Government Laboratory
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The Government Laboratory (GL) is committed to contributing to the sustainable development of measurement science and scientific infrastructure in Hong Kong by fostering collaborations and positive partnerships with counterparts, professional organizations and client departments involving in scientific investigations.
GL often organizes talks and seminars to facilitate the local testing sector in building their testing capabilities and preparing for laboratory accreditation to ISO/IEC 17025:2005.
Briefing sessions
Over the years, GL continued organizing technical seminar for the commercial sector to provide a platform for technical exchange. Among others, more than 10 briefing sessions on food testing covering determination of preservatives, veterinary drug residues, pesticide residues, food additives, food dyes, toxins and etc had been organized. These briefing sessions provided opportunities for GL to share its experience with local commercial laboratories and enhance their interests in the provision of food testing service.
| Briefing Session Title | Date |
| International / National Standards for Heavy Metals in Food | 27 Oct 11 |
| Technical Seminar on Aflatoxins Analysis in Food | 25 Oct 10 |
| Testing of Sudan Dyes in General Foodstuffs | 29 Oct 09 |
| Chemical testing of melamine in dairy products | 23 Sep 08 |
| Analysis of Pesticide Residues in Food | 15 Jul 08 |
| Briefing Session on Analysis of Nitrate/Nitrite and Propionic Acid in Food | 23 May 08 |
| Briefing Session on Chemical Testing of Preservatives in Food | 23 May 08 |
| 18 Apr 08 | |
| Briefing Session on Organochorine Pesticide Residues in Fruit & Vegetables | 14 Mar 08 |
| Briefing Session on Analysis of Sulphur Dioxide in Food | 14 Mar 08 |
| Briefing Session on Analysis of Sweeteners in Food | 14 Feb 08 |
| Analysis of malachite green in fish (Part B) | 14 Sep 05 |
| Analysis of malachite green in fish (Part A) | 14 Sep 05 |
Abstracts of analytical methods presented in the afore-mentioned briefing sessions are provided as per the attached table for reference.
| Parameters | Test Method Information | ||||||||||||||||
Aflatoxin |
Aflatoxin B1, B2, G1 and G2 in general food are extracted with 70% methanol and then purified by immunoaffinity column. The purified extract is then analysed using an HPLC with post-column derivatisation with iodine. The extraction and clean-up method for aflatoxin M1 is depending on the food types. Aflatoxin M1 in cheese, butter or ice-cream sample is extracted with chloroform. The extract is then dried and concentrated. The concentrated extract is cleaned up by passing through a silica Sep-Pak (SPE) cartridge. While the aflatoxin M1 in liquid milk or milk powder sample is simply defatted prior to cleanup by a specific immunoaffinity column, the concentration of aflatoxin M1 is then determined by HPLC using a C18 column and detected by a fluorescence detector. Any positive sample found will be further confirmed using LC-MS/MS according to the European Union Standard. |
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Boric acid |
In the qualitative test, sample solutions are acidified and tested with turmeric paper. The presence of borate is indicated by the turning of turmeric paper from yellow to red. This method provides a rapid screening test for the compound. In the quantitative test, the sample is ashed and the ash is dissolved in dilute hydrochloric acid. The resultant solution is allowed to react with azomethine H which forms an intense yellow colour with boron. The developed colour, which is proportional to the amount of boron present, is measured at 420 nm by spectrophotometer. For further confirmation, the amount of boron as boric acid, after acid digestion by microwave, can be determined by inductive couple plasma optical emission spectrometry. |
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Propionic acid |
The sample is steam distilled and the distillate is anlysed by gas chromatography (GC) after acidification with formic acid. Butyric acid is used as internal standard. |
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Nitrite/Nitrate |
Nitrite and nitrate in meat and meat products are extracted by borax solution with the addition of activated charcoal and Carrez solutions. The determination of nitrite is based on its reaction with sulphanilamide and N-1-(naphthyl)ethylene diamine in forming a red azo dye. The dye formed is measured at 540 nm by flow injection analysis. Nitrate content is obtained by the difference of the total nitrite after reduction by the use of a cadmium column and the nitrite content by bypassing the cadmium reduction column. Further quantitative confirmation for non-compliant sample can be done by ion chromatography with ultra-violet detection (IC-UV) with reference to BS EN 12014-4:2005. |
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Nitrite/Nitrate |
The determination of nitrite and nitrate in milk and milk products is referenced to BS EN ISO 14673-3:2004. |
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Sudan dyes |
The sample is first homogenized and spiked with internal standards Sudan I-d5 and Sudan IV-d6. The Sudan dyes and related dyes are then extracted by acetonitrile. Any dye present is detected by the LC-MS/MS method. |
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Melamine |
Melamine in the food sample is dissolved in water and then clean-up by dichloromethane. Solid phase extraction using MCX column may be employed to further clean-up the extract to achieve lower detection limit if required. The final extract with isotropic internal standard is then analyzed by LC-MS/MS technique. |
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Sulphur dioxide |
AOAC (1990) 975.32., AOAC (1990) 961.09, AOAC (2000) 47.3.41. and AOAC 990.28. |
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Sulphur dioxide |
This method measures sulphite by flow injection analysis (FIA) using reaction with malachite green. The sample is firstly extracted with sodium tetrachloromercurate (TCM) followed by FIA analysis. In the FIA system, the test solution is first reacted with NaOH to liberate aldehyde-bound sulphite. Then, the solution stream is acidified to produce SO2 gas, which diffuses across a Teflon membrane in a gas diffusion cell into a flowing stream of malachite green, which is discolored. Degree of discoloration of malachite green is measured at 620 nm and it is proportional to amount of sulphite in the test sample solution. This method is not recommended for dry products, such as dry mushroom, fungi and dry shrimps. |
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Benzoic acid, Sorbic acid, salicylic acid and methyl, ethyl and propyl parabens |
The method is for the simultaneous determination of the preservatives in starchy food, meat products and beverage. The preservatives are extracted from food with 70% acidified ethanol followed by high performance liquid chromatography (HPLC) using a C18 column. |
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Benzoic acid and Sorbic acid |
The preservatives in comminuted food are extracted by steam distillation in an acidic medium. Benzoic acid and sorbic acid are measured by HPLC using a C-18 column and with ultraviolet detection at 272 nm and 254 nm respectively. |
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Benzoic acid and Sorbic acid |
Benzoic acid and sorbic acid are isolated from food samples by extraction with diethyl ether, followed by successive partition into aqueous sodium hydroxide. The aqueous extract is then acidified and re-extracted by dichloromethane. Subsequently, the preservatives are converted to trimethysilyl (TMS) esters and determined by gas chromatograph with flame ionization detector. The presence of the preservatives is also confirmed by gas chromatography with mass spectrometry. Phenylacetic acid and caproic acid are used as internal standards for benzoic acid and sorbic acid respectively. |
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Organochlorine pesticides in general foodstuff |
This method determines 35 organochlorine pesticide residues in food samples. The target pesticides include Aldrin, Chlorfenapyr, Chlorothalonil, Dichlorbenil, Dicofol, Dieldrin, Endrin, α-Endosulfan, β-Endosulfan, Endosulfan sulphate, Trans-Chlordane, cis-Chlordane, Oxychlordane, o,p'-DDT, p,p'-DDT, o,p'-DDD, p,p'-DDD, o,p'-DDE, p,p'-DDE, Heptachlor, Heptachlor-epoxide, Hexachlorobenzene, α-Hexachlorocyclohexane, β-Hexachlorocyclohexane, δ-Hexachlorocyclohexane, Lindane, Methoxychlor, Mirex, Quintozene, Pentachloroaniline, Procymidon, Methyl- pentachlorophenyl sulphide, Tetradifon, Trifluralin and Vinclozolin. The analytes are extracted by ethyl acetate and then cleaned-up by gel permeation chromatography and solid phase extraction. The amount of pesticide residues present is determined using gas chromatography with electron capture detection. For positive results, further confirmation using dual column analysis or mass spectrometry will be conducted. The reporting limit for the pesticide residues concerned is 0.01 mg/kg. |
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Organophosphorus pesticides in general foodstuff |
This method determines 44 organophosphorus pesticide residues in food samples. The target pesticides include Acephate, Azinphos-methyl, Carbophenthion, Chlorfenvinphos, Chlorpyrifos, Chlorpyrifos-methyl, Coumaphos, Crufomate, Diazinon, Dichlorvos, Dimethoate, Disulfonton, Edifenphos, Ethion, Ethoprophos, Fenamiphos, Fenchlorphos, Fenitrothion, Fensulfothion, Fenthion, Isocarbophos, Isofenphos, Malathion, Methamidophos, Methidathion, Mevinophos, Monocrotophos, Omethoate, Parathion-ethyl, Parathion-methyl, Phenthoate, Phorate, Phosalone, Phosmet, Phosphamidon, Pirimiphos-Methyl, Profenophos, Prothiophos, Pyrazophos, Quinalphos, Sulfotep, Tetrachlorvinphos, Triazophos and Trichlorfon. The analytes are extracted by ethyl acetate and then cleaned-up by gel permeation chromatography. The amount of pesticide residues present is determined using gas chromatography with flame photometric detection. For positive results, further confirmation using dual column analysis or mass spectrometry will be conducted. The reporting limit for the pesticide residues concerned is 0.1 mg/kg. |
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Pyrethroids in general foodstuff |
This method determines 8 pyrethroids residues in food samples. The target pesticides include Bifenthrin, Cyfluthrin, Cyhalothrin, Cypermethrin, Deltamethrin, Fenpropathrin, Fenvalerate and Permethrin. The analytes are extracted by ethyl acetate and then cleaned-up by gel permeation chromatography and solid phase extraction to remove matrix interferences. The amount of pesticide residues present is determined using gas chromatography with electron capture detection. For positive results, further confirmation using dual column analysis or mass spectrometry will be conducted. The reporting limit for the pesticide residues concerned is 0.1 mg/kg. |
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N-methyl carbamates in general foodstuff |
This method determines 16 N-methyl carbamates in food samples. The target pesticides include Aldicarb, Aldicarb sulfone, Aldicarb sulfoxide, Bendiocarb, Butocarboxim, Carbaryl, Carbofuran, 3-hydroxycarbofuran, Ethiofencarb, Isoprocarb, Methiocarb, Methomyl, Metolcarb, Oxamyl, Promecarb and Propoxur. The analytes are extracted by ethyl acetate and then cleaned-up by gel permeation chromatography. The amount of pesticide residues present is determined using liquid chromatography with post-column derivatization and fluorescence detection. For positive results, further confirmation using liquid chromatography mass spectrometry will be conducted. The reporting limit for the pesticide residues concerned is 0.1 mg/kg. |
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Metals in general foodstuff |
The method determines 7 metals in food samples. The target metals include Antimony (Sb), Arsenic (As2O3), Cadmium (Cd), Chromium (Cr), Lead (Pb), Mercury (Hg) and Tin (Sn). The food samples are homogenised and digested with nitric acid under microwave-assisted digestion conditions. The digested samples are subsequently diluted with water. The amounts of metals are determined by inductively coupled plasma - mass spectrometry and/or inductively coupled plasma - atomic emission spectrometry. The reporting limits for the seven metals concerned are as follows:
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By actively engaging in international seminars, forums and research committees, we have maintained a visible presence in the scientific arena and positive partnerships with professional bodies from all over the world. In 2010, 111 staff members participated in international seminars, workshops and conferences held in the Mainland, USA, UK, Germany, Japan, Singapore, Belgium, Ireland, etc. At the events, research papers were presented to promote knowledge sharing.
Furthermore, we have established solid networks with our counterparts through visits and attachments. In 2010, we received about 70 visitors from professional bodies such as General Administration of Quality Supervision, Inspection and Quarantine of PRC, Shenzhen Academy of Metrology and Quality Inspection, Forensic Science Centre of Guangdong Provincial Public Security Department, Japan National Police Agency and District Public Prosecutors Office, Central Narcotics Bureau of Singapore, Victoria Traffic Police on Drink and Drug Driving of Australia, etc.
To help build the scientific infrastructure and to promote the use of science in serving the public, we often conduct relevant courses, lectures and briefings to our client departments.
In 2010, we conducted 37 lectures and briefings for Hong Kong Police Force, Customs and Excise Department, Fire Services Department, Hong Kong Correctional Services, etc. Courses such as Traffic Investigation Course, DNA Buccal Swab Training Course, Probationary Inspector Course, Criminal Investigation Course, Fire Investigation Course, etc. were customized to meet the specific learning needs, in light of the work contexts and job needs, of participants.
Customized briefings on relevant scientific subjects have also been conducted for departments such as Social Welfare Department, Department of Health and Department of Justice to provide participants with continuous learning opportunities for enriching their work-related scientific knowledge.
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