A distant global control region is essential for normal expression of anterior HOXA genes during mouse and human craniofacial development

Craniofacial abnormalities account for approximately one third of birth defects. The regulatory programs that build the face require precisely controlled spatiotemporal gene expression, achieved through tissue-specific enhancers. Clusters of coactivated enhancers and their target genes, known as superenhancers, are important in determining cell identity but have been largely unexplored in development. In this study we identified superenhancer regions unique to human embryonic craniofacial tissue. To demonstrate the importance of such regions in craniofacial development and disease, we focused on an ~600 kb noncoding region located between NPVF and NFE2L3. We identified long range interactions with this region in both human and mouse embryonic craniofacial tissue with the anterior portion of the HOXA gene cluster. Mice lacking this superenhancer exhibit perinatal lethality, and present with highly penetrant skull defects and orofacial clefts phenocopying Hoxa2-/- mice. Moreover, we identified two cases of de novo copy number changes of the superenhancer in humans both with severe craniofacial abnormalities. This evidence suggests we have identified a critical noncoding locus control region that specifically regulates anterior HOXA genes and copy number changes are pathogenic in human patients.

Pregnancy termination at a viable stage in daily clinical practice: A nationwide mortality follow-back study in Flanders, Belgium

OBJECTIVE

Congenital malformations are frequently diagnosed prenatally even at a viable stage. No adequate registration of incidence and characteristics of late termination of pregnancy (TOP) or abortion for medical reasons exists in Flanders.

METHODS

Nationwide mortality follow-back survey sent to physicians signing death certificates of all stillbirths for 22 weeks gestation onward (September 2016-December 2017) in Flanders, Belgium. Questions measured whether late TOP preceded stillbirth, and which clinical and sociodemographic characteristics were indicated. Questionnaire data were linked with sociodemographic information from death certificates.

RESULTS

Response rate was 56% (203/366). 38% of stillbirths (77/203) concerned late TOP. In 88.3% of late TOPs, physicians classified congenital anomalies of the foetus as serious or very serious (incompatibility with life outside the womb or severe neurological or physical impairment). In 26% of cases, late TOP was first suggested by the physician rather than spontaneously requested by parents (73%). 88% of late TOPs were discussed in open team meetings.

CONCLUSIONS

2/5 stillbirths were preceded by late TOP, indicating severe underreportation by existing registrations and a dire need for adequate registration methods. Although late TOP was most often explicitly requested by parents, in ¼ cases termination was suggested first by physicians. Parents are sometimes hesitant to bring up late TOP themselves, indicating that TOP should always be counselled as an equivalent option.

Components of Perinatal Palliative Care: An Integrative Review

When a severe diagnosis is made before or after birth, perinatal palliative care (PPC) can be provided to support the infant, parents and involved healthcare providers. An integrative and systematic overview of effectiveness and working components of existing PPC programs was needed. An integrative search was conducted in MEDLINE, Embase, CENTRAL, CINAHL, PsycInfo and Web of Science. Study designs examining the effect of PPC compared to regular care, and (empirical) articles describing the components of care included in existing PPC initiatives were included. Three independent authors reviewed titles, abstracts and full texts against eligibility criteria. PRISMA guidelines were followed; 21.893 records were identified; 69 publications met inclusion criteria. Twelve publications (17.4%) discussed the effect of a PPC program. Other publications concerned the description of PPC programs, most often by means of a program description (22/69; 31.9%), guidelines (14/769; 20.3%) or case study (10/69; 14.5%). Outcome measures envisioned four main target categories: care coordination, parents and family members, care for the fetus/neonate and healthcare providers. No trials exist to date. Analysis of working components revealed components related to changes directed to the policy of the hospital wards and components involving actual care being provided within the PPC program, directed to the fetus or infant, the family, involved healthcare providers or external actors. PPC is a growing research field where evidence consists mainly of descriptive studies and guidelines. The extensive list of possible PPC components can serve as a checklist for developing future initiatives worldwide. PPC includes several important actors: the fetus/infant and their family and included healthcare providers on both maternity and neonatal wards. This leads to a large variety of possible care components. However, while some studies show proof of concept, an evidence base to determine which components are actually effective is lacking.

Healthcare professionals' attitudes towards termination of pregnancy at viable stage

INTRODUCTION

Upon prenatal diagnosis of congenital malformations, termination of pregnancy (TOP) may be an option, sometimes at a gestational age when the fetus is already viable (late TOP). We aimed to study attitudes towards late TOP of all tertiary healthcare professionals involved in late TOP practice.

MATERIAL AND METHODS

A mail survey was conducted among all physicians and paramedical professionals involved in late TOP decision-making in all eight centers with a Neonatal Intensive Care Unit in Flanders, Belgium (N = 117). The questionnaire contained general and case-based attitude items.

RESULTS

Response rate was 79%. Respondents were either physicians (51.1%) or paramedical professionals (49.9%). The composition of professionals involved in late TOP decision-making was heterogeneous between the eight centers. Late TOP was highly accepted in both lethal fetal conditions (100%) and serious (but not lethal) fetal conditions (95.6%). Where the fetus is healthy, 19.8% of respondents agreed with late TOP for maternal psychological problems and fewer respondents (13.2%) agreed with late TOP in the case of maternal socio-economic problems (P = .002). Physicians more often preferred feticide over neonatal palliative care in the case of non-lethal fetal conditions compared with paramedical professionals (68.1% vs 53.2%, P = .013). Almost nine out of ten respondents (89.1%) agreed that in the event of a serious (non-lethal) neonatal condition, administering drugs with the explicit intention to end neonatal life was acceptable. Behavioral intentions indicate that even in situations with an unclear diagnosis and unpredictable prognosis, 85.6% of professionals would still consider late TOP.

CONCLUSIONS

Healthcare professionals practicing late TOP in Flanders, Belgium have a high degree of tolerance towards late TOP, irrespective of sociodemographic factors, and are demanding legislative change regarding active life-ending in the fetal and neonatal periods. Further research should explore the correlation of attitudes to late TOP with actual medical decisions taken in daily clinical practice.

Risk factors for neonatal brachial plexus palsy: a systematic review and meta-analysis

AIM

To provide a comprehensive update on the most prevalent, significant risk factors for neonatal brachial plexus palsy (NBPP).

METHOD

Cochrane CENTRAL, MEDLINE, Web of Science, Embase, and ClinicalTrials.gov were searched for relevant publications up to March 2019. Studies assessing risk factors of NBPP in relation to typically developing comparison individuals were included. Meta-analysis was performed for the five most significant risk factors, on the basis of the PRISMA statement and MOOSE guidelines. Pooled odds ratios (ORs), 95% confidence intervals (CIs), and across-study heterogeneity (I² ) were reported. Reporting bias and quality of evidence was rated. In addition, we assessed the incidence of NBPP.

RESULTS

Twenty-two observational studies with a total sample size of 29 419 037 live births were selected. Significant risk factors included shoulder dystocia (OR 115.27; 95% CI 81.35-163.35; I² =92%), macrosomia (OR 9.75; 95% CI 8.29-11.46; I² =70%), (gestational) diabetes (OR 5.33; 95% CI 3.77-7.55; I² =59%), instrumental delivery (OR 3.8; 95% CI 2.77-5.23; I² =77%), and breech delivery (OR 2.49; 95% CI 1.67-3.7; I² =70%). Caesarean section appeared as a protective factor (OR 0.13; 95% CI 0.11-0.16; I² =41%). The pooled overall incidence of NBPP was 1.74 per 1000 live births. It has decreased in recent years.

INTERPRETATION

The incidence of NBPP is decreasing. Shoulder dystocia, macrosomia, maternal diabetes, instrumental delivery, and breech delivery are risk factors for NBPP. Caesarean section appears as a protective factor.

WHAT THIS PAPER ADDS

The overall incidence of neonatal brachial plexus palsy is 1.74 per 1000 live births. The incidence has declined significantly. Shoulder dystocia, macrosomia, maternal diabetes, instrumental delivery, and breech delivery are the main risk factors. Prevention is difficult owing to unpredictability and often labour-related risk.

Neonatologists and neonatal nurses have positive attitudes towards perinatal end-of-life decisions, a nationwide survey

AIM

Perinatal death is often preceded by an end-of-life decision (ELD). Disparate hospital policies, complex legal frameworks and ethically difficult cases make attitudes important. This study investigated attitudes of neonatologists and nurses towards perinatal ELDs.

METHODS

A survey was handed out to all neonatologists and neonatal nurses in all eight neonatal intensive care units in Flanders, Belgium in May 2017. Respondents indicated agreement with statements regarding perinatal ELDs on a Likert-scale and sent back questionnaires via mail.

RESULTS

The response rate was 49.5% (302/610). Most neonatologists and nurses found nontreatment decisions such as withholding or withdrawing treatment acceptable (90-100%). Termination of pregnancy when the foetus is viable in cases of severe or lethal foetal problems was considered highly acceptable in both groups (80-98%). Physicians and nurses do not find different ELDs equally acceptable, e.g. nurses more often than physicians (74% vs 60%, p = 0.017) agree that it is acceptable in certain cases to administer medication with the explicit intention of hastening death.

CONCLUSION

There was considerable support for both prenatal and neonatal ELDs, even for decisions that currently fall outside the Belgian legal framework. Differences between neonatologists' and nurses' attitudes indicate that both opinions should be heard during ELD-making.

Sero-epidemiological status and risk factors of toxoplasmosis in pregnant women in Northern Vietnam

Background

In Vietnam, few studies have determined the epidemiological status of toxoplasmosis in pregnant women and no routine prenatal screening is in place. This study was conducted to evaluate the seroprevalence of this zoonotic parasitic infection in pregnant women in Northern Vietnam and to assess the association with awareness, risk factors and congenital toxoplasmosis.

Methods

Approximately 800 pregnant women were included in the study from two hospitals, one in Hanoi and one in Thai Binh province, which is known to have a dense cat population. Serological immunoglobulin G (IgG) and immunoglobulin M (IgM) detection was performed to estimate the seroprevalence of toxoplasmosis and sero-incidence of maternal and congenital toxoplasmosis. In addition, a survey was conducted about awareness, clinical history, presentation of signs and symptoms relating to toxoplasmosis and to detect biologically plausible and socio-demographic risk factors associated with toxoplasmosis. Associations with seroprevalence were assessed using univariable and multivariable analysis.

Results

The mean IgG seroprevalence after the full diagnostic process was 4.5% (95% confidence interval(CI): 2.7–7.0) and 5.8% (95% CI: 3.7–8.6) in Hanoi and Thai Binh hospital, respectively, and included one seroconversion diagnosed in Thai Binh hospital. Only 2.0% of the pregnant women in Hanoi hospital and 3.3% in Thai Binh hospital had heard about toxoplasmosis before this study.

Conclusion

Since the percentage of seronegative, and thus susceptible, pregnant women was high and the awareness was low, we suggest to distribute information about toxoplasmosis and its prevention among women of child bearing age. Furthermore, future studies are recommended to investigate why such a low seroprevalence was seen in pregnant women in Northern Vietnam compared to other countries in South East Asia and globally.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3885-7) contains supplementary material, which is available to authorized users.

A post-mortem population survey on foetal-infantile end-of-life decisions: a research protocol

BACKGROUND

The death of a child before or shortly after birth is frequently preceded by an end-of-life decision (ELD). Population-based studies of incidence and characteristics of ELDs in neonates and infants are rare, and those in the foetal-infantile period (> 22 weeks of gestation - 1 year) including both neonates and stillborns, are non-existent. However, important information is missed when decisions made before birth are overlooked. Our study protocol addresses this knowledge gap.

METHODS

First, a new and encompassing framework was constructed to conceptualise ELDs in the foetal-infantile period. Next, a population mortality follow-back survey in Flanders (Belgium) was set up with physicians who certified all death certificates of stillbirths from 22 weeks of gestation onwards, and infants under the age of a year. Two largely similar questionnaires (stillbirths and neonates) were developed, pilot tested and validated, both including questions on ELDs and their preceding decision-making processes. Each death requires a postal questionnaire to be sent to the certifying physician. Anonymity of the child, parents and physician is ensured by a rigorous mailing procedure involving a lawyer as intermediary between death certificate authorities, physicians and researchers. Approval by medical societies, ethics and privacy commissions has been obtained.

DISCUSSION

This research protocol is the first to study ELDs over the entire foetal-infantile period on a population level. Based on representative samples of deaths and stillbirths and applying a trustworthy anonymity procedure, the research protocol can be used in other countries, irrespective of legal frameworks around perinatal end-of-life decision-making.

Prenatal diagnosis and prevention of toxoplasmosis in pregnant women in Northern Vietnam: study protocol

Background

In Vietnam, no systematic prenatal toxoplasmosis screening is in place, and only few studies have assessed the prevalence and importance of this zoonotic parasite infection. In addition, no studies have been conducted to assess the risk factors associated with toxoplasmosis. This study protocol was developed to determine the seroprevalence of toxoplasmosis in pregnant women in Hanoi and Thai Binh, Northern Vietnam, and to evaluate the association with risk factors and congenital toxoplasmosis. The protocol was developed in a way that it could potentially evolve into a countrywide prenatal diagnosis and prevention program, with the main focus on primary prevention.

Methods

The collaborating gynaecologists will invite eligible pregnant women attending antenatal care for the first time to participate in the study. At first consult, information about toxoplasmosis and its prevention will be provided. All participants will be asked to fill in a questionnaire, which is designed to analyse socio-demographic and biologically plausible risk factors associated with toxoplasmosis, and blood samples will be collected to determine the seroprevalence of toxoplasmosis in pregnant women. In case there is suspicion of a primary infection during pregnancy, the concerned women will be followed-up by the gynaecologists according to a predefined protocol. Every participant will be informed on her serological status, risk factors and prevention measures and is offered appropriate medical information and medical follow-up if required.

Discussion

The hypothesis is that congenital toxoplasmosis is an important but currently under-diagnosed public health problem in Vietnam. This study can strengthen sustainable control of toxoplasmosis in Vietnam, provide a protocol for prenatal diagnosis, boost overall awareness, improve the knowledge about toxoplasmosis prevention and can be essential for evidence-based health policy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2446-1) contains supplementary material, which is available to authorized users.

Analysis of erythromycin and benzoylperoxide in topical gels by liquid chromatography

Gels containing a combination of erythromycin and benzoylperoxide are frequently used in the treatment of acne vulgaris. A method was developed to determine the content of both erythromycin and benzoylperoxide in these gels. Erythromycin was extracted from the gel in conditions where the oxidative power of benzoylperoxide was neutralised by addition of ascorbic acid and this extract was analysed on an Xterra RP(18) column, with a mobile phase containing acetonitrile-0.2 M K2HPO4-water (35:5:60, v/v/v). The detection wavelength was 215 nm. A second extraction procedure was developed for the analysis of benzoylperoxide. The extraction solution was analysed on a Hypersil C(18) BDS column and a mobile phase containing acetonitrile-water (58:42, v/v). Detection was performed at 254 nm. The flow rate was 1.0 ml/min in both methods. The selectivity, repeatability, linearity and recovery of both methods were examined. Special attention was given to determination of the recovery and the uncertainty on the recovery. This allowed evaluation of the bias of the extraction method. The method developed was used to examine the stability of a gel for topical use.

Determination of kanamycin in serum by solid-phase extraction, pre-capillary derivatization and capillary electrophoresis

An effective method based on solid-phase extraction (SPE) and capillary electrophoresis (CE) for the determination of kanamycin in human serum was developed and validated. Off-line SPE was employed for the isolation of kanamycin from serum on a carboxypropyl-bonded phase (CBA) weak cation-exchange cartridge. A mixture of 0.2 M borate (pH 10.5)-methanol (50:50, v/v) was used as analyte eluting solvent. After pre-capillary derivatization with o-phthalaldehyde/mercaptoacetic acid reagent, the sample was analyzed by CE with a separation buffer of 30 mM borax, pH 10.0, containing 16% (v/v) methanol. A linear response over the concentration range 5-40 microgram/ml was obtained with a detection limit of 2 microgram/ml. Intra-day and inter-day precision were 6.2 and 10.3% RSD, respectively. Recoveries of approximately 90% were found. For the determination of lower levels of kanamycin (<5 microgram/ml), NH(4)OH (25%, w/v)-methanol (30:70, v/v) was used for analyte elution. After evaporation, reconstitution and derivatization, the sample was analyzed by on-line field-amplified sample stacking (FASS) CE. Good linearity in the concentration range 0.4-5 microgram/ml was obtained with a detection limit of 0.1 microgram/ml. Intra-day and inter-day RSD were 3.4 and 11.2%, respectively. Recoveries of approximately 60% were found. The method was successfully applied to the analysis of kanamycin in sera of tuberculosis patients at peak level and trough level concentrations.

Analysis of unknown compounds in azithromycin bulk samples with liquid chromatography coupled to ion trap mass spectrometry

A selective reversed-phase liquid chromatography/mass spectrometry (LC/MS(n)) method is described for the identification of azithromycin impurities and related substances in commercial azithromycin samples. Mass spectral data are acquired on an LCQ ion trap mass spectrometer equipped with an atmospheric pressure chemical ionization interface operated in positive ion mode. The LCQ provides on-line LC/MS(n) capability, making it ideally suited for identification purposes. In comparison with UV detection, this hyphenated technique provides as its main advantage efficient identification of novel substances without time-consuming isolation and purification procedures. Using this technique, six novel related substances detected in commercial azithromycin samples have been studied.

Isocratic liquid chromatographic method for the analysis of azithromycin and its structurally related substances in bulk samples

An isocratic liquid chromatographic method with UV detection at 215 nm, which is suitable for the analysis of azithromycin (AZT) in bulk samples, is described. AZT is separated from its synthesis intermediates and a degradation product as well as from six unknown impurities on an XTerra RP18 column at 70 degrees C using a mobile phase consisting of acetonitrile-pH 6.5 0.2M K2HPO4-water (35:10:55, v/v/v) at 1.0 mL/min. The XTerra stationary phase contains methyl groups that are incorporated in the bulk structure of the material. This allows for special selectivities. Robustness is evaluated by a full factorial design experiment. The method shows good selectivity, repeatability, linearity, and sensitivity.

Study of the stability of polymyxins B(1), E(1) and E(2) in aqueous solution using liquid chromatography and mass spectrometry

Polymyxins B(1), E(1) (colistin A) and E(2) (colistin B) were subjected to degradation in aqueous solutions of different pH values (1.4, 3.4, 5.4 and 7.4) and at different temperatures (37, 50 and 60 degrees C) in order to investigate the characteristics of decomposition. The progress of decomposition was followed by reversed-phase liquid chromatography on YMC-Pack Pro, C-18 stationary phase. The degradation curves showed (pseudo) first order kinetics. The pH-rate profiles indicate that colistin is more susceptible to degradation in solutions of pH above 5 and is more stable in acidic media. The degradation of polymyxin B(1) was most rapid at pH 7.4. Qualitative analysis of the degradation products by LC/MS reveals that racemization is the major mechanism of degradation in both acidic and neutral media.

Analysis of a formulation containing lincomycin and spectinomycin by liquid chromatography with pulsed electrochemical detection

A reversed phase ion-pair liquid chromatographic method using a base deactivated column and pulsed electrochemical detection on a gold electrode is described. It allows the separation of a mixture of spectinomycin sulfate, lincomycin hydrochloride and their related substances. A step gradient was necessary to obtain a good separation together with a reasonable analysis time of 40 min. The mobile phases consisted of an aqueous solution of 3.3 or 0.55 g/l pentanesulfonic acid, 10 mM acetic acid and 20 ml/l tetrahydrofuran. Both mobile phases were adjusted to pH 4.0 with diluted sodium hydroxide. The influence of the different chromatographic parameters on the separation was investigated. Two commercial samples were analyzed using the described method. In total 12 components could be separated.

Analysis of spectinomycin by liquid chromatography with pulsed electrochemical detection

Until now, no LC method is described to determine the purity and content of spectinomycin without prior derivatization. A reversed-phase ion-pair LC method using a base deactivated column and pulsed electrochemical detection is described. The mobile phase consisted of an aqueous solution containing 5.8 g/l pentafluoropropionic acid, 1.25 g/l potassium dihydrogen phosphate and 5.5 ml/l tetrahydrofuran. The pH was adjusted to 6.25 using dilute NaOH solution. An experimental design was used to optimize the chromatographic parameters and to check the robustness. The quality of separation was investigated on different stationary phases. The method allows the separation of spectinomycin from its related substances as well as some other components of unknown identity. The total time of analysis is 65 min. A number of commercial samples were examined using this method.

Analysis of clindamycin by micellar electrokinetic chromatography with a mixed micellar system

This study details the development and validation of an optimized method with micellar electrokinetic chromatography for the analysis of clindamycin. The method uses a mixed micellar phase containing anionic sodium dodecylsulfate (SDS) and non ionic Brij 35 on an untreated fused-silica capillary. The influences of buffer concentration, pH, SDS, Brij 35 and organic modifier were investigated. Special attention was given to the role of the non ionic Brij 35 in the mixed micellar system. Optimization with a central composite design resulted in optimal separation conditions: background electrolyte containing 25 mM sodium tetraborate pH 7.75, 90 mM SDS, 14 mM Brij 35 and 21% acetonitrile. The applied voltage was 15 kV and the capillary temperature 15 degrees C. The method was robust and gave good linearity and repeatability. The limits of detection and quantitation were 0.05 and 0.15%, respectively, relative to a 2.5 mg/ml clindamycin solution. Two commercial bulk products were analysed with this system.

Electrophoretically mediated microanalysis of gentamicin with in-capillary derivatization and UV detection

This paper describes a system for integration of a one-step-microscale chemical derivatization and analysis by a methodology known as electrophoretically mediated microanalysis (EMMA). Differential electrophoretic mobility between an analyte, reagent, and their product offers EMMA a unique capability to selectively carry out electrophoretic mixing, control product formation, and separation. This system was successfully applied to perform derivatization and separation of the multicomponent aminoglycoside antibiotic gentamicin using 1,2-phthalic dicarboxaldehyde and mercaptoacetic acid as labeling reagents. A multivariate approach based on central composite experimental design was used to optimize the derivative yield. Full automation of the derivatization and analytical procedure, high derivatization efficiency, high sample throughput, and precision are the excellent features of the present method. In addition, this methodology offers short analysis time, as well as selectivity and sensitivity suitable for impurities determination. Separation of gentamicin C1, C1a, C2, C2a, C2b, sisomicin, and several minor components was achieved. For the first time separation and identification of three impurities, namely garamine, 2-deoxystreptamine, and paromamine are described.

Analysis of vancomycin and related impurities by micellar electrokinetic capillary chromatography. Method development and validation

A fast and highly selective micellar electrokinetic capillary chromatography (MEKC) method for quantitative analysis of vancomycin and related impurities is described. Among the tested surfactants, cetyltrimethylammonium chloride (CTAC) offered the best selectivity. Another important parameter, which strongly influenced the selectivity, was buffer pH. It was found that the selectivity increased with buffer pH decreasing from 9 to 5. Using Tris-phosphate buffer containing CTAC, satisfactory separation could be obtained in the pH range from 5.0 to 5.5. Excellent repeatability in terms of migration time and peak area could be obtained when the capillary was carefully washed between two runs. In order to obtain optimal conditions and to evaluate the method robustness, a central composite experimental design was carried out. The optimal conditions were: 44 cm length of fused-silica capillary with 50 microm ID, 120 mM Tris-phosphate buffer (pH 5.2) containing 50 mM CTAC, -15 kV applied voltage, UV detection at 210 nm, and a column temperature of 25 degrees C. Under the optimal conditions, more than 20 peaks could be separated within 8 min. The method has a linearity range from 0.004 to 1.2 mg/ml (concentration of vancomycin B, active component). The limit of detection (LOD) and limit of quantitation (LOQ) were 0.4 microg/mL vancomycin, equivalent to 0.3 microg/mL vancomycin B (0.04%) and 1.1 microg/mL vancomycin, equivalent to 0.9 microg/mL vancomycin B (0.1%), respectively.

Development and validation of a simple capillary zone electrophoresis method for the analysis of kanamycin sulfate with UV detection after pre-capillary derivatization

Capillary zone electrophoresis was successfully applied to separate eight related substances of kanamycin and several minor unknowns from the main component. Strategies to enhance derivatization and selectivity and to optimize separation parameters involved the application of experimental designs. This chemometrical approach considers main effects as well as interactions of the influential parameters, thus conducting a more thorough investigation of the method than the common step-by-step approach. Central composite face centered designs established optimal separation conditions: 30 mM borax buffer, pH 10.0 containing 16.0% (v/v) methanol and optimal composition of derivatization reagent: 27 mg/ml 1,2-phthalic dicarboxaldehyde and 25 microl/ml mercaptoacetic acid in borate buffer, pH 10.4. The standard curves were linear over the concentration range of 0.007-1.01 mg/ml for the main component and 0.003-0.1 mg/ml for the related substances. The limit of quantitation was 0.14% (m/m) for the related substances and impurities (S/N= 10). The assay method was used to determine the composition of several commercial samples. Quantitative analysis indicates potential usefulness of capillary electrophoresis as an alternative to the assay method prescribed in the European Pharmacopoeia and the United States Pharmacopeia.

Isolation and structural characterization of colistin components

Preparative-scale separation of colistin sulphate bulk sample was carried out on a preparative poly(styrene-divinylbenzene) stationary phase. Isocratic elution with acetonitrile-sodium sulphate solution (0.7% m/v; pH adjusted to 2.5 with TFA) - water (16:50:34, % v/v/v) was carried out at a flow rate of 4.0 ml min(-1). Six colistin components were isolated and characterized using 1H and 13C NMR. The molecular weights were confirmed by mass spectrometry. The structures of 2 components were determined for the first time. Polymyxin E7 was identified as having the same composition as polymyxin E1, except that the fatty acid moiety was 7-methyloctanoic acid. Isoleucine polymyxin E8 was characterized as having the same composition as isoleucine polymyxin E1 with 7-methylnonanoic acid as the fatty acid moiety.

Isolation and structural characterization of polymyxin B components

Polymyxin B is a peptide antibiotic complex present as sulphate. The components were separated preparatively on a poly(styrene-divinylbenzene) (PLRP-S), 1000 A, 8 microm, 250 x 12.5 mm I.D. stationary phase maintained at 60 degrees C and using 215 nm detection. Elution was carried out with acetonitrile-sodium sulphate solution (0.7%, m/v; pH adjusted to 2.5 with trifluoroacetic acid)-water (18:50:32, v/v) at a flow-rate of 4.0 ml/min. Seven polymyxin B components were isolated and characterized using 1H and 13C NMR. The molecular masses were confirmed by mass spectrometry. The structures of two components were determined for the first time. Polymyxins B5 and B6 were identified as having the same composition as polymyxin B1 except that the fatty acid moiety was nonanoic acid and 3-hydroxy-6-methyloctanoic acid, respectively.

Analysis of bacitracin by micellar electrokinetic capillary chromatography with mixed micelle in acidic solution

A method used for quantitative analysis of bacitracin with micellar electrokinetic capillary chromatography (MEKC) is described. As capillary zone electrophoresis gave poor separation selectivity, MEKC was preferable. It was found that a zwitterionic surfactant, 3-(N,N-dimethylhexadecylammonium)-propanesulfonate (PAPS) gave the best selectivity among the several surfactants studied. As the analytes tend to adsorb onto the capillary wall due to their positive charge, an acidic solution composed of Tris-phosphate buffer at pH 2.5 was necessary to diminish such adsorption. The peak tailing caused by relatively strong ion pair interaction between the analyte and PAPS micelle could be reduced by adding nonionic surfactant Brij 35 to the PAPS solution. This phenomenon is possibly explained by a mixed micelle mechanism. In order to obtain the optimal conditions and to test the method robustness, a central composite experimental design was performed. The optimal conditions are as follows: 44 cm length of fused-silica capillary with 50 microm inner diameter, 90 mM Tris-phosphate buffer (pH 2.5) containing 17 mM PAPS and 0.3% w/v-Brij 35, 18 kV applied voltage, UV detection at 192 nm and 25 degrees C column temperature. Under the optimal conditions, more than 50 peaks could be obtained in 30 min. The method had a linearity range from 1 to 0.05 mg/mL (concentration of bacitracin A). The limit of quantitation (LOQ) and limit of detection (LOD) were 0.005 and 0.0012 mg/mL, respectively.

Liquid chromatography of troleandomycin

Until now no liquid chromatography (LC) method is described to determine the purity and content of troleandomycin and its related substances. A simple, robust, sensitive and selective isocratic liquid chromatographic method suitable for the determination of the antibiotic troleandomycin and its related substances is described. This method utilizes as a stationary phase: XTerra RP18 5 microm (25 cm x 4.6 mm I.D.) at 30 degrees C and as mobile phase: acetonitrile-0.2 M ammonium acetate buffer (pH 6.0)-water (45:5:50, v/v), delivered at a flow-rate of 1.0 ml/min. UV detection is performed at 205 nm. Troleandomycin is separated from the partially acetylated related substances and from several unknown impurities present in commercial samples. The robustness of the method was evaluated by a full-factorial experimental design.

Analysis of metacycline by capillary electrophoresis

The development and validation of an optimized capillary electrophoresis method for the determination of metacycline in the presence of its related substances by capillary electrophoresis is shown. The influence of methanol as organic modifier, buffer pH, buffer concentration, capillary length, column temperature, Triton X-100 and methyl-beta-cyclodextrin was investigated. A central composite design was performed in order to optimize the method. The optimal separation conditions were: uncoated fused-silica capillary (39 cm total length, 31 cm effective length, 50 microm ID); as background electrolyte a solution of 160 mM sodium carbonate and 1 mM EDTA (pH 10.35)/methanol (89:13 v/v); temperature, 15 degrees C; voltage, 12 kV. The method showed good selectivity, repeatability, linearity, and sensitivity. The limits of detection and quantitation are 0.024% and 0.06%, respectively, relative to a 2.5 mg/mL solution. Six commercial samples were analyzed quantitatively.

Structure elucidation of four related substances in gramicidin with liquid chromatography/mass spectrometry

A selective reversed phase liquid chromatography/mass spectrometry (LC/MS(n)) method is described for the identification of related substances in commercial gramicidin samples. Mass spectral data are acquired on an LCQ ion trap mass spectrometer equipped with an electrospray interface operated in the positive and the negative ion mode. The LCQ is ideally suited for identification of related substances because it provides on-line LC/MS(n) capability. Compared with UV detection the main advantage of this hyphenated LC/MS(n) technique is the efficient identification of novel related substances without time-consuming isolation and purification procedures. Using this method four novel related substances were separated and identified in a commercial sample.

Liquid chromatographic analysis of streptomycin sulfate

The analysis of streptomycin sulfate using a column packed with base deactivated reversed phase silica gel and ultraviolet (UV) detection at 205 nm is described. The mobile phase consists of an aqueous solution containing 14 g/l of sodium sulfate, 1.5 g/l of sodium octanesulfonate, 50 ml/l of acetonitrile and 50 ml/l of a 0.2 M phosphate buffer at pH 3.0. The method allows separating streptidine, streptomycin B, streptomycin and dihydrostreptomycin, as well as several other components, which were not yet identified. The total time of analysis is 50 min. The effects of the different chromatographic parameters on the separation were investigated. A number of commercial samples were analyzed using this method.

Capillary electrophoresis analysis of gentamicin sulphate with UV detection after pre-capillary derivatization with 1,2-phthalic dicarboxaldehyde and mercaptoacetic acid

A selective, sensitive, and rapid pre-capillary derivatization method for determination of the multicomponent aminoglycoside antibiotic gentamicin is described. The derivatization reagents 1,2-phthalic dicarboxaldehyde and mercaptoacetic acid were used and the thioisoindole derivative was UV detected at 330 nm. A central composite experimental design was performed to optimize selectivity and derivatization conditions. Baseline separation of gentamicin C1, C1a, C2, C2a, C2b, sisomicin and several minor components was achieved with a background electrolyte containing 30 mM sodium tetraborate, 7.5 mM beta-cyclodextrin and 12.5% (v/v) methanol at pH 10. Quantitative analysis was performed and illustrated the potential use of capillary electrophoresis for the identification and quantitation of gentamicin as an alternative to methods prescribed in the United States Pharmacopeia and European Pharmacopoeia.

Analysis of doxycycline by capillary electrophoresis. Method development and validation

An optimized capillary electrophoresis method for the analysis of doxycycline is described. The influence of methanol as organic modifier, buffer pH, buffer concentration, capillary length, column temperature, Triton X-100 and methyl-beta-cyclodextrin was systematically investigated. A central composite design was performed in order to optimize the method. The optimal separation conditions were: capillary, uncoated fused-silica [40 cm (32 cm effective length) x 50 microm I.D.]; background electrolyte, a solution of 145 mM sodium carbonate and 1 mM EDTA brought to pH 10.3-methanol (89:11, v/v); temperature, 15 degrees C; voltage, 12 kV. The method showed good selectivity, repeatability, linearity and sensitivity. Six commercial samples were quantitatively analyzed. The results were compared with those established by the liquid chromatography method from the European Pharmacopoeia.

Analysis of tobramycin by liquid chromatography with pulsed electrochemical detection

The determination of tobramycin by liquid chromatography using a column packed with poly(styrene-divinylbenzene) and pulsed electrochemical detection on a gold electrode is described. The mobile phase consisted of an aqueous solution containing 52 g/l of sodium sulfate, 1.5 g/l of sodium octanesulfonate and 50 ml/l of a 0.2 M phosphate buffer pH 3.0. The total time of analysis was not more than 30 min. The effects of the different chromatographic parameters on the separation were also investigated. When a number of commercial samples of tobramycin was analyzed using this method, nine different components were separated, five of which are of unknown identity.

Analysis of colistin sulfate by capillary zone electrophoresis with cyclodextrins as additive

A method for the quantitative analysis of colistin sulfate by capillary zone electrophoresis is described. Since colistin components have five free amino groups, they tend to adsorb onto the capillary wall and cause peak tailing. It was found that triethanolamine (TEA)-phosphate buffer at pH 2.5 was useful to reduce such adsorption. Methyl-beta-cyclodextrin (M-beta-CD) and 2-propanol (IPA) were found necessary for selectivity enhancement. In order to optimize the separation parameters and predict the method robustness, a central composite design was performed including three variables, namely concentration of M-beta-CD, TEA, and IPA. The effects of capillary length and applied voltage on separation were also investigated. The optimal conditions established were: 140 mM TEA-phosphate buffer containing 5 mM M-beta-CD and 6% v/v IPA, a capillary with 55 cm total length (50 microm inner diameter, 47 cm from inlet to detection window) and 24 kV applied voltage. The method was found to be robust when the variables were changed in the following range: 4-6 mM M-beta-CD, 5-7% v/v IPA, and 130-150 mM TEA. Further, the linearity, limit of detection (LOD), and limit of quantitation (LOQ), as well as repeatability for both colistin A and B were examined and three commercial samples were quantitatively analyzed.

Analysis of polymyxin B sulfate by capillary zone electrophoresis with cyclodextrin as additive. Method development and validation

A capillary zone electrophoresis method for analysis of polymyxin B sulfate is described. In this method, triethanolamine (TEA)-phosphate buffer at pH 2.5 was employed to reduce the adsorption of analyte onto the capillary wall. Methyl-beta-cyclodextrin (M-beta-CD) and 2-propanol (IPA) were found to be necessary for selectivity enhancement. In order to optimize the method and to control its robustness, a central composite design was performed with four parameters, i.e. concentration of M-beta-CD, TEA, IPA and buffer pH. The optimal separation conditions were as follows: capillary, 55 cm (50 microm I.D., 47 cm effective length); 130 mM TEA-phosphate buffer (pH 2.5) containing 5 mM M-beta-CD and 5% IPA; 24 kV (51 microA) applied voltage; column temperature, 20 degrees C. Further, linearity and limits of detection quantification were examined. Three commercial samples were analyzed quantitatively.

A stability study of ticlopidine products from 18 countries

The results of the stability study of ticlopidine formulations (250 mg and 100 mg) show that products available in many countries worldwide exhibit different stability characteristics. Stability testing under the International Conference on Harmonization (ICH) accelerated test conditions (40 degrees C/75% relative humidity [RH], 3 and 6 months) was performed on a total of 43 products obtained from 18 countries. The samples were visually examined for physical change and analyzed for their content of degradation products, remaining ticlopidine, and in vitro dissolution characteristics (in the case of tablets). Only 6 (16%) of all the samples submitted to this study had a good stability profile. Their appearance remained unchanged during the study; assay results were between 95% and 100%; their impurity content did not exceed 0.25%; and in the dissolution test, at least 75% of ticlopidine was dissolved after 30 min. Three samples had excellent dissolution properties and showed a very high purity level (viz. 21, 40, and 43) over the course of the study.

Separation of erythromycin and related substances on base-deactivated reversed-phase silica gel columns

An official liquid chromatographic method for the analysis of erythromycin and related substances, which is based on a polymer reversed-phase, is described in the European Pharmacopoeia and in the United States Pharmacopeia. The pH of the mobile phase used in this system is 9.0. Recent advanced technology has led to the introduction of a new generation of silica-based reversed-phase column packings, which are claimed to be much more stable towards bases. They are useful for the analysis of basic compounds. Studies to verify the separation of erythromycin and related substances on Hypersil BDS C18, Luna C18(2), Inertsil ODS-2 and Supelcosil ABZ+ have been performed and the results are presented. It is shown that these base-deactivated phases give a better sensitivity and selectivity towards erythromycins than the polymer phase, provided that an adapted mobile phase is used. This is the first liquid chromatographic method described for the separation of erythromycin D from erythromycin A.

Liquid chromatography of polymyxin B sulphate

A reversed-phase liquid chromatography method for analysis of polymyxin B sulphate is described. The method uses a YMC-Pack Pro, C18, 5 microm, 250x4.6 mm I.D. column maintained at 30 degrees C. The mobile phase comprises acetonitrile-sodium sulphate (0.7%, m/v)-phosphoric acid (6.8%, v/v dilution of 85%, m/m phosphoric acid)-water (22.25:50:5:22.75) at a flow-rate of 1.0 ml/min. Detection was by UV at 215 nm. The method is able to resolve polymyxin B1, the major component, from more than thirty other components present in the complex. Robustness was evaluated by performing a full-factorial design experiment. The method showed good selectivity, repeatability, linearity and sensitivity.