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2018.06.28
CIC analysis for volatile liquid samples; June 22-24, 2017 at Osaka University
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34th Joint Symposium
84th Organic micro analysis research meeting, Japan Analytical Chemistry Association,
104th The Society of Instrument and Control Engineers (SICE),
Technical Committee on Mechanical Metrology
At Suita Campus, Osaka University, June 22 – 24, 2017

Abstract: P-06

Speed-up of halogens and sulfur auto-combustion analytical system and application to multi-elemental analysis: Analysis of volatile liquid samples

Hisomu Nagashima*1, Takeshi Matsuzaki*2

A multifunctional halogens and sulfur analytical system has been developed by coupled combustion/ion chromatography (CIC). In this study, we have established a simultaneous determination for halogens (F, Cl, Br, I) and sulfur (S) in volatile liquid samples, based upon conductivity detection after decomposition in this automatic system using clean air. It introduces some application examples, (1) Use of Para-film sheet for oxygen combustion flask or combustion-IC method, (2) Use of tin capsules to volatile liquid samples, (3) Trace analysis of 4 halogens (< 1.0ppm) in light oil, and (4) Trace analysis of total S (< 0.01ppm) in liquefied CO2 gas.

1. Introduction

In these 10 and few years duration, we have developed 3 kinds of halogens/sulfur automatic combustion analysis system such as:
1. For organic micro elemental analysis
2. For environmental samples conformed to JIS regulation
3. For inorganic/organic samples compatible high temperature type system
In organic micro elemental analysis, multi-elements (4 halogens and sulfur) simultaneous analysis has achieved as well as ultra-micro analysis method with ultra-micro amount of samples, furthermore, high speed realization of analysis operation including combustion time and chromatogram development, in order to approach effectively to mainstream CHN (O) analysis method 1). Tremendous development has achieved in solid samples, while changing the viewpoint to liquid samples, such application is still not sufficient enough. For instance, property is significantly different from respective sample each other, such as in volatile solvent, petroleum product, suspension and viscous liquid, sample containing large amount of matrix, and so forth. Therefore, it is extremely difficult to measure within sequential operational processes by utilizing current automatic liquid auto-sampler. In the advancement of current combustion/ion chromatograph (CIC) method and further halogens/sulfur analysis in liquefied petroleum gas (LPG), some analysis examples for liquid samples are introduced here.

*1 NAC Techno Service Co., Ltd. (Tokyo and Chiba, Japan)
*2 Research Support Co., Ltd. (Tokyo, Japan)

2. Analysis of liquid samples

2-1. Para-film method

Oxygen flask combustion method was introduced into our country in the beginning of 1960s, but application to the liquid samples was initially pending issue. At that time, author and colleagues considered weighing method for the liquid samples and using para-film for combustion method
(Fig. 1), and published reports to annual corporate report at that time 2), 3). By this method, sufficient results were obtained and the method was applied to chlorine analysis in chloroform and sulfur analysis in carbon disulfide. This method is utilized for combustion-IC method, but a certain obstacle such as soot is produced when the para-film was big and operation was troublesome. Even so, this method is utilized as of today. 17th amendment of Japanese Pharmacopoeia (JP) was implemented in April, 2016, but it is no amendment in general testing method of “Oxygen flask combustion method”. After combustion, precipitation titration method with silver nitrate and barium salt is still used for determination of both halogens and sulfur. As there is no specific regulation in the JP, para-film method is still dependent on at present for analysis of liquid samples.

Fig.1

Fig.2

Fig. 2
Tin capsule for liquid sample

2-2. Tin capsule method

In this investigation, tin capsule (Ludi Swiss AG, 5.0φ x 13mm) is used; liquid sample is introduced into the capsule with the syringe, and open part is crimped by tweezers (Fig. 2).
Tin capsule has soft material and enables to seal impeccably.
In the collection example of 100µL methanol solution, no significant mass decrease was recognized over one hour.
Moreover, tin capsule combusts as flash in oxygen flow, but explosive combustion caused by material and vessel sealing is not recognized in air supportive gas flow.
Thin cloudiness in absorbed solution is recognized when temperature of combustion furnace sets at 1,200℃.
Therefore, it is desirable to use the moving furnace at less than 900℃.

Fig.3

Fig. 3
JIS magnetic boat with liquid sample

2-3. Direct introduction method for sample solution

SQ-1 type combustion furnace is conformed on JIS K2541 (crude oil and petroleum products), so determination of 4 halogens in No. 3 light oil can be implemented by directly weighing 500 to 600mg (ca. 700µL) on the magnetic boat, and combusted (Fig. 3).

Analyzed values (ppm, w/w) are as follows;
F: 0.07, Cl: 0.29, Br: <0.2, I: <0.1 (by UV detection) Total : less than 0.66ppm It can be confirmed that total concentration of 4 halogens is less than 1.0ppm, which is regulated as total halogen allowable quantity.

2-4. Next generation type analysis of liquid samples

Combustion/IC method is widely applied for various fields, such as liquefied petroleum gas (LPG), natural gas, etc. Here, total sulfur analysis in liquefied carbon dioxide has applied.
SQ-1 type combustion furnace is adopted suction method using clean air as carrier gas.
Hence, constant quantity of carbon dioxide from the cylinder is introduced into the suction gas, and it is led to combustion tube and absorption unit, so that sulfur concentration in the absorption solution can be measured (Fig. 4).
In actual way, when liquefied carbon dioxide from the cylinder is introduced at the flow rate 0.92L/min in 30 minutes, CO2 mass conversion quantity becomes at 33 grams, and lower limit of total sulfur converted by sulfuric acid becomes as 0.002ppm (w/w).
It assures sufficiently regulated value of the product as S: <0.01ppm. So, this method can be adequately adopted in the field of liquefied petroleum gas (LPG).

Fig.4

Fig. 4
Total sulfur analysis in liquefied carbon dioxide
A: Sample cylinder → Flowmeter
B: Quartz tube → Combustion furnace → Absorption unit → IC

Bibliography

1) H. Nagashima, Y. Dewa, Analytical chemistry, 66, 81 (2017)
2) K. Ono, H. Nagashima, Ann. Sankyo. Res. Lab., 18, 51 (1966)
3) H. Nagashima, K. Ono, Ann. Sankyo. Res. Lab., 21, 40 (1969)