MyMedR

Comparison of solvent extraction and solid-phase extraction for the determination of organochlorine pesticide residues in water

Tan GH

Analyst, 1992 Jul;117(7):1129-32.

PMID: 1524230

Solid-phase extraction (SPE) of organochlorine pesticide residues from environmental water samples was evaluated using octadecyl (C18)-bonded porous silica. The efficiency of SPE of these pesticide residues from reagent water samples at 1-5 micrograms dm-3 levels was compared with those obtained by solvent extraction with hexane and Freon TF (trichlorotrifluoroethane). Average recoveries exceeding 80% for these organochlorine pesticides were obtained via the SPE method using small cartridges containing 100 mg of 40 microns C18-bonded porous silica. The average recovery by solvent extraction with hexane and Freon TF exceeded 90% in both instances. It was concluded that the recoveries and precision for the SPE of organochlorine pesticides were poorer than those for the solvent extraction method. Organochlorine pesticide residue levels in environmental water samples from two major rivers flowing through predominantly rice-growing areas were monitored by gas chromatography using the solvent extraction method with hexane. Exceptionally high levels of organochlorine pesticide residues such as BHC, DDT, heptachlor, endosulfan and dieldrin were found in these water samples.

Residue levels of phthalate esters in water and sediment samples from the Klang River basin

Tan GH

Bull Environ Contam Toxicol, 1995 Feb;54(2):171-6.

PMID: 7742623

Fulltext Ergonomic task analysis in electronics industries: some case studies

Tan GL

J Hum Ergol (Tokyo), 1996 Jun;25(1):49-62.

PMID: 9551132 DOI: 10.11183/jhe1972.25.38

The analyses of a few tasks were carried out in an electronics factory. The main objectives are to identify the ergonomic and biomechanical hazards of problem work tasks, to analyze each task systematically in order to evaluate the workers' exposures to the risk factors of force, posture pressure and repetition and to make recommendations to reduce the risks and hazards. The methodology includes objective measures--detailed analysis by going through training manuals, job description and production records. Subjective measures include interviewing the operator and supervisors informally, the operators were also required to fill in a structured questionnaire. The paper concludes by making recommendations to reduce the ergonomic hazards by engineering solutions, redesign or administrative controls or the implementation of procedures.

Organochlorine pesticide residue levels in peninsular Malaysian rivers

Tan GH, Vijayaletchumy K

Bull Environ Contam Toxicol, 1994 Sep;53(3):351-6.

PMID: 7919710

Fulltext Spontaneous internal ilio-iliac fistula in an elderly woman presenting as heart failure

Tan G, Abdullah B, Kunanayagam S

Biomed Imaging Interv J, 2006 Apr;2(2):e13.

PMID: 21614225 MyJurnal DOI: 10.2349/biij.2.2.e13

Acquired intra-abdominal arteriovenous fistulas (AVFs) are a rare disorder where the communication most commonly occurs between abdominal aorta and inferior vena cava. Ilio-iliac AVF has been reported previously, but is exceedingly rare. We present a case of spontaneous ilio-iliac AVF in an elderly woman who presented with symptoms of right heart failure where the diagnosis was not considered. The computed tomographic (CT) and angiographic features are described. The current status of management as well as a review of the literature is also presented.

Fulltext Resection of large primary chest wall chondrosarcoma with reconstruction: 2 case reports

Wong PS, Tan GP

Med J Malaysia, 2000 Dec;55(4):516-9.

PMID: 11221168

We report two cases of large chest wall primary chondrosarcoma, one of the sternum and the other of the lateral chest wall. Both were treated by radical resection and reconstruction using marlex mesh and methyl methacrylate "sandwich" prosthesis and pedicled latissiumus dorsi flap.

Trace monitoring of water-borne phenolics in the Klang River Basin

Tan GH, Chong CL

Environ Monit Assess, 1993 Feb;24(3):267-77.

PMID: 24227384 DOI: 10.1007/BF00545983

The Klang River Basin is located in the most densely populated region in Malaysia, with its heavy concentration of industries and population. A systematic study of the pollution to this river system caused by phenolic compounds have been carried out under this project. Analyses of water samples from the Klang River by high performance liquid chromatography (HPLC) with an ultraviolet (UV) detector at 280 nm have shown the presence of some priority phenolic pollutants.

Effect of oxytocin on plasma testosterone levels in the male macaques (Macaca fascicularis)

Tan GJ, Kwan TK

Contraception, 1987 Sep;36(3):359-67.

PMID: 3677679

The effect of oxytocin on testicular function was examined in the adult male long-tailed macaques (Macaca fascicularis). The monkeys were either infused with increasing concentrations of synthetic oxytocin (16-128 m.i.u./min for 3 h) or injected daily for a week with the same hormone (20 i.u., i.v.) and the plasma testosterone levels measured. The results of the present study show that acute infusion or chronic injection of oxytocin does not significantly affect the plasma testosterone levels, suggesting that systemic control of testicular endocrine function by oxytocin may be unimportant.

Virtual meeting in pathology: Time to adapt to the new-norm

Wong YP, Tan GC

Malays J Pathol, 2021 Apr;43(1):1.

PMID: 33903298

No abstract available.

Heterogeneity in studies of p16 in cervical lesions in different Malaysian institutions: Time to consider collaborative study

Naicker MS, Tan GC

Malays J Pathol, 2018 Dec;40(3):319-323.

PMID: 30580363

INTRODUCTION: Clinical decision making becomes difficult when clinical and methodological heterogeneity does not permit synthesis of results of multiple small studies.

AIM: For studies done in Malaysia, to identity the sample sizes and heterogeneity present in the various studies which used p16 in evaluating lesions of the cervix. To evaluate if it would be possible for a single study to answer the various questions posed by the original authors. To highlight areas where the design features of future studies can be optimised.

MATERIALS AND METHODS: Various databases were searched using synonyms for p16 AND cervix AND Malaysia. These were assessed for broad conformity to a Diagnostic Test Accuracy format. Methodological and clinical heterogeneity indicators were extracted into standardised fields.

RESULTS: There were 5 studies eligible for inclusion. Each sought to study different aspects of the disease such as diagnostic grade stratification and pathogenesis. The study type broadly conformed to a Diagnostic Test Accuracy format. The study design used was either consecutive or non-consecutive. Sample size ranged from 75 to 201. Clinical heterogeneity was present in the choice of controls with some using normal and some using inflamed tissue. Methodological heterogeneity in applying the reference test, index test and different antibody clones were present.

CONCLUSION: There was both clinical and methodological heterogeneity making synthesis of studies difficult. It is possible to design a study which would be able to answer all the questions posed by the original authors with internal validity while at the same time increasing sample size.

Challenges of Covid-19 testing

Tan GC, Cheong SK

Malays J Pathol, 2020 Apr;42(1):1.

PMID: 32342925

No abstract available.

Opportunity in a time of crisis: New technology in pathology

Tan GC, Wong YP

Malays J Pathol, 2021 Dec;43(3):339.

PMID: 34958054

No abstract available.

Digital pathology as a solution for working from home

Tan GC, Wong YP

Malays J Pathol, 2021 Aug;43(2):201.

PMID: 34448785

No abstract available.

SARS-CoV-2: Reflection beyond the lungs

Tan GC, Wong YP

Malays J Pathol, 2022 Dec;44(3):365.

PMID: 36591706

No abstract available.

Fulltext Bilateral internal carotid artery hypotrophy in malignant osteopetrosis

Ramli N, Rahmat K, Tan GP

Singapore Med J, 2008 Jul;49(7):e175-7.

PMID: 18695851

Malignant osteopetrosis is associated with petrous carotid canal and internal carotid artery stenosis in the skull base. We present a four-year-old boy with malignant osteopetrosis who developed right frontal lobe infarction as a result of bilateral internal carotid artery hypotrophy.

MJP going green

Tan GC, Cheong SK

Malays J Pathol, 2023 Dec;45(3):315.

PMID: 38155374

No abstract available.

Recent developments and applications of liquid phase microextraction in fruits and vegetables analysis

Abdulra'uf LB, Sirhan AY, Huat Tan G

J Sep Sci, 2012 Dec;35(24):3540-53.

PMID: 23225719 DOI: 10.1002/jssc.201200427

The sample preparation step has been identified as the bottleneck of analytical methodology in chemical analysis. Therefore, there is need for the development of cost-effective, easy to operate, and environmentally friendly miniaturized sample preparation technique. The microextraction techniques combine extraction, isolation, concentration, and introduction of analytes into analytical instrument, to a single and uninterrupted step, and improve sample throughput. The use of liquid-phase microextraction techniques for the analysis of pesticide residues in fruits and vegetables are discussed with the focus on the methodologies employed by different researchers and their analytical performances. Analytes are extracted using water-immiscible solvents and are desorbed into gas chromatography, liquid chromatography, or capillary electrophoresis for identification and quantitation.

A direct high-performance liquid chromatographic method for the determination of therminol 66 contamination in commercial glycerin and fatty acids

Moh MH, Tang TS, Tan GH

J Chromatogr Sci, 2001 Dec;39(12):508-12.

PMID: 11767238

A simple and sensitive high-performance liquid chromatographic method for the determination of Therminol 66 thermal heating fluid in glycerin and fatty acids is developed. Sample solutions dissolved in methanol-tetrahydrofuran (50:50, v/v) are injected directly into a reversed-phase C18 column and eluted with a methanol and water mixture (88:12, v/v). The concentration of the thermal heating fluid is monitored by fluorescence detection at 257 nm (excitation) and 320 nm (emission). The calibration graph obtained from various concentrations of the thermal heating fluid in the methanol and tetrahydrofuran mixture is linear (correlation coefficient = 0.999), and the limit of detection is 0.01 microg/mL. Spiked glycerin containing 0.1 to 1.0 microg/g of the thermal heating fluid also gives good linearity with a mean recovery of 95.3%. The mean intra- and interassay precision are 1.80-6.51% and 5.71-9.03%, respectively, at the 0.1-microg/g level. The method is simple and does not require any pretreatment step, thus it is ideal for quality assurance purposes.

Optimization of headspace solid-phase microextraction for the determination of pesticide residues in vegetables and fruits

Chai M, Tan G, Lal A

Anal Sci, 2008 Feb;24(2):273-6.

PMID: 18270422

A headspace solid-phase microextraction method has been developed for the determination of 8 pesticides in vegetables and fruits by using gas chromatography with an electron capture detector. Two types of fibers (polyacrylate, 85 microm and polydimethylsiloxane, 100 microm) have been assayed and compared. The main factors: extraction and desorption parameters, ionic strength, and the effects of dilution and organic solvents, were studied and optimized. The optimized procedures resulted in more than 80% recovery for all the investigated vegetable and fruit samples with RSD values below 10%.

Multiresidue analysis of pesticides in fruits and vegetables using solid-phase extraction and gas chromatographic methods

Lal A, Tan G, Chai M

Anal Sci, 2008 Feb;24(2):231-6.

PMID: 18270414

A new extraction and cleanup procedure with gas chromatography was developed for the sensitive determination of acephate, dimethoate, malathion, diazinon, quinalphos, chlorpyrifos, profenofos, alpha-endosulfan, beta-endosulfan, chlorothalonil and carbaryl using 1-chloro-4-fluorobenzene as an internal standard in fruits and vegetables. Several extracting and eluting solvents for solid-phase extraction were investigated. The overall extracting solvent with a mixture of acetone:ethyl acetate:hexane (10:80:10, v/v/v) and a eluting solvent of 5% acetone in hexane used with the RPC18 cartridge gave the best recovery for all of the investigated pesticides, and minimized the interference from co-extractants. Under the optimal extraction and clean-up conditions, recoveries of 85 - 99% with RSD < 5.0% (n = 3) for most of the pesticides at the 0.02 - 0.5 mg/kg level were obtained. The limit of detection was between 0.005 - 0.01 mg/kg and the limit of quantification was 0.01 mg/kg. This analytical procedure was characterized with high accuracy and acceptable sensitivity to meet requirements for monitoring pesticides in crops.

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