Outcomes following intensive day rehabilitation for young people in Western Australia.

OBJECTIVE: Intensive rehabilitation aims to improve and maintain functioning in young people who experience disability due to illness or injury. Day rehabilitation may have advantages for families and healthcare systems over inpatient models of rehabilitation. METHODS: This study evaluated the goals and outcomes of a cohort of young people in Western Australia who attended a specialist intensive day rehabilitation programme ("iRehab") at Perth Children's Hospital. Analysis of the iRehab service database was performed. Rehabilitation goals and outcomes were recorded as per the Canadian Occupational Performance Measure (COPM), Children's Functional Independence Measure (WeeFIM), and Goal Attainment Scale (GAS). RESULTS: There were 586 iRehab admissions between August 11, 2011, and December 31, 2018. Admissions were divided by diagnosis: Cerebral Palsy (228, 38.5%), Acquired Brain Injury (125, 21.3%), Spinal Cord Disorders (91, 15.5%), and Other (141, 24.2%). Mean COPM Performance increased by 2.78 points from admission to discharge (95% CI 2.58 to 2.98, p < 0.001). Mean COPM Satisfaction was 3.29 points higher at discharge than admission (95% CI 3.07 to 3.51, p < 0.001). Mean total WeeFIM score improved by 6.51 points between admission and discharge (95% CI 5.56 to 7.45, p < 0.001), and by 3.33 additional points by six months post discharge (95% CI 2.14 to 4.53, p < 0.001). Mean GAS T-scores increased by 27.85 (95% CI 26.73 to 28.97, p < 0.001) from admission to discharge, and by 29.64 (95% CI 28.26 to 31.02, p < 0.001) from admission to six months post discharge, representing improvement consistent with team expectations. CONCLUSION: This study describes a model by which intensive rehabilitation can be delivered in a day rehabilitation setting. A diverse population of young people who experienced disability achieved significant improvements in occupational performance, independence, and goal attainment after accessing intensive day rehabilitation. Improvements were measured in all diagnostic subgroups and were maintained six months after discharge.

Health service utilisation for acute respiratory infections in infants graduating from the neonatal intensive care unit: a population-based cohort study.

BACKGROUND: Despite advances in neonatal intensive care, babies admitted to Neonatal Intensive Care Units (NICU) suffer from adverse outcomes. We aim to describe the longer-term respiratory infectious morbidity of infants discharged from NICU using state-wide population-based linked data in Western Australia. STUDY DESIGN: We used probabilistically linked population-based administrative data to analyse respiratory infection morbidity in a cohort of 23,784 infants admitted to the sole tertiary NICU, born 2002-2013 with follow up to 2015. We analysed incidence rates of secondary care episodes (emergency department presentations and hospitalisations) by acute respiratory infection (ARI) diagnosis, age, gestational age and presence of chronic lung disease (CLD). Poisson regression was used to investigate the differences in rates of ARI hospital admission between gestational age groups and those with CLD, after adjusting for age at hospital admission. RESULTS: From 177,367 child-years at risk (i.e., time that a child could experience an ARI outcome), the overall ARI hospitalisation rate for infants and children aged 0-8 years was 71.4/1000 (95% confidence interval, CI: 70.1, 72.6), with the highest rates in infants aged 0-5 months (242.9/1000). For ARI presentations to emergency departments, equivalent rates were 114/1000 (95% CI: 112.4, 115.5) and 337.6/1000, respectively. Bronchiolitis was the most common diagnosis among both types of secondary care, followed by upper respiratory tract infections. Extremely preterm infants (< 28 weeks gestation at birth) were 6.5 (95% CI: 6.0, 7.0) times more likely and those with CLD were 5.0 (95% CI: 4.7, 5.4) times more likely to be subsequently admitted for ARI than those in NICU who were not preterm or had CLD after adjusting for age at hospital admission. CONCLUSIONS: There is an ongoing burden of ARI in children who graduate from the NICU, especially those born extremely preterm, that persists into early childhood. Early life interventions to prevent respiratory infections in these children and understanding the lifelong impact of early ARI on later lung health are urgent priorities.

Evaluation of real-life clinical outcomes in Australian youth with type 1 diabetes on hybrid closed-loop therapy: A retrospective study.

AIM: To determine the clinical outcomes and evaluate the perspectives of children with Type 1 diabetes (T1D) and their parents managing their child on hybrid closed-loop (HCL) therapy. METHODS: Children with T1D on HCL attending a tertiary diabetes centre between April 2019 and July 2021 were included. A retrospective analysis of glycaemic data was conducted to determine the clinical outcomes. Time spent in closed loop, time in target glucose range (TIR 3.9-10 mmol/L), hypoglycaemia and hyperglycaemia were collected at baseline, 4 weeks, 3 and 6 months post-HCL. User experience was assessed by questionnaires administered to parents of children with T1D. RESULTS: Seventy-one children, mean (SD) age of 12.2 (3.2) years were commenced on HCL. Ten (14%) discontinued HCL use, with 60% discontinuing within the first 6 months. Glycaemic outcomes were analysed in 52 children. Time spent in closed loop was 78 (21) % at 4 weeks, declined to 69 (28) % at 3 months (P = 0.037) and 63 (34) % at 6 months (P = 0.001). The mean %TIR increased from 59.8 at baseline to 67.6 at 3 months and 65.6 at 6 months with a mean adjusted difference of 7.8% points [95% CI 3.6, 11.9] and 5.5% points [95% CI 1.4, 9.5], respectively. There was a reduction in time > 10 mmol/L and time < 3.9 mmol/L from baseline to 6 months. Although families faced challenges with technology, better glucose control with reduced glycaemic fluctuations were reported. CONCLUSIONS: HCL therapy is associated with improved glycaemia; however, adequate support and education are required for best outcomes.

Ten year analysis of the clinic profile of the tertiary paediatric endocrine service in Western Australia.

OBJECTIVES: There is a paucity of information regarding the profile of entire paediatric endocrine clinics and how they are changing. This study aimed to analyse the clinic profile of the Western Australian tertiary paediatric endocrine outpatient service over 10 years and compare to national and international data. METHODS: Retrospective analysis of the Western Australian Paediatric Endocrine Database (WAPED) between 2007 and 2017 looking at the frequency, proportion and longitudinal change of diagnosis categories, specific diagnoses, and gender breakdown. RESULTS: In total, 2,791 endocrine diagnoses were recorded for 2,312 patients. The most frequent reason for referral (22.1% of patients), was for evaluation of abnormalities in thyroid function. The most common diagnosis being hypothyroidism (76.7%). Evaluation of short stature was the reason for referral in 19.2% of patients, 14.6% of whom were diagnosed with growth hormone deficiency. Evaluation of puberty disorders, syndromes with endocrine features and disorders of calcium and phosphate metabolism were other common reasons for clinic referral, seen in 11.3, 9.8 and 8.2% of patients respectively. Between 2007 and 2017, the odds ratio of a thyroid diagnosis increased by 1.07 per year (95% CI: 1.02-1.12), whilst the odds ratio of a short stature diagnosis decreased by 0.91 per year (95% CI: 0.87-0.95). CONCLUSIONS: The profile of the WAPED is similar to previously published national and international data. The analysis of the profile of diagnoses and its longitudinal change over a ten-year period offer a unique opportunity to guide clinic planning, resource allocation and future research.

Acceptability of OP/Na swabbing for SARS-CoV-2: a prospective observational cohort surveillance study in Western Australian schools.

OBJECTIVES: When the COVID-19 pandemic was declared, Governments responded with lockdown and isolation measures to combat viral spread, including the closure of many schools. More than a year later, widespread screening for SARS-CoV-2 is critical to allow schools and other institutions to remain open. Here, we describe the acceptability of a minimally invasive COVID-19 screening protocol trialled by the Western Australian Government to mitigate the risks of and boost public confidence in schools remaining open. To minimise discomfort, and optimise recruitment and tolerability in unaccompanied children, a combined throat and nasal (OP/Na) swab was chosen over the nasopharyngeal swab commonly used, despite slightly reduced test performance. DESIGN, SETTING AND PARTICIPANTS: Trialling of OP/Na swabbing took place as part of a prospective observational cohort surveillance study in 79 schools across Western Australia. Swabs were collected from 5903 asymptomatic students and 1036 asymptomatic staff in 40 schools monthly between June and September 2020. OUTCOME MEASURES: PCR testing was performed with a two-step diagnostic and independent confirmatory PCR for any diagnostic PCR positives. Concurrent surveys, collected online through the REDCap platform, evaluated participant experiences of in-school swabbing. RESULTS: 13 988 swabs were collected from students and staff. There were zero positive test results for SARS-CoV-2, including no false positives. Participants reported high acceptability: 71% of students reported no or minimal discomfort and most were willing to be reswabbed (4% refusal rate). CONCLUSIONS: OP/Na swabbing is acceptable and repeatable in schoolchildren as young as 4 years old and may combat noncompliance rates by significantly increasing the acceptability of testing. This kind of minimally-invasive testing will be key to the success of ongoing, voluntary mass screening as society adjusts to a new 'normal' in the face of COVID-19. TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trials Registry-ACTRN12620000922976.

Frequency of protracted bacterial bronchitis and management pre-respiratory referral.

AIM: To determine the frequency of protracted bacterial bronchitis (PBB) in children referred to tertiary care with chronic cough and describe management prior to referral. METHODS: A retrospective cohort study of all new patients with a history of ≥4 weeks of cough seen at the only tertiary paediatric outpatient respiratory service in Western Australia between July 2018 and June 2019. Medical records were reviewed until a final diagnosis was documented or otherwise for a period of 18 months. RESULTS: PBB was the most common cause and comprised 37.9% of all children referred to tertiary respiratory care with chronic cough. In children with PBB, the median cough duration at the time of first specialist review was 5.1 months (IQR 2.1-12.0 months). The most common referral source of PBB was primary practice (40.9%) and the most common working diagnosis pre-referral was asthma (15.9%). Seventy-eight percent of children with PBB had an ongoing cough at their first respiratory review, and of these, only 13.5% had been prescribed 4 weeks of antibiotics prior to their respiratory review. Asthma treatment had been prescribed for 34.0% of children with PBB. CONCLUSION: PBB is the most common cause of chronic cough in children referred to tertiary respiratory care and is frequently misdiagnosed and undertreated pre-referral. There is a need to facilitate diagnosis and optimal management of PBB in primary care, which could result in earlier symptom resolution and potentially limit disease progression to bronchiectasis.

The utility of continuous glucose monitoring systems in the management of children with persistent hypoglycaemia.

OBJECTIVES: Glucose monitoring is vital in children with persistent hypoglycaemia to reduce the risk of adverse neuro-behavioural outcomes; especially in children with hyperinsulinism. The role of continuous glucose monitoring (CGM) systems in monitoring glucose levels in this cohort is limited. The objective of this study was to ascertain the effectiveness of CGM and to evaluate parents' experience of using CGM for monitoring glucose levels in children with hypoglycaemia. METHODS: Retrospective analysis of sensor glucose (SG) values from Dexcom G4 CGM with paired finger-prick blood glucose (BG) values was performed to determine the accuracy of CGM. The parent experience of CGM was assessed using a questionnaire administered to families of children with congenital hyperinsulinism currently attending the clinic. RESULTS: SG data from 40 children (median age 6 months) with persistent hypoglycaemia (60% Hyperinsulinism) were analysed. The mean difference between 5,650 paired BG and SG values was 0.28 mmol/L. The sensitivity and specificity of CGM to identify severe hypoglycaemia (BG < 3.0 mmol/L) were 54.3% (95% CI: 39.0%, 69.1%) and 97.4% (95% CI: 96.9%, 97.8%) respectively. Parents (n=11) reported less anxiety (n=9), better sleep at night (n=7) and preferred to use CGM for monitoring (n=9). CONCLUSIONS: Although the high number of false-positive readings precludes the routine use of CGM in the evaluation of hypoglycaemia, it avoids unnecessary BG testing during normoglycaemia. It is an acceptable tool for parents for monitoring their children who are at risk of hypoglycaemia. Newer CGM systems with improved accuracy at lower glucose levels have the potential to further improve monitoring.

Evaluation of focus and deep learning methods for automated image grading and factors influencing image quality in adaptive optics ophthalmoscopy.

Adaptive optics flood illumination ophthalmoscopy (AO-FIO) is an established imaging tool in the investigation of retinal diseases. However, the clinical interpretation of AO-FIO images can be challenging due to varied image quality. Therefore, image quality assessment is essential before interpretation. An image assessment tool will also assist further work on improving the image quality, either during acquisition or post processing. In this paper, we describe, validate and compare two automated image quality assessment methods; the energy of Laplacian focus operator (LAPE; not commonly used but easily implemented) and convolutional neural network (CNN; effective but more complex approach). We also evaluate the effects of subject age, axial length, refractive error, fixation stability, disease status and retinal location on AO-FIO image quality. Based on analysis of 10,250 images of 50 × 50 µm size, at 41 retinal locations, from 50 subjects we demonstrate that CNN slightly outperforms LAPE in image quality assessment. CNN achieves accuracy of 89%, whereas LAPE metric achieves 73% and 80% (for a linear regression and random forest multiclass classifier methods, respectively) compared to ground truth. Furthermore, the retinal location, age and disease are factors that can influence the likelihood of poor image quality.

Retinal Differential Light Sensitivity Variation Across the Macula in Healthy Subjects: Importance of Cone Separation and Loci Eccentricity.

Purpose: Microperimetry measures differential light sensitivity (DLS) at specific retinal locations. The aim of this study is to examine the variation in DLS across the macula and the contribution to this variation of cone distribution metrics and retinal eccentricity. Methods: Forty healthy eyes of 40 subjects were examined by microperimetry (MAIA) and adaptive optics imaging (rtx1). Retinal DLS was measured using the grid patterns: foveal (2°-3°), macular (3°-7°), and meridional (2°-8° on horizontal and vertical meridians). Cone density (CD), distribution regularity, and intercone distance (ICD) were calculated at the respective test loci coordinates. Linear mixed-effects regression was used to examine the association between cone distribution metrics and loci eccentricity, and retinal DLS. Results: An eccentricity-dependent reduction in DLS was observed on all MAIA grids, which was greatest at the foveal-parafoveal junction (2°-3°) (-0.58 dB per degree, 95% confidence interval [CI]; -0.91 to -0.24 dB, P < 0.01). Retinal DLS across the meridional grid changed significantly with each 1000 cells/deg2 change in CD (0.85 dB, 95% CI; 0.10 to 1.61 dB, P = 0.03), but not with each arcmin change in ICD (1.36 dB, 95% CI; -2.93 to 0.20 dB, P = 0.09). Conclusions: We demonstrate significant variation in DLS across the macula. Topographical change in cone separation is an important determinant of the variation in DLS at the foveal-parafoveal junction. We caution the extrapolation of changes in DLS measurements to cone distribution because the relationship between these variables is complex. Translational Relevance: Cone density is an independent determinant of DLS in the foveal-parafoveal junction in healthy eyes.

The course and prognostic capability of motor difficulties in infants showing early signs of autism.

Delays within the motor domain are often overlooked as an early surveillance marker for autism. The present study evaluated motor difficulties and its potential as an early predictive marker for later autism likelihood in a cohort of infants (N = 96) showing early behavioral signs of autism aged 9-14 months. The motor domain was evaluated using the motor subscales of the Mullen Scales of Early Learning at baseline, and at a 6-month follow-up. The Autism Diagnostic Observation Schedule - Toddler Module (ADOS-T) was completed at follow-up as a measure of autism likelihood. Motor difficulties were common at baseline, with 63/96 (65.6%) infants scoring very low or below average in the gross motor domain and 29/96 (30.2%) in the fine motor domain. At follow-up, gross motor difficulties had resolved for many, with 23/63 (36.5%) infants maintaining these difficulties. Fine motor difficulties resolved in fewer infants, with 20/29 (69.0%) continuing to present with fine motor delays at follow-up. Adjusted linear regression models suggested that fine motor scores at baseline (ß = -0.12, SE = 0.04) and follow-up (ß = -0.17, SE = 0.05) were associated with higher ADOS-T scores; with difficulties across both timepoints (ß = 5.60, SE = 1.35) the strongest (largest in magnitude) association with ADOS-T scores of the predictors examined. Motor difficulties are prominent in children displaying emerging signs of autism, with persistent fine motor difficulties predictive of the developing autism phenotype. The findings indicate the potential clinical value of including evaluation of motor skills within early autism surveillance measures. LAY SUMMARY: This prospective study evaluated motor development over a 6-month period in infants showing early behavioral signs of autism. Atypical motor development was a common feature of infants showing early signs of autism and persistent fine motor difficulties were predictive of the emerging autism phenotype.

Topical treatment of vulvodynia, dyspareunia and pudendal neuralgia: A single clinic audit of amitriptyline and oestriol in organogel.

BACKGROUND: Vulvodynia and pudendal neuralgia comprise significant contributors to vulvar-related pain and its impact on daily life. AIM: A retrospective clinical audit was conducted at the Women's Health & Research Institute of Australia, Sydney, to determine the pattern of use and the efficacy of the application of topical amitriptyline 0.5% plus oestriol 0.03% in organogel (AOO), to the vulvar vestibule in reducing the impact of pain on daily life. MATERIALS AND METHODS: There were 1174 patients who received a script from May 2017 until February 2020: 1054 patients agreed to be contacted and had a valid email address. RESULTS: There were 376 (35.7%) patients who replied. Pain with intercourse was the main indication for use. Treatment was rated effective by 51.2% (95% CI: 35.4-66.8%) of patients less than 30 years of age, 66.7% (95% CI: 57.3-74.9%) of patients 30-50 years of age, and 58.3% (95% CI: 50.9-65.4%) in patients over 50. Stinging at the site of application was the most commonly reported side effect. CONCLUSION: Topical AOO is an effective and well-tolerated treatment for vulvar pain.

Investigating associations between birth order and autism diagnostic phenotypes.

BACKGROUND: Birth order effects have been linked to variability in intelligence, educational attainment and sexual orientation. First- and later-born children have been linked to an increased likelihood of an Autism Spectrum Disorder (ASD) diagnosis, with a smaller body of evidence implicating decreases in cognitive functioning with increased birth order. The present study investigated the potential association between birth order and ASD diagnostic phenotypes in a large and representative population sample. METHODS: Data were obtained from an ongoing prospective diagnostic registry, collected between 1999 and 2017, including children (1-18 years of age, n = 5,404) diagnosed with ASD in the state of Western Australia. Children with ASD were ranked relative to sibling's birth to establish birth order within families at time of ASD diagnosis. Information reported to the registry by health professionals at the time of diagnostic evaluation included demographic and family characteristics, functional abilities and intellectual capacity. RESULTS: Adaptive functioning and intelligence scores decreased with increasing birth order, with later-born children more likely to have an intellectual disability. Compared to first-born children with siblings, first-born children without siblings at the time of diagnosis also exhibited decreased cognitive functioning. CONCLUSIONS: These findings demonstrate for the first time an association between increasing birth order and variability in ASD clinical phenotypes at diagnosis, with potential evidence of reproductive curtailment in children without siblings. Taken together, these findings have significant implications for advancing understanding about the potential mechanisms that contribute to heterogeneity in ASD clinical presentations as a function of birth order and family size.

Application of 2D-HPLC coupled with principal component analysis to study an industrial opiate processing stream.

Principal component analysis (PCA) loading plots were used to elucidate key differences between two-dimensional high performance liquid chromatography (2D-HPLC) fingerprint data from samples collected from stages along the Papaver somniferum industrial process chemistry workflow. Data reduction was completed using a 2D-HPLC peak picking approach as a precursor to chemometric analysis. Using comparisons of the final stages of product extraction as an example, PCA analysis of characteristic 2D-HPLC fingerprints accounted for 84.9% of variation between the two sample sets measured in triplicate, with 64.7% explained by PC1. Loadings plots of PC1 on each sample set identified where the significant changes were occurring and normalised bubble plots provided an indication of the relative importance of each of these changes. These findings highlight 2D-HPLC with appropriate chemometric analysis as a useful tool for the exploration of bioactive molecules within biomass.

Elemental and molecular profiling of licit, illicit, and niche tobacco.

The recognition of differences between regulated large-scale mass manufactured products and the uncontrolled cultivation of tobaccos for illicit purposes plays a significant role within identification of provenance. This research highlights X-ray fluorescence and Fourier transform infrared spectroscopy as useful analytical techniques for the rapid identification of tobacco samples of unknown provenance. Identification of key discriminative features within each technique allowed for the development of typical characteristic profiles for each type of tobacco. Analysis using X-ray fluorescence highlights chlorine, potassium, calcium and iron as key elemental indicators of tobacco provenance. Significant levels of chlorine seen within Snüs samples prompted attempts to visualise chlorine containing regions and structures within the sample. Scanning electron microscopy images showed crystalline structures visible within the Snüs tobacco, structures which Energy dispersive X-ray spectroscopy qualitatively confirmed to contain chlorine. Chloride levels within Snüs samples were quantified using ion chromatography with levels found to range between 0.87mgmL(-1) and 1.28mg. Additionally, FTIR indicated that absorbances attributed to carbonyl stretching at 1050-1150cm(-1), alkane bending at 1350-1480cm(-1) and amide I stretching at 1600-1700cm(-1) highlighting a spectral fingerprint region that allowed for the clear differentiation between different types of tobaccos using PCA analysis, but was limited by differentiation between provenance of cigarettes and hand rolled tobacco. X-ray fluorescence and Fourier transform infrared spectroscopy yielded different information with regards tobacco discrimination and provenance, however both methods overall analysis time and cost reduced indicating usefulness as potential handheld analytical techniques in the field.

In-silico optimisation of two-dimensional high performance liquid chromatography for the determination of Australian methamphetamine seizure samples.

In-silico optimisation of a two-dimensional high performance liquid chromatography (2D-HPLC) separation protocol has been developed for the interrogation of methamphetamine samples including model, real world seizure, and laboratory synthesised samples. The protocol used Drylab(®) software to rapidly identify the optimum separation conditions from a library of chromatography columns. The optimum separation space was provided by the Phenomonex Kinetex PFP column (first dimension) and an Agilent Poroshell 120 EC-C18 column (second dimension). To facilitate a rapid 2D-HPLC analysis the particle packed C18 column was replaced with a Phenomenex Onyx Monolithic C18 withought sacrificing separation performance. The Drylab(®) optimised and experimental separations matched very closely, highlighting the robust nature of HPLC simulations. The chemical information gained from an intermediate methamphetamine sample was significant and complimented that generated from a pure seizure sample. The influence of the two-dimensional separation on the analytical figures of merit was also investigated. The limits of detection for key analytes in the second dimension determined for methamphetamine (4.59×10(-4)M), pseudoephedrine (4.03×10(-4)M), caffeine (5.16×10(-4)M), aspirin (9.32×10(-4)M), paracetamol (5.93×10(-4)M) and procaine (2.02×10(-3)M).

Blind column selection protocol for two-dimensional high performance liquid chromatography.

The selection of two orthogonal columns for two-dimensional high performance liquid chromatography (LC×LC) separation of natural product extracts can be a labour intensive and time consuming process and in many cases is an entirely trial-and-error approach. This paper introduces a blind optimisation method for column selection of a black box of constituent components. A data processing pipeline, created in the open source application OpenMS®, was developed to map the components within the mixture of equal mass across a library of HPLC columns; LC×LC separation space utilisation was compared by measuring the fractional surface coverage, fcoverage. It was found that for a test mixture from an opium poppy (Papaver somniferum) extract, the combination of diphenyl and C18 stationary phases provided a predicted fcoverage of 0.48 and was matched with an actual usage of 0.43. OpenMS®, in conjunction with algorithms designed in house, have allowed for a significantly quicker selection of two orthogonal columns, which have been optimised for a LC×LC separation of crude extractions of plant material.

Screening of cannabinoids in industrial-grade hemp using two-dimensional liquid chromatography coupled with acidic potassium permanganate chemiluminescence detection.

Widely known for its recreational use, the cannabis plant also has the potential to act as an antibacterial agent in the medicinal field. The analysis of cannabis plants/products in both pharmacological and forensic studies often requires the separation of compounds of interest and/or accurate identification of the whole cannabinoid profile. In order to provide a complete separation and detection of cannabinoids, a new two-dimensional liquid chromatography method has been developed using acidic potassium permanganate chemiluminescence detection, which has been shown to be selective for cannabinoids. This was carried out using a Luna 100 Å CN column and a Poroshell 120 EC-C18 column in the first and second dimensions, respectively. The method has utilized a large amount of the available separation space with a spreading angle of 48.4° and a correlation of 0.66 allowing the determination of more than 120 constituents and mass spectral identification of ten cannabinoids in a single analytical run. The method has the potential to improve research involved in the characterization of sensitive, complex matrices.

Assessing the detectability of antioxidants in two-dimensional high-performance liquid chromatography.

This paper explores the analytical figures of merit of two-dimensional high-performance liquid chromatography for the separation of antioxidant standards. The cumulative two-dimensional high-performance liquid chromatography peak area was calculated for 11 antioxidants by two different methods--the areas reported by the control software and by fitting the data with a Gaussian model; these methods were evaluated for precision and sensitivity. Both methods demonstrated excellent precision in regards to retention time in the second dimension (%RSD below 1.16%) and cumulative second dimension peak area (%RSD below 3.73% from the instrument software and 5.87% for the Gaussian method). Combining areas reported by the high-performance liquid chromatographic control software displayed superior limits of detection, in the order of 1 × 10(-6) M, almost an order of magnitude lower than the Gaussian method for some analytes. The introduction of the countergradient eliminated the strong solvent mismatch between dimensions, leading to a much improved peak shape and better detection limits for quantification.

Protocols for finding the most orthogonal dimensions for two-dimensional high performance liquid chromatography.

The selection of two high performance liquid chromatography (HPLC) columns with vastly different retention mechanisms is vital for performing effective two-dimensional (2D-) HPLC. This paper reports on a systematic method to select a pair of HPLC columns that provide the most different separations for a given sample. This was completed with the aid of a HPLC simulator that predicted retention profiles on the basis of real experimental data, which is difficult when the contents of sample matrices are largely-or completely-unknown. Peaks from the same compounds must first be matched between chromatograms to compare the retention profiles and optimised 2D-HPLC column selection. In this work, two methods of matching peaks between chromatograms were explored and an optimal pair of chromatography columns was selected for 2D-HPLC. First, a series of 17 antioxidants were selected as an analogue for a coffee extract. The predicted orthogonality of the standards was 39%, according to the fractional surface coverage 'bins' method, which was close to the actual space utilisation of the standard mixture, 44%. Moreover, the orthogonality for the 2D-HPLC of coffee matched the predicted value of 38%. The second method employed a complex sample matrix of urine to optimise the column selections. Seven peaks were confidently matched between chromatograms by comparing relative peak areas of two detection strategies: UV absorbance and potassium permanganate chemiluminescence. It was found that the optimal combinations had an orthogonality of 35% while the actual value was closer to 30%.

DryLab® optimised two-dimensional high performance liquid chromatography for differentiation of ephedrine and pseudoephedrine based methamphetamine samples.

In-silico optimised two-dimensional high performance liquid chromatographic (2D-HPLC) separations of a model methamphetamine seizure sample are described, where an excellent match between simulated and real separations was observed. Targeted separation of model compounds was completed with significantly reduced method development time. This separation was completed in the heart-cutting mode of 2D-HPLC where C18 columns were used in both dimensions taking advantage of the selectivity difference of methanol and acetonitrile as the mobile phases. This method development protocol is most significant when optimising the separation of chemically similar chemical compounds as it eliminates potentially hours of trial and error injections to identify the optimised experimental conditions. After only four screening injections the gradient profile for both 2D-HPLC dimensions could be optimised via simulations, ensuring the baseline resolution of diastereomers (ephedrine and pseudoephedrine) in 9.7 min. Depending on which diastereomer is present the potential synthetic pathway can be categorized.