Influence of helium and nitrogen as carrier gases during capillary GC
analysis
Yuki TSUKADA, Yumiko KURANAMI, Minori KIMURA and Takashi WATANABE
Food and Agricultural Materials Inspection Center, Agricultural Chemicals Inspection Station,
2-772 Suzuki-cho, Kodaira-Shi, Tokyo 187-0011, Japan
Helium is normally used as a carrier gas for capillary gas chromatography (GC) in Japan. However, helium faces the possibilityof decreasing supply because of difficulties at helium plants in the USA and the rapidly increasing demand of helium for technicaland medical uses, especially in developing countries. Helium and hydrogen are recommended as carrier gases by CIPAC (Collaborative International Pesticide Analytical Council Limited), which is the international organization that publishes guidelines fordeveloping analysis methods for pesticides used in agriculture and public health. Because hydrogen is explosive, many laboratories
in Japan do not use it as a carrier gas for GC. Since nitrogen is not explosive and is stable and inexpensive, the suitability of nitrogen as an alternative gas to helium was studied herein.
Keywords: pesticides, GC, carrier gas, helium, nitrogen

Introduction

phase, inner diameters, and film thicknesses. A polar column for bioallethrin and a non-polar column for etofenprox
and procymidone were used.

Inert gases such as helium, hydrogen, and nitrogen are routinely used as carrier gases in capillary GC. In particular,
helium and hydrogen are used for capillary GC because
they have a high resolution at high line velocity, leading toshort analysis times.

Materials and methods
1. Chemicals and reagents

Although the supply of helium has become unstable inrecent years, it is mainly used as a carrier gas for capillary
GC analytical work at FAMIC (Food and Agricultural Materials Inspection Center). In the event of helium shortfall,works such as the analysis of pesticide samples submitted
by applicants for registration and formulations that are taken
for on-site inspection from manufacturers risk being suspended. To avoid such suspension of work, an alternative of
helium is needed.

Bioallethrin (97.1% purity) and procymidone (99.9% purity) were purchased from Hayashi Pure Chemical.
Etofenprox (99.3% purity) was purchased from Wako Pure
Chemical Industries.
Dibutyl sebacate (97% purity) and dicyclohexyl phthalate(99% purity) were purchased from Wako Pure Chemical
Industries; m-terphenyl (99% purity) was purchased from
Sigma-Aldrich Japan.

At CIPAC (Collaborative International Pesticide Analytical Council Limited), helium and hydrogen are recommended as carrier gases for capillary GC 1). However, hydrogen is an explosive gas. Therefore, nitrogen was studied
as an alternative to helium because nitrogen is inert likehelium and hydrogen, is not explosive, and is easy to obtain.
However, nitrogen has a lower resolution at high line velocity than helium 2). During the analysis of a formulation, a
few peaks of the a.i. (active ingredient), IS (internal standard), and some impurities are obtained, and therefore, highresolution is not needed for formulation analysis unlike residue analysis. Hence, nitrogen was suggested. The influenceon the analysis by the difference in carrier gas (between
helium and nitrogen) was studied using some pesticides andcolumns.

Acetone (JIS (Japanese industrial standards) guaranteed
reagent) and methanol (HPLC grade) were purchased from
Wako Pure Chemical Industries.
2. Preparation of standard solutions
The standard solutions of pesticides were prepared by the
CIPAC method 3-5).
2.1 Bioallethrin
About 1.2 g of m-terphenyl was dissolved in acetone (100mL), and this solution was called ISb (internal standard solution for bioallethrin). About 100 mg of bioallethrin was
weighed into a 100 mL volumetric flask (to the nearest 0.1mg); ISb (5.0 mL) was added by pipette and dissolved completely. The flask was filled up to volume with acetone andmixed well. This solution was prepared in duplicate and thesolutions were called Cb100(1) and Cb100(2). Cb100(1) was further
diluted with acetone 100 and 10 times and these solutions

The linearity, limit of detection, HETP (height equivalentof one theoretical plate), and contents of a.i. were measured
using several columns with various polarities of liquid1were called Cb100(1)/100 and Cb100(1)/10, respectively.

About 15 mg of etofenprox was weighed into a 25 mL
volumetric flask (to the nearest 0.1 mg); ISe (2.5 mL) andmethanol (0.5 mL) were added by pipette and dissolved
completely. Then, it was filled up to volume with acetone
and mixed well. This solution was called Ce50. The solution
was diluted by acetone 100 and 10 times and these solutions
were called Ce50/100 and Ce50/10, respectively.

About 50 mg of bioallethrin was weighed into a 100 mL
volumetric flask (to the nearest 0.1 mg); ISb (5.0 mL) was
added by pipette and dissolved completely. Then, it wasfilled up to volume with acetone and mixed well. This solution was called Cb50, and it was diluted with acetone 100
and 10 times and the resulting solutions were called Cb50/100
and Cb50/10, respectively.

About 60 mg of etofenprox was weighed into a 25 mL
volumetric flask (to the nearest 0.1 mg); ISe (2.5 mL) andmethanol (0.5 mL) were added by and dissolved completely.
Then, it was filled up to volume with acetone and mixed
well. This solution was called Ce200. It was diluted with acetone 100 and 10 times and these solutions were called
Ce200/100 and Ce200/10, respectively.

About 200 mg of bioallethrin was weighed into a 100 mL
volumetric flask (to the nearest 0.1 mg); ISb (5.0 mL) was
added by pipette and dissolved completely. Then, it wasfilled up to volume with acetone and mixed well. This solution was called Cb200; it was diluted with acetone 100 and 10
times and these solutions were called Cb200/100 and Cb200/10,
respectively.

3. Preparation of sample solutions
The formulation of bioallethrin could not be obtained because bioallethrin is not registered in Japan. The sample
solutions of procymidone 6) and etofenprox 7) were preparedbased on the CIPAC method.

2.2 Procymidone
About 1.6 g of dibutyl sebacate was dissolved in acetone(200 mL) and the resulting solution was called ISp (internal
standard solution for procymidone). Next, about 50 mg ofprocymidone was weighed into a 50 mL volumetric flask (tothe nearest 0.1 mg); ISp (5.0 mL) was added by pipette anddissolved completely. Then, it was filled up to volume withacetone and mixed well. The solution obtained was prepared in duplicate and called Cp100(1) and Cp100(2). Cp100(1) was
diluted with acetone 100 and 10 times and these solutions
were called Cp100(1)/100 and Cp100(1)/10, respectively.

3.1 Procymidone
Here, 50% wettable powder of procymidone was used andcalled 50WP.
About 200 mg of 50WP was weighed into a 20 mL volumetric flask (to the nearest 0.1 mg) and 10 mL of ISp wasadded by pipette. This operation was repeated in quintuplicate. Then, the solutions were shaken mechanically for 10
min and the supernatants were filtered through 0.45 m
PTFE (polytetrafluoroethylene) filters (SYRINGE FILTER,
Whatman). Next, 1.0 mL of filtrate solutions were pipetted
into 20 mL volumetric flasks and 9 mL acetone was added
by a measuring cylinder. These solutions were called Sp1,
Sp2, Sp3, Sp4, and Sp5.

About 25 mg of procymidone was weighed into a 50 mL
volumetric flask (to the nearest 0.1 mg); ISp (5.0 mL) was
added by pipette and dissolved completely. Then, it wasfilled up to volume with acetone and mixed well. The solution was called Cp50, which was diluted with acetone 100
and 10 times. The resulting solutions were called Cp50/100
and Cp50/10, respectively.
About 100 mg of procymidone was weighed into a 50 mL
volumetric flask (to the nearest 0.1 mg); ISp (5.0 mL) was
added by pipette and dissolved completely. Then, it wasfilled up to volume with acetone and mixed well. This solution was called Cp200; it was diluted with acetone 100 and 10
times and these solutions were called Cp200/100 and Cp200/10,
respectively.

3.2 Etofenprox
Here, 20% emulsifiable concentrate of etofenprox was chosen and this sample was called 20EC.
About 300 mg of 20EC was weighed into a 50 mL volumetric flask, and then, 1 mL of methanol and 5 mL of ISewere added by pipette. This operation was repeated in quintuplicate. Then, the resulting solutions were filled to themark with acetone and mixed well, and were called Se1, Se2,
Se3, Se4, and Se5.

2.3 Etofenprox
About 1.0 g of dicyclohexyl phthalate was dissolved in acetone (100 mL) and this solution was called ISe (InternalStandard Solution for etofenprox). About 30 mg ofetofenprox was weighed into a 25 mL volumetric flask (tothe nearest 0.1 mg); ISe (2.5 mL) and methanol (0.5 mL)
were added by pipette and dissolved completely. Then, it
was filled up to volume with acetone and mixed well. Thissolution was prepared in duplicate, called Ce100(1) and Ce100(2).
Ce100(1) was diluted with acetone 100 and 10 times and thesolutions obtained were called Ce100(1)/100 and Ce100(1)/10, respectively.

4. GC conditions
An Agilent 6890N gas chromatograph with FID (flame ionization detector) was used.
Gas chromatographic conditions for bioallethrin, procymidone, and etofenprox are shown in Table 1 (1)-(3),respectively.
DB-FFAP for bioallethrin is a highly polar column and theDB-1 column for procymidone and etofenprox is a
non-polar column. These columns were purchased from2

Agilent Technologies.

locity for procymidone could not be set over 50 cm/s using
nitrogen with some columns because the total flow exceeded 200 mL/min.

5. Linearity

HETP was calculated as follows2):

The C50, C100(1), and C200 solutions of bioallethrin, procymidone and etofenprox (1 L) were injected in duplicate
and the correlation coefficient (r) was calculated.

HETP = L / N
where L: column length [mm], N: theoretical plate number,calculated as follows:
N = 5.545×(tr / W1/2)2

6. Limits of detection

where tr: retention time of the peak [min], W1/2: half widthof the peak [min].

The C50/100, C100(1)/100, C200/100, C50/10, C100(1)/10, C200/10, C50,
C100(1), and C200 solutions of bioallethrin, procymidone, andetofenprox (1 L) were injected in duplicate. The correction
coefficient calculated by the results of C50/100, C100(1)/100, andC200/100 was called r/100; that calculated based on the resultsof C50/10, C100(1)/10, and C200/10 was called r/10; and the one
calculated by the results of C50, C100(1), and C200 was called
r/1. The limit of detection was determined as the lowest value in the measurement range, which had good linearity (r >0.99).

8. Sample analysis
All samples except for bioallethrin were determined by thebracketing method8).
Then, 1 L each of the C100(1), C100(2) standard solutions
and S1-S5 sample solutions was injected as follows:
C100(1), S1, S1, C100(2), S2, S2, C100(1), …, S5, S5, C100(2)The concentrations of S1-S5 were determined, and the average and coefficient of variation (CV %) of the results were
calculated.

7. Influence of line velocity
C1 (1 L) was injected at line velocities ranging from low(20 cm/s) to high (60 cm/s) at steps of 5 cm/s and the HETP
was calculated at each line velocity. However, the line veTable 1. GC conditions(1) bioallethrin
DB-FFAP column[inner diameter / length / thickness]

injection port

detection port

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 0.25 µm

He

N2

He

N2

He

N2

He

N2

oven temperature
[℃]

240

240

240

240

240

240

240

240

line velocity [cm/sec]

35

35

35

35

35

35

35

35

temperature [℃]

250

250

250

250

250

250

250

250

split ratio

30/1

30/1

30/1

30/1

30/1

30/1

30/1

30/1

volume [µl]

1.0

1.0

1.0

1.0

1.0

1.0

1.0

1.0

detector

FID

FID

FID

FID

FID

FID

FID

FID

temperature [℃]

250

250

250

250

250

250

250

250

hydrogen flow
[ml/min]

40

40

40

40

40

40

40

40

air flow [ml/min]

450

450

450

450

450

450

450

450

make up flow (N2)
[ml/min]

15

15

15

15

15

15

15

15

carrier gas

column0.25 mm / 30 m / 0.25 µm

3Table 1. GC conditions(2) procymidone
DB-1 column[inner diameter / length / thickness]

0.32 mm / 30 m / 0.25 µm

0.53 mm / 30 m / 1.00 µm

N2

He

N2

He

N2

He

N2

oven temperature
[℃]

240

240

240

240

240

240

240

240

line velocity [cm/sec]

35

35

35

35

35

35

35

35

temperature [℃]

250

250

250

250

250

250

250

250

split

70.9/170.9/170.9/170.9/170.9/170.9/170.9/1

30.6/1volume [µl]

1.0

1.0

1.0

1.0

1.0

1.0

1.0

1.0

detector

FID

FID

FID

FID

FID

FID

FID

FID

temperature [℃]

300

300

300

300

300

300

300

300

hydrogen flow
[ml/min]

40

40

40

40

40

40

40

40

air flow [ml/min]

450

450

450

450

450

450

450

450

make up flow (N2)
[ml/min]

15

15

15

15

15

15

15

15

injection port

detection port

0.32 mm / 30 m / 1.00 µm

Hecarrier gas

column0.25 mm / 30 m / 1.00 µm(3) etofenprox
DB-1 column[inner diameter / length / thickness]

injection partdetection part0.32 mm / 30 m / 1.00 µm

0.32 mm / 30 m / 0.25 µm

0.53 mm / 30 m / 1.00 µm

He

N2

He

N2

He

N2

He

N2

oven temperature[℃]

260(40 min)→10/min→300(3 min)260(33min)→10/min→300(3min)260(23min)→10/min→300(3min)260(23min)→10/min→300(3min)260(15min)→10/min→300(3min)260(12min)→10/min→300(3min)260(15min)→10/min→300(11min)260(15min)→13/min→300(2min)line velocity [cm/sec]

45

45

45

45

45

45

45

45

temperature [℃]

300

300

300

300

300

300

300

300

split

30/1

30/1

30/1

30/1

30/1

30/1

30/1

30/1

volume [µl]

1.0

1.0

1.0

1.0

1.0

1.0

1.0

1.0

detector

FID

FID

FID

FID

FID

FID

FID

FID

temperature [℃]

300

300

300

300

300

300

300

300

hydrogen flow
[ml/min]

40

40

40

40

40

40

40

40

air flow [ml/min]

450

450

450

450

450

450

450

450

make up flow (N2)
[ml/min]

15

15

15

15

15

15

15

15

carrier gas

column0.25 mm / 30 m / 1.00 µm

4Results and discussions

trogen as a carrier gas were between 0.9999 and 1.0000.
The difference between carrier gas, inner diameter, liquid
phase, and thickness of the column had no effect on the linearity.

1. Linearity
The correction coefficients are shown in Table 2.
Correction coefficients using helium as carrier gas were
between 0.9997 and 1.0000, while that obtained using niTable 2. Results of correction coefficients for linearity
bioallethrin
DB-FFAP column[inner diameter / length / thickness]

0.25 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 0.25 µm

carrier gas

He

N2

He

N2

He

N2

He

N2

correction coefficient (rb)1.00001.00001.00000.99991.00001.00001.00001.0000procymidone
DB-1 column[inner diameter / length / thickness]

0.25 mm / 30 m / 1.00 µm

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 1.00 µm

carrier gas

He

N2

He

N2

He

N2

He

N2

correction coefficient (rp)1.00001.00001.00000.99991.00001.00000.99971.0000etofenprox
DB-1 column[inner diameter / length / thickness]

0.25 mm / 30 m / 1.00 µm

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 1.00 µm

carrier gas

He

N2

He

N2

He

N2

He

N2

correction coefficient (re)0.99990.99991.00001.00001.00001.00001.00001.00002. Limits of detection
The correlation coefficients and the limits of detection are
shown in Table 3 (1)-(3), and the typical chromatographs areshown in Fig. 1-3.
The retention times of the peaks did not change when helium is replaced by nitrogen.
The limits of detection of bioallethrin and procymidone
using helium were 5 ng/mL, while those obtained using nitrogen were 5-50 ng/mL.
The limits of detection of etofenprox using helium and nitrogen were 6 ng/mL.
The limits of detection of etofenprox using helium and nitrogen were the same, but those of bioallethrin and procymidone using helium and nitrogen were the same or lower.
It was considered that the peak became too wide when nitrogen is used.
Fig. 1. Chromatograms of bioallethrin and ISb by varying carrier
gas and inner diameter of the DB-FFAP column.
The column length and thickness are 30 m and 0.25 m. The
carrier gas and the column inner diameter are:(A) He, 0.25 mm, (B) N2, 0.25 mm, (C) He, 0.32 mm(D) N2, 0.32 mm, (E) He, 0.53 mm, (F) N2, 0.53 mm

5

Fig. 2. Chromatograms of procymidone and ISp by varying the

Fig. 3. Chromatograms of etofenprox and ISe by varying the car-carrier gas and inner diameter of DB-1 column.

rier gas and inner diameter of DB-1 column.

The column length and thickness are 30 m and 1.00 m; the carri-

The column length and thickness are 30 m and 1.00 m; the carri-er gas and the column inner diameter are:er gas and the column inner diameter are:(A) He, 0.25 mm, (B) N2, 0.25 mm, (C) He, 0.32 mm,(A) He, 0.25 mm, (B) N2, 0.25 mm, (C) He, 0.32 mm,(D) N2, 0.32 mm, (E) He, 0.53 mm, (F) N2, 0.53 mm(D) N2, 0.32 mm, (E) He, 0.53 mm, (F) N2, 0.53 mm

trations of procymidone in 50WP were between 496.0 and
499.7 g/kg, and their CV% values were between 0.11% and0.30%.

3. Influence of line velocity
It was observed that the HETP using nitrogen (HETPN2) was
equal to or smaller than that obtained using helium gas(HETPHe) at a low line velocity (20-30 cm/s). In contrast, at
higher line velocity, HETPN2 was larger than HETPHe (Fig.
4-6). There were no differences with the column and sample.
Nitrogen provides the best efficiency when the line velocity
is low. In brief, a low line velocity using nitrogen is needed
to obtain the same HETP using helium. As a result, because
a longer time of analysis is needed, the use of nitrogen is notrecommended. Therefore, it was considered that helium issuperior to nitrogen as the carrier gas at high line velocities.
4. Sample analysis
The contents of a.i. are shown in Table 4 (1) and (2).
The concentrations of procymidone in 50WP were between
496.7 and 498.6 g/kg, and their CV% values were between
0.08% and 0.70% using helium. Using nitrogen, the concen-

6

The concentrations of etofenprox in 20EC were between
201.9 and 208.4 g/kg, and their CV% values were between
0.45% and 0.86% using helium. Using nitrogen, the concentrations of etofenprox in 20EC were between 200.7 and
208.5 g/kg, and their CV% values were between 0.11% and0.30%.
Differences of column polarity, inner diameter of column,
thickness, and carrier gases had no effect on the analysis of
50WP and 20EC. Therefore, it was considered that whenanalyzing pesticide formulations, nitrogen can be used as analternative carrier gas to helium.

Table 3. Limits of detection(1) bioallethrin
DB-FFAP column[inner diameter / length / thickness]

0.25 mm / 30 m / 0.25 µm

carrier gas

correction
coefficient

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 0.25 µm

He

N2

He

N2

He

N2

He

N2

5 – 20[ng/ml]r/100

0.9994

0.99880.9996

0.9981

0.99890.98200.99940.999850 – 200[ng/ml]r/10

1.00001.00000.99991.00000.99990.99950.99991.0000500 – 2000
[ng/ml]r/1

1.00001.00001.00001.00001.00000.99991.00001.0000

5

5

5

5

5

50

5

5

limit of detection [ng/ml](2) procymidone
DB-1 column[inner diameter / length / thickness]

0.25 mm / 30 m / 1.00 µm

carrier gas

correction
coefficient

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 1.00 µm

He

N2

He

N2

He

N2

He

N2

5 – 20[ng/ml]r/100

0.99230.97800.9961－0.99970.93980.9984

0.991050 – 200[ng/ml]r/10

1.00001.00001.00000.99681.00001.00001.00000.9999500 – 2000
[ng/ml]r/1

1.00000.99991.00001.00001.00001.00001.00001.0000

5

50

5

50

5

50

5

5

limit of detection [ng/ml](3) etofenprox
DB-1 column[inner diameter / length / thickness]

0.25 mm / 30 m / 1.00 µm

carrier gas

correction
coefficient

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 1.00 µm

He

N2

He

N2

He

N2

He

N2

6 – 24[ng/ml]r/100

0.99780.99530.9937

0.99690.99890.99910.9991

0.997960 – 240[ng/ml]r/10

1.00001.00001.00001.00001.00001.00000.99991.0000600 – 2400
[ng/ml]r/1

1.00001.00001.00001.00001.00001.00000.99980.9999

6

6

6

6

6

6

6

6

limit of detection [ng/ml]

7

Table 4. Results of analysis(1) procymidone 50WP
DB-1 column[inner diameter / length / thickness]

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 1.00 µm

He

N2

He

N2

He

N2

He

N2

Sp1

500.0

499.9

498.1

494.1

495.7

497.8

491.9

496.2

Sp2

498.7

498.8

497.9

496.1

496.0

498.0

499.9

497.5

Sp3

498.3

499.2

498.9

497.5

497.8

499.2

499.3

498.4

Sp4

498.2

499.2

497.9

494.8

496.9

498.3

494.4

497.6

Sp5

498.9

501.6

498.3

497.3

497.1

498.5

498.5

498.5

Average

498.6

499.7

498.2

496.0

496.7

498.4

496.8

497.6

0.17

0.22

0.08

0.30

0.17

0.11

0.70

0.18

carrier gas

concentration [g/kg]

0.25 mm / 30 m / 1.00 µm

coefficient of variation (CV %)(2) etofenprox 20EC
DB-1 column[inner diameter / length / thickness]

0.32 mm / 30 m / 0.25 µm

0.32 mm / 30 m / 1.00 µm

0.53 mm / 30 m / 1.00 µm

He

N2

He

N2

He

N2

He

N2

Se1

207.6

207.9

208.3

207.4

207.7

207.9

200.9

202.7

Se2

207.7

208.5

208.3

208.3

208.1

207.9

200.5

200.3

Se3

206.9

207.7

207.6

208.0

207.8

207.6

202.4

203.1

Se4

208.0

208.1

207.9

207.7

208.0

207.9

200.9

197.6

Se5

209.7

210.4

210.0

210.3

210.5

210.7

204.7

199.7

Average

208.0

208.5

208.4

208.3

208.4

208.4

201.9

200.7

0.50

0.52

0.45

0.55

0.56

0.62

0.86

1.13

carrier gas

concentration [g/kg]

0.25 mm / 30 m / 1.00 µm

coefficient of variation (CV %)Fig. 4. HETP by difference of line velocities for bioallethrin using

Fig. 5. HETP by difference of line velocities for procymidone

a DB-FFAP column.

using DB-1 column.

The length, inner diameter, and thickness of the column are:

The length, inner diameter, and thickness of the column are:(A) 30 m / 0.25 mm / 0.25 m, (B) 30 m / 0.32 mm / 0.25 m,(A) 30 m / 0.25 mm / 1.00 m, (B) 30 m / 0.32 mm / 0.25 m,(C) 30 m / 0.32 mm / 1.00 m, (D) 30 m / 0.53 mm / 0.25 m(C) 30 m / 0.32 mm / 1.00 m, (D) 30 m / 0.53 mm / 1.00 m

8

that nitrogen is a potential alternative carrier gas to helium.
References
1) http://www.cipac.org/images/pdf/
CIPAC4105R.pdf (Accessed 25 Oct 2016)2) http://www.agilent.com/cs/library/slidepresentation/
Public/Converting%20Helium%20Carrier%20Gas%
20GC%20Methods%20to%20Nitrogen%20and%20
Hydrogen.pdf (Accessed 25 Oct 2016)
3) W DOBRAT and A MARTIJN: CIPAC HANDBOOK L(203/TC/M2/3) (2006)
4) W DOBRAT and A MARTIJN: CIPAC HANDBOOK K(383/TC/M/3) (2003)

Fig. 6. HETP by difference of line velocities for etofenprox

5) W DOBRAT and A MARTIJN: CIPAC HANDBOOK K(471/TC/M/3) (2003)

using a DB-1 column.
The length, inner diameter, and thickness of the column are:

6) W DOBRAT and A MARTIJN: CIPAC HANDBOOK K(383/WP/M/3) (2003)(A) 30 m / 0.25 mm / 1.00 m, (B) 30 m / 0.32 mm / 0.25 m,(C) 30 m / 0.32 mm / 1.00 m, (D) 30 m / 0.53 mm / 1.00 m7) W DOBRAT and A MARTIJN: CIPAC HANDBOOK K(471/EC/M/3) (2003)8) http://www.cipac.org/images/pdf/study.pdf (Accessed 25
Oct 2016)

Conclusions
When the carrier gas was changed from helium to nitrogen,the HETP increased, peaks became broader, and the limit ofdetection became higher. However, no differences were observed in the analytical results of pesticide formulation between nitrogen and helium when pesticides were analyzed
under different column conditions such as polarity of liquid
phase, film thickness, length, and inner diameter. Hence,
based on the analysis of a.i. in formulation and after checking the separation of a.i., IS, and impurities, it is concluded

9