sugars, triglycerides) presently employing refractometrric detection, could be conveniently analysed by LC-ELSD. ELS detection is regarded as robust and relatively simple, although not particularly sensitive. A key feature of ELSD is that - unlike refractometry - it can operate in gradient mode, thus allowing application of more selective liquid chromatographic methods. ELSD can also be used to set up MS-compatible methods, as the mobile phase constraints are essentially the same. Due to all the above, ELSD is becoming increasingly used in pharmacopoeial methods.

Cp*Rh-Based Indicator-Displacement Assays for the Identification of Amino Sugars and Aminoglycosides

Indicator-displacement assays based on the organometallic complex [{Cp*RhCl2}2] (Cp*=pentamethylcyclopentadienyl) and the dye gallocyanine were used to sense amino sugars and aminoglycosides in buffered aqueous solution by conducting UV-visible spectroscopy. The data of three assays at pH 7.0, 8.0, and 9.0 were sufficient to distinguish between the amino sugars galactosamine, glucosamine, mannosamine and the aminoglycosides kanamycin A, kanamycin B, amikacin, apramycin, paromomycin, and streptomycin. Furthermore, the assays were used to characterize mixtures of aminoglycosides and obtain quantitative information about the respective analytes.

Analysis of etimicin sulfate by liquid chromatography with pulsed amperometric detection

A new method for determination of etimicin's (ETM) purity and content is developed by liquid chromatography (LC) and pulsed amperometric detection (PAD). A reversed-phase ion-pair LC method with pulsed amperometric detection on a gold electrode after post-added NaOH is described. The mobile phase consisted of an aqueous solution containing 0.033 mol L(-1) oxalic acid, 0.012 mol L(-1) heptafluorobutyric acid, and 210 mL L(-1) acetonitrile with pH 3.40 adjusting by dilute NaOH solution. The total analysis time was not more than 30 min. The effects of the different chromatographic parameters on the separation were also investigated. A number of commercial samples of etimicin sulfate were analyzed using this method.

Rapid and sensitive determination of aminoglycoside antibiotics in water samples using a strong cation-exchange chromatography non-derivatisation method with chemiluminescence detection

A simple and sensitive chemiluminescence (CL) detection approach was developed for the direct analysis of aminoglycoside antibiotics in water samples following strong cation-exchange chromatographic (SCX-HPLC) separation. This detection system, which eliminates the need for sample derivatisation, is based on the inhibitory effect of aminoglycosides on the CL reaction between luminol and hydrogen peroxide catalysed by copper(II). As the operational and chemical variables that affect the CL signal were optimised, ionic strength and the Triton X-100 micelles turned out to be the keys to obtain maximum CL efficiency. Aminoglycosides were successfully separated in 10 min on a SCX column using a mobile phase consisting of an aqueous solution containing 5.0 x 10(-3)mol/l sodium acetate and 0.65 mol/l sodium chloride at pH 6.1. Sample volumes of 50 ml were preconcentrated by passage through a weakly acidic IRC-50 exchange column. Limits of detection from 0.7 to 10 microg/l and relative standard deviations from 2.7 to 5.4% were thus obtained. The proposed method surpasses other chromatographic alternatives in terms of the limit of detection, sample requirements for analysis and cost.

1H and 13C NMR data for indolo[2,3-b]quinoline-aminoglycoside hybrids, a novel potent anticancer drug family

The complete NMR signal assignment of title compounds were carried out by extensive use of 1D and 2D NMR techniques (1H, 13C, GCOSY, GHSQC and GHMBC).

Comparative study on the analytical performance of three waveforms for the determination of several aminoglycoside antibiotics with high performance liquid chromatography using amperometric detection

A preliminary comparative study was carried out on the analytical performances of a new six-potential waveform and other two detection waveforms, triple-potential waveform and quadruple-potential waveform. The analytical performances compared included signal response, background noise, signal/noise ratio and signal stability. Compared with triple-potential waveform and quadruple-potential waveform, the new six-potential waveform had higher signal response, signal/noise ratio, and sensitivity. As for determination reproducibility, the six-potential waveform also exhibited a slightly better performance than the other two waveforms. Under the selected experimental conditions based on the six-potential waveform, there is a linear correlation between peak area and concentration over two to three orders of magnitude for nine aminoglycoside antibiotics with a correlation coefficients better than 0.998 and the detection limits measured as three times the peak height signal-to-noise ratio for the nine aminoglycoside antibiotics were in the range of 0.0198-0.889 microg/mL. The proposed method had been used to analyze real gentamicin sulphate drug sample.

Determination of 11 aminoglycosides in meat and liver by liquid chromatography with tandem mass spectrometry

A method using liquid chromatography with tandem mass spectrometry was developed for the determination of 11 commonly used aminoglycoside antibiotics in meat. The proposed method is sufficiently sensitive (detection limits of 15 to 40 ppb for the various antibiotics) and highly selective. It is suitable for the quantitation and confirmation of aminoglycosides in a variety of matrixes (pork muscle, fish, and veal liver). Any multiresidue method for aminoglycosides must take into account their high affinity toward sample proteins and the significantly different pK values of the various analytes. The developed method uses a low-pH extraction with trichloracetic acid to ensure complete extraction of the analytes from the matrix. An anion-exchange step is used to remove the acid from the centrifuged extract. Aminoglycosides in this solution of low ionic strength can be quantitatively retained and afterwards eluted from a weak cation-exchanger solid-phase extraction (SPE) cartridge. The highly selective SPE steps produce clean extracts, which minimize possible suppression of the mass spectrometer signal.

Stability indicating reversed-phase ion-pairing liquid chromatographic determination of vertilmicin sulfate as bulk drug and in injections

A simple reversed-phase high performance liquid chromatographic method was developed for the analysis of vertilmicin sulfate, a novel aminoglycoside (AG). UV detection was used to determine vertilmicin sulfate and its related compounds in drug substance and products without sample derivatization. The method was used to determine the content of vertilmicin and its related compounds and test the stability of vertilmicin sulfate as drug substance and in injections, which was required for registration of new drug.

Simple confirmatory assay for analyzing residues of aminoglycoside antibiotics in bovine milk: hot water extraction followed by liquid chromatography–tandem mass spectrometry

A simple, selective and sensitive procedure for determining nine widely used aminoglycoside antibiotics (AGs) in bovine whole milk is presented. It is based on matrix solid-phase dispersion with heated water, at 70 degrees C, as extractant followed by liquid chromatography (LC)-tandem mass spectrometry (MS) using an electrospray ion source. After acidification and filtration, 0.2 ml of the aqueous extract was injected into the LC column. MS data acquisition was performed in the multi reaction monitoring mode, selecting two (three, when possible) precursor ion > product ion transitions for each target compound. Analyte recoveries ranged between 70 and 92%. Using aminosidine (an AG not used in veterinary medicine) as surrogate internal standard, the accuracy of the method at three spike levels varied between 80 and 107% with R.S.D. not larger than 11%. The limits of quantification were between 2 ng/ml (apramycin) and 13 ng/ml (streptomycin). They are well below the tolerance levels set by both the European Union and the U.S. Food and Drug Administration.

Mass spectrometric study to characterize thioisoindole derivatives of aminoglycoside antibiotics

Aminoglycoside antibiotics are widely used to treat serious Gram-negative and Gram-positive bacterial infections. The lack of a UV chromophore presents a problem in the analysis of aminoglycosides. Derivatization with 1,2-phthalic dicarboxaldehyde (OPA) in the presence of a thiol made it possible to introduce a UV chromophoric thioisoindole moiety. A qualitative mass spectrometry study was carried out to confirm the molecular identity of the products formed. The conditions described earlier to derivatize gentamicin and kanamycin yielded products in which all primary amino groups are fully derivatized. On the other hand, with tobramycin and amikacin, there was also formation of incompletely derivatized products that contained one thioisoindole group less than the fully derivatized product. This study has therefore brought an additional insight into the nature of the OPA-aminoglycoside derivatives studied.

Preparation of macrocyclic 15N-labelled oligoaminodeoxysaccharides as probes for RNA-binding

Two macrocyclic aminoglycosides were prepared from a 1,4-butanediol linked 2-deoxy-L-rhamnal which was O-allylated at the 4- and 4'-positions via the precursor allyl 3,4-di-O-acetyl-2,6-dideoxy-alpha-L-arabino-hexoside employing olefin metathesis and ring closing metathesis in a sequential manner. The macrocycles were 15N-labelled at all four amino groups in order to study interactions with regulatory RNA structures in solution by NMR spectroscopy. A key step for the introduction of the 15N-label was a reductive amination step using commercially available 15NH4OAc. The reductive amination proceeds with excellent stereocontrol. As a by-product the unusual acyclic amino nitrile was isolated which originated from intramolecular imine formation followed by cyanide addition to the intermediate C=N double bond.

[Electrospray ion trap mass spectrometry of eight aminoglycoside antibiotics]

AIM

To study the dissociation pathways of aminoglycoside antibiotics.

METHODS

In positive mode, eight aminoglycoside antibiotics were elucidated by use of electrospray ion trap mass spectrometry in the multi-stage MS full scan mode.

RESULTS

It was demonstrated that the eight aminoglycoside antibiotics gave abundant product ions at m/z 322 (gentamicin, micronomicin and sisomicin), m/z 350 (etimicin, netilmicin and vetilmicin) and m/z 324 (kanamycin and tobramycin) by loss of the C-ring (amino-alpha-D-glucopyranose) in MS2 full scan mode. In MS3 full scan mode, the prominent fragmentation ions at m/z 163 as well as m/z 191 were formed from the fragmentation ions at m/z 322, m/z 350 and m/z 324 by loss of the A-ring (amino-alpha-D-glucopyranose), separately, while the characteristic fragmentation ions at m/z 160 as well as m/z 162 were formed from m/z 322, m/z 350 and m/z 324 by loss of the B-ring (2-deoxy-D-streptamine), separately.

CONCLUSION

The structural information was obtained via collision-activated dissociation and these characteristics are applicable to the structural elucidation and quantitative analysis of aminoglycoside compounds.

Determination of Aminoglycosides and Quinolones in Food Using Tandem Mass Spectrometry: A Review

The widespread use of antibiotics in dairy cattle management may result in the presence of antibiotic residues in food. While rapid screening tests are commonly used to detect the presence of antibiotics in food, more accurate chromatographic-mass spectrometric methods combined with tandem mass spectrometry (MS/MS) are required to determine the identity and quantity of the antibiotic present. These methods (HPLC/MS/MS) may have the greatest potential for accomplishing direct multi-residue identifications in complex biological matrices, such as food. This study reviews recent applications of tandem mass spectrometry in the determination of antibiotic residues, such as aminoglycosides and quinolones in food.

Cloning and characterization of sanO, a gene involved in nikkomycin biosynthesis in Streptomyces ansochromogenes

AIMS

To clone and characterize sanO, a gene involved in the biosynthesis of nikkomycins in Streptomyces ansochromogenes.

METHODS AND RESULTS

A 4.5-kb BamHI-KpnI fragment was cloned and sequenced. Sequence analysis revealed that this fragment contains three complete open reading frames. The largest one with 2034 bp was designated sanO, which encodes a protein consisting of 667 amino acids with high similarity to module of peptide synthetase. sanO disruption mutants produced no nikkomycin X, but formed nikkomycin Z at almost the same level of the wild-type strain. The production of nikkomycin X can be recovered by genetic complementation of sanO disruption mutants. Primer extension also revealed that transcription start point(tsp) of sanO was localized 87 bp upstream of the potential start codon (GTG).

CONCLUSIONS

sanO was essential for the biosynthesis of nikkomycin X.

SIGNIFICANCE AND IMPACT OF THE STUDY

Nikkomycins have received increased interest of study because of their prospective application in agriculture and medicine. Cloning and characterization of genes involved in the nikkomycin biosynthesis will help to elucidate the whole biosynthetic pathway of nikkomycins.

A new micellar electrokinetic capillary chromatography method for separation of the components of the aminoglycoside antibiotics

Aminoglycoside antibiotics are always a mixture of structurally related amino sugars, which do not have a chromophore or fluorophore. The aim of the study was to find one method for evaluation of the components and impurities of the antibiotics. Derivatization with o-phthaldialdehyde and thioglycolic acid is found to be appropriate for all antibiotics. The components of gentamicin (GM), sisomicin, netilmicin, kanamycin, amikacin, and tobramycin were tried to separate by means of micellar electrokinetic chromatography. The background electrolyte was composed of sodium tetraborate (100 mM, pH 10.0), sodium deoxycholate (20 mM), and beta-cyclodextrin (15 mM). This method is valid for evaluation of GM, kanamycin, and tobramycin. It has to be improved for amikacin and netilmicin. In addition, 46 bulk samples of GM of different manufacturer or pharmaceutical companies were investigated. Many samples were found to contain many minor products and different amounts. Beside different patterns of the main compounds GM C1, GM C1a, GM C2a, and GM C2, many lots were found consisting of a substantial number of minor products. The appearance of a high number of minor products is always associated with the existence of sisomicin, which is not found in "pure" samples. However, almost all samples met the requirements of the European Pharmacopoeia (EP) and United States Pharmacopoeia (USP).

Resonance Rayleigh scattering spectra for studying the interaction of aminoglycoside antibiotics with pontamine sky blue and their analytical applications

In a weakly acid medium, some aminoglycoside antibiotics, such as kanamycin (KANA), gentamicin (GEN), tobramycin (TOB), and neomycin (NEO), or acid bisazo dye pontamine sky blue (PSB) can only produce very weak resonance Rayleigh scattering (RRS) signals. However, when the two agents react with each other to form the ion association complexes, the RRS intensity can be enhanced greatly and a new RRS spectrum and a significant enhancement of the RRS intensity in the wavelength range 350-600 nm can be observed. The maximum scattering peak is at 580 nm. There is a linear relationship between the RRS intensity and the antibiotic concentration in the range 0.01-6.0 microg mL(-1) at 580 nm. This RRS method has therefore been developed for the determination of trace levels of aminoglycoside antibiotics. The detection limits (3 sigma) of the four antibiotics, whose order of sensitivity is KANA>NEO>TOB>GEN, are 5.8-6.9 ng mL(-1). This method has a good selectivity and has been successfully applied to the quick determination of antibiotics not only for injections and ear drops, but clinic serum samples as well. In addition, quantum chemistry-based analysis of the reaction mechanism, the factors influencing the RRS spectra, and the reasons for the enhancement of RRS are discussed.

Reversed-phase liquid chromatographic method for the analysis of aminoglycoside antibiotics using pre-column derivatization with phenylisocyanate

A pre-column derivatization liquid chromatographic method has been developed for the analysis of aminoglycoside antibiotics using phenylisocyanate as a derivatization reagent. Derivatives including kanamycin, neomycin and gentamicin were formed by reaction of the analytes with phenylisocyanate in the presence of triethylamine. Phenylisocyanato groups were attached to corresponding amino groups of aminoglycoside and their molecular mass was confirmed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). The experimental conditions for derivatization and separation of aminoglycoside derivatives were optimized and validated. A simple liquid chromatographic method for the determination of aminoglycoside antibiotics was demonstrated.

[Analysis of the response factors of different aminoglycoside antibiotics detected by evaporative light-scattering detector]

AIM

To analyze if the response factors of different aminoglycoside antibiotics detected by evaporative light-scattering detector (ELSD) are the same. If they are, then ELSD can be applied to the quality analysis of this class of antibiotics.

METHODS

The response factors of five different aminoglycosides (amikacin, sisomicin, netilmicin, etimicin and vertilmicin) detected by ELSD were determined by using a Diamonsil C18 column (150 mm x 4.6 mm, 5 microns) as analytical column and 0.2 mol.L-1 trifluoroacetic acid-methanol (94:6) as mobile phase at a flow rate of 0.6 mL.min-1, the temperature of the drift tube was set at 110 degrees C, and the flow of carrier gas at 2.80 L.min-1. Detector responses (A) and the amount of injection of each substance (m) were fitted to the logarithmic regression: logA = blogm + loga.

RESULTS

The linear regression equation obtained were amikacin: Y = 1.46X + 5.07, gamma = 0.9997; sisomicin: Y = 1.51X + 5.03, gamma = 0.9997; netilmicin: Y = 1.52X + 4.88, gamma = 1.000; etimicin: Y = 1.46X + 4.85, gamma = 0.9999; vertilmicin: Y = 1.41X + 4.90, gamma = 0.9998. The differences between them were negligible.

CONCLUSION

Different aminoglycosides can give the same responses with ELSD detection. So, the HPLC-ELSD methods can be applied to the analysis of impurities, the control of the ratio of multi-components drug and the determination of new substances by using another substance as reference, etc.