Zhong-yu Li, Jiang-hua Zhao, Shan Cao, Yan-bing Han

Xi’an Center of Geological Survey, China Geological Survey, Ministry of Natural Resources, Xi’an 710054, China

1. Objectives

The laboratory of Xi’an Center, China Geological Survey has long been engaged in the testing of oil and gas geochemical samples. Among the different indexes, the measurement of the polycyclic aromatic hydrocarbon needs to be completed by the fluorescence spectrophotometer which is made in PE Company. According to the standard method, the fluorescence intensity values of three emission wavelengths under a certain excitation wavelength should be provided. The instrument software can only provide the visible fluorescence intensity, but it cannot record and save data, the data only be recorded on the paper, then input into the computer as the original record after the end of the test. It is a great waste of time, and it’s easy to make mistakes in this way. To improve working, the authors use AutoIt v3 (Luo P, 2012) to develop special software that can be operated by a single person,recycling operation, and automatic numbering and record data. This software can be used to test oil and gas geochemical samples. It is a great improvement on the original method (Table 1).

Table 1. The characteristics comparison of the original and new methods.

2. Methods

The method is suitable for the determination of polycyclic aromatic hydrocarbons in geochemical exploration for oil and gas samples (GB/T 29173-2012). It is aimed at the improvement and optimization of the measuring method of the fluorescence intensity of samples by the LS-55 fluorescence spectrophotometer made by PE Company (Fig. 1).The specific method is as follows: Weigh 20 g samples in a triangular flask with stopper and add 30 mL n-hexane.Oscillate for 20 min and leave for more than 12 h. Oscillate for another 20 min and leave for 1 h. The clear liquid was extracted, and 0.5 g anhydrous sodium sulfate was added, to be measured. Boot up and preheated fluorescence spectrophotometer, measure it at the emission wavelengths of 320 nm, 360 nm and 405 nm under the condition of excitation wavelength of 265 nm. The invention includes the following steps (Fig. 2):

Fig. 1. LS-55 fluorescence spectrophotometer.

Fig. 2. Software nested loop algorithm.

Step 1: Run the fluorescence spectrophotometer, start the instruction of “new Microsoft Office Excel worksheet”, and create a fixed format Excel file for data storage in the root directory of disk D; At the same time, open the test software interface N.

Step 2: Access the internal ID button and the key parameters which can control the fluorescent spectrophotometer to start testing. According to the ID button and key parameters, begin to determine the using the Control-Click function to fluorescence spectrophotometer determination of sample’s instructions, adjust the xenon lamp wavelength to 265 nm, irradiation samples, determine the fluorescence intensity values under 320 nm, 360 nm, 405 nm wavelength.

Step 3: Obtain basic attribute and the INSTANCE value of three Text boxes in fluorescence spectrophotometer form properties. At the end of the measurement of a group, read three textboxes value respectively, by Control Get Text Function, then stored them in computer memory. Then begin to test the next group of samples, the value in the computer will be written in the corresponding position of the excel sheet according to the INSTANCE Order.

Step 4: Replace the next sample, and use While-WEnd and Switch-Case- EndSwitch nested loop algorithms to make sample testing, data reading and data entry recyclable.

Step 5: After testing all the samples, store the data in the excel file in the root directory of disk D, and count the number of samples.

3. Results

Compared with the original method, the method of this invention has the following advantages:

(i) Liberate the manpower: The whole operation process can be completed by one person.

(ii) Accurate data: The program automatically reads and inputs the measured results into the specified files. There is no misreading.

(iii) Improve efficiency: The data entry is completed instantaneously, and the analysis of the next sample is started immediately, which saves time greatly.

(iv) Data traceability: The generated data file can be saved on the computer disk as the original record of the analysis test, which is convenient to call or view.

(v) The software is the expansion of the software functions of the instrument.

4. Conclusion

The authors have improved the fluorescence spectrophotometer method for the determination of polycyclic aromatic hydrocarbons in hydrocarbon geochemical samples.At the same time, the sample analysis data will be automatically saved in the computer, so that the test data can be easily viewed and traceable.

The invention is an optimization and improvement of an index testing process in oil and gas geochemical samples and will be strong support for oil and gas geochemical analysis.

This equipment has obtained the national invention patent and the patent number is ZL 2016 1 0668152.8 (Fig. 3).

Fig. 3. Certificate of the patent.

CRediT authorship contribution statement

Zhong-yu Li conceived of the presented idea. Shan Cao,Yan-bing Han developed the theory. Zhong-yu Li, Jiang-hua Zhao collected the specimens and analyzed the samples.Zhong-yu Li wrote the original draft. Jiang-hua Zhao, Shan Cao, and Yan-bing Han reviewed and edited the manuscript.All authors discussed the results and contributed to the final manuscript.

Declaration of competing interest

The authors declare no conflict of interest.

Acknowledgment

This study was funded by the project “Research on general technical standards of land reclamation and ecological restoration, determination of petroleum in reclaimed land samples” (2017YFF0206804-24).