This standard applies to the determination of total hydrocarbons in the air. In this method, a syringe is used to collect air samples, which are directly measured by a gas chromatograph with a hydrogen flame ionization detector. The sample is introduced into the detector through an empty column or a glass bead damping column to determine the total hydrocarbon content. 1 Scope of application 1.1 This standard applies to the determination of total hydrocarbons in the air. 1.2 In this method, a syringe is used to collect air samples, which are directly measured by a gas chromatograph with a hydrogen flame ionization detector. The sample is introduced into the detector through an empty column or a glass bead damping column, and the total hydrocarbon content is determined. 1.3 Method detection range: Different instruments are used, and the measuring range of the method is different. The lower limit of determination of total hydrocarbon is 0.14mg / m3. When nitrogen is used as the carrier gas to determine the total hydrocarbon content in the air, the total hydrocarbon peak includes oxygen components. Because oxygen in the sample has an effect on the response value, here, the blank value is obtained by purifying the air with hydrocarbon removal, and the total hydrocarbon peak Deduct the oxygen component value. 2 Definition Total hydrocarbons: The hydrocarbons (Cl ~ C8) measured by the hydrogen flame detector are total hydrocarbons, calculated as methane. 3 Reagents and materials 3.1 Carrier gas and auxiliary gas 3.1.1 Nitrogen: 99.9% pure nitrogen. Purify with 5A molecular sieve purification tube. 3.1.2 Hydrogen: 99.9%. Purify with a silica gel and activated carbon purification tube. 3.1.3 Air: It is supplied by high-pressure steel cylinders or oil-free air compressors, and purified with silica gel and activated carbon purification tubes. 3.1.4 Purified air: processed by a purified air device for removing hydrocarbons (see Appendix A for details). 3.2 Reagents and materials used in the preparation of chromatographic columns 3.2.1 For the preparation of chromatographic columns and packings, please refer to Section 4.3. 3.2.2 Chromatography standard: methane standard gas with nitrogen as the base gas at 7.1mg / m3 (10ppm). 4 instruments 4.1 Instrument: Gas chromatograph equipped with hydrogen flame ionization detector. 4.1.1 The main components of the instrument: with hydrogen flame ionization detector, with column heating furnace, temperature regulator, inlet heater, detector heater and corresponding temperature regulator, amplifier, etc. 4.1.2 Pressure gauge, flow meter and auxiliary gas indicating flow meter for controlling carrier gas. 4.2 Sampler: The instrument comes with a stainless steel sample inlet or six-way valve, 1ml quantitative tube. 4.2.1 Syringe: 1ml, 5ml, 50ml and 100ml syringes. 4.3 Column: 4.3.1 Chromatographic column type: empty column calibration or packed column. 4.3.2 Number of chromatographic columns: 2 to 3. 4.3.3 Characteristics of chromatographic column: 4.3.3.1 Material: stainless steel. 4.3.3.2 Length: 1 ～ 2m. 4.3.3.3 Inner diameter: φ5mm. 4.3.3.4 Shape: spiral. 4.3.4 Filling: 4.3.4.1 Silanized glass beads or no packing (empty column). 4.3.4.2 Particle size: 60 ～ 80 mesh. 4.3.5 Filling method: One end of the stainless steel column is plugged with glass wool and connected to the vacuum pump; the other end of the column is connected to the funnel through a hose, and the support is slowly loaded into the chromatography column through the funnel. While loading the support, turn on the vacuum pump to draw air, and gently tap the chromatographic column to make the support packed tightly and evenly in the chromatographic column. After filling, plug it with glass wool. In order to prevent the glass wool and the support from being drawn into the vacuum pump, a capillary tube and a buffer bottle are connected between the vacuum pump and the chromatographic housing. 4.3.6 Aging of chromatographic column: Connect one end of the packed chromatographic column to the inlet of the instrument and the other end without a detector. Pass the carrier gas with a low flow rate (about 10ml / min). The column temperature is raised to 100 ° C and aged for about 24h. Connect to the chromatography system and wait until the baseline is straight. 4.4 Detector: hydrogen flame ionization detector. 4.5 Recorder: Range 5 ～ 10mV. 5 samples 5.1 Sample properties 5.1.1 Sample name: ambient air sample. 5.1.2 Sample condition: gas. 5.2 Sampling and storage methods Use a 100ml syringe to take a sample of the air to be tested at the height of the person's breathing zone. After repeated replacement three times, take a 100ml sample and seal the needle with a rubber cap to send to the laboratory for testing; the sample is analyzed on the same day. 6 operating steps 6.1 Adjusting the instrument 6.1.1 Vaporization chamber: 70 ～ 100 ℃. 6.1.2 Column temperature: 70 ° C. 6.1.3 Carrier gas flow rate The flow rates of hydrogen and air are selected according to the specific conditions of the instrument. 6.1.4 Detector temperature: 150 ° C. 6.1.5 Recorder: 6.1.5.1 Attenuation: adjust the attenuation of the recorder according to the concentration of the tested component in the sample. 6.1.5.2 Paper speed: 5mm / min. 6.2 Calibration 6.2.1 External standard method 6.2.1.1 Number of calibrations: According to the stability of the instrument, generally in a batch of samples, it can be calibrated once at the beginning, middle and last. 6.2.1.2 Preparation of standard samples: prepare a series of standard gases with standard methane gas and a syringe with nitrogen as the base gas within the linear range of the instrument. 6.2.2 Use conditions of standard samples 6.2.2.1 The injection volume of the standard sample is the same as the sample injection volume, and the response value of the standard sample should be close to the response value of the sample. 6.2.2.2 Standard samples used: only a single peak is required and no other interfering substances are required. 6.3 Test 6.3.1 Injection 6.3.1.1 Sampling method: use a syringe or a six-way valve for sampling. 6.3.1.2 Injection volume: 1ml. 6.3.1.3 Operation: Use a syringe to draw the sample to be tested, and after three replacements, draw 1ml accurately and quickly inject it into the chromatography system. 6.4 Inspection of chromatogram 6.4.1 The standard chromatogram is shown below. 6.5 Quantitative analysis 6.5.1 Measurement of chromatographic peaks Taking the connecting line of the start point and the end point of the peak as the bottom of the peak, a vertical line from the maximum value of the peak height to the time axis, the corresponding time is the retention time, and the line segment from the top of the peak to the bottom of the peak is the peak height. 6.5.2 Calculation The total hydrocarbon is calculated as follows: In the formula: C total-total hydrocarbon concentration in the gas sample (calculated in methane), mg / m3; E——Methane standard gas concentration, mg / m3, namely ppm × 16 / 22.4, 16 / 22.4 is the conversion factor; H1——The peak height of the total hydrocarbons in the sample (including the response of oxygen), cm; Ha—— Peak height of air purification and purification of hydrocarbons, cm; Hs——The height of methane standard gas passing through the total hydrocarbon column, cm. 7 Expression of results 7.1 Qualitative results According to the retention time of methane standard gas on the column, determine the total hydrocarbons of the tested sample. 7.2 Quantitative results Calculate the total hydrocarbon content in the sample according to the calculation formula, and the result is expressed in three significant figures. 8 Precision and accuracy Five laboratories analyzed uniform methane standard samples containing 1.42mg / m3 and 3.55mg / m3. 8.1 Precision 8.1.1 Repeatability The relative standard deviations of repeatability were 3.28% and 2.23%, respectively. 8.1.2 Reproducibility The relative standard deviations of reproducibility were 3.64% and 2.26%, respectively. 8.2 Accuracy The relative errors were + 3.48% and -3.8%, respectively, and the recovery rate of the ambient air samples was 96.3% ± 14.6%. 9 Instrument lower limit When the baseline of the chromatograph is stable when the power is turned on, the baseline noise of the test sample is 2 times the lower limit of the instrument. This method requires that the sensitivity of the instrument is not less than 10-10g / s. Appendix A Air Purifying Device for Hydrocarbon Removal (Supplementary) A1 Reagents and materials used for air purification A1.1 reagent A1.1.1 Palladium catalyst, AR. A1.1.2 Silicone, AR. A1.1.3 Alkali asbestos, AR. A1.1.45A molecular sieve, AR. A1.2 Material High-temperature tube furnace or self-made heater, air compressor or air cylinder, flow meter, steady flow valve, a stainless steel tube with a length of 2m and an internal diameter of 4mm The connection is shown in Figure A1. A2 Operation steps A2.1 Preparation of hydrocarbon removal catalytic tube The U-shaped tube is a stainless steel tube with an inner diameter of 4 mm, containing 10 g of catalyst, and the bed height is about 7 to 8 cm. A 1 m long stainless steel preheating tube with an inner diameter of 4 mm is connected in front of the U-shaped tube. A2.2 Inspection of dehydrocarbon air The device for removing hydrocarbons and purifying air returns to indoor air or air cylinders. After the furnace temperature rises to 450 to 500 ° C and the temperature is constant for 2 hours, remove the hydrocarbons and purifying the air until GDX-502 column chromatography determines that there is no peak. Note: 1) Palladium-6201 catalyst takes a certain amount of palladium chloride (PdCl2) and dissolves it in deionized water under acidic conditions. The amount of solution should be able to submerge 10g of 60-80 mesh 620l support. Leave it for 2h, evaporate it with gentle agitation, then put it in a U-shaped tube, place it in a heating furnace, and dry it at 100 ° C with air for 30min. After heating to 500 ℃ for 4h, the temperature was lowered to 400 ℃, and after replacing with nitrogen for 10min, hydrogen was added to reduce it for 9h. Replace with nitrogen for 10 minutes. The black brown palladium-620l catalyst was obtained.
Shop dining room and kitchen chairs in modern and contemporary style. We supply Dining Chairs with Outstanding Service, Unique Designs, exceptional quality, value pricing and fast delivery. Dine in comfort and style with Dining Room Chairs from Modern Luxury Furniture factory directly. Choose our elegant, creative and stylish dining chairs to compliment your deco. The unusual designer dining chairs are widely accepted by our valuable clients including furniture dealer, shop and architect companies from US and Europe. 2018 new designs of dining chairs in extremely comfortable and exceptional quality are becoming popular with our reliable after sales service. Choose Modern Luxury Furniture factory, choose the business partner in fast growing lane. Our selection includes Upholstered, Wooden, Stainless steel, fiberglass, fabric and leather dining chairs. These simple, yet classic, designs never seem to go out of style.
New Design Dining Chair,European Style Dining Chair,American Style Dining Chair,Contemporary Dining Chair DELO SOFA , https://www.modernluxuryfurnitures.com