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GB/T 18204.26-2000 PDF in English

GB/T 18204.26-2000 (GB/T18204.26-2000, GBT 18204.26-2000, GBT18204.26-2000)
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GB/T 18204.26-2000: PDF in English (GBT 18204.26-2000)

GB/T 18204.26-2000
Methods for determination of
formaldehyde in air of public places
Issued by. State Quality Technical Supervision Bureau
Table of Contents
Foreword ... 3 
1.  Scope ... 4 
Method One Phenol reagent spectrophotometry ... 4 
2.  Principal ... 4 
3.  Reagents... 4 
2  Instruments and equipment ... 6 
3  Sampling ... 6 
4  Analysis steps ... 6 
7 The results of the calculation ... 7 
8 Determination range, interference and troubleshooting ... 8 
Method Two Gas chromatographic method ... 8 
9 Principles... 8 
10 Reagents and materials ... 9 
11 Instruments and equipment ... 9 
12 Sampling ... 9 
13 Analysis steps... 10 
14 Calculation ... 11 
Annex A ... 13 
Annex B ... 14 
This standard is developed to enforce the implementation of “Public places Hygienic
Management Regulations”, GB 9663~9673-1996, and GB 16153-1996 “Public Places
Hygienic Standard”; and to strengthen the supervision and management of public place
Hygiene. The methods in this standard are the monitoring and testing methods that match
with GB 9663~9673-1996 and GB 16153-1996.
This first method of this standard is arbitration method.
This standard is released for first-time.
Annex A of this standard is normative.
Annex B of this standard is informative.
This standard was proposed by Ministry of Health of People's Republic of China.
Drafting organizations of this standard. Wuhan sanitary and anti-epidemic station, and
Liaoning Providence sanitary and anti-epidemic station.
Main drafters of this standard. Zhang Qisheng, Wang Hanping (phenol reagent method),
Jiang Shuqiu, Gao Wei, and Gao Guichun (gas chromatographic method).
Methods for determination of
formaldehyde in air of public places
1. Scope   
This standard specified the methods for determination of formaldehyde concentration in
air of public places.
This standard applies to the determination of formaldehyde concentration in air of public
Method One    Phenol reagent spectrophotometry 
2. Principal   
Formaldehyde in the air reacts with phenol reagent to generate triazine. Triazine is
oxidized by ferric ion in an acidic solution to form blue-green compound. The colorimetric
quantification shall be compared according to the color depth.
3. Reagents 
The water used in this method is re-distilled water or deionized exchange water; the purity
of agent used is usually analytically pure.
1.1 Original solution of absorbing solution. weight 0.10g of phenol reagent [C6H4SN (CH3)
C. NNH2•HC1, abbreviated as MBTH]. Add water to dissolve it. Pour into 100 mL
measuring cylinder with stopper. Add water to the mark. Store it in the refrigerator, and it
can be kept stably for three days.
1.2 Absorbing solution. weight 5 ml of original absorbing solution. Add 95 ml of water.
That is the absorbing solution. When sampling, prepare it when using.
1.3 1% ammonium iron sulfate solution. weight 1.0 g of ammonium iron sulfate [NH4Fe
(SO4)2•12H2O]. Use 0.1 mol/L hydrochloric acid to dissolve. Dilute to 100 ml.
1.4 Iodine solution [c(½ I2) = 0.1000 mol/L]. Weight 40 g of potassium iodide. Dissolve it
in 25 ml of water. Add 12.7 g of iodine. After it has been dissolved completely, dilute it with
water to 100mL. Then move it into a brown bottle; store it in dark place.
1.5 1 mol/L sodium hydroxide solution. weight 40 g of sodium hydroxide. Dissolve it in
A0 - Absorbance of blank solution;
Bg - The calculation factor obtained in 6.1, the unit is μg/absorbance;
V0 - The conversed sampling volume under standard condition, the unit is L.
8    Determination range, interference and troubleshooting 
8.1 Determination range
Use 5 mL of sample solution; the determination range of this method is 0.1 -1.5 μg; when
the volume of sample is 10 L, the determinable concentration range is 0.01 - 0.15 mg/m3.
8.2 Sensitivity
The sensitivity of this method is 2.8 μg / absorbance.
8.3 Detection lower limit
This method detects 0.056 μg formaldehyde.
8.4 Interference and troubleshooting
20 μg of phenol, 2 μg of aldehyde, and nitrogen trichloride have no interference effect on
this method. When they coexist with sulfur dioxide, the determination result will be lower.
Therefore, the interference of sulfur dioxide shall not be ignored. It may use
manganese sulfate filter-paper filter (see Annex B) to remove it.
8.5 Reproducibility. when the formaldehyde content is 0.5, 0.6 or 1.5μg/5 mL respectively,
the re-determined variable coefficient is 5%, 5% or 3% correspondingly.
8.6 Recovery. when the formaldehyde content is 0.4 ~ 1.0 μg / 5 mL, the recovery of the
sample and standard is 93%~101%.
Method Two    Gas chromatographic method 
9    Principles   
Formaldehyde in the air is absorbed on the supporter coated with 2,4 dinitrophenyl
hydrazine (2,4-DNPH) 6201; then generate stable formaldehyde hydrazone. After being
eluted by carbon disulfide and separated by 0V- chromatographic column, use hydrogen
flame ionization detector to determine; so as to retain the time qualitation and peak height
The detection lower limit is 0.2μg/mL (the eluant of injection sample is 5 μL).
L/min. after sampling, use plastic cap to cover it; record the temperature and atmospheric
pressure at sampling point.
13    Analysis steps 
13.1 Gas chromatography test conditions
When analyzing, it shall formulate the best test conditions to analyze formaldehyde
according to the model and performance of gas chromatograph. The test conditions listed
below is an example.
Chromatographic column. a glass tube with column length of 2 m and inner diameter of 3
mm; it is filled with 0V-1 + Shimalitew supporter.
Column temperature. 230°C.
Temperature at testing room. 260°C.
Temperature at vaporization chamber. 260°C.
Flow rate of carrier gas (N2). 70 mL / min.
Oxygen flow rate. 40 mL / min.
Air flow rate. 450 mL / min.
13.2 Draw standard curve and determine correction factor
Draw standard curve and determine correction factor when determining samples.
13.2.1 Draw standard curve. take five sampling tubes; remove glass wool at one end of
each tube. Add one drop (about 50 μL) of 20 mol/L hydrochloric acid solution on the
surface of adsorbent directly. Add formaldehyde standard solution (1.00 mL contains 1 mg
of formaldehyde) accurately by using micro syringe into each tube, so as to prepare such
standard tubes that there are five concentration points – the formaldehyde content is
within range 0-20 μg - on adsorbent in the tube; fill with glass wool; react for 10 minutes.
Then transfer the adsorbent in each standard tube to five 5 mL color-comparison tubes.
Add 1.0 mL of carbon disulfide in each tube. Shake it gently and soak it for 30 minutes.
These are the elution standard series tubes of solution of formaldehyde. Then, take 5.0 μL
of standard eluant with different concentration points; add into chromatographic column to
get chromatographic peak and retention time. Repeat three times for each concentration
points; determine the average value of peak. Take the concentration (μg/mL) of
formaldehyde as abscissa, and take the average peak height (mm) as ordinate; calculate
the slope of regression line. Take the slope value as the calculation factor Bs [μg /
(mL•mm)] in determining samples.
13.2.2 Determine correction factor. Within the determination range, single-point
V1 - The total volume of sample elution solution, the unit is mL;
Es - The average elution efficiency determined experimentally, the unit is mL;
V0 - The converted sample volume under the standard condition, the unit is L.
14.2 Calculate the concentration of formaldehyde in the air by using the single-point
calibration method according to formula (6).
c - The concentration of formaldehyde in the air;
h - The average value of peak height of sample solution, the unit is mm;
h0 - The average value of peak height of reage...
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.