JJG 178-2007 PDF English
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JJG 178-2007: PDF in English JJG 178-2007
NATIONAL METROLOGICAL VERIFICATION
SPECIFICATION OF THE PEOPLE’S REPUBLIC OF CHINA
Ultraviolet, Visible, Near-Infrared Spectrophotometers
ISSUED ON: NOVEMBER 21, 2007
IMPLEMENTED ON: MAY 21, 2008
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of the People’s Republic of China
Table of Contents
1 Scope ... 5
2 Normative References ... 5
3 Overview ... 5
4 Requirements for Metrology Performance ... 6
4.1 Maximum allowable error of wavelength ... 6
4.2 Wavelength repeatability ... 6
4.3 Noise and drift ... 7
4.4 Minimum spectral bandwidth ... 7
4.5 Maximum allowable error of transmittance ... 7
4.6 Transmittance repeatability ... 7
4.7 Baseline flatness ... 8
4.8 Adaptability of power supply voltage ... 8
4.9 Stray light ... 8
4.10 Compatibility of the absorption tank ... 9
5 General Technical Requirements ... 9
5.1 Safety performance ... 9
5.2 Marking ... 9
5.3 Appearance ... 9
5.4 Absorption tank ... 10
6 Control of Metrological Instrument ... 10
6.1 Verification Conditions ... 10
6.2 Verification Items ... 11
6.3 Verification method ... 11
6.4 Processing of verification results ... 16
6.5 Verification period ... 17
Appendix A Reference Wavelength of Wavelength Standard Substance ... 18
Appendix B Transmittance of Potassium Dichromate Standard Solution at
Different Temperatures and Different Spectral Bandwidths under
Corresponding Wavelengths ... 20
Appendix C Preparation Method of the Standard Solution ... 21
Appendix D Verification Certificate Inner Page Format ... 22
Appendix E Verification Record Format of Ultraviolet, visible and Near-Infrared
Spectrophotometer ... 23
Ultraviolet, Visible, Near-Infrared Spectrophotometers
1 Scope
This regulation is applicable to the initial verification, subsequent verification and in-use
inspection of visible, ultraviolet-visible, ultraviolet-visible-near-infrared spectrophotometers
with wavelengths ranging from 190nm to 2600nm and with continuously adjustable
wavelengths.
2 Normative References
This Regulation quoted the following references:
International Recommendation OIML R135 Edition 2004 Spectrophotometers for Medical
Laboratories
JJF 1001-1998 General Terms in Metrology and their Definitions
JJF 1059-1999 Evaluation and Expression of Uncertainty in Measurement
When using this Regulation, pay attention to use the effective edition of the above quoted
references.
3 Overview
Ultraviolet-visible-near-infrared spectrophotometer (hereinafter referred to as the instrument)
is an instrument for the quantitative analysis and qualitative identification of the substance
based on the selective absorption of radiation (light) in the ultraviolet, visible and near-infrared
regions by the molecules against the substance, and the Lambert-Beer law.
The mathematical expression of the Lambert-Beer law is:
Where:
A – absorbance of the substance;
transmittance valley value or absorbance peak wavelength λi; and measure 3 times
continuously.
When selecting a mercury lamp, place the mercury lamp in the light source room so that
the light of the mercury lamp is incident on the entrance slit of the monochromator. Select
the energy measurement method of the instrument; set an appropriate gain; and adjust
the position of the mercury lamp to maximize the energy value. Then measure the peak
wavelength corresponding to the maximum energy value in one-way and point-by-point
near the peak wavelength; record the λi; and measure 3 times continuously.
b) Automatic scanning instrument
Set the wavelength scanning range (if the wavelength scanning range is wide, segment
scanning is allowed), common spectral bandwidth, slow scanning, sampling interval less
than the wavelength repeatability index of the instrument (if the wavelength sampling
interval cannot be set, a slower scan speed shall be selected) of the instrument according
to the selected verification wavelength. When using a solution or filter standard
substance, the transmittance or absorbance measurement method is used. According to
the set scanning parameters, use air as a blank to perform baseline calibration of the
instrument; and use a light baffle to perform dark current correction. Then place the
standard substance vertically on the sample optical path; set an appropriate recording
range; scan 3 times continuously; and detect (or measure) the transmittance valley value
or absorbance peak wavelength λi, respectively.
When using a low-pressure quartz mercury lamp, scan 3 times continuously according
to 6.3.2.2a) to detect (or measure) the peak wavelength λi of the energy, respectively.
6.3.2.3 Calculation of the result
Calculate the wavelength indication error for each measurement wavelength according to
Formula (1):
Where:
– average value of the 3 measurements;
λs – standard value of wavelength.
Calculate the wavelength repeatability according to Formula (2):
Where:
λmax, λmin – maximum and minimum values of the 3 measurement wavelengths, respectively.
6.3.3 Noise and Drift
According to the working waveband range of the instrument, select Section-A 250nm, Section-
B 500nm, Section-C 1500nm as the measurement wavelength of noise; and 500nm as the
measurement wavelength of drift.
Set the scanning parameters of the instrument as: time scanning mode (or constant wavelength
scanning), spectral bandwidth 2nm (not setting for instruments with fixed spectral bandwidth),
time sampling interval (or integration time) 1s, photometric measurement mode as
transmittance, recording range 99%~101% (not setting for non-scanning instruments), at each
measurement wavelength, both the reference beam and the sample beam are treated as air
blanks, adjust the transmittance of the instrument to 100%, scan for 2 min, and measure the
difference (for non-scanning instrument, record the maximum and minimum values within 2
minutes) between the maximum and minimum values on the spectrum, which is the noise with
100% instrument transmittance. Insert a light baffle in the sample optical path to adjust the
transmittance of the instrument to 0%; scan for 2 min; and measure the difference (for non-
scanning instrument, record the maximum and minimum values within 2 min) between the
maximum and minimum values on the spectrum, which is the noise with 0% instrument
transmittance.
When the wavelength is switched, allow the visible light to stabilize for 5min.
Automatic scanning instrument, after testing the noise with transmittances of 0% and 100%
according to the above requirements, set the wavelength at 500nm, scan for 30min; read out the
difference between the maximum value and the minimum value of the center line of the
envelope of the scanning spectrum, which is the drift of the line with 100% instrument
transmittance.
6.3.4 Minimum spectral bandwidth
For instruments with a deuterium lamp, select the 656.1nm characteristic spectral line of the
deuterium lamp. For instruments without a deuterium lamp, choose the 546.1nm (or 253.7nm)
characteristic spectral line of the mercury lamp; select the minimum spectral bandwidth; and
record the characteristic spectral lines of the deuterium lamp or mercury lamp according to the
method in 6.3.2.2; measure the half-peak width, which is the minimum spectral bandwidth.
6.3.5 Maximum allowable error of transmittance and repeatability
6.3.5.1 Verification steps
a) Using the standard substance and standard absorption tank in 6.1.2.1, measure the
transmittance for three times at 235nm, 257nm, 313nm, and 350nm, respectively.
It can also be measured by the ultraviolet transmittance filter in 6.1.2.2.
b) Using spectral neutral filters with nominal transmittance values of 10%, 20%, and 30%,
measure the transmittance for three times at 440nm, 546nm, and 635nm, respectively,
with air as a reference.
6.3.5.2 Calculation of the result
Calculate the transmittance indication error according to Formula (3):
Where:
– average value of the 3 measurements;
Ts – standard value of the transmittance.
Calculate the transmittance repeatability according to Formula (4):
Where:
Tmax, Tmin – maximum and minimum values of 3 measurement transmittances.
6.3.6 Baseline flatness
After baseline calibration according to the requirements of the instrument, set the spectral
bandwidth of the instrument to 2 nm (not setting for instruments without spectral bandwidth
adjustment block), the scanning speed to medium, the sampling interval to 1 nm; and the
appropriate absorbance range is set according to the instrument manual; scan with 10 nm being
added to the lower wavelength limit, and 50nm being minus to the upper limit of the wavelength;
and measure the difference between the absorbance at the starting point in the spectrum and the
absorbance deviating from the starting point (taking the maximum deviation point) as the
baseline flatness (a momentary beat is allowed when the light source or receiver is replaced).
6.3.7 Adaptation of power supply voltage
Use the voltage regulator to input 220V voltage; at the selected wavelengths of 250nm, 500nm,
and 1500nm, adjust the transmittance indication value to 100%. Change the input voltage;
record the transmittance indication value of the instrument at 198V and 242V, respectively; and
calculate the difference from 100%, which is the adaptability of power supply voltage.
6.3.8 Stray light
Select the stray light measurement standard substance specified in 6.1.3; measure the
transmittance of the standard substance at the corresponding wavelength; and the transmittance
value is the stray light of the instrument at the wavelength.
a) Use sodium iodide standard solution (or cut-off filter) at 220nm for Section-A; sodium
nitrite standard solution (or cut-off filter) at 360nm (tungsten lamp), 10nm standard
quartz absorption tank; distilled water as reference, and at the spectral bandwidth of 2nm
(not setting for the instrument without the spectral bandwidth adjustment block) to
measure its transmittance indication value.
b) Section-B prism-type instrument, use a cut-off filter, at a wavelength of 420nm, with air
as a reference, to measure its transmittance value.
c) Use H2O, at the wavelength of 1420nm, in the Section-C to measure the indication value
of its transmittance, taking air as the reference.
d) When it is necessary to measure the low stray light value of the instrument, an attenuator
shall be used. First measure the transmittance of the attenuator; and then use the
attenuator as a reference to measure the transmittance of the above standard substance;
and the product of the two transmittances is the stray light.
6.3.9 Compatibility of the absorption tank
In the same optical path absorption tank attached to the instrument, put distilled water at 220nm
(quartz absorption tank) and 440nm (glass absorption tank); adjust the transmittance of one
absorption tank to 100%; and measure the transmittance value of other tanks. The difference is
the compatibility of the absorption tank.
For instruments whose transmittance range is only 0~100%, 95% can be used instead of 100%.
6.3.10 For other types of spectrophotometers whose measurement methods are not completely
included in the scope of this regulation, the main technical indicators can be verified by
referring to the above verification methods; and the technical requirements can be referred to
the exit-factory technical indicators requirements of the instrument.
6.4 Processing of verification results
6.4.1 The newly-manufactured instruments shall be fully verified according to the first
verification items in Table 10 of 6.2. Subsequent verification and in-use inspection shall, in
principle, be carried out according to the content of the subsequent verification and in-use
inspection specified in Table 10; and shall be carried out according to the requirements of the
first verification, if necessary.
6.4.2 For the instruments that have passed the verification according to this regulation, a
verification certificate shall be issued; and the qualification level of the instrument shall be
indicated with the lowest level in the verification results. If there is one item that fails the
verification items (excluding 4.10), which is judged to be unqualified; issuing a verification
notice, and indicating the unqualified item.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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