An interlaboratory study was conducted on an HPLC method with UV absorbance detection, previously validated using AOAC single-laboratory validation guidelines, for the determination of the six major ginsenosides (Rg1, Re, Rb1, Rc, Rb2, and Rd) in Panax ginseng C.A. Meyer and Panax quinquefolius L. root materials, extracts, and finished products. Fourteen participating laboratories analyzed five test materials (P. ginseng whole root, P. ginseng powdered extract, P. quinquefolius whole root, P. quinquefolius powdered extract, and P. ginseng powdered extract spiked in a matrix blank) as blind duplicates, and two test materials (P. ginseng powdered whole root tablet and P. quinquefolius powdered extract hard-filled capsule) as single samples. Due to the variability of the ginsenosides (low level concentration of Rb2 in P. quinquefolius raw materials and in P. ginseng spiked matrix blanks, and the possibility of incomplete hydrolysis of the finished products during processing), it was deemed more applicable to analyze total ginsenosides rather than individual ones. Outliers were evaluated and omitted using the Cochran's test and single and double Grubbs' tests. The reproducibility RSD (RSD(R)) for the blind duplicate samples ranged from 4.38 to 5.39%, with reproducibility Horwitz Ratio (HorRat(R)) values ranging from 1.5 to 1.9. For the single replicate samples, the data sets were evaluated solely by their repeatability HorRat (HorRat(r)), which were 2.9 and 3.5 for the capsule and tablet samples, respectively. Based on these results, the method is recommended for AOAC Official First Action for the determination of total ginsenosides in P. ginseng and P. quinquefolius root materials and powdered extracts., Peer-reviewed article, Published.
A multilaboratory collaborative study was conducted on a high-performance liquid chromatographic (HPLC) method utilizing UV detection, previously validated using AOAC single-laboratory validation guidelines for determination of hydrastine and berberine in goldenseal (Hydrastis canadensis L.) raw materials, extracts, and dietary supplements at levels ranging from 0.4 to 6% (w/w). Nine collaborating laboratories determined the hydrastine and berberine content in 8 blind samples. Sample materials included powdered botanical raw materials, whole root material, and 4 finished product dietary supplements containing either goldenseal powdered root material or extract. The materials were extracted with an acidified water and acetonitrile solution. HPLC analyses of the extracts were performed on a C18 column using UV detection at 230 nm. Results for powdered root material and capsule products ranged from about 0.2% (w/w) for each alkaloid to about 4% (w/w) for each alkaloid. Liquid tincture results were approximately 4000-5000 microg/mL for each alkaloid. Reproducibility relative standard deviations (RSDR) for hydrastine ranged from 2.68 to 6.65%, with HorRat values ranging from 0.77 to 1.89. RSDR for berberine ranged from 5.66 to 7.68%, with HorRat values ranging from 1.32 to 2.12. All finished products containing goldenseal extract yielded HorRat values <2.0. Based on these results, the method is recommended for Official First Action for determination of hydrastine and berberine in goldenseal raw materials and dietary supplement finished products containing powdered goldenseal and goldenseal extract., Peer-reviewed article, Published.
During the design of a new building or retrofitting of an existing one, it is important to reliably assess the indoor humidity levels of the building as it can potentially affect the building envelope durability, occupants? comfort and health risks associated with mould growth. Simplistic assumptions of indoor humidity profiles, which ignore the dynamic coupling of the indoor environment and building enclosure, may lead to inaccurate conclusions about the indoor environment and moisture performance of the building enclosure. In this paper, a whole-building hygrothermal model called HAMFitPlus, which takes into account the dynamic interactions between building envelope components, mechanical systems and indoor heat and moisture generation mechanisms, is used to assess the indoor humidity condition of an existing occupied house. HAMFitPlus is developed on SimuLink development platform and integrates COMSOL multiphysics with MatLab. The basic input parameters of the model are discussed in detail, and its simulation results are presented. In general, the HAMFitPlus simulation results are in good agreement with the measured data., Peer reviewed article, Published article and manuscript
A method previously validated to determine caftaric acid, chlorogenic acid, cynarin, echinacoside, and cichoric acid in echinacea raw materials has been successfully applied to dry extract and liquid tincture products in response to North American consumer needs. Single-laboratory validation was used to assess the repeatability, accuracy, selectivity, LOD, LOQ, analyte stability (ruggedness), and linearity of the method, with emphasis on finished products. Repeatability precision for each phenolic compound was between 1.04 and 5.65% RSD, with HorRat values between 0.30 and 1.39 for raw and dry extract finished products. HorRat values for tinctures were between 0.09 and 1.10. Accuracy of the method was determined through spike recovery studies. Recovery of each compound from raw material negative control (ginseng) was between 90 and 114%, while recovery from the finished product negative control (maltodextrin and magnesium stearate) was between 97 and 103%. A study was conducted to determine if cichoric acid, a major phenolic component of Echinacea purpurea (L.) Moench and E. angustifolia DC, degrades during sample preparation (extraction) and HPLC analysis. No significant degradation was observed over an extended testing period using the validated method., Peer-reviewed article, Published.
Mitragyna speciosa (kratom) is a tree indigenous to Southeast Asia, and its leaves are used in herbal formulations because they contain indole alkaloids mitragynine and 7-hydroxy (7-OH) mitragynine. An HPLC method was developed, optimized, and validated using single-laboratory validation guidelines to quantify mitragynine in kratom raw materials and finished products. The method optimization evaluated several extraction parameters including solvent type, solvent volume, time, and extraction method. The separation of the mitragynine alkaloids was achieved in 18 min with a fused-core C18 EVO column using gradient separation with ammonium bicarbonate (pH 9.5) and acetonitrile. The calibration range for mitragynine was 1.0–500 μg/mL with correlation coefficients of ≥99.9% throughout method development and validation. The method detection limit and LOQ were 0.2 and 0.6 μg/mL, respectively for mitragynine. Eight test samples were obtained to evaluate method repeatability. RSDr ranged from 0.4 to 1.0%, whereas intermediate precision ranged from 3.7 to 7.3%, with HorRat values from 0.68 to 1.96. 7-OH mitragynine was below the LOQ for all samples, therefore, spikes repeatability sample RSD values were <1%. The validation data presented meet the Standard Method Performance Requirements as specified by the AOAC INTERNATIONAL Kratom Working Group., Peer-reviewed article, Published. Received July 12, 2016; Accepted by AP September 12, 2016.
A collaborative study was conducted to evaluate an HPLC method for determining phenolic compounds in Echinacea spp. raw materials, powdered extracts, and tinctures. Eleven collaborating laboratories received three practice samples representing each matrix type, phenolic reference standards, eight test samples as blind duplicates, the validated analytical method, and instructions. Test samples included two raw materials, four extracts (including one in combination with astragalus and reishi), one ethanolic tincture in combination with goldenseal, and one glycerite tincture. Each material was extracted with a 60% methanol aqueous solution, separated on a C18 column, and detected at 330 nm. Results reported by laboratories for total phenolics in Echinacea roots, aerial parts, and extracts ranged from 9.5 to 62.9 mg/g with RSDR ranging from 3.64 and 7.95% and Horwitz ratio (HorRat) values ranging from 1.06 to 2.01. Total phenolics in the ethanolic tincture ranged from 4837 to 5962 μg/mL, with an RSDR of 6.35% and a HorRat value of 1.45. The glycerite tincture showed poor interlaboratory precision with a HorRat value of 3.32, an RSDR of 21.8%, and reported total phenolic values ranging from 257 to 539 μg/mL., Peer-reviewed article, Published. Received May 4, 2016; Accepted by AP May 25, 2016.
A single-laboratory validation study was completed for the determination of β-N-methylamino-L-alanine (BMAA), N-(2-aminoethyl)glycine (AEG), and 2,4-diaminobutyric acid (DAB) in bulk natural health product supplements purchased from a health food store in Canada. BMAA and its isomers were extracted with acid hydrolysis to free analytes from protein association. Acid was removed with the residue evaporated to dryness and reconstituted with derivatization using 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AccQ-Fluor). Chromatographic separation and detection were achieved using RP ultra-performance LC coupled to a tandem mass spectrometer operated in multiple reaction monitoring mode. Data from biological samples were evaluated for precision and accuracy across different days to ensure repeatability. Accuracy was assessed by spike recovery of biological samples using varying amino acid concentrations, with an average recovery across all samples of 108.6%. The analytical range was found to be 764-0.746 ng/mL prior to derivatization, thereby providing a linear range compatible with potentially widely varying analyte concentrations in commercial health food products. Both the U. S. Food and Drug Administration (FDA) and U. S. Pharmacopeia definitions were evaluated for determining method limits, with the FDA approach found to be most suitable having an LOD of 0.187 ng/mL and LLOQ of 0.746 ng/mL. BMAA in the collected specimens was detected at concentrations lower than 1 μg/g, while AEG and DAB were found at concentrations as high as 100 μg/g. Finding these analytes, even at low concentrations, has potential public health significance and suggests a need to screen such products prior to distribution. The method described provides a rapid, accurate, and precise method to facilitate that screening process., Peer-reviewed article, Published. Received April 15, 2015; Accepted by SG June 22, 2015.
Proceedings of the 2017 International Conference on Rehabilitation Robotics (ICORR) QEII Centre, London, UK, July 17-20, 2017. One of the main challenges in the use of a powered lower limb exoskeleton (LLE) is to ensure that balance is maintained throughout the operation of the device. Since no control strategy has yet been implemented that prevents falls in the case of a loss of balance, head or other serious injuries may occur during independent use of LLEs in the event of a fall. These safety concerns limit LLEs in the community to supervised use only. Using the backward fall as a model, we used optimization techniques to develop safe fall control strategies in order to avoid head impact and mitigate the impact velocity of the hips. From available human biomechanics data, we first developed an optimization methodology to study falls of healthy people. The results showed similar kinematic and dynamic characteristics to findings of previous studies on real-life human falls. Second, we extended the optimization methodology to include characteristics of a hypothetical LLE and to generate optimal joint trajectories and optimal torque profiles for the fall duration. The results revealed that by applying the optimal fall strategy, the severity of a simulated fall was minimized compared to when the device fell with locked joints (i.e., how currently used exoskeletons fall): head impact was avoided and hip impact velocity was reduced by more than 50%., Conference paper, Published.
Proceedings of 11th International Conference on Durability of Building Materials and Components: 11 May 2008, Istanbul, Turkey. This paper presents a new hygrothermal model (HAMFit) for simulating the transport of heat, air and moisture across building envelopes. The model is based on partial differential equations solved simultaneously for air velocity, temperature, and moisture distributions for given interior and exterior conditions using finite-element-based commercial software called COMSOL Multiphysics and MatLab. The model is benchmarked using internationally-published numerical model test cases., Conference paper, Published. A version of this document is published in: 11th International Conference on Durability of Building Materials and Components, Istanbul, Turkey, May 11-14, 2008, pp. 1-8.
Proceedings of 17th International Conference of the Engineering in Medicine and Biology Society, Montreal, Quebec, Canada, on 20-23 Sept. 1995. The measurement of pressure at a device/tissue interface is desirable in many biomedical engineering applications such as tourniquets and mammography in order to optimize the design or performance of the device. Testing of a selection of existing interface transducers has demonstrated that many are dependent on device and tissue compliance. Such a transducer is only useful in an application where it has been calibrated for specific device/tissue compliance combinations. To overcome this limitation the authors have developed an interface pressure transducer whose output signal is not affected by changes in interface compliance. This enables the transducer to quantitatively measure pressure in many applications without the need to calibrate the transducer for varying compliance conditions. The signal from such a transducer could be incorporated into a control system to measure and control the pressure applied by a mammography machine to the breast., Conference paper, Published.
Home support workers (HSWs) work in clients’ homes assisting with rehabilitation and activities of daily living. Like all health-care professionals, HSWs are at an increased risk for developing back injuries. Lift devices have been shown to reduce injuries to the worker. Presently, there are few lifting devices for home use that cost under $4000 CDN. Our study involved designing a safe and affordable lift device (retail cost under $2000 CDN) to be used by HSWs in the home and evaluating it in a typical bathroom. Thirty-eight HSWs and three seniors evaluated the BCIT lift, a commercially available lift (BHM Medical Inc.) and the manual method of transfer and lift. Results indicated that the BCIT lift was an improvement over the manual method of transferring, and approximated the more expensive, automatic lift in terms of perceived exertion, ease of use and safety. Feedback provided to the researchers has been incorporated into a new, ergonomically sound and marketable lift device., Peer-reviewed article, Published. Received 1 February 2003, Revised 27 January 2004, Accepted 23 February 2004, Available online 6 May 2004.
The measurement of the interface pressure between a biomedical device and part of the human body is useful to aid in the design or improve the performance and safety of such devices. Therefore, a need exists for a transducer to measure interface pressure in these applications. The development and evaluation of an interface pressure transducer was the main goal of this research. Surgical retraction, surgical tourniquets and mammography were selected as demonstration applications for the developed transducer. These target applications were selected because they represented a wide spectrum of device and tissue characteristics and properties, and were in common use. A review of the available clinical, commercial and engineering literature identified a wide range of transducers and transducer technologies used for interface pressure measurement. The transducers included pneumatic/hydraulic, fibre-optic, strain based, capacitive and micromachined technologies. No standard method of measuring interface pressure was described and, in many cases, investigators cautioned against comparing-interface pressure measurements obtained using different measurement systems. From this review and an examination of the biomedical applications mentioned, the design criteria and optimal design specifications for an interface pressure transducer were defined. To gain a better understanding of the mechanical response of the interface between a device, transducer, and tissue to an applied loading, a preliminary finite element model was developed and studied. The model demonstrated the potential for shear stresses to develop between the transducer and interface materials. Furthermore a calibration system which simulated interface conditions was developed to evaluate both existing and developed transducers for use as interface pressure transducers. This evaluation demonstrated the lack of a transducer whose output was independent of the compliance of the interface materials. As well, an essential characteristic was identified for an effective interface pressure transducer that could be used in several applications where the interface material compliance was different. Based on the knowledge gained from the finite element analysis and existing transducer evaluation results, a novel interface pressure transducer was developed and evaluated both in the calibration system and via demonstration applications of surgical retraction and tourniquets. Under laboratory conditions in the calibration system, the transducer met many of the desired design specifications. The transducer was tested in the lab under both pneumatic and nonpneumatic tourniquet cuffs. The transducer worked well under the pneumatic cuff but required ] further development for use under the non-pneumatic cuff. The transducer was also integrated into a surgical retractor and evaluated in five clinical trials. It met many of the desired specifications for this application., Thesis, Published.